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LAWRENCE L. YEE, M.D.*; ALEXANDER S. RUBIN, M.D.†; AND RONALD F. BELLAMY, M.D.‡

*Formerly, Major, Medical Corps, U.S. Army; Staff Anesthesiologist, Walter Reed Army Medical Center, Washington, D. C. 20307-5001;currently, Staff Anesthesiologist, O’Connor Hospital, 2105 Forest Avenue, San Jose, California 95128

†Formerly, Major, Medical Corps, U.S. Army; Staff Anesthesiologist, Walter Reed Army Medical Center, Washington, D. C. 20307-5001;currently, Staff Anesthesiologist, Frederick Memorial Hospital, Frederick, Maryland 21702

‡Colonel, Medical Corps, U.S. Army; Managing Editor and Officer in Charge, Textbook of Military Medicine, Borden Institute, Walter ReedArmy Medical Center, Washington, D. C. 20307-5001

THORACIC INJURIES

Chapter 19

INTRODUCTION

TYPES OF INJURYPenetrating MissilesBlunt and Blast Injuries

OVERVIEW OF COMBAT THORACIC TRAUMA

GENERAL PRINCIPLES OF MANAGEMENTIndications for ThoracotomyPreoperative Evaluation and PreparationMonitoringInduction of AnesthesiaMaintenance of AnesthesiaPositioning for OperationPostoperative Care

DIAGNOSIS AND MANAGEMENT OF SPECIFIC INJURIESRib FracturesFlail ChestSucking Chest WoundAcute Traumatic HemothoraxCardiac TamponadeCardiac ContusionsCardiac RuptureInjuries to the Coronary ArteriesInjuries to the Great VesselsPneumothoraxTracheal and Bronchial InjuriesParenchymal Lung LacerationsTraumatic Rupture of the Diaphragm

SUMMARY

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INTRODUCTION

The casualty suffering thoracic trauma usuallyposes a lesser challenge to the military traumaanesthesiologist than might be supposed. As wediscussed in Chapter 1, Combat Trauma Over-view, the reasons for this are simple: (1) mostcasualties who are wounded in the chest die onthe battlefield, and (2) only a minority of thosewho reach a medical treatment facility alive re-quire a formal thoracotomy. Most survivors re-quire only the insertion of a chest tube. Thus,thoracic trauma in combat casualties has some of

the all-or-none characteristics of an airplanecrash: the victim is either killed outright or has ainjury that is treatable by simple interventions.Nevertheless, there are exceptions (eg, the casu-alty who suddenly exsanguinates when a medi-astinal hematoma ruptures, the casualty whosetracheobronchial tree is filling with blood, thecasualty who suddenly develops massive arte-rial air embolism when mechanical ventilation isstarted) that can push even the most competentanesthesiologists to their limits.

Thoracic trauma can be the result of one or moreof the four basic mechanisms of injury: penetrating(ballistic), blunt, blast, and thermal. Thermal injuryresulting from the inhalation of hot, poisonous gasesis an important cause of combat mortality and mor-bidity in the navy and among soldiers who crewarmored fighting vehicles. Inhalation injury is dis-cussed in Chapter 22, Burn Injuries; therefore, itwill not be further discussed in this chapter.

Penetrating missiles have been far and away themajor source of thoracic trauma in combat casual-ties, as seen in Table 19-1, which presents data fromtwo countries and two wars. The data from the U.S.Army in the Vietnam War covers a 14-month period(September 1968–November 1969) at the 24th Evacu-ation Hospital.1 During this interval, the hospitalserved as a specialty center for neurological, headand neck, and thoracic casualties. Data from theRambam Medical Center covers the period 6 to 29June 1982 (during the military operation in Leba-non that the Israelis call Peace in Galilee).2

Because penetrating trauma is the cause of theoverwhelming majority of combat casualties withthoracic injuries, and because it is generally agreedthat missile wounds are distributed randomly, theoverall prevalence of thoracic trauma should ap-proximate the fraction of the body surface area thatoverlies the thorax: about 16 in 100. Most casualtieswith thoracic trauma are killed; therefore, the actualpercentage of the casualty population who will re-quire treatment for thoracic trauma will be somewhatsmaller and usually ranges between 5% and 10%.3

Penetrating Missiles

The nature of the medical problems caused bypenetrating missiles, whether they are bullets from

small arms or fragments from explosive munitions,is due to three factors:

1. the function of the organ or organs struck,2. the physical characteristics of the missile,

and3. the biophysics of the interaction between

the missile and the tissue that is struck.

It should be readily apparent that the first fac-tor—the nature of the organ hit—is of paramountimportance in determining the medical outcome ofa ballistic injury. A missile wound of the brainstemis likely to be much more serious than a hit made bya similar missile to the little toe. Unfortunately, thethoracic cavity has more than its share of organs—the heart, great vessels, and lungs—the injury ofwhich will be immediately catastrophic.

The second factor—the physical characteristicsof the missile—is usually assessed in terms of ki-netic energy (calculated as 1⁄2MV2, where M repre-sents the projectile’s mass and V its velocity). Tis-sue destruction caused by a ballistic injury is relatedin a general sense to the kinetic energy transferredto the target tissue such that

1⁄2M(Vent – Vext)2

where Vent and Vext represent the velocity of themissile when it enters and exits the body, respec-tively. When the missile does not exit but stopswithin the body, the kinetic energy transferredequals 1⁄2MVent

2. Fragments usually do not exitfrom the body, while bullets, unless they deform orfragment, frequently cause perforating wounds.Bullets that fragment (ie, rounds fired from theM16 series of assault rifles) or deform (ie, many

TYPES OF INJURY

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TABLE 19-1

ETIOLOGY OF THORACIC TRAUMA

24th EvacuationHospital RambamUS Army, Medical CenterVietnam1 Haifa, Israel2

energy transfer. The density of the tissue is anotherdeterminant of the projectile–target interaction. Themore dense the tissue, the more complete the en-ergy transfer. Thus, projectile energy transfer ismaximal in bone but minimal in the least-densebody tissue, the lung. (A more complete discus-sion of the biophysics of wound ballistics can befound in the Textbook of Military Medicine volumeConventional Warfare: Ballistic, Blast, and Burn Inju-ries.)4

Wound ballistics as it applies to the thorax is bestsummarized in the official history of thoracic sur-gery in World War II:

[H]igh-velocity missiles that traverse the pulmo-nary tissue therefore often cause surprisingly littlepulmonary damage. The high immediate lethalityof high-velocity wounds of the chest is apparentlydirectly related to the percentage chance of damageto vital structures, particularly the heart and greatvessels. If the high-velocity missile does not inflicta mortal wound, then it often traverses the chestwith considerably less damage to the thoracic con-tents than is caused by a low-velocity shellfragment.5(p59)

Blunt and Blast Injuries

In the field, nonpenetrating injuries to the chestare caused either by forceful contact with a bluntobject or by blast overpressure. Blunt chest traumasuch as may occur in motor vehicle accidents resultsfrom gross compression of the thorax, which maycause rib fractures and a variable degree of dis-placement of intrathoracic viscera such as the heart.In extreme circumstances, the heart may be so dis-placed that stretch-and-shear strain affecting theproximal descending aorta may cause it to rupture.With blunt trauma, but not with blast injury, themore serious the injury, the greater the likelihood ofrib fractures. Fractures of the upper five ribs areusually associated with the most serious, and oftenoccult, injuries.

The exact mechanisms that produce visceral in-jury within the thoracic cavity following blunt andblast injury are poorly understood, but it is nolonger thought that acceleration–deceleration of thebody is an important mechanism per se. Extensiveexperimental studies using living animals and hu-man cadavers indicate that the probability of injurycan best be understood in terms of (a) the magni-tude of compression of the thorax and (b) the veloc-ity at which the compression occurs (Figure 19-1).6,7

When compression is applied slowly (< 1 m/s; eg,in vigorous closed-chest cardiopulmonary resuscita-

Total Casualties 7,500 938

Chest Trauma 900* 64

Intrathoracic Injury 547 63

Fragment 443 41

Bullet 76 7†

Blunt 28 6‡

Blast 6§

*Including superficial missile wounds as well as blunt trauma tothe chest wall but without any intrathoracic component

†There were, in addition, two casualties with both bullet andfragment wounds

‡There was a seventh casualty with both fragment and bluntthoracic trauma

§All six casualties with pulmonary blast injury also had frag-ment wounds of the thorax

Data sources: (1) McNamara JJ, Messersmith JK, Dunn RA,Molot MD, Stremple JF. Thoracic injuries in combat casualties inVietnam. Ann Thor Surg. 1970;10:389–401. (2) Rosenblatt M,Lemer M, Best LA, Peleg H. Thoracic wounds in Israeli battlecasualties during the 1982 evacuation of wounded from Leba-non. J Trauma. 1985;25:350–354.

commonly available bullets used by civilian hunt-ers and law-enforcement agencies) typically areassociated with much greater energy transfer thanoccurs with intact bullets that cause perforatingwounds.

