Postoperative hypothermia—The chilling consequences

Home Study Program

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Home Study Program Postoperative hypothermia— The chilling consequences

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he article “Postoperative hypothermia—The chilling consequences” is the basis for this AORN Journal independent study. The behavioral objectives and examination for this program were prepared by Rebecca Holm, RN, MSN, CNOR, clinical editor, with consultation from Susan Bakewell, RN, MS, BC, education program professional, Center for Perioperative Education. Participants receive feedback on incorrect answers. Each applicant who successfully completes this study will receive a certificate of completion. The deadline for submitting this study is May 31, 2009. Complete the examination answer sheet and learner evaluation found on pages 1069-1070 and mail with appropriate fee to

AORN Customer Service c/o Home Study Program 2170 S Parker Rd, Suite 300 Denver, CO 80231-5711 or fax the information with a credit card number to (303) 750-3212. You also may access this Home Study via AORN Online at http://www.aorn.org/journal/homestudy/default.htm.

BEHAVIORAL OBJECTIVES After reading and studying the article on postoperative hypothermia, nurses will be able to

1. discuss the physiology of normothermia, 2. describe the implications of hypothermia, 3. identify methods of preventing postoperative hypothermia, and 4. explain Roy’s Adaptation Model as it applies to unintended hypothermia.

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This program meets criteria for CNOR and CRNFA recertification, as well as other continuing education requirements. A minimum score of 70% on the multiplechoice examination is necessary to earn 3.1 contact hours for this independent study. Purpose/Goal: To educate perioperative nurses about the consequences of postoperative hypothermia and methods of prevention.

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Home Study Program Postoperative hypothermia— The chilling consequences Kelly K. Good, RN; Jill A. Verble, RN; Janet Secrest, RN; Barbara R. Norwood, RN

H

ypothermia, defined as a core body temperature of lower than 36° C (96.8° F),1 is a common problem for patients undergoing surgery. Nurses have contributed to the literature on hypothermia, particularly in the area of shivering and treatment modalities. Much of the research demonstrating the direct physiological effects of hypothermia, however, is found in the medical literature. This article reviews research on the physiological effects of postoperative hypothermia, offering nurses additional evidence to support interventions for temperature correction in patients with hypothermia. Clinical practice guidelines for prevention and treatment of postoperative hypothermia are provided. Current research on effective rewarming measures also is discussed.

PHYSIOLOGY

OF

NORMOTHERMIA

Body temperature is the result of a balance between heat production and heat loss. Heat is a byproduct of the body’s natural metabolic processes, but as it is produced, it also is lost to the environment. Regulation of body temperature occurs through a negative feedback system in the central nervous system, primarily the hypothalamus. The hypothalamus acts as a thermostat, and as changes in body temperature occur, it initiates heat-increasing vasoconstriction or heat-decreasing vasodilatation. As a result, body temperature is maintained within a normal range, ensuring a constant rate of metabolism, enhanced nervous system conduction, and optimal skeletal muscle contraction.1

PATHOPHYSIOLOGY OF PERIOPERATIVE HYPOTHERMIA Hypothermia has long been recognized as problematic during the perioperative period. Events that can decrease body temperature during surgery include • a cold OR environment, • administration of unwarmed IV fluids, • medication-induced vasodilatation, • decreased basal metabolic rate, • anesthetic-induced impairment of the hypothalamic thermostat, • exposure of body cavities to room temperature air, and • loss of heat from the lungs when warm air in the lungs is mixed with unwarmed inhaled gases. In addition, general anesthesia lowers the threshold for vasoconstriction, which normally protects the body from hypothermia. This causes a 1° C

ABSTRACT •

UNPLANNED HYPOTHERMIA is commonly encountered in the perioperative period. Nursing has contributed to the literature on hypothermia with studies on shivering and treatment modalities; however, the direct physiological consequences of postoperative hypothermia have been reported mainly in the medical literature.

•

RESEARCH ON THE PHYSIOLOGICAL effects of postoperative hypothermia offers nurses further evidence to support interventions for temperature correction in patients with hypothermia. Evidence indicates that forced-air warming is the most effective method for warming hypothermic patients.

•

THE ROY ADAPTATION MODEL is explained as a framework for nursing care of patients with hypothermia. Clinical practice guidelines for unplanned perioperative hypothermia also are provided. AORN J 83 (May 2006) 1055-1066.

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Table 1 Causes and Physiological Consequences of Perioperative Hypothermia Definition of hypothermia Core body temperature lower than 36° C (96.8° F)

Causes of hypothermia

• • • • • • •

Cold OR suite Administration of unwarmed IV fluids Medication-induced vasodilatation Decreased metabolic rate Anesthesia-induced impairment of the hypothalamic thermostat Exposure of body cavities Heat loss from the lungs to warm inhaled gases

Consequences of hypothermia

• • • • • • • • • • •

Increased energy expenditure as a result of increased oxygen consumption Shivering due to hypothermia, which increases oxygen consumption by 400% to 500% Increased mortality particularly in patients < 55 years of age who experience prolonged hypothermia Decreased production of interleukin 2 (ie, a key mediator in various immune responses) Increased risk for cardiac events (eg, increased blood pressure, myocardial ischemia) for patients with coronary artery disease Increased need for transfusion of red blood cells, plasma, and platelets Dysfunction of extrinsic and intrinsic pathways of the coagulation cascade Increased incidence of surgical wound infection Increased need for postoperative mechanical ventilation Reduced medication metabolism with an increased duration of action Decreased production of new tissue and decreased repair of injured tissue compared to patients who are normothermic

to 5° C (1.8° F to 9° F) decrease in core body temperature during the first hour of general anesthesia.1 This decrease is caused by redistribution of heat from the warmer core to the periphery.2 Intravenous fluids that are not warmed and are administered at room temperature during surgery cause a decrease in mean body temperature of approximately 0.25° C (0.35° F).2 Hypothermia can increase the length of stay in the postanesthesia care unit (PACU) and is identified as

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one of the most frequent adverse outcomes in the immediate postoperative period.2

IMPLICATIONS OF POSTOPERATIVE HYPOTHERMIA It has long been apparent that patients’ body temperatures drop when patients are undergoing general anesthesia. Recognizing that patients whose body temperatures are decreased often experience higher incidences of complications in the postoperative period led to some of the initial research on hypothermia. A number of physiologic changes occur in the body with a drop in core body temperature below 36° C (96.8° F). Table 1 summarizes the causes and physiological consequences of perioperative hypothermia. Nurses play a pivotal role in preventing hypothermia and intervening for patients with hypothermia to minimize the physiological effects as well as to provide comfort. ENERGY EXPENDITURE. One group of researchers evaluated the effects of hypothermia on energy expenditure in the postoperative period.3 Rectal temperatures were measured in 24 adults between the ages of 18 and 79 years at frequent intervals before, during, and for several hours after surgery. By collecting and analyzing timed samples of expired air from a tight-fitting anesthetic mask with a lightweight valve, researchers were able to measure oxygen consumption and minute ventilation. Despite the many limitations of this study, it was determined that a decrease in rectal temperature of 0.2° C (0.3° F) produced a small increase in oxygen consumption (7%, n = 4), whereas a temperature decrease of 0.3° C to 1.2° C (0.4° F to 2.2° F) produced an average increase of 92% in oxygen consumption (n = 15). Patients whose temperature dropped more than 1.2° C (2.2° F), experienced an increase in

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oxygen consumption of 40%; however, most of these patients (n = 5) were older adults and were unable to increase their rate of metabolism to the same degree as younger patients. In addition, across all temperature changes, the increase in minute ventilation was proportional to the increase in oxygen consumption. EFFECT OF AGE ON HYPOTHERMIA. An early study demonstrated that patients older than 55 years of age are at an increased risk of becoming hypothermic after surgery, yet they do not have an increased mortality rate.3 In contrast, patients younger than 55 years of age who were subjected to prolonged hypothermia were less able to compensate for the decreased temperature, and the mortality rate for this group increased significantly as a result.4 SHIVERING AND OXYGEN CONSUMPTION. Hypothermia-induced shivering causes increased oxygen consumption. Shivering associated with cutaneous vasodilatation, which occurs during general anesthesia, not only causes discomfort for the patient but also increases the metabolic demand of the patient’s tissues by 400% to 500%.5 The dramatic increase in oxygen demand is compensated for by an increase in minute ventilation and cardiac output to facilitate oxygen uptake.6 Oxygen consumption can increase more than 65% with a decrease in core body temperature of 0.2° C (0.3° F) and up to 92% with reductions in temperature of 0.3° C to 1.2° C (0.4° F to 2.2° F).4 In addition to increased oxygen consumption, shivering was found to affect the measurements obtained via standard PACU monitoring. Heart rate and mean arterial blood pressure were found to be significantly higher in hypothermic patients.6 PROLONGED HYPOTHERMIA AND INCREASED MORTALITY. In one study, the temperature of each patient (N = 100) was measured before surgery; during surgery; after surgery (ie, time zero); and at two,

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four, and eight hours postoperatively. An association was found between prolonged hypothermia and mortality after surgery.4 Although intraoperative hypothermia and hypothermia at time zero were not associated with increased mortality rates, patients who were hypothermic two hours postoperatively had a significantly higher mortality rate compared to that of normothermic patients (ie, seven of 29 The results of one patients died compared to two of 45 patients [P < study suggest .01]). Mortality also was significantly increased in that maintaining patients who were hypothermic at four and eight intraoperative hours after surgery, and patients also were at innormothermia creased risk for postoperative complications if they and rapidly were hypothermic four hours after surgery. rewarming Despite the limitations of this study, the results sugpatients may gest that maintenance of intraoperative normotherlessen morbidity mia and rapid postoperative rewarming may lessen and improve morbidity and improve survival after surgery. survival after MORBID CARDIAC EVENTS. Hypothermia also has surgery. been identified as an independent predictor of morbid cardiac events (relative risk, 2.2; 95% confidence interval 1.1-4.7; P = .04) with a 55% decrease in risk when normothermia is maintained.7 During a three-year study period, researchers measured the relationship of body temperature to cardiac morbidity by assigning patients undergoing abdominal, thoracic, and vascular procedures (N = 300) to a routine thermal care group (n = 158) and a supplemental warming group (n = 142). All patients included in the study either AORN JOURNAL •

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had documented coronary artery disease or were considered to be at high risk for coronary disease. Cardiac outcomes were assessed in a double-blind fashion, and eight body sites were monitored with an electric thermometer. Mean core temperature in the hypothermic group was 35.4° C ± 0.1° C (95.7° F ± 0.18° F) compared to the mean core temperature of the normothermic group (36.7° C ± 0.1° C [98.0° F ± 0.18° F]) (P < .001). Morbid cardiac events occurred more often in the hypothermic group (6.3%) compared to the normothermic group (1.4%) (P = .02). NEED FOR BLOOD TRANSFUSIONS AND PLATELETS. In a Hypothermia meta-analysis comparing outcomes from 20 studies causes a on hypothermia, one dysfunction of the group of researchers evaluated the magnitude of differences in negative coagulation outcomes, such as an cascade pathways, increased need for red blood cells and platelets in the hypothermic group so mean compared to the norprothrombin time mothermic group.8 The researchers also evaluated and partial the resulting costs and the most beneficial intervenprothrombin time tion for preventing these outcomes. A total of 1,575 increase when patients were assigned to either the hypothermic or plasma normothermic groups for comparison of outcomes. temperature Overall, these groups did not differ in age, body decreases. surface area, or length of anesthesia; therefore, the differences in final outcomes were attributed to core body temperature. In the hypothermic group, there was an increased need for transfusion of red blood cells, plasma, and platelets (P < .05). According to supporting research,

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hypothermia causes a dysfunction of both the extrinsic and intrinsic pathways of the coagulation cascade.9 As a result, both the mean prothrombin time and the partial prothrombin time increase with a decrease in plasma temperature. Patients in the normothermic groups required 86% fewer units of red blood cells, 79% fewer units of plasma, and 78% fewer units of platelets than patients in the hypothermic group.8 The increased need for allogenic blood transfusions in the hypothermic group produces an additional risk to the patient because of the inherent risks of infection, transfusion reactions, and immune suppression associated with transfusions. OTHER ADVERSE OUTCOMES. Other adverse outcomes identified in the meta-analysis8 that were significantly higher in the hypothermic group included • increased incidence of surgical wound infection, • reduced medication metabolism, • increased incidence of morbid cardiac events (P < .05), and • increased need for postoperative mechanical ventilation. For example, in the normothermic group, health care-acquired infections occurred 64% less often, mortality rates were 55% lower, myocardial infarctions occurred 44% less often, and patients were 34% less likely to need mechanical ventilation compared to those in the hypothermic group. In addition, patients in the normothermic group experienced significantly shorter lengths of stay in the hospital (P < .05), spent 43% less time in the intensive care unit, and were discharged from the hospital 40% earlier. OTHER PHYSIOLOGIC IMPLICATIONS. Numerous studies have examined additional physiologic implications of hypothermia. For example, during intraoperative hypothermia, hepatic blood flow decreases, contributing to prolonged medication metabolism of many common anesthetic agents and an increased duration of

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action.10,11 Additionally, hypothermia profoundly affects the cardiovascular system by causing increased incidences of myocardial ischemia and postoperative cardiac morbidity, higher arterial blood pressure, and increased incidences of hypokalemia contributing to dysrythmias.12-14 One group of researchers found increased levels of norepinephrine and epinephrine in patients with hypothermia.15 Increased levels of catecholamines can cause coronary vasoconstriction, reducing blood flow to the coronary arteries.15 IMMUNE SYSTEM AND POSTOPERATIVE WOUND HEALING. Hypothermia also affects the immune system and postoperative wound healing. A group of researchers measured esophageal temperatures in 60 patients who were assigned to either a routine thermal care group (n = 30) or a forced-air warming group (n = 30).16 Venous blood samples were obtained before surgery and up to two days after surgery. The white blood cells were separated and frozen to test for cytokine production, mitogen-induced proliferation, and natural killer cell cytotoxicity. In this study, the core body temperature of the hypothermic group decreased approximately 1° C (1.8° F) and remained low until three hours after surgery, compared to the normothermic group that maintained normal body temperature throughout this same time period. In the hypothermic group, the mitogenic process by which the body produces new cells for the growth of new tissue and repair of injured tissue was less than that measured in the normothermic group. In addition, the production of interleukin 2, a key mediator in various immune responses, was less in the hypothermic group. As a result, it is likely that immune defense mechanisms will be impaired, increasing susceptibility to infections. Supporting these findings, researchers in another study evaluating

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the effects of hypothermia on wounds discovered that not only was the incidence of infection higher with hypothermic patients compared to normothermic patients, but the infection also contributed to delayed removal of sutures and longer lengths of stay in the hospital.17

PREVENTING POSTOPERATIVE HYPOTHERMIA In 1998, a multispecialty guideline development panel wrote clinical practice guidelines for the prevention of unplanned perioperative hypothermia that include preoperative, intraoperative, and postoperative management for preventing and treating hypothermia (Table 2).18 Preoperative management involves Interleukin 2 assessing the patient for risk factors of unplanned production perioperative hypothermia. Risk factors include a was less in the low temperature (ie, lower than 36° C [96.8° F]) on hypothermic admission and other signs of hypothermia, such as group; thus, shivering and piloerection. Specific nursing intervenimmune defense tions that are recommended to address these risk mechanisms may factors include applying warmed blankets and be impaired, socks and applying forcedair warming devices that increasing warm patients by convection. A thermostatically susceptibility to controlled heater delivers warm air through a hose infections. connected to a blanket through which the air is distributed evenly to the patient (Figures 1 and 2). Intraoperative prevention includes continuously assessing the patient for signs of hypothermia. Nursing interventions to treat hypothermia include applying warmed blankets, using forced-air warming devices, warming IV fluids AORN JOURNAL •

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TABLE 2

Summary of Clinical Practice Guidelines for the Prevention of Unplanned Perioperative Hypothermia1 Assessment Preoperative

Intraoperative

Postoperative

• Identify risk factors. • Assess patient’s temperature

• Identify risk factors. • Determine thermal comfort

• Identify risk factors. • Assess patient’s temperature

on admission.

• Determine thermal comfort level by asking patient if he or she is cold. • Assess patient for signs of hypothermia (eg, shivering, piloerection).

level by asking patient if he or she is cold before induction. • Assess patient for signs of hypothermia (eg, shivering, piloerection). • Monitor temperature continuously.

• •

on admission; if temperature is < 36° C (96.8° F); measure patient’s temperature at least every 30 minutes. Determine thermal comfort level by asking patient if he or she is cold. Assess for signs of hypothermia (eg, shivering, piloerection).

Intervention Preoperative

Intraoperative

Postoperative

• Institute preventive warming measures (eg, warm blankets, socks). • Institute active rewarming if temperature is < 36° C (96.8° F) (eg, forced air warming, warmed IV fluids).

• Institute passive insulation (eg, warm blankets, socks). • Institute active warming interventions (eg, increase ambient room temperature, warm IV fluids and irrigants, humidify and warm oxygen and anesthetic gases).

• If patient is normothermic,

•

institute preventive warming measures (eg, provide warm blankets, socks; increase ambient room temperature to between 20° C and 23.9° C [68° F and 75° F]; assess patient’s comfort level every 30 minutes; assess for signs of hypothermia; assess patient’s temperature before discharge). If patient’s temperature is < 36° C (96.8° F), apply forcedair warming blanket, warm IV fluids, warm oxygen, provide passive insulation, increase room temperature 20° C to 23.9° C (68° F to 75° F); evaluate patient’s temperature every 30 minutes.

1. American Society of PeriAnesthesia Nurses, "Clinical guideline for the prevention of unplanned perioperative hypothermia," Journal of PeriAnesthesia Nursing 16 (October 2001) 305-313. Also available at http://www.aspan.org/PDFfiles/HYPOTHERMIA_GUIDELINE10-02.pdf (accessed 7 March 2006).

and anesthetic gases, and humidifying anesthetic circuits. The circulating nurse can maintain ambient room temperature at 20° C to 23.9° C (68° F to 75° F). Guidelines for preventing and treating unplanned hypothermia suggest that maintaining a core body temperature above 36° C (96.8° F) during the intraoperative phase will result in a positive postoperative outcome.18 The guidelines also include postoperative interventions beginning with

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assessing the patient’s temperature and observing for signs of hypothermia (eg, shivering, piloerection). Even if the patient is normothermic, preventive warming measures are recommended, which include applying warm blankets. If the patient is hypothermic, applying a forced-air warming device is indicated.18 Forced-air warming consistently has proven to be more effective than • using cotton blankets, • using circulating water blankets,

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Figures 1 and 2 • Demonstration of an intraoperative patient undergoing forced-air rewarming.

•

warming humidified air, • using space blankets, and the environ• warming ment.7 Heat loss is minimized with forced-air warming so patients reach a normal body temperature faster compared to negative pressure rewarming (ie, causing vasodilation of peripheral blood vessels with warmth and subatmospheric pressure; the warmed blood then flows to the body’s core).19

SUPPORT FOR USE OF FORCED-AIR WARMING Findings that support the use of forced-air warming devices are validated in a study that measured the difference in time to rewarming and time to discharge from the PACU in three groups of patients treated with • radiant heat lights (n = 30), • warmed blankets (n = 31), and • forced-air warming devices (n = 29).20 The participants all had PACU admission temperatures lower than 35° C (95° F). There were no differences in the groups with respect to mean age, admission temperature, duration of anesthesia, and intraoperative fluid volume. An automatic electronic thermometer was used to monitor temperature changes after warming measures were initiated. Patients who were warmed with forced air achieved a temperature of 36° C (96.8° F) faster than patients in the other two groups, although this result did not reach statistical significance because of the large temperature variability within

the groups. When the data were analyzed with respect to the presence of shivering, the mean rewarming times were identical in all three groups. Of the patients who did not shiver (n = 46), however, those treated with a forced-air warming device achieved normothermia significantly faster than patients in the other groups (ie, 122 minutes for forced-air warming, 185 minutes for radiant heat lamps, 199 minutes for warmed blankets; P = .01). The results of this study clearly demonstrate the positive effect that rewarming can have on returning patients to normothermia.9 One study, however, did not find a difference between forced-air warming devices and fluid-filled warm circulating blankets, although the authors reported a AORN JOURNