hypothermia: one nursing diagnosis or three?

Dr. Summers Associate Professor at the University of Kansas, Kan- sas City, Kansas, and Research Consultant to the University postanesthesia care unit. She is Past-President of Mid-America Regional Nursing Diagnosis Con- ference Group. She is co-author/ co-editor with Diane Ebbert on a text entitled, Ambulatoly Surgical Nursing a Nursing Diagnosis Ap- proach (1992) (J.B. Lippincott Co., Philadelphia). She has pre- sented papers at NANDA confer- ences, authored three chapters on hypothermia, hyperthermia, and risk for altered body temperature in a forthcoming book by K.V. Gettrust and P.D. Brabec entitled, Nursing Diagnosis in Clinical Practice: Guides for Care Planning (Delmar Publishers, Al- bany, NY), scheduled for distri- bution Spring 1992.

Hypothermia: One Nursing Diagnosis or Three? Sharon Summers, PhD, RN

' f i e nursing diagnosis of hypofhmnia has been described by various authors a s having multiple defining characteristics. A major problein identified was a lack of consistency on an exact temperature value for this nursing diagnosis. A review of the literature on hypothermia showed three distinct types of hypothermia: inadvertent, accidental, and intentional. Each o f these t y p s were distinguished by etiologies and defining characteristics and are pre- sented using the hypothetic model case approach.

Key Words: body temperature, hypothermia. nursing diagnosis.

I n examining various author's criteria for the nursing diagnosis of hypothemia, little agreement was found (Carpenito, 1989; Kim, McFarland, & McLane 1989; Miller-Carroll, 1989; North American Nursing Diagnosis Association [NANDA], 1990). Lack of agreement about diagnostic criteria may lead to credibility issues from within and from outside the profession as nursing diagnoses become com- monplace in nursing practice. If nursing diagnoses are to be useful to guide the independent practice of nursing, then the labels need to be clearly defined, described, and validated through research studies. The purpose of this article is to review the literature on the phenomena of hypothermia and to describe three types of hypothermia commonly discussed based on their etiologies. In addition, the model case technique derived from concept analysis will be used to create a framework for designating etiologies and defining characteristics into three separate nursing diagnoses.

Literature Review

Hypothermia

As a homeothermic (warm-blooded) creature, humans have been concerned with remaining warm during exposure to cold and remaining cool during exposure to heat. This concern is in part physiologically driven (homeostasis depends on the hypothalamus to regulate temperature within a rather limited range) and partly to maintain a sense of comfort. Hypothermia is a medical term used to describe a symptom and has been used since the early 1900s (Lloyd, 1986). Although Herodotus (484-420 BC) recognized that sailors died from exposure to cold water, the hypothermia phenomenon was not validated by research until the works of Currie in 1796 and later examples documented related to the sinking of the Titanic (Lloyd, 1986).

2 Volume 3, Number 1, January/ March 1992

Hypothermia has been diagnosed based on core temperature measurement. Core temperatures can be measured with esophageal, tympanic, and rectal thermometers. Esophageal temperatures are usually measured during general anesthesia by a sensor attached to the esophageal stetho- scope. Tympanic temperatures, an indirect measure of the hypothalamic temperature, can be measured noninvasively with a digital thermometer that is placed at the external ear canal to read infrared rays emitted from the tympanic membrane. The microprocessor continually calibrates itself from a present target temperature. Summers (1991) found no significant difference (paired t = 1.01, p = .069) in surgical patient's last esophageal temperature reading, as recorded on the anesthesia record, and the first digital tympanic temperature in the postanesthesia care unit. Rectal temperatures have been the traditional method of measuring core temperatures in patients who are very young, combative, or comatose (Sorensen & Luckmann, 1986). Rectal temperatures have now been found to be a less reliable measure of core temperature because temperatures may vary depending on the position of the thermometer (Lloyd, 1986).