A second important physical characteristic is theshape of the projectile. Streamlined bullets can passthrough tissue with little reduction in velocity, whileirregular fragments from explosive munitions slowrapidly and, therefore, can transfer a much greaterfraction of their kinetic energy—with a correspond-ing increase in the potential for tissue damage.

The third factor determining the medical conse-quences of ballistic injury has to do with the inter-action of the projectile and the tissue along its path-way. Obviously, the longer the wound tract, themore damage that is likely to occur. This is truebecause (a) the bullet passes through more tissue,and (b) it is more likely that the bullet will destabi-lize (either yaw [ie, the long axis of the bullet devi-ates from the direction of flight] or tumble [ie,the bullet flips end over end]), greatly increasing

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tion), a decrease in the thoracic anteroposteriordiameter of at least one third must occur beforethere is a high risk of damage to internal viscera.However, when compression occurs at a faster ve-locity (> 3 m/s), the same injury can occur withmuch less compression. When compression is ap-plied very slowly, the viscera have time to adjust tothe distortion produced by their displacement. Withmore rapid compression, however, this compensationis impaired because it involves a time-dependentvariable: namely, the internal displacement of layerupon layer of tissue as they slide over one another.The sliding is resisted by the inherent viscosity ofthe tissue much as a the viscosity of a flowing liquidcauses hydraulic resistance. When the sliding can-

not keep up with the velocity of compression, shear-ing forces arise that cause tissue laceration, rupture,or fractures. Such trauma, which results from amechanical process that is determined by both thevelocity of the compression and the viscoelasticityof the tissue, is known as a viscous injury.

Blast injury may be thought of as occupying theopposite end of the compression–velocity con-tinuum depicted in Figure 19-1. With blast injury,the compression causes a tiny displacement (mea-sured in a fraction of a millimeter) that occurs at aspeed approaching that of sound. Blast overpres-sure is especially likely to injure very light, feeblysupported structures such as the alveolar capillar-ies and tympanic membranes.

Fig. 19-1. In this depiction of the relation between theamount and the speed of compression, the curved lineindicates a constant probability of the occurrence of athoracic injury of a specified lethality. The magnitude ofcompression is given as the percentage of the anteroposteriordiameter of the thorax. Data sources: (1) Viano DC, Lau IA.A viscous tolerance criterion for soft tissue injury assess-ment. J Biomechanics. 1988;21(5):387–399. (2) Viano DC.Live fire testing: Assessing blunt impact and accelerationinjury vulnerabilities. Milit Med. 1991;156:589–595.

OVERVIEW OF COMBAT THORACIC TRAUMA

As seen in reports from three recent wars (theexperience of the U.S. Army’s 24th Evacuation Hos-pital in Vietnam1; Rambam Medical Center in Haifa,Israel2; and the Basrah, Iraq, Teaching Hospital in a6-month period in 1981 during the Iran–Iraq War3),the most common thoracic clinical problems werecombined hemothorax and pneumothorax, hemo-thorax, pneumothorax, pulmonary contusion, car-diac tamponade, pulmonary hematoma, rib or ster-nal fractures or both, perforation of the diaphragm,and laceration of the heart or great vessels (Table19-2). These data clearly show that the most com-mon medical treatment problems—collections ofblood and air within the pleural space—are theresult of pulmonary lacerations. It is important torecognize that the thoracic injury is unlikely to bethe only injury present: 85% of the casualties in the24th Evacuation Hospital report1 and 80% of the casu-alties reported from Rambam2 had one or more addi-tional injuries involving another part of the body.

The specific nature of the medical interventionsrequired to treat combat casualties with thoracicinjuries is shown in Table 19-3. It is apparent thatonly a minority of thoracic casualties required aformal thoracotomy.

When treating a casualty with a thoracic injury,the military trauma anesthesiologist is much morelikely to provide anesthesia for a major operation insome other body part than for an operation on thethorax. Published series, with the exception of thework of one surgeon in Lebanon (which is dis-cussed below), indicate that a formal thoracotomyis needed in only about 10% to 20% of casualtieswith thoracic injuries who reach a military hospitalalive.8 In most thoracic casualties, the interventionsrequired for the treatment of the thoracic injuryconsist of inserting a chest tube and providing localcare to the wounds of entrance and exit. However,military trauma anesthesiologists should be awarethat some thoracic surgeons perform what is really

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n Compression Injury

Viscous Injury

Blast Injury

10

10 100

Velocity of Compression (m/s)

35%

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TABLE 19-2

DIAGNOSIS OF THORACIC CASUALTIES

24th Evac. Hospital Rambam Medical Center Basrah TeachingDiagnosis US Army, Vietnam1 Haifa, Israel2 Hospital, Iraq3

Combined hemo- and pneumothorax 230 15

Hemothorax 199 9 81

Pneumothorax 100 13 37

Pulmonary contusion 99 5 20

Cardiac tamponade 7 1 4

Pulmonary hematoma 15

Rib/sternal fractures 14 12*

Diaphragmatic perforation 17

Heart or great-vessel laceration 4

*Listed as flail chestData sources: (1) McNamara JJ, Messersmith JK, Dunn RA, Molot MD, Stremple JF. Thoracic injuries in combat casualties in Vietnam.Ann Thor Surg. 1970;10:389–401. (2) Rosenblatt M, Lemer M, Best LA, Peleg H. Thoracic wounds in Israeli battle casualties duringthe 1982 evacuation of wounded from Lebanon. J Trauma. 1985;25:350–354. (3) Suleman ND, Rasoul HA. War injuries of the chest.Injury. 1985;16:382–384.

pelling evidence stems from the experience of onecivilian surgeon who treated 1,992 thoracic casual-ties of the civil war in Lebanon (1969–1982).9 Of thecasualties this surgeon treated, 282 had a cardiacinjury, 1,251 had a noncardiac thoracic injury as themajor treatment problem, and 456 had one or moreinjuries in addition to thoracic trauma. Of thenoncardiac thoracic casualties, a formal thoracotomy

TABLE 19-3

THERAPEUTIC INTERVENTIONS IN THORACIC TRAUMA

24th Evac. Hospital Rambam Medical Center Basrah TeachingProcedure US Army, Vietnam1 Haifa, Israel2 Hospital, Iraq3

Tube thoracostomy 448 38 113

Thoracotomy 78 6 11

Debridement of thoracic wounds 30

Thoracentesis or no treatment 2 26 31

Major operation outside the thorax ~ 400 35

Data sources: (1) McNamara JJ, Messersmith JK, Dunn RA, Molot MD, Stremple JF. Thoracic injuries in combat casualties in Vietnam.Ann Thor Surg. 1970;10:389–401. (2) Rosenblatt M, Lemer M, Best LA, Peleg H. Thoracic wounds in Israeli battle casualties during the1982 evacuation of wounded from Lebanon. J Trauma. 1985;25:350–354. (3) Suleman ND, Rasoul HA. War injuries of the chest. Injury.1985;16:382–384.

a mini-thoracotomy when they carry out localwound management. Under general anesthesia,one or both wounds are extended so that it is pos-sible to inspect the pleural space and lung and, ifnecessary, to repair accessible intrathoracic injuries.

Perhaps medical officers will need to reconsiderthe consensus that only a minority of thoracic casu-alties require a formal thoracotomy. The most com-

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was performed in 818 (54.5% of the total proce-dures), and of these, an anatomical pulmonary re-section was performed in 310. Although the U.S.Army Medical Department’s experience during thePersian Gulf War was quite limited, anecdotal ob-servations10 from that war suggest that a greaterfraction of thoracic casualties was treated bythoracotomy than during the Vietnam War. It islikely that in future wars, thoracotomy will increas-ingly be established as the standard of care forthoracic casualties.

Military trauma anesthesiologists need also to beaware of a variant of thoracic trauma: thethoracoabdominal injury (Figure 19-2). In about10% of the casualties seen during World War II, thewounding missile was found to have passed fromthe chest through the diaphragm into the abdo-

men.11 The vast experience of surgeons in WorldWar II indicates that in most such casualties, theabdominal component was the more life threaten-ing. This is probably because the casualties whohad more-serious thoracic components died beforethey could be evacuated from the battlefield. Theanesthetic management of the casualty with athoracoabdominal wound will be similar to that ofany abdominal casualty but with this importantexception: unimpaired drainage of air and bloodfrom the chest must be assured prior to the induc-tion of anesthesia. Once the abdomen is opened, thehole in the diaphragm establishes a direct connec-tion between the atmosphere and the left pleuralspace. Collapse of the left lung is prevented bypositive-pressure ventilation through an endotra-cheal tube and a functioning chest tube.

