anesthesia and the obese parturient · 2018-04-02 · anesthesia)and)the)obese)parturient...
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Anesthesia and the Obese Parturient
Presented by: Mark Green, CRNA, MSN
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Anesthesia and the Obese Parturient
The Problem22% of women were obese before pregnancy in 2002-‐2003 BMI > 30 = obese (NIH: 20% more than ideal body weight or 2x ideal body weight) BMI > 40 = morbidly obese
Obesity increases the risk for cesarean section and thus the need for anesthesia C/S rate is 47.4% in morbidly obese
Maternal and fetal morbidity is increased
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The Problem
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Describe the implications of obesity during pregnancy.
Describe the implications of Preeclampsia and the anesthetic management of these patients.
OBJECTIVES
Physiologic ChangesCardiovascular:
• Increase in Blood Volume
• Increase in Cardiac Output
Respiratory Changes:
• Elevation of the diaphragm
• Decreased FRC
• Increased ventilation and respiratory drive
• Respiratory alkalosis and increased arterial O2
tension6
Pulmonary Changes
Increase MV leads to: • Decreased CO2 to ~ 30-‐32 mmHg • Increased PaO2 to ~ 100 mmHg Uterine growth upward increases pressure on diaphragm causing:
Decreased FRC Similar to RestricGve Lung Disease
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Pulmonary Changes
Progesterone is a direct respiratory sGmulant • Normally produced by the corpus luteum • At 8 weeks gestaGon, producGon shiQs to
the placenta (ovarian-‐placenta shiQ) • EssenGal hormone for uterine health and
homeostasis Increased minute venGlaGon (MV) is iniGated by a rise in progesterone
• Increased diaphragm use
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Clinical SignificanceConsider the normal lung where:
MV= Minute VenGlaGon VT = Tidal Volume f = Frequency as Respiratory Rate (RR) • MV = 500 ml x 12/min = 6,000 ml/min
Dead Space (VD): Anatomical + Alveolar = Physiologic • Approx. 150 ml of VT is VD
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Clinical Significance
VD / VT = 150 ml / 500 ml = 0.3 or 30% This means that only 70% of VT is available for gas exchange.
Recall that: Alveolar venGlaGon (VA): the amount of fresh gas involved in gas exchange.
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Clinical SignificanceVA = (VT – VD) x f (respiratory rate) VA = (500 – 150) x 12 VA = 4,200 ml/min available for gas exchange aQer accounGng for dead space
Now consider the pregnant state, as the uterus grows to term: VT increases 40% 700 ml (500 ml) f increases 10% 14/min Therefore: MV is increased 50% 7,700 ml/min
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Clinical SignificanceIn the normal lung:
DenitrogenaGon (PreoxygenaGon) FRC = FiO2 x 2,400 ml = 2,400 ml stored O2 O2 ConsumpGon = 250 ml/min Time to desaturaGon = 2,400/250 = ~10 min
In the parturient DenitrogenaGon (PreoxygenaGon)
FRC decreased 20 % = 1920 ml O2 consumpGon is increased 20% = 300 ml/min At best, Gme to desaturaGon = 1920/300 = ~6 min 12
Clinical Significance
WITHOUT DENITROGENATION (RA02 = 21%) Normal lung:
FRC contains 2,400 ml x 0.21 = 504 ml O2
O2 consumpGon = 250 ml/min DesaturaGon in 504/250 = ~2 minutes
Parturient lung: FRC is 1920 x 0.21 = 403 ml O2
ConsumpGon is 300 ml/min DesaturaGon in 403/300 = ~1 minute
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HypoxemiaHypoxemia more common in obese parturient •Worse in supine position (such as in C/S) •Body weight increases O2 consumption and CO2 production
•Work of breathing increased d/t chest wall weight= Restrictive Lung Disease
•Prone to rapid oxygen desaturation •Obstructive sleep apnea is common •Use of CPAP to improve PaO2
HypoxemiaMechanism
•Decreased FRC and
•Increased Closing Capacity resulting in
•Right to Left Shunt
•High FiO2 worsens shunt 2o contribution of atelectasis
•BMI correlates to atelectasis and shunting
Shunts > 30% = no improvement in PaO2 with high O2 concentrations
15(Miller)
More Bad StuffNormal increase in CO2 associated w/ pregnancy is exaggerated in obese patient, as extra fat demands extra perfusion
Cardiac stress is greater in obese pts, who also have more cardiac risk factors, ie: HTN, Diabetes
Aortocaval Compression Syndrome: decreased cardiac output and placental perfusion due to large uterus •exacerbated by large panniculus •May result in CV collapse and sudden death in obesity
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The Problem
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The Problem
Labor AnalgesiaFetal macrosomia is a risk factor for painful and complicated labor (greater need for analgesia)
Obese body habitus makes regional techniques more challenging •Midline difficult to determine •Obese pts have difficulty assuming good position
•Epidural space is deeper •Catheters tend to migrate when pt moves
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The Problem
A study by Jordan showed 74% of morbidly obese pts required more than one attempt at epidural with 14% needing more than 3 attempts.
Accidental dural puncture: 4% for MO vs 0.5%-‐2.5% for normal weight (Jordan)
Epidural Failure: 42% failure rate versus 6% in normal weight (Hood)
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Labor Analgesia
Regional Anesthesia / Analgesia
Regional is strongly preferred over GA for C/S
In morbid obesity: consider early placement of epidural or spinal catheter before need arises •Anticipate difficult placement •Allows time for testing to confirm function •In case of emergency, catheter can provide immediate surgical analgesia
•Decreases need for risky emergent GA •Must be prepared for rapid control of the airway
General AnesthesiaGA associated with much higher maternal mortality vs. regional anesthesia •Maternal death usually due to inability to secure an airway for general anesthesia (Closed Claims)
•As high as 0.35% (Samsoon and Young) incidence of difficult or failed intubation in the morbidly obese for C/S
High risk of aspiration due to increased abdominal pressure, lower gastric pH, slower gastric emptying assoc. w/ obesity
General AnesthesiaIn obese patients, it is essential to: •Premedicate with antacids, metoclopromide, PPI
•Pre-‐oxygenate for several minutes •Position patient with a ramp •Have an additional pair of experienced hands to assist anesthesia provider Consider awake fiberoptic intubation •Not appropriate for emergency C/S
Empty stomach with OG tube prior to waking Extubate when fully awake and cooperative
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25-‐degree head-‐up position
Post-‐Partum CareIncreased post-‐partum morbidity in obesity •Hemorrhage, endometritis, infection, DVT, PE, atelectasis, respiratory depression, hypoxemia, cardiomyopathy are all more common in obese pts
•Monitor hourly for 24 hours after C/S is recommended
•Consider ICU admission post-‐op
Increased need for narcotics post-‐op •Respiratory insufficiency, circulatory collapse •Need is decreased with neuraxial analgesia
Anesthesia Mgmt Considerations
All morbidly obese pregnant patients should have an ante partum anesthesia evaluation
All obese patients with concerning co-‐morbidities should also be evaluated well in advance of planned delivery
Develop a multidisciplinary plan (OB, Peds, OR crew, consider transfer to tertiary if CAH)
Antepartum evaluation
Airway
Examine regional landmarks
Review pt history for co-‐morbidities
Review chart for prior anesthetic records •Chart needs to be available with referral
Discuss analgesia and anesthesia plans with patient and family •Discuss risks and answer questions
Patient TransferThe anesthesia departmental policy for transferring any obstetric patient is left to the discretion of the obstetric provider
Simply being obese/morbidly obese is not grounds for automatic transfer from an anesthetic standpoint
Anesthesia may recommend transfer for medical indications discovered during the ante partum evaluation
L&D Tasks
When a morbidly obese patient presents in labor: •Ensure OR table can handle the patient’s weight Notify anesthesia immediately upon arrival •Early neuraxial catheter may be placed •OR may be prepared •Difficult airway cart, ramp, etc
Sources•Obstetric anesthesia for the obese and morbidly obese patient: an ounce of prevention is worth more than a pound of treatment. Soens et al. Acta Anesthesiol. Scand 2008; 52: 6-‐19
•Obesity and obstetric anaesthesia. Saravanakumar et al. Anaesthesia 2006; 61: 36-‐48
•Obesity, obstetric complications and cesarean delivery rate – A population-‐based screening study. Weiss et al. American Journal of Obstetrics and Gynecology 2004; 190: 1091-‐7
•Relative Risk Analysis of Factors Associated with Difficult Intubation in Obstetric Anesthesia Rocke, et al. Anesthesiology 1992; 77: 67-‐73
•Anesthetic and Obstetric Management of High Risk Pregnancy, 3rd Ed. Chapter 6: “The morbidly obese pregnant woman”, pp 53-‐65
•Miller, RD et al. Miller’s Anesthesia 7th ed. Churchill Livingston: p 386,2009
•Machado, Lovina SM, North American Journal of Medical Sciences, January 2012; Vol. 4, Issue 1, pp 13-‐18
• Jordan H, et al. Massive maternal obesity and perioperative cesarean morbidity. Am J Obstet Gynecol 1994; 170: 560-‐5.
• Hood DD, et al. Anesthesia outcome in the morbidly obese parturient. Anesthesiology 1993; 79: 1210-‐1218.
• Soens MA, et al. Obstetric anesthesia for the obese and morbidly obese: an ounce of prevention is worth more than a pound of treatment. Acta Anesthesio Scand 2008; 52: 6-‐19.
• Djabatey, EA., Barclay, PM. Difficult and failed intubation in 3430 general anaesthetics. Anaesthesia, 2009; 64: 1168-‐1171.
• Quinn, AC et al, Failed tracheal intubation in obstetric anaesthesia: 2 year national case -‐ control study in the UK. British Journal of Anaesthesia 2013; 110 (1): 74-‐80.
• Gurinder, M et al, Management of the difficult and failed airway in obstetric anesthesia. J Anesth 2008; 22: 38-‐48.
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Sources
PreeclampsiaThe leading cause of maternal and neonatal morbidity and mortality
Characterized by:
•Hypertension: SBP ≥ 140 mmHg and DBP ≥ 90 mmHg
•Proteinuria: ≥ 30 mg/day
•Edema
•Progression mainly affects the brain, kidney and liver.33
PreeclampsiaEpidemiology:
•Multisystem disorder complicating 3-‐8% of pregnancies.
•When eclampsia is included, it is directly associated with 10-‐15% of maternal deaths.
•Higher in women with a maternal history of the disorder.
• Incidence ranges from 3%-‐7% in healthy nulliparas and 1%-‐3% in multiparas.
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PreeclampsiaRisk Factors:
•Antiphospholipid Antibody Syndrome
•Renal Disease
•Prior preeclampsia
•Nulliparity
•Chronic HTN
•DM
•High Altitude35
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•Multiple gestations
•Strong FmHx of CV disease (≥ 2 first degree relatives
•Obesity
•FmHx of preeclampsia in 1st degree relative
•Age > 35
Preeclampsia
Pathophysiology
Normal trophoblast formation does not occur.
•Normal spiral arteries invade myometrium, losing their endothelium and most muscle fibers becoming low resistance vessels.
•Normal processes do not occur in preeclampsia.
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Preeclampsia
Difficult to differentiate among hypertensive disorders
Difficult to predict adverse outcomes and pre-‐term delivery
Complex pathophysiology-‐ abnormal placentation.
Genetic and Immunologic interaction are the most common theories.
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From: Cold Spring Harb Perspect Med doi: 10.1101/cshperspect.a006585
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From: Indian J Med Res, July 2013
HELLP SyndromeOccurs in 0.5%-‐0.9% of all pregnancies
Occurs in 5%-‐10% of cases of severe PE
Characteristics:
•Thrombi in the microvasculature of several organs.
•Thrombocytopenia
•Mechanical hemolytic anemia
•Various organ failure41
Morbidity and MortalityMaternal Complications •Placental Abruption/hemorrhage •Eclampsia •Cerebral Vascular Accidents •Organ Failure •DIC Maternal Deaths •Intracranial Hemorrhage •Cerebral Infarction •Acute Pulmonary Edema •Respiratory Failure •Acute Hepatic Failure/Rupture
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Morbidity and Mortality
Fetal Complications:
•Fetal Growth Restriction
• Intrauterine Fetal Demise
•Preterm Birth
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Maternal/Child RisksMaternal:
•Hypertension
•Premature Ischemic Heart Disease
•Cerebrovascular Accidents
Child:
•Stroke
•Coronary Heart Disease
•Metabolic Syndrome in Adult Life44
Anesthesia Management
Regional technique vs. GA
Avoid fluid overload
Manage hypertension
Magnesium administration
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Anesthetic ManagementTreatment: • Control Hypertension
-‐Labetalol-‐first line choice -‐Hydralazine-‐ up to 15 minutes to take
effect -‐Esmolol-‐ may cause fetal bradycardia -‐Sodium Nitroprusside-‐ cyanide
metabolite crosses placental barrier -‐Nifedipine-‐ associated with cerebral
infarct, MI, complete heart block and death.
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Magnesium Prevent/control seizures with MgSo4 • Eliminated by renal excreGon • InteracGon with non-‐depolarizers-‐
prolonged relaxaGon • Effect uterine tone-‐tocolysis • Interact with CCBs-‐ severe hypotension and
prolonged relaxaGon. Non-‐reassuring FHR
• PotenGate vasodilaGon and negaGve inotropic effects of anestheGcs
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Sources• Lakshmi, Tanuja P., et. al. Biomarkers for the management of
preeclampsia in pregnant women. Indian J Med Res; July 2013
• Uzan, Jennifer, et. al., Preeclampsia: Pathophysiology, Diagnosis and Management. Vascular Health and Risk Management, 2011: 7; 467-‐474
• Sofia, Ana and Karumanchi, SA. Angiogenic Factors in Preeclampsia and Related Disorders. Cold Spring Harb Perspect Med doi: 10.1101/cshperspect.a006585, (Advanced Online Article)
• Arnvind, P. What’s New in Obstetric Anesthesia? The 2013 Gerard W. Ostheimer Lecture. Anes-‐Analg, Feb 2014; 118 (2): 360-‐366
• Crovetto, Francesca, et. al. The Genetics of the Alternative Pathway in the Pathogenesis of HELLP Syndrome. The Journal of Maternal-‐Fetal Neonatal Medicine, 2012; 25 (11): 2322-‐2325.
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Sources•Dennis, AT. Management of pre-‐eclampsia: issues for anaesthetists. Anaesthesia, 2012; 67: 1009-‐1020.
•Norwitz, ER., Repke, JT. Preeclampsia: Management and prognosis. In UpToDate, Lockwood, CJ (Ed), UpToDate, Waltham, MA. (Accessed April 20, 2014.)
•Chutatape, A., Teoh, WHL. Third nerve palsy associated with preeclampsia and HELLP syndrome. J Anesth, 2013; 27: 757-‐760.
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