Hypothermia has been operationally defined by authors using a variety of core temperature readings. Hardy (1 986) defined hypothermia as a rectal temperature less than or equal to 35°C. Dembert (1982), Holdcroft (1980), Lloyd (1986), MacLean and Emslie-Smith (1977), Matz (1986), and Reed and Anderson (1 988) defined hypothermia as a core temperature less than or equal to 35°C. Holdcroft, MacLean and Emslie-Smith, and Matz did not specify a method or location for measuring core temperature. Dembert (1 982) preferred thermistor thermometers but did not specify a measurement site; Lloyd (1 986) specified esophageal and tympanic as the most reliable sites; and Jenkins and Loscalzo (1 990) suggested the use of esophageal thermometers in comatose patients.

Reed and Anderson (1988) preferred the placement of a high rectal thermometer, Jenkins and Loscalzo (1 990) indicated that a rectal thermistor thermometer should be inserted 5 cm, Sor- ensen & Luckmann (1 986) specified thermometer insertion of 7.5 cm (3 inches in adults), and Hardy (1 986) did not specify placement criteria. Lloyd (1 986) found rectal temperatures to be a less reliable measure of core temperature since tempera-

tures may vary depending on the position of the thermometer.

Cork, Vaughn, & Humphrey (1983) studied the accuracy of seven temperature sites on the precision of core temperature measurement in surgical patients. Temperatures were measured at seven sites: nasopharynx, esophagus, rectum, bladder, axillary, forehead, and great toe. These seven sites were compared with tympanic temperatures that Cork et al. described as the most accurate site for core measurement. Results of the study indicated that the great toe, forehead, and axillary temperatures were less accurate than na- sopharyngeal, esophageal, rectal, and bladder temperatures on anesthesia induction. Great toe, forehead, and axillary temperatures did improve in accuracy after 1 to 2 hours when compared with tympanic readings. Thus, the literature supports the need for accurate core temperature measurement to validate the symptom of hypothermia, and agreement was found that esophageal, tympanic, and rectal measures were the preferred methods.

Lloyd also found that even if the core temperature ranges from 35" to 37"C, patients experi- ence the stressors of cold. Lloyd further suggested three categories of cold stress and three categories of hypothermia.

1 .

2.

3.

4.

5.

6.

Mild cold stress: normal core temperature and normal total body heat; Moderate cold stress: normal core temperature but with reduced total body heat; Severe cold stress: core temperature below normal to 35°C; Mild hypothermia: core temperature 32" to 35" c; Moderate hypothermia: core temperature 28" to 32" C; and Severe hypothermia: core temperature less than 28" C (Lloyd, p. 43, 1986).

Jenkins and Loscalzo (1 990) classified hypothermia, as measured by a rectal thermometer, as mild (> 32.0"C or 89.6"F), moderate (> 26.0"C or 78.B°F), and severe (< 26.0" or 78.8"F).

Related Factors

Whether the terms "cold stress" or "hypothermia," or categories of mild, moderate, and severe are used to define hypothermia, there are four related factors that accompany hypothermia.

Nursing Diagnosis 3

Matz (1 986) further defined hypothermia and con- comitant related factors that may develop as core body temperature decreases below normal values. A s can be seen in Figure 1, the factors range from sensation of cold, confusion, stumbling, disorien- tation (36°C or 96.8"F) to isoelectric electroencephalogram (17°C or 62.6"F) (Matz, p. 47, 1986). The pathophysiologic changes associated with lowered body temperatures were primarily discussed in relation to accidental hypothermia; however, medications and general anesthetic agents used during surgery were included (Matz, 198ti). Some of the pathophysiologic changes described are not seen in surgical patients, who niay become hypothertnic, since anesthesiologists or nurse anesthetists nionitor and provide physiologic support t o control patient symptoms (Matz, 1 OXG).

Miller- (1987) indicated that shivering is an rarly physiologic mechanism to generate heat; however, the heat is not retained and muscle en- erh?- stores may be quickly depleted. Augustine (1 990) indicated that shivering in the anesthetized patient niay be detected only by palpation of the masseter, neck, or chest muscles. Factors that may exacerbate hypotherniia include pre-existing malnutrition, alcohol intoxication, burn injury, and \asodilating medications (Lloyd, 1986).

Jenkins and Loscalzo (1 990) described physiologic changes associated with the mild, moderate, aiici severe categories. Mild hypothermia was man- ifcsted hy shivering, which may reach maximal lev- cis with a body temperature of 35°C (95°F) and cearc at 3!?"(; (81).6"F), in addition to confusion, staggering gait, muscle rigidity, and a cold appear- x i ( e. Syrnptotns of moderate hypotherniia in- ( lutle ttecrcased mental status, cardiac arrhyth- niias, decrcased vital signs, fixed pupils, and loss of' reflexes and muscle activity. Severe hypother- rnia ~ v a s characterized by unconsciousness arid hypotension. .4t 1 9°C (66.2"F) brain waves are flat a t i d at 1 .Go(; (50°F) cardiac standstill occurs (Jew kinx and I.oscalzo, l!NO).

Mechanisms of Heat Loss

€i\potli(*t n i i ~ i n a k be piecipitnted when heat I \ lost f o u r iiiechmrwis conduction, coniec- t r o t i . r x t i ' i t i o t i , ,irid e\aporatton (Augustine, 1080, (;niiotig. 108.5, Gu\ ton, 1986, Lennon, €lo&ing, ( o r i o i e ~ , X- Perkin\, 1990; Ltlh, 1987,

Morrison, 1988; Vick, 1986). Heat loss by conduction occurs when warm surfaces are in direct contact with cold surfaces, thereby transferring heat to the cold surface (Augustine, 1988; Guy- ton, 1986, Lilly, 1987, Morrison, 1988). Heat loss by conduction is self-limiting and accounts for 3% of body heat loss (Guyton, 7986).

Heat loss by convection occurs when air is cir- culated over body surfaces (also known as the wind-chill factor) (Augustine. 1989; Guyton, 1986, Lilly, 1987, Morrison, 1988). Guyton (1 986) suggested that heat loss by convection ac-

counts for 15% of body heat loss, whereas Morri- son (1 988) indicated that the elderly may lose 25% to 35% of their body heat during surgery.

Heat loss by radiation occurs when infrared or electromagnetic waves radiate from the warm body t o cold surfaces (Augustine, 1989; Guyton, 1986; Lilly, 1987; Morrison, 1989). Heat loss by radiation accounts for 60% of body heat loss, where as much as 50% may be lost from an uncovered head (Augustine, 1989; Guyton, 1986; Morrison, 1988).

Heat loss by evaporation occurs from perspiration, and water loss occurs through respiration (Aubpistine, 1989; Guyton, 1986; Lilly, 1987; Morrison, 1988). Heat loss is 0.58 calories per 1 g of water loss through evaporation and accounts for 22% of thermal loss (Guyton, 1986).

Miller (1 987) further categorized heat loss by three rates: acute, subacute, arid gradual. Acute is defined as heat loss by conduction from the nor- mothermic patient by immersion in cold water, re- sulting in hypothermia in 1 hour (Miller, 1987). Subacute is defined as heat loss by conduction, convection, radiation, and evaporation to hypothermic levels a t id may persist several hours (Miller, 1987). Gradual is defined as hypothermia that occurs over several days or weeks, and is seen especially in the elderly living in the urban setting (Miller, 1987).

4 Volume 3, Number 1, January/March 1992

DEGREES OF HYPOTHERMIA AND ASSOCIATED ZFFECTS

- 98.6 37 96.8 36

0,

al 2- Y m v)

C 0,

2

5

L al- ?c

95 35

34

- 91.4 33 32

31

Hypoventilation (3 or 4 breathslmin), 80 30

Hypotension, spontaneous ventricular fibrillation

24

.E

$ L

rn

C Y .? ’ %

‘P +? .-

.E ’5 E i -

5: x .u

al

Mechanisms and countermeasures. Hospital Practice. January 30: 54-7 1.

Skin extremely cold to touch, slurred speech, incoordination, introversion

Amnesia

Cardiac arrhythmias (particularly a t r i a l fibrillation), bradycardia

73.4 23 Apnea

22

Cardiac standstill n 69.8 21

20 -

Lowest accidental hypothermia associated with survival n 66.2 19

18

lsoelectric electroencephalogram M 62.6 17

Lowest artificially induced hypothermia 48’2 9y associated with recovery

Nursing Diagnosis 5

Types of Hypothermia

Heat loss also can be categorized by type. Three types of hypothermia were found in the literature: inadvertent, accidental, and intentional.

Inadvertent Hypothermia

Inadvertent is unintentional hypothermia that results from surgical patient's exposure to the cold operating room environment and is considered a side effect of surgery (Ackley, 1984; Augus- tine, 1989; Birdsall, 1985; Blitt, 1985; Burkle, 1988; Carlson, 1988; Fallacaro, Fallacaro & Ra- del, 1985; Fraulini, 1987; Lilly, 1987; Morrison, 1988; Sessler, Rubinstein 8c Eger, 1987).

Inadvertent hypothermia has been studied ex- tensively in regard to preoperative and intraoperative medications that depress hypothalamic temperature regulation mechanisms and promote heat loss through vasodilatation. The anesthetized patient beconies poikilotherniic (cold-blooded) arid body temperatures tend to approach ambient levels (Lilly, 1987; Morrison, 1988).

Miller-Carroll (1989) conducted a study of post anesthesia care unit nurses (n=16) to validate the tiefining characteristics of the nursing diagnosis of hyfloth~mmirr in postanesthesia patients. Data 1vel-e collected using the five-point Likert scale, lvhere subjects rated 40 sicgns and symptoms of h)p)therrriia that were derived from the literature. Subjects were asked to identify those defin- iiig characteristics that were present in hypother- uiic postanesthesia patients 60% 1 0 100% of the t i r i i t , .

lkfiriing characteristics identified as present 60% t o 100% of- the time were shivering, cool skin, tachycardia, altered nail-bed color, hypertension, and piloerection. Data were then weighted and analyzed for content validity. Critical defining characteristics were identified as shivering and c.001 skin. Significant defining characteristics were pallor, slow capillary refill, tachycardia, altered nail-bed color, hypertension, and piloerection. I he researcher concluded that mild arid moderate categories could he used t o classify hypothermia, although thcre was no mention of temperature values that designated hypothennia or methods used t o measure body temperature in these postanesthesia patients.

The temperature of many operating rooms is niaintained between 60" and 64°F (1 5.5"- 17.7"C). Riirkle ( 1 988) reported that low tempera-

I _

tures and low humidity are thought to inhibit microbial growth, decrease static electricity, and maintain the comfort of the surgical team. Heat loss in anesthetized patients can rapidly become a critical problem. Augustine (1989, 1990) stated that the incidence of inadvertent hypothermia is estimated to be 12 to 16 million surgical patients annually. Thus, anesthesiologists have defined inadvertent hypothermia in surgical patients as core temperatures less than or equal to 36°C (9'7 F) (Augustine, 1989; Lennon et al., 1990; Lilly, 1987; Morrison, 1988). Table 1 summariLes the etiology and major defining characteristics of inadvertent hypothermia.

Accidental Hypothermia

Accidental hypothermia, with temperatures less than or equal to 35.0"C (95"F), occurs from a variety of causes such as burn injuries and loss of thermal regulating dermal layers; persons stranded outdoors during winter weather; exposure to wind, snow, or rain from participation in winter sports; exposure of the very young or elderly to the cold environment when wearing inappropriate clothing; from near drowning when im- mersed in very cold water; and vasodilatation secondary to alcohol intoxication. Accidental hypothermia also may occur in individuals who lack heat in the home o r who are homeless, who have hypothyroidism, or who are immobile (Cooper & Ross, 1960; DeLapp, 1983; Dembert, 1982; Guyton, 1986; Lehmann, 1982; Lloyd, 1986; Matz, 1986; Reed & Anderson, 1988; Vick, 1986). Table 2 summarizes the etiology and the major defining characteristics of accidental hypothermia.

Intentional Hypothermia

Intentional hypothermia is purposeful cooling of patients for surgical procedures such as cardiac bypass graft or cardiac transplant to temperatures ranging from 26" to 32°C (80"-90"F) (Guyton, 1986; Hudak, Lohr, & Gallo, 1987; Jo- achimsson, Nystrom, & Tyden, 1987; Vick, 1986; Woodcock, Murkin, Farrar, Tweed, Guiraudon, & McKenzie, 1987). Table 3 summarizes the ctiology and major defining characteristics of intentional hypothermia. Table 4 compares temperatures designated by the three types.

Thus, this review of literature of the concept of hypothermia provided support for three types of hypothermia that were operationally defined by

6 Volume 3, Number 1, January/March 1992

Table 1 . Defining Characteristics of Inadvertent Hypothermia

Etiology: Exposure to cold operating room with heat loss by conduction, convection. radiation, and evaporation Defining characteristics 1 Core temperature 536" C (96 8" F) 2 Cool skin temperature (no known established criteria) 3 Heat lost by

A Conduction: heat loss from a warm patient to a cold operating room table, cold antiseptic solutions, room temperature intravenous fluids or cold transfusions, laying on wet sheets, cold anesthesia gases, and cold instruments

B Convection: heat loss from a warm patient because of cold, circulating air moving across exposed body parts C Radiation: heat loss from a warm patient into the cold room, where 50% may be lost from the uncovered head, from

open wounds, and as a result of medications that produce maximum muscle relaxation and vasodilatation during surgery Inactivity and inappropriate clothing add to heat loss by radiation

D Evaporation: loss of heat and water through the respiratory tract and from open wounds 4 Shivering as detected by masseter muscle tetany (shivering unrelated to hypothermia is frequently seen postanesthesia

related to autonomic nervous system overstimulation from stressors of surgery and medications) 5 Cyanotic nail beds from rebound vasoconstriction after reversal of vasodilating anesthetics and medications 6 Capillary refill greater than 5 seconds 7 Pale skin or pale mucous membrane color 8 Increased metabolism-the stress response for tissue repair begins when the incision is made

three different temperatures and three different etiologies. These findings prompted the need to clarify the nursing diagnosis of hypothermiu, using model cases adapted from concept analysis.

pothermia while attempting to include most of the critical attributes. When these model cases were developed, there was no distinction made as to major or minor characteristics.

Model Cases Model Case: Inadvertent Hypothermia

Model cases (Walker and Avant, 1989) were used to define and describe the three types of hy-

Jim Smith, a 29-year-old white man, injured his left knee while running a long distance race.

Table 2. Defining Characteristics of Accidental Hypothermia

Etiology: Accidental exposure to environmental factors that lead to heat loss by conduction. convection, radiation. and

Defining characteristics evaporation

1 2 3

4 5 6 7 8 9

10 11 1 2

Core temperature 1 3 5 " C (95" F) Cold skin temperatures that may include tissue injury or frostbite damage Heat lost by A Conduction: snow, rain, contact with cold surfaces or cold water B Convection: exposure to the wind C Radiation: the very young and very old lose heat rapidly where loss from the exposed head may be 40%-50%. alcohol

intake produces vasoconstriction then vasodilatation, exposure to cold environment, inappropriate clothing, homelessness, and inadequate housing

D Evaporation: heat loss from respiration, perspiration, and exposure of the skin to cold water Mental confusion Decreased vital signs Drowsiness Shivering Decreased metabolism Cardiac arrhythmias Piloerection Decreased metabolism Malnutrition documented by height and weight and serum albumin levels

~~

Nursing Diagnosis 7

Table 3. Defining Characteristics of Intentional Hypothermia

Etiology: Surgical procedure that requires extracorporeal cooling, for purposeful induction of cardiac arrhythmias and to

Defining characteristics decrease tissue ischemia, in addition to heat loss by conduction. convection, radiation, evaporation

Core temperature 525"-29" C (80"-85" F) Heat lost by A Conduction: heat loss from a warm patient to a cold operating room table, cold prep solutions. room temperature or

cold intravenous fluids or transfusions, laying on wet sheets, cold anesthesia gases, and cold instruments, bypass pump results in heat loss when blood is pumped through the heat exchanger

B Convection: heat loss from a warm patient because of cold, circulating air moving across exposed body parts C Radiation: heat loss from a warm patient into a cold room, where 50% may be lost from the uncovered head,

open wounds, and as a result of medications that produce maximum muscle relaxation and vasodilatation during surgery Inactivity and inappropriate clothing add to heat loss

D Evaporation: loss of heat and water through the respiratory tract and from open wounds Shivering as detected by masseter muscle tetany (shivering unrelated to hypothermia is frequently seen postanesthesia) Cyanotic nail beds from rebound vasoconstriction after reversal of vasodilating anesthetics and medications Left shift IP oxyhemoglobin dissociation curve decreases the unloading of oxygen despite 98%-100% saturation on pulse azirnetry related to increased oxygen consumption secondary to increased metabolism to support shivering \low capillary refill P d k skin or pale mucous membrane color In( reased metabolism-the stress response for tissue repair begins when the incision is made

This 5'8", 1 .N-pound, normotherniic man was diagnosed as having a torn medial meniscus, and was scheduled for an arthroscopy and meniscus repair. Upon arrival in the 64°F (1 7.7"C) operating room, MI-. Smith was placed on the operating table. The operative procedure required the place- niriit of a pneumatic tourniquet on the left leg and scruthing of the leg for 10 minutes with room teniperature antiseptic solutions, where the solutions saturated the sheet beneath the patient's hips. Heat was lost by conduction (cold antiseptic solutions, rooni temperature intravenous solutions, cold instruments), convection (cold circulating I-ooni air), radiation (from patient to room,

Table 4. Temperatures For the Three Types of Hypothermia

Type Temperature

lncid\ertent Acc dental liitei ticma!

236" C (96 8" F) ' 535" C (95 0" F)' 526"-29" C (80"-85" F)?

1985 Failacaro. Fallacaro & Radel. 1985, Ltlly, 1987,

from patient to wet sheets, inactivity, inadequate clothing), and evaporation (from wound and respiratory tract). After 4 hours in surgery, Mr. Smith was transferred to an ambient temperature cart, covered with a clean sheet, and transported to the postanesthesia care unit (PACU). Upon admission to the PACU, his Core temperature, measured at the tympanic site using a digtal thermometer, was 35.6"C (95.8"F). Mr. Smith's surface skin temperature also was measured using a digtal thermometer placed on the right quadriceps, and the terri- perature was 29°C (84.6"F). Shivering was noted by tetany of masseter muscles, skin was pale, capillary refill was greater than or equal to 5 seconds, and the nail beds were cyanotic, despite a 98% oxygen saturation on pulse oximetry. Nursing care included removing wet sheets, placing a warnied blanket underneath Mr. Smith, wrapping his head with a warnied towel, and placing the Bair Hugger (Augustine Medical, Inc., Eden Prairie, MN), an electric convection warming device set on high (maximum 115"F), over him while nionitor- ing his temperature every 15 minutes. He was discharged from the PACU after 90 minutes, with a core temperature of 36.1 "C (97°F) and a wrface temperature of 36.6"C (98°F).

Model Case: Accidental Hypothermia

Brian Bradley, a 16-year-old boy, was admitted to the intensive care unit (ICU) after a near-


drowning episode while ice skating on a pond. Eye witnesses estimated that Brian was underwater ap- proximately 4 minutes. He responded to immedi- ate cardiopulmonary resuscitation. His core temperature was measured at the tympanic site by digital thermometer, and on admission it was 31.1 "C (88°F). His right quadriceps surface temperature also was measured with a digital thermometer and it was 26.6"C (SOOF), indicating heat loss by conduction (cold pond water), convection (cold air circulating over cold, wet skin surfaces), radiation (from the body to cold water and wet clothing), and evaporation (cold water on skin, cold water aspiration). Brian was drowsy, and his vital signs were: blood pressure, 90/60 mmHg; pulse, 60 beats per minute; and respiration, 12 breaths per minute. He was intubated and placed on a ventila- tor (arterial blood gases were PO, of 60 and pC0, of 60 mmHg). Brian was monitored for frostbite damage to the toes, fingers, and face. External warming methods were instituted to decrease un- controlled shivering (a normal response for heat generation) and to decrease muscle energy deple- tion. Rewarming also was necessary to correct a left shift in the oxyhemoglobin dissociation curve, indicating that hemoglobin was not unloading oxygen to the tissues. Central nervous system integ- rity was maintained with steroid therapy, hyper- ventilation, diuresis, and monitoring fluid intake and output. Brian also was monitored for cardiac arrhythmias, although these did not develop. After 6 days in the hospital, he was discharged home, free of residual effects.

Model Case: Intentional Hypothermia

George Aldrich was admitted to the hospital with chest pain. After cardiac catheterization, he was taken to surgery for a triple coronary artery bypass graft. He was placed on the operating table; the ambient room temperature was 64°F. He was given general anesthesia and his left leg and chest were scrubbed for 10 minutes at room temperature with antiseptic solutions. Mr. Aldrich lost heat by convection (cold circulating air), radiation (cold antiseptic solutions and cold ambient temperature), and evaporation (cool, wet skin surfaces; inhalation of cool anesthetics). He lost heat by conduction as his heparinized blood was circu- lated through the bypass pump and his body was purposefully cooled from 24" to 28°C (75"-83"F) to promote ventricular fibrillation (Lloyd, 1986) and to decrease tissue ischemia and damage (The-

lan, Davie, & Urden, 1990). Mr. Aldrich was in surgery for 6 hours and was gradually rewarmed as he was taken off the bypass pump. The last esophageal temperature recorded by the anesthe- siologist was 29.4"C (85°F ). He was transferred to an ambient temperature bed, covered with a

clean sheet, and transported to the ICU. Upon admission to the ICU, Mr. Aldrich's core temperature, measured at the tympanic site by a digtal thermometer, was 30.0"C (86.O"F). His right quadriceps skin temperature, also measured with a digital thermometer, was 29°C (84.6"F). Shiver- ing was noted by tetany of masseter muscles, skin was pale, capillary refill was greater than 5 seconds, and his nail beds were cyanotic, despite a 98% oxygen saturation on pulse oximetry. Nurs- ing care included warmed blankets to the head and extremities only to allow monitoring of the leg and the chest wound for bleeding related to residual effects of heparin therapy. His vital signs were monitored and he stabilized within 24 hours at which time his core temperature was 36.1"C (97°F) and his surface temperature was 36.6"C (98°F). He was transferred to the cardiac rehabili- tation unit 48 hours postoperatively and recov- ered uneventfully.

Discussion and Recommendations This review supports the notion that the con-

cept of hypothermia exists as three different types: inadvertent, accidental, and intentional. As can be seen in Tables 1 to 4, the three types of hypothermia differ in specific core temperature values, etiology, and in defining characteristics. Support also was found to justify the formulation of three nursing diagnoses instead of one to assist nurses in implementing care for these three types of hypothermia in the practice setting. A single nursing diagnosis of hypothermia had been defined and described by selected authors in several different ways. Some objective characteristics were omitted from nursing diagnosis descriptions, such

Nursing Diagnosis 9

as the exact temperature measurement for mild, moderate, and severe (Miller-Carroll, 1988). When three types of hypothermia are collapsed into a single diagnosis, a defining characteristic, such as malnutrition, is inappropriate for inadvertent or intentional types.

The reviewed literature supported the notion that heat is lost by conduction, radiation, evaporation, and convection and yet these terms are not used to group characteristics within the nursing diagnosis label. In addition, the nursing diagnosis of hypothmia contains a variety of characteristics (Carpenito, 1987, 1989; Kim et al., 1989; Miller- Carroll, 1989; NANDA, 1990) that did not per- tain to the postanesthesia hypothermic patient arid yet this occurs in 12 to 16 million surgcal patients annually (Augustine, 1989, 1990). Vague- ness in defining characteristics for a nursing diagnosis may influence the extent to which nursing phenomena will be perceived as valid among other healthcare providers.

As these three nursing diagnoses are further developed, it is recommended that the four methods of heat loss (conduction, convection, radiation, and evaporation) be considered for inclusion. The literature from other disciplines also should be reviewed so that the world view of the concepts is represented.

Future research studies are needed to validate the three types of hypothenia in nursing practice to determine the applicability for nursing diagnosis inclusion. I t is recommended that nurses from clinical specialties validate the three types of hypothermia. For example, nurses practicing in the operating room and postanesthesia setting could validate inuduertent hypothenia; nurses practicing in the emergency room and intensive care could validate accidrntal hypothermia, and nurses practicing in the operatirig room and intensive care unit could validate intentional hypothermia. Inclusion of practicing nurses in nursing diagnosis validation, to define and clarify major characteristics for each type. can only strengthen the applicability of the derived diagnoses for nursing practice.

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Nursing Diagnosis 11

hypothermia: one nursing diagnosis or three?

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