Fig. 19-2. A shell fragment entered this casualty’s chest atthe inferior-posterior portion of the left hemithorax at thesite of the hemostat. It passed through the left lung,diaphragm, spleen, and small bowel before exitingthrough the left upper quadrant. The small bowel haseviscerated through the wound of exit. Notice that thechest tube is vented to the atmosphere. Suction applied tothe tube would have caused ambient air to be suckedthrough the hole in the diaphragm into the thorax. Pho-tograph: Wound Data and Munitions Effectiveness Teamslide collection.

GENERAL PRINCIPLES OF MANAGEMENT

Indications for Thoracotomy

Generally accepted indications for immediate orearly thoracotomy are as follows12:

• an opacified hemothorax on the initial ra-diograph;

• initial drainage of 1,500 mL of blood, fol-lowed by 500 mL or more during the nexthour;

• drainage of 200 to 300 mL of blood per hourfor more than 4 hours;

• massive air leak with continuous bubblingthroughout the respiratory cycle;

• radiographic evidence of massive pulmo-nary contusion or hematoma, with clinicaland laboratory evidence of a life-threaten-ing shunt or airway compromise secondary

to bleeding into the airway; and• physical signs of pericardial tamponade or

suspicion of tamponade or shock, and ra-diographic evidence of a missile in proxim-ity to the heart.

Most casualties with penetrating thoracic inju-ries will require some type of local wound manage-ment, which may or may not require general anes-thesia. Casualties with large chest defects, such aswould be associated with a sucking chest wound,will certainly require operative closure using gen-eral endotracheal anesthesia.

Preoperative Evaluation and Preparation

The U.S. Army Medical Department was one ofthe first supporters of the American College of

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In the American College of Surgeons’ Advanced Trauma Life Support (ATLS) approach, the initial manage-ment of the trauma victim is carried out in the following sequence, with the definitive-care phase beingdone later:

Secondary SurveyHistoryPhysical examination, including the following

areas:HeadMaxillae and faceCervical spine and neckChestAbdomenPerineum/rectum/vaginaMusculoskeletal systemNeurological systems

Additional laboratory and radiographic studiesas needed

Primary SurveyAirway management with cervical spine controlBreathing and ventilationCirculation with hemorrhage controlNeurological statusExposure

Resuscitation, includingInserting airways, chest tubes, and large-bore

intravenous linesInfusing crystalloid fluidObtaining blood samplesInserting urinary and gastric cathetersEstablishing vital-sign monitorsObtaining appropriate radiographic studies

EXHIBIT 19-1

INITIAL MANAGEMENT OF TRAUMA VICTIMS

Source: Committee on Trauma, American College of Surgeons. Initial assessment and management. In: Advanced Trauma LifeSupport Program for Physicians: Instructor Manual. 5th ed. Chicago, Ill: American College of Surgeons; 1993: 17–37.

Surgeons’ Advanced Trauma Life Support (ATLS)approach to the initial management of the traumavictim and has long emphasized such training—especially for medical personnel assigned to thefield echelons. Military anesthesiologists serving atthird- or fourth-echelon hospitals should, there-fore, expect to find that the acute lifesaving inter-ventions—the ATLS ABCs (airway, breathing, andcirculation)—have already been performed beforethe casualty arrives at their hospital (Exhibit 19-1).Nevertheless, there are exceptions. In fact, duringmuch of the Vietnam War, given the atrophy of theunit and division echelons of care, casualties com-monly arrived at third-echelon hospitals withouthaving received any care.13 An equivalent situa-tion—the lack of a mature field medical system—will likely exist in the future whenever the U.S.military becomes involved in peacekeeping or na-tion-building missions. As a member of the medicalunit, the anesthesia provider should be involved inthe resuscitation the moment the patient arrives tothe receiving area.

After the initial management has been performed,the military anesthesiologist will be involved inthe definitive care phase of management. Be-cause the definitive-care phase may involve an

emergency thoracotomy, the anesthesia providershould perform a specific preanesthesia evaluationonly if time permits. In the conscious patient, abrief history and physical examination should betaken (Exhibit 19-2); laboratory investigation shouldinclude recent arterial blood-gas and hematocritlevels.

Because time is of the essence when dealing withtrauma patients, it is important to have a resuscita-tion area and an operating room prepared to man-age a trauma victim. The anesthesia machine andmonitors should be ready for immediate use. Intra-venous tubing and fluid warmers should be avail-able for use, requiring only priming with the intra-venous fluid when the patient arrives. Syringesshould be labeled and cardiac drugs immediatelyavailable. A functioning defibrillator should alsobe ready.

The essential step that must be taken in pre-paring the casualty with thoracic injuries for gen-eral anesthesia, especially when the operationalso involves another part of the body, is to as-sure that the potential for the development of anintraoperative hemothorax or pneumothorax isminimized by the placement of a functioningchest tube. Finally, it cannot be stressed too greatly

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that the military trauma anesthesiologist manag-ing the casualty with a penetrating thoracic injurywill constantly strive to keep the airway free ofsecretions.

Monitoring

In addition to the usual noninvasive monitors(electrocardiograph, pulse oximeter, end-tidal CO2monitor, automatic blood pressure cuff, precordialstethoscope), arterial, central venous pressure, andurinary output monitoring are essential. However,precious time should not be spent attempting toplace these monitors in unstable, exsanguinatingpatients.

Induction of Anesthesia

Unconscious, moribund patients are intubatedimmediately without anesthesia, and surgery isperformed without anesthesia until the patient’svital signs or state of consciousness indicate a needfor anesthesia. The anesthesiologist is performinga resuscitation in this scenario, rather than ananesthetic. Concerns about possible intraoperativerecall may be overstated: providing an ideal, com-

plete anesthetic to a trauma patient at the riskof hemodynamic instability and possible cardiacarrest is inappropriate. Scopolamine may beadministered as an amnestic agent, but valuabletime should not be spent to locate or administer thisdrug when other, more-important lifesaving tasksneed to be performed. Midazolam may be used butits hypotensive effect, particularly in the presenceof hypovolemia or when given concurrently withnarcotics, may preclude its use in the trauma pa-tient. Patients in a state of shock are particularlysusceptible to the adverse effects of thiobarbi-turates, which should be administered only withextreme caution. To allow the surgeon to arresthemorrhage, ketamine has been advocated as thedrug of choice for induction of anesthesia inhypovolemic, hemorrhaging patients who requireanesthesia (for further discussion, see Chapter 10,Intravenous Anesthesia). However, the direct myo-cardial-depressant effects of ketamine may be un-masked in the patient who is severely physicallystressed and is relying on maximal intrinsic cat-echolamine secretion to maintain adequate vitalsigns. In most cases, though, the anesthesiologistwill have had sufficient time to replace intravascu-lar fluid deficits; therefore, thiobarbiturates or otherinduction agents can safely be used. Trauma isfrequently associated with decreased gastric emp-tying, which places these patients at greater riskof aspiration pneumonitis; a rapid-sequence in-duction after preoxygenation is usually indicated.An awake intubation must certainly be consideredin patients with obvious or suspected airway ab-normalities.

Maintenance of Anesthesia

Successful resuscitation of patients with majorchest trauma requires teamwork; blood and fluidreplacement must be prompt and given in appro-priate quantities. If patients do not respond tovolume replacement, then ongoing hemorrhage,tension pneumothorax, or pericardial tamponademust be suspected. Loss of infused fluid through anundiagnosed hole in the superior or inferior venacava may explain why some patients fail to respondto fluid therapy. After the surgeon has entered thechest cavity, compression of the aorta above thesite of bleeding may provide the valuable timeneeded to restore blood volume. Although patientsin shock require little, if any, anesthesia, their con-sciousness rapidly returns when the blood volume

EXHIBIT 19-2

HISTORY AND PHYSICAL EXAMINATIONOF THE CONSCIOUS PATIENT

Brief history:

1. Review of systems

2. Past medical history

3. Past surgical history

4. Previous anesthesia difficulties

5. Family history of anesthetic complications

6. Current medications

7. Allergies

8. Time of last oral intake

Brief physical examination:

1. Global assessment

2. Evaluation of the airway

3. Respiratory and cardiovascular examinations

4. Vital signs

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is restored. At this point, anesthesia can be main-tained with oxygen, narcotics, neuromuscularblocking drugs, amnestics, and small quantities ofinhalational agents, if required. It is prudent toavoid nitrous oxide in patients with chest traumabecause the gas tends to collect in the dependentareas of the lung. The risk is that nitrous oxide willexpand in the closed chest and create a pneumo-thorax. (Nitrous oxide is not available in deployablehospitals.)

Special considerations with the use of neuromus-cular blocking agents in the trauma patient deservemention. Succinylcholine, the rapid-acting depo-larizing relaxant often used for rapid-sequence in-ductions, is known to cause profound hyperkalem-ia in patients who have extensive muscle damage,particularly if the drug is given 24 to 36 hours afterthe traumatic insult. Alternatives include thenondepolarizing relaxants, such as vecuroniumgiven at 0.28 mg/kg, for conditions requiring rapidintubation. This agent is useful during the mainte-nance of anesthesia because it has minimal hemo-dynamic effects. The vagolytic actions of pan-curonium may be undesirable because the tachy-cardia may lead to further confusion in distinguish-ing drug effect from hypovolemia or inadequatelevels of anesthesia. d-Tubocurarine and atracuriumshould probably be avoided because of their hista-mine-mediated hypotensive effects. It is importantto remember that all neuromuscular blocking agentsare subject to aberrant behavior in the presence ofchanging acid–base status, altered metabolism andexcretion, hypothermia, and certain antibiotics. Forthis reason, it is mandatory to monitor the status ofthe neuromuscular blockade.

Hypothermia is a major problem in traumatizedpatients undergoing exploratory surgery, and ev-ery effort should be made to maintain a normal corebody temperature. Heated humidifiers, low gasflows, warmed intravenous and irrigating fluids,and a warmed operating room can help maintainnormothermia. Certainly, heating lamps, warmingblankets, and plastic to wrap exposed body surfacescan also be used.

Positioning for Operation

The position of patients with thoracic injuries(whose major injury does not involve the thorax)will obviously depend on the location of that injury;the usual position will be with the trunk supine.The position of casualties who are to have an actual

thoracic procedure will depend on the indicationfor the operation. Most thoracic surgeons use ananterolateral incision for the casualty who is agonal(ie, a casualty who exhibited one or more signs oflife [motion, spontaneous respiration, palpablepulse] shortly before arrival at the hospital, but whois now lifeless) or in profound shock, although afew prefer a median sternotomy for the operativeapproach. Thus, the desired position for an emer-gency operation is supine. Because the neededoperation is best done through a posterolateralthoracotomy incision with the patient in the rightlateral decubitus position, there are two exceptionsto this rule:

1. the unusual casualty who is known to havean injury to the proximal left subclavianartery, and

2. the casualty who has sustained blunttrauma to the chest and has radiographicevidence of a left hemothorax and a wid-ened superior mediastinum, and who,therefore, may have a proximal descend-ing aortic disruption.

Patients who are undergoing thoracic surgery inwhich the indications are less emergent (eg, controlof nonexsanguinating hemorrhage, a large air leak,repair of a chest-wall defect, or simply to debridethe wounds of entrance or exit) are placed in thedecubitus position so that a posterolateral incisioncan be made. Care must be taken to ensure thatthere is no pressure on the brachial plexus of thedependent arm, and that the thorax and abdominalwall are free to move without restricting respira-tions. Endotracheal tube position and the positionof all monitors must be checked for dislodgementfollowing patient positioning. Patients with con-current orthopedic injuries may be difficult to posi-tion because of pain and the potential for disloca-tion or worsening of the injury.

Postoperative Care

Most patients presenting for surgery secondaryto battlefield chest trauma require postoperativecare in an intensive care unit until an adequate levelof physiological homeostasis can be achieved. Themilitary trauma anesthesiologist is expected to playa significant role in the postoperative care of thesepatients, especially in the realm of acute pain andventilatory management.14

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DIAGNOSIS AND MANAGEMENT OF SPECIFIC INJURIES

fractures of three or more ribs in two places on thesame side. This produces a segment of the chestwall that responds to changes in pleural pressure,as opposed to the muscular action of the chest wall,resulting in a paradoxical respiratory pattern. Thisinjury is most commonly associated with blunttrauma to the chest wall and involves the antero-lateral aspect of the chest. The posterior wall israrely involved because it is heavily fortified withmuscle. The flail chest injury is rarely isolated andis usually an ominous sign, indicating serious un-derlying injuries to intrathoracic or intraabdominalorgans or both. This condition is often difficult todiagnose and may go unnoticed for extended peri-ods, often overshadowed by more-overt injuries.Chest radiography may not reveal fractures unlessthe films are overpenetrated and oblique views aretaken. Flail chest may not be apparent on simpleinspection, as chest-wall muscular spasm may beable to splint the segment until the muscles becomefatigued. Palpation is more likely to be diagnosticthan inspection, with the presence of crepitus andabnormal respiratory motion aiding in the diagno-sis. Serial blood-gas measurements can help estab-lish the diagnosis, because the clinical hallmark offlail chest is hypoxemia.

Flail chest can cause hypoxemia by two mecha-nisms: (1) intrapulmonary shunting due to perfu-sion of the poorly ventilated, contused lung; and (2)atelectasis caused by compromised ventilatory me-chanics. The pendelluft phenomenon, which is a to-and-fro movement of air from the damaged to thenormal lung, was once thought to make a signifi-cant contribution to hypoxemia. However, it hasbeen shown that there is an increase in ventilationand improved gas exchange on the injured side.17

The hypoxia observed in flail chest is now recog-nized to be caused by abnormalities in the contusedlung underlying the flail segment.18 Thus, the mod-ern treatment of flail chest focuses on preventingthe arterial desaturation (that results from the shunt-ing) from reaching life-threatening proportions.Stabilization of the flail segment, maintenance ofadequate ventilation, oxygen enrichment, physicaltherapy, and effective pain relief should all be tried;however, a period of intubation and ventilationmay be necessary. The criteria for intubation, whichshould only serve as a guide, include:

• partial pressure of arterial oxygen (PaO2)< 70 mm Hg with oxygen enrichment,

Rib Fractures

The ribs are the most commonly injured compo-nent of the thoracic cage, and the incidence of seri-ous complications increases with the number of ribsfractured. This increase is a reflection of the greatertraumatic forces associated with multiple rib frac-tures. As a general rule, a young, otherwise healthy,active-duty recruit with a flexible chest wall is lesslikely to sustain a rib fracture than is a geriatricpatient with thoracic trauma. With this in mind, thepresence of multiple rib fractures in young patientsimplies a sizable transfer of force. Multiple ribfractures most commonly involve the sevenththrough tenth ribs and thus are often associatedwith hepatic or splenic lacerations. Acute gastricdilation commonly accompanies left-sided frac-tures and may increase the likelihood of acid aspi-ration. Fractures of the upper ribs (first throughthird) should be regarded as harbingers of seriousblunt trauma to the chest. The bony framework ofthe upper limb and its muscular attachments pro-vide a barrier to injury in this area. Therefore,severe maxillofacial, cervical, neurological, pulmo-nary, and vascular injuries may accompany upper-rib fractures.15

Rib fractures, even in the absence of underlyingcardiopulmonary trauma, may contribute to seri-ous pulmonary complications. The associated painand reflex muscle splinting can exacerbate alveolarhypoventilation, resulting in retention of secretions,atelectasis, and respiratory failure. Taping or bind-ing the ribs will cause even more splinting andfurther compromise. A tidal volume of less than 5mL/kg or a forced vital capacity of less than 10 mL/kg indicates severe splinting.16 Adequate analgesiais essential in the management of rib fractures. Theuse of intercostal nerve blocks is attractive becauseit avoids the respiratory depression associated withsystemic narcotic administration. Comparable an-algesia of longer duration and with less potentialfor systemic toxicity may be achieved with continu-ous thoracic epidural analgesia. Intrapleural injec-tion of local anesthetics is another form of analgesiafor rib fractures. The efficacy of this technique,however, is controversial at this time.

Flail Chest

Flail chest may be defined as an abnormal move-ment of the chest wall occurring as a result of

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• partial pressure of arterial carbon dioxide(PaCO2) > 50 mm Hg,

• pH < 7.25,• tachypnea > 30/min,• vital capacity < 15 mL/kg, and• negative inspiratory force < –20 cm water.

Both external stabilization of the flail segment bytraction and internal fixation with intramedullarypinning of the fractured ribs have been described.19,20

Continuous electrocardiographic monitoring isessential because flail chest can often be associ-ated with cardiac contusions, from which arrhyth-mias may arise. Frequent arterial blood-gas analy-ses, along with other laboratory studies, justify plac-ing an arterial line. Pulmonary artery catheterization,which may be available in deployable hospitals,may help with the evaluation of cardiac perfor-mance and guide fluid management. This is espe-cially necessary because the injured lung under-lying the flail segment is sensitive to bothunderresuscitation of shock and fluid overload, thelatter condition leading to pulmonary edema in theinjured lung tissue and a further impairment of gasexchange.21 In intubated, ventilated patients, exces-sive airway pressure can also cause an iatrogenicinjury by mechanically disrupting damaged alveo-lar capillary membranes in the lung underlying theflail segment. This may enlarge the volume of the

contusion, but a more serious problem is the in-creased likelihood of systemic air embolism.22

Sucking Chest Wound

An open, sucking, or blowing chest wound is aserious injury that is usually found at the site wherea yawing or tumbling bullet has exited or where alarge fragment from an explosive munition hasentered. The most serious component of the woundis usually the injury to the underlying lung. Thecharacteristic appearance is of bloody foam beingalternately sucked into and blown from the wound(Figure 19-3). In this condition, intrapleural pres-sure equalizes with the atmosphere, resulting in adiminished movement of air on the affected side.The immediate treatment of this condition is toocclude the defect but provide for egress of air fromthe chest cavity by inserting a chest tube with a one-way valve. Sucking chest wounds are not especiallycommon among combat casualties. In the Israeliseries, they accounted for only seven (11%) of thetotal of the thoracic casualties.2 The reason for theirlow prevalence is that the intrathoracic componentof the injury is much more likely to be life-threaten-ing than is the hole itself. Once the intrathoraciccomponent has been treated, surgical treatment isdirected toward achieving an air-tight closure ofthe chest wall defect.

Acute Traumatic Hemothorax

Hemothorax can occur with both penetratingand nonpenetrating thoracic trauma and is usuallycaused by blood emanating from injuries of theheart, great vessels, pulmonary parenchyma, orchest wall.23 The diagnosis of hemothorax is madeon the basis of history and clinical examination ofthe chest. When a significant quantity of blood hasaccumulated in the chest cavity, the trachea may bedeviated, the chest wall is dull to percussion, andbreath sounds are diminished on auscultation. Achest radiograph and an electrocardiogram shouldbe obtained for all patients except those presentingin extremis. Approximately 500 mL of blood mustaccumulate in the chest cavity before it is radiologi-cally detectable.

Because hypovolemia from blood loss is the mostcommon problem in patients who present with sig-nificant chest injury, the immediate treatment shouldbe directed toward restoring blood volume. Twolarge-bore intravenous cannulae should be insertedas soon as possible. Central venous pressure moni-

Fig. 19-3. This casualty had a sucking chest wound. Alarge fragment entered his back; frothy material can beseen in the base of the wound. Photograph: Wound Dataand Munitions Effectiveness Team slide collection.

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toring may be useful in both diagnosing and man-aging patients who have mechanical interferencewith ventilation, as the central venous pressure islow in the presence of severe hypovolemia butelevated in the presence of a chest cavity full ofblood. Oxygen therapy is mandatory. Tubethoracostomy should be performed as soon as pos-sible because it is not only therapeutic, it also pro-vides an assessment of cumulative and ongoingblood loss, facilitates reexpansion of the lung, andsimplifies autotransfusion when major bleeding isencountered. In most cases, the source of the bleed-ing is the pulmonary vessels, which normally havelow perfusion pressures. On the other hand, bleed-ing from systemic vessels or the heart is usuallymore persistent and voluminous.

For casualties who have an indication for opera-tive intervention but who are stable (ie, blood pres-sure > 100 mm Hg, pulse rate < 100, good peripheralperfusion and ventilation), the thoracotomy is per-formed in the operating room. Immediatethoracotomy in the admitting area of the hospitalmay be indicated in patients who become agonal onarrival. The best results have been obtained incasualties who have penetrating thoracic injuries,and the poorest results in those sustaining blunttrauma—especially when the abdomen is involved.Regardless of the etiology, survival in this group ofcasualties is poor. In one recent series,24 survivalwas 6% in those with blunt trauma and 27% forcasualties with penetrating wounds of the chest.

The reasons for performing a thoracotomy are to

• decompress a tension pneumothorax orpericardial tamponade, if present;

• perform open-chest cardiac massage; and• stop bleeding if it arises within the thorax

or, by occluding the descending aorta, toslow bleeding if it arises from the abdomen.

After the airway has been intubated, if necessaryvia cricothyroidotomy, an anterolateral incision is

made on the side of injury, the pericardial sacopened, and cardiac compressions begun. Bleedingsites are controlled by direct pressure or by applica-tion of a clamp or Rommel tourniquet around thehilum of the lung. The military trauma anesthesi-ologist should anticipate the need to correct severemetabolic acidosis and to manage a variety of ma-lignant cardiac arrhythmias. The patient is thentransported to the operating room for definitivetreatment.

The management of agonal casualties is verylabor and resource intensive. The likely poor out-come, even with the best of care, has led someauthorities25 to argue that emergency thoracotomyfor agonal victims of truncal trauma has no place incombat casualty care. The military trauma anesthe-siologist, in consultation with the hospital thoracicor trauma surgeon and the hospital commander,should develop an agreed-upon triage policy forsuch casualties. By necessity, any such policy willhave to take account of the existing tactical situation.

Cardiac Tamponade

Although cardiac tamponade is found in casual-ties who require emergency thoracotomy, its occur-rence is not limited to this group. In some casual-ties, the presentation of cardiac tamponade may bequite subtle (Figure 19-4). Acute, traumatic pericar-dial tamponade is caused by the collection of bloodor other fluid (eg, serous exudate) within an intactpericardial sac. This sac is composed of a fibrous,poorly compliant membrane. Rapid accumulationof 100 to 200 mL of fluid in this closed space restrictsfilling of the cardiac chambers during diastole, whichproduces a fixed, low, cardiac output. Positive-pressure ventilation will lower cardiac output evenfurther, as will any cardiac depressant.

The diagnosis of cardiac tamponade requires ahigh degree of clinical suspicion. It should alwaysbe suspected in patients with wounds in the vicinityof the neck, precordium, or upper abdomen, and

Fig. 19-4. (a) This casualty was wounded when a grenade fragment penetrated his back. He was initially neither hypotensivenor in much distress but while being observed developed tachycardia, dyspnea, and distended neck veins. (b) The chestradiograph shows a fragment within the silhouette of a globular-shaped heart. A thoracotomy was performed because ofthe casualty’s deteriorating clinical state and the appearance of the radiograph. (c) The pericardium has been opened andseveral blood clots have been extruded. (d) The removed clots. (e) A small defect, which was not then bleeding, in the freewall of the left ventricle. (f) The fragment after its removal from the myocardium. The tip of the hemostat serves as a referencefor size. The left ventricular wall had not been perforated, possibly because of the fragment’s small size. Other fragmentslacerated the stomach and spleen; these were found during a subsequent laparotomy. Photographs: Swan Vietnam SurgicalSlide Collection.

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da

c

f

b

e

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especially in patients who are in shock. The classicsigns, although present in only 41% of patients withpenetrating cardiac wounds,26 include Beck’s triad:hypotension, distended neck veins, and distantheart sounds. Other signs include pulsus paradoxus,which is a decline in systolic blood pressure of 10mm Hg or more on inspiration. This is of limitedvalue in the field, however, as continuous arterialpressure monitoring may not be possible.27 Para-doxical filling of neck veins on inspiration(Kussmaul’s sign) may be too subtle to detect inuncooperative, struggling patients. If significantblood loss has occurred, distension of neck veinsmay not occur. Equalization of pressures across theheart, measured by a pulmonary artery catheter, isvery suggestive of tamponade. The chest radio-graph may reveal a large, globular heart shadow,and the electrocardiogram will be either normal orshow nonspecific ischemic changes. Occasionally,the electrocardiogram will show electrical alternans,which is usually diagnostic of tamponade.

Again, it should be emphasized that heavy reli-ance is placed on clinical impression in diagnosingpatients on the battlefield with cardiac tamponade.Shock and a wound in the anterior chest indicate cardiactamponade until proven otherwise. Elevation of thecentral venous pressure is strong confirmatory evi-dence of the diagnosis, and treatment should bestarted immediately. The definitive treatment ofthis condition is surgery as soon as possible.Pericardiocentesis may be used to relieve thetamponade in rapidly deteriorating patients. How-ever, this is of limited value because blood rapidlyreaccumulates in the pericardial sac.

The patient should be prepared and draped forsurgery, and an arterial line should be insertedprior to the induction of anesthesia. The administra-tion of a general anesthetic to a patient with a significanttamponade is potentially lethal.28,29 Almost any ma-neuver, other than administration of 100% oxygen,including positive-pressure ventilation, causes de-terioration.30 Inhalational agents or thiopental causefurther cardiac depression and impairment of dia-stolic filling. Peripheral vasodilation associated withthese agents further impairs filling. Anesthetic goalsinclude maintaining adequate preload with copi-ous volume infusion (central venous pressure atleast 15 cm H2O), and avoiding vagotonic medica-tions (eg, narcotics). It is important to maintainsinus tachycardia in the face of limited stroke vol-ume to maximize cardiac output. The combinationof ketamine and pancuronium is ideal for this pur-pose. The recommended dose of ketamine for pa-

tients with diminished cardiac output is 0.25 to 0.50mg/kg. Despite careful anesthetic management,the patient’s condition may deteriorate before thetamponade is relieved. If deterioration occurs,isoproterenol has been advocated,31 infused at arate of 0.1 µg/kg/min, and titrated to effect. Whenthe pericardium is decompressed, the patient’s vi-tal signs usually improve instantaneously.

Cardiac Contusions

Myocardial contusion is the most common car-diac injury due to nonpenetrating trauma. Depend-ing on the sophistication of the diagnosticarmamentarium and the definition of the condition,cardiac contusions have been reported in approxi-mately 15% to 70% of trauma patients who sustainblunt chest trauma. Rapid deceleration occurringduring motor vehicle accidents is the most commoncause of cardiac contusions. The heart is subjectedto marked anteroposterior compression resultingin rupture of the intramyocardial vessels, whichbleed into the myocardium. Subsequently, myocytesmay die and undergo fragmentation. Iatrogenictrauma caused by closed-chest massage during car-diopulmonary resuscitation may also be respon-sible for myocardial contusion. The right ventricleis injured more frequently than the left during car-diopulmonary resuscitation, due to its proximity tothe chest wall. However, the valves in the left sideof the heart, especially the aortic valve, are moresusceptible to injury than those in the right side ofthe heart.16

Symptoms of myocardial contusion may be simi-lar to those of myocardial infarction or pericarditis,because anginal chest pain is the most commonpresenting complaint. However, contusion pain isnot relieved by nitroglycerin. Many trauma pa-tients with myocardial contusion report few or nosymptoms from their cardiac injuries. Ventriculararrhythmias are the most common clinical sign ofcardiac contusion. Conduction disturbances aremore commonly associated with injuries to the rightatrium and ventricle.32 Other signs may be a currentof injury on the electrocardiogram or a pericardialfriction rub; there may be no change at all in cardiacexamination. The diagnosis of cardiac contusion canbe a real dilemma for the clinician, as most routineand sophisticated tests have proven unreliable.

Casualties presenting with myocardial contu-sion should be treated in the same manner as thosepresenting with myocardial infarctions. Many ca-sualties with this condition need immediate sur-

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gery to treat their other injuries. Because the rightventricle is particularly vulnerable to contusionowing to its proximity to the anterior chest wall,right ventricular dysfunction and failure may com-plicate perioperative management. The right ven-tricle is sensitive to afterload; therefore, conditionsthat may increase pulmonary vascular resistance(ie, hypoxia, hypercarbia) should be avoided. Ad-equate preload is usually necessary in the setting ofright ventricular dysfunction; intravascular volumeresuscitation is therefore mandatory.

Cardiac Rupture

Rupture of the heart is a common cause of imme-diate death in victims of blunt trauma. Innonpenetrating injuries, severe compression mayso raise cardiac chamber pressure and wall stressthat the myocardium ruptures. Thus, the mecha-nism is similar to the process that gives rise tomyocardial contusion. Puncture of the heart by ribsbroken by blunt trauma has also been described. Incombat casualties, penetrating injuries are a morefrequent cause of cardiac perforations than is blunttrauma. Although right ventricular perforationsmay appear to predominate, a comparable inci-dence of left ventricular injuries has been described.33

Because of the higher immediate mortality associ-ated with ventricular trauma, patients with atrialperforations are more frequently encountered inthe operating room.

The clinical presentation of cardiac rupture orperforation is determined by the status of thepericardium. With an open pericardial wound,blood extravasating from the heart drains freelyinto the pleural space, producing a rapidly fatalhemothorax. If the pericardial defect is small, or ifit is occluded (as may happen on rare occasions byclotted blood or by the adjacent lung), the patientmay not exsanguinate but live long enough to de-velop the signs of cardiac tamponade. The anes-thetic management of cardiac rupture is similar tothat for pericardial tamponade, except thatexsanguination makes emergency thoracotomymore common.

Cardiopulmonary bypass, although usually notavailable in combat zone hospitals, may be requiredto repair some cardiac defects. Although traumaticventricular septal defects may close spontaneously,most of them require surgical closure through theleft ventricle, utilizing cardiopulmonary bypass.

Vasodilators often produce some degree of clini-cal and hemodynamic improvement. However,

it should be emphasized that vasodilatorsare contraindicated in severely hypovolemic pa-tients.

Injuries to the Coronary Arteries

The incidence of coronary artery laceration fol-lowing penetrating cardiac injuries has been re-ported34 to be about 4%. Division of a coronaryartery invariably leads to hemorrhage and tamponade,and may cause myocardial infarction. Because theright coronary artery is protected by the sternum,most injuries involve the left coronary artery or itsbranches. Coronary artery occlusion after bluntchest trauma has been reported.35 In these cases,myocardial infarctions evolved after the traumaticinjury in patients without preexisting coronary ath-erosclerosis.

Several mechanisms may be involved in thepathogenesis of myocardial infarction after bluntchest trauma. In perhaps the simplest scenario, theforces accompanying an episode of blunt traumacould dislodge a previously adherent intramuralplaque, resulting in intraluminal obstruction of theinvolved coronary artery.36 Patients with preexist-ing atherosclerotic heart disease also may be atincreased risk for infarction because of trauma-induced hemorrhage into a plaque, which is knownto be richly vascularized with fragile, thin-walledcapillaries.37 A third possible mechanism of ischemicinjury is trauma-induced coronary vasospasm. Al-though spasm also occurs in normal vessels,angiographically visualized spasm often occurs at asite of atherosclerotic narrowing.38 Other etiologiesof traumatic infarction include coronary thrombosisdue to vascular trauma, direct transection of thecoronary arteries, coronary embolization, and dis-secting aneurysm.39

In the absence of cardiac tamponade, the anes-thetic management of these casualties should besimilar to that for patients with coronary arterydisease with unstable angina. A variety of tech-niques are consistent with the hemodynamic goalsof avoiding tachycardia and extremes of blood pres-sure. In young soldiers with good ventricular func-tion, a combined technique with high-dose narcot-ics and an inhalational anesthetic agent is ideal:intraoperative sympathetic reflexes are reliablyblunted, while myocardial contractility and oxygenconsumption are appropriately depressed. Al-though there may be no ideal induction techniquefor the patient with ischemic heart disease and a fullstomach, a moderate dose of narcotic (eg, 10–15 µg/kg

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fentanyl) combined with etomidate (0.1–0.2 mg/kg)and succinylcholine results in a stable induction,with adequate blunting of autonomic responsesto laryngoscopy. In the setting of severe skeletalmuscle injury, particularly if more than 24 to 36hours have elapsed since the injury, nondepolarizingrelaxants may be preferable because of the possibil-ity of succinylcholine-induced hyperkalemia.

The common presentation of the casualty with acoronary artery injury caused by penetrating traumais pericardial tamponade. Because direct repair ofthe arterial laceration in a beating heart is usuallynot feasible, and because the cardiopulmonary by-pass apparatus that would allow the construction ofan aortocoronary saphenous graph bypass is notlikely to be available in field hospitals, the militarysurgeon has little option but to ligate the injuredartery. Given this circumstance, the military traumaanesthesiologist should be prepared to treat poten-tially life-threatening cardiac arrhythmias and car-diogenic shock.

Injuries to the Great Vessels

The thoracic aorta can be injured as a result ofpenetrating or blunt trauma to the chest. The result-ing hemorrhage is usually devastating, allowingonly approximately 15% of patients to reach a fieldhospital alive.40

In the U.S. military, the great majority of aorticruptures result from motor vehicle accidents andairplane crashes. Abrupt deceleration of the thorax(a) causes compression and displacement of theheart and (b) creates shearing and bending stressesin the aortic wall, which are greatest at the origin ofthe subclavian artery and, in the ascending aorta, atthe level of the coronary arteries.41 A minority ofthese patients (perhaps 10%) survive because ofcontainment and tamponade of the hemorrhage byadjacent mediastinal structures. In the proximaldescending aorta, the aortic adventitia may remainintact and temporarily prevent exsanguination.Sudden aortic rupture may develop in these pa-tients at a later time.

Penetrating chest trauma may also involve thegreat vessels. Depending on whether the vesselsare injured at an intrapericardial or an extraperi-cardial location, the clinical presentation is usuallyone of acute tamponade or massive hemothorax.These casualties may have sustained one or morepenetrating cardiac injuries as well, but severehypovolemia may account for the frequently atypi-cal hemodynamic findings.

The clinical findings of aortic rupture include thediagnostic triad that is seen in more than 50% ofcases42:

• increased arterial pressure and pulse am-plitude in the upper extremities,

• decreased pressure and pulse amplitude inthe lower extremities, and

• a widened superior mediastinum seen onthe chest radiograph.

Other clinical and radiographic findings are in-cluded in Exhibit 19-3. An active search for theseclinical and radiographic findings is important dur-ing evaluation because as many as one third ofpatients with aortic rupture have minimal or noexternal signs of chest trauma.43,44

When dealing with injuries to the major thoracicvessels, the foremost goal of the anesthesiologist isto simply maintain an adequate blood volume, whichallows the surgeon the time needed to find thesource of bleeding and, if possible, to repair theinjured vessel. Ischemia of the abdominal visceraand spinal cord may occur during the period ofproximal aortic clamping; the reported incidence of

EXHIBIT 19-3

CLINICAL AND RADIOGRAPHICFINDINGS OF AORTIC RUPTURE

Clinical:Increased arterial pressure and pulse ampli-

tude of upper extremitiesDecreased arterial pressure and pulse ampli-

tude of lower extremitiesRetrosternal or interscapular painHoarsenessSystolic flow murmur over the precordium or

medial to the left scapulaNeurological deficits in the lower extremities

Radiographic:Widened mediastinumUnsharp aortic contoursWidened paraspinal interfacesOpacified pulmonary windowBroadened paratracheal stripeDisplacement of the left main-stem bronchusRightward deviation of the esophagusSternal or upper-rib fractures or bothLeft hemothorax

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paraplegia in survivors ranges from 1.0% to 11.7%.41

Prophylactic measures for preserving spinal cordviability include partial cardiopulmonary bypass,heparin-coated shunts, partial bypass of the leftside of the heart, draining the cerebrospinal fluid,and inducing systemic hypothermia.

The presumed mechanism of paraplegia in thesepatients is ischemia of the spinal cord caused bydamage to the intercostal vessels that supply thespinal cord. Monitoring of somatosensory evokedpotentials may be useful in heralding spinal cordischemia but is not practicable in field hospitals.45

The kidney is the abdominal organ at greatestrisk for ischemic injury during the period of aorticocclusion. Preserving distal perfusion with shuntsor partial bypass is associated with a lower inci-dence of postoperative renal dysfunction; however,because the needed equipment is not available inthe field, the military trauma anesthesiologist hasno other recourse than to use mannitol, renal-dosedopamine, and/or diuretics as part of a strategy forrenal protection similar to that used for abdominalaortic aneurysm surgery.46

Intraoperative monitoring should include plac-ing a right radial arterial line and a lower-extremityarterial line for monitoring distal aortic pressure.The surgeon’s possible clamping of the left subcla-vian artery would make monitoring the left radialarterial pressure impossible during that time. In allbut the most emergent cases, pulmonary arterialcatheterization is desirable because proximal aorticocclusion imposes a severe afterload stress on theleft ventricle.

A double-lumen endotracheal tube is desirablebecause it allows the left lung to be collapsed tofacilitate surgical exposure. Equally important,however, is the fact that the dependent right lungcan be isolated from the parenchymal hemorrhagethat may occur in the left lung as a result of pulmo-nary contusion.

Pneumothorax

Pneumothorax occurs secondary to blunt or pen-etrating trauma to the chest wall. Less obviouspneumothoraces occur as a result of penetration of thechest wall and lung by sharp objects, such as bullets,knives, or rib fragments. Pneumothoraces of less than20% are usually not clinically detectable. Patients maycomplain of chest pain, which is accentuated by deepbreathing. Cyanosis may be evident, and with largerpneumothoraces, the trachea can be deviated. Percus-sion of the chest reveals a tympanitic sound, and

breath sounds may be diminished or absent. Condi-tions that can mimic pneumothorax include hemo-thorax or atelectasis. Radiological examination is thebest diagnostic aid available, and all films should beexposed during expiration, if possible.47 The presenceof rib fractures or surgical emphysema should pro-vide a clue to the diagnosis. In trauma patients,pneumothoraces with a volume greater than 10%should be treated by tube thoracostomy. Temporiz-ing the treatment is inappropriate for the patient whomay require intubation and positive-pressure ventila-tion during surgery for extrathoracic injuries, as thepneumothorax may enlarge under these conditions.Therefore, the prophylactic insertion of a chest tubeis indicated.

A tension pneumothorax occurs when air entersthe pleural cavity during inspiration but, owing toa ball-valve action, cannot escape during expiration.In conscious patients, rapid deterioration is noted.The cardinal signs of a tension pneumothorax are

• cyanosis,• marked decrease in pulmonary compliance,• rapid deterioration of vital signs,• diminished or absent breath sounds, and• tracheal deviation.

This condition can be easily confused with peri-cardial tamponade or shock, secondary to hypo-volemia; however, the hypertympanic percussionnote over the ipsilateral chest usually makes differ-entiation possible.

The casualty shown in Figure 19-5 is a particu-larly dramatic presentation of a tension pneumo-thorax. However, it is important to stress that atension pneumothorax is a clinical rather than aradiological diagnosis. Two factors contribute tothe hemodynamic deterioration: (1) hypoxia fromdecreased gas exchange and (2) increased imped-ance of venous return into the chest due to themechanical distortion of the mediastinum that iscaused by the expanding pneumothorax. Duringgeneral anesthesia, a dramatic decrease in pulmo-nary compliance should alert the anesthesiologistto the problem. Nitrous oxide should be discontin-ued if it is being administered, as it accentuates thesize of the pneumothorax.48 As soon as a hemody-namically significant tension pneumothorax is sus-pected, the anesthesiologist might need to performtemporizing measures, including the immediateinsertion of a large-bore needle into the secondintercostal space along the midclavicular line. A“hissing” sound may be created by the escaping,

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1. Sudden, forceful compression is the mostcommon insult causing tracheobronchialinjuries during blunt thoracic trauma. Thisanteroposterior compression combinedwith simultaneous lateral expansion of thelungs can result in severe traction on thepericarinal portion of the trachea.

2. Acute increase in intrabronchial pressuremay be caused by reflex glottic closure atthe moment of impact.

3. Shearing forces at points of fixation of theintrathoracic airways, caused by rapid de-celeration, may account for the preponder-ance of disruptions near the carina.

Dyspnea, cough, painful hemoptysis, and subcu-taneous emphysema are the most common clinicalfindings in patients with tracheobronchial disrup-tion. However, 10% of patients are nearly asymp-tomatic,51 which accounts for the frequent delays indiagnosis. Auscultation of the heart may reveal acrunching sound associated with pericardial air,also known as Hamman’s sign. When the site ofdisruption freely communicates with the mediasti-nal pleura, pneumothorax results, and tubethoracostomy and suction often fail to reexpand theaffected lung. When the pleural space and the siteof disruption do not communicate, there is little orno pneumothorax, and mediastinal air may be theonly radiographic abnormality. In addition topneumothorax and pneumomediastinum, indica-tive radiographic findings include subcutaneousand deep cervical emphysema. With completetransection of a main bronchus, the superior marginof the affected lung drops below the level of thetransection. This occurs because the lung is deprivedof its normal bronchial tethering in the thoracic cage.

All patients with suspected tracheal or bronchialinjury require diagnostic bronchoscopy as soon asthey are stable. Blind endotracheal intubation with-out endoscopic visualization of the tracheobron-chial tree is unlikely to be successful and may pro-duce further trauma because the distal trachea isdisplaced posteriorly. In addition, acute airwayobstruction may develop when the endotrachealtube enters a false passage and occludes the tra-cheal lumen. Both a surgically guided oralintubation of the distal tracheal segment and re-moval of the initial surgical airway are acceptablemeans of allowing surgical repair of the trachealseparation.

When the disruption and distal segment can bevisualized clearly, a double-lumen tube can be in-serted distal to the tracheal tear or, in the case of

Fig. 19-5. This casualty was killed by a perforating gun-shot wound of the right hemithorax. A radiograph wastaken before the autopsy was performed. A tensionpneumothorax with massive shift of the mediastinum isapparent. Photograph: Wound Data and Munitions Ef-fectiveness Team slide collection.

pressurized air. Intravenous extension tubing canthen be attached to the catheter and placed underwater seal (ie, submerging it in a liter bottle ofsterile water). Care must be taken to keep the waterbottle lower than the patient; otherwise, the flowmay be reversed, causing a hydrothorax. Tempo-rizing measures should be replaced as soon as pos-sible by the more definitive closed-system tubethoracostomy.

Tracheal and Bronchial Injuries

Tracheal and bronchial injuries are uncommonsequelae of thoracic trauma but are among the mostserious encountered in thoracic surgery. Althoughmost penetrating wounds to these structures arecaused by fragments, these injuries also occur fol-lowing blunt trauma associated with high-speedtravel. A 2.8% incidence of tracheobronchial rup-ture has been reported49 in patients who succumbedto blunt chest trauma. Approximately 80% of tracheo-bronchial disruptions occur within 2.5 cm of the ca-rina. Three mechanisms may explain this finding50:

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bronchial disruption, into the contralateral bron-chus. Alternatively, the area of disruption can bevisualized directly with a fiberoptic bronchoscope;then the instrument can be used as a guide overwhich an endotracheal tube can blindly be passedinto the distal tracheal segment. This approach isequally acceptable for bronchial disruption, al-though it is preferable to intubate the uninjuredbronchus selectively for ventilation during bron-chial repairs. Therefore, the military trauma anes-thesiologist must have available a variety of sterileendotracheal tubes that can be passed into the op-erative field and used to intubate the distal airwayprior to and during its anastomosis to the proximalsegment. Alternative techniques such as simplyinsufflating oxygen into the distal airway or em-ploying high-frequency jet ventilation usinguncuffed catheters in the contralateral bronchushave also been described.52

Parenchymal Lung Lacerations

Extensive laceration of the lung parenchyma—such as might occur when an assault-rifle bulletyaws and tumbles during its passage through thelung—can create one of the most difficult therapeu-tic problems for the military trauma anesthesiolo-gist. Not only will there be massive leakage of airinto the pleural space, which will make difficult themaintenance of an acceptable tidal volume, but thenormal anatomical proximity of airways and bloodvessels in the lungs potentiates (1) the passing ofblood into airways and (2) the passing of air into thecirculation. The first condition causes an airwayobstruction as the casualty literally drowns in blood.The second causes rapidly fatal systemic airembolization. The simultaneous leakage of air intothe pleural space and passage of blood into thetracheobronchial tree can best be managed by hav-ing the anesthesiologist pass a standard endotra-cheal tube into the bronchus of the uninjured lung.(The use of a double lung tube in this situation is tootime consuming to be safe.) Once the injured lunghas been isolated by the anesthesiologist, the sur-geon, after exposing the injured lung, can thencross-clamp the pulmonary hilum. The appropriatesurgical management may be to perform an ana-tomical pulmonary resection—a lobectomy orpneumonectomy—rather than to attempt a repairof the laceration (Figure 19-6).53

Systemic air embolism is a catastrophic compli-cation that suddenly converts a previously stablepatient into one who is agonal. Increasingly, evi-dence shows that cerebral and coronary air emboli

are common causes of death in victims of penetrat-ing lung injuries.22 There is frequently a causalrelation to the application of positive pressure tothe airway. The treatment, insofar as there is one,consists of

• immediate performance of a thoracotomy,• application of a large clamp or Rommel

tourniquet around the hilum of the injuredlung to prevent further embolization, and

• exposure of the heart to confirm the diag-nosis (air bubbles should be visible in thecoronary vessels).

If the diagnosis is confirmed, the surgeon manu-ally occludes the ascending aorta and manuallycompresses the heart so as to drive the air bubblesthrough the coronary arteries and into the coronarysinus. The management of the cerebral componentis a matter for conjecture.

Traumatic Rupture of the Diaphragm

Traumatic rupture of the diaphragm is a rela-tively uncommon injury, seen in 2% to 3% of pa-tients with blunt chest trauma.18 In the context ofmilitary operations, it is most frequently seen incasualties who are injured when the vehicle in whichthey are riding detonates a buried antitank mine.The soldier shown in Figure 19-7 was killed duringthe Vietnam War when the jeep in which he wasriding was destroyed by a mine. The chest radio-graph explains the scaphoid appearance of his ab-domen: his stomach and much of his gut have her-niated into the left hemithorax.

Rupture of the left hemidiaphragm accounts for70% to 75% of these injuries, presumably because ofthe shielding effect of the underlying mass of theliver on the right.54 Traumatic diaphragmatic her-nia may be discovered at the casualty’s initialevaluation or incidentally at thoracotomy orlaparotomy performed for other reasons. The casu-alty may be asymptomatic or may present with respi-ratory distress. Patients with chronic rupture usuallypresent with symptoms of intestinal obstruction.

Diaphragmatic hernia is caused by three factorsin blunt trauma55:

1. The abdominothoracic pressure gradientmay exceed the usual maximum value of100 cm H2O if the trauma patient gaspsagainst a closed glottis at the instant that alarge external force raises the intraab-dominal pressure.

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2. Thoracic compression during blunt traumadistorts the anatomy of the diaphragm andtears it with large shearing forces.

3. The trauma patient may have a congenitalweakness of the diaphragm.

The diagnosis of diaphragmatic trauma requiresa high degree of clinical suspicion by the militaryanesthesiologist. Trauma to the diaphragm shouldbe suspected in casualties who have (a) injuries

below the fifth intercostal space and (b) injuriesassociated with high-energy impact (eg, fracturesof the clavicles, upper ribs, scapulae, sternum, pel-vis, or thoracolumbar spine). This condition mustbe suspected when unexplained changes in pulmo-nary compliance occur intraoperatively in patientswho have sustained serious chest injury. Patientswith significant migration of viscera into the chestcavity also appear to be at greater risk from aspira-tion pneumonitis. Postoperative difficulties in

b

a c

Fig. 19-6. This casualty presented with aparenchymal lung laceration due to a perfo-rating gunshot wound of the chest. (a) Thechest radiograph taken after insertion of achest tube shows that the damaged lungremained collapsed. Although the chest tubekinked, it was patent. This finding, in addi-tion to the magnitude of the air leak and theconsequent difficulty of providing adequateventilation, constituted an indication forthoracotomy. (b) A huge laceration wasfound in the right upper lobe of the lung. Alobectomy was performed. (c) The postopera-tive chest radiograph shows expansion of theresidual lung. Photographs: Swan VietnamSurgical Slide Collection.

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ba

Fig. 19-7. (a) The external appearance of this dead soldier is notable for his scaphoid abdomen and his distended chest.(b) The chest radiograph shows several transverse lines in the left hemithorax, which are caused by the walls of hollowviscera that have herniated into the chest. The left diaphragm is not apparent. Massive displacement of the mediastinuminto the right hemithorax has occurred. Photographs: Wound Data and Munitions Effectiveness Team slide collection.

weaning a patient with thoracic trauma from me-chanical ventilation should arouse suspicion of amissed diaphragmatic hernia.

Operative positioning for the repair of a traumaticdiaphragmatic hernia depends on the side of theinjury and its chronicity. The more common left-side

hernia is best repaired through a laparotomy whenthe diagnosis is made soon after the injury, andwhen there is no evidence of a significant intratho-racic injury. Chronic left-side hernias are best treatedthrough a low posterolateral incision. Right-side her-nias are nearly always repaired through a thoracotomy.

SUMMARY

Thoracic injuries in combat constitute 10% of thesurgical workload in wartime. Most of these injuriesare caused by penetrating missiles. In caring forsoldiers with such injuries, the military trauma anes-thesiologist will encounter a paradoxical situation:more often than not, it will be not the thoracic injuryitself but an injury to another body part that will be thecenter of professional attention. The thoracic injurycan usually be managed by such simple interventionsas inserting a chest tube and debriding wounds.

In most cases in which thoracotomy is indicated,it will be performed for control of (a) bleeding from

lacerated lung parenchyma or from the chest walland (b) air leaks from lacerated lung parenchyma.Hemorrhage from a laceration, perforation, or rup-ture of the heart or great vessels will rarely beencountered: such injuries are so rapidly fatal thatfew casualties will survive long enough to reach amedical treatment facility. If such a casualty doesarrive, the military trauma anesthesiologist maybe confronted with the need to resuscitate an ago-nal patient; from the practical standpoint, thismeans being able to orchestrate an emergency thora-cotomy.

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Among the more severe intraoperative problemslikely to be seen by the military trauma anesthesiolo-gist are (a) an air leak that is so massive that tidal volumeis inadequate, (b) airway obstruction due to accumula-tion of bloody secretions, and (c) systemic air embo-lism. These problems are best managed by selectiveintubation of the bronchus of the uninjured lung.

Pulmonary contusion and flail chest are the two

treatment problems most likely to be seen in asso-ciation with blunt trauma. Severe cases will requireintubation and mechanical ventilation. As a gen-eral rule, the military trauma anesthesiologist will bemost successful when treating a casualty with a tho-racic injury if he or she prioritizes the many tasks athand in terms of the elementary ATLS principles ofairway, breathing, and circulation management.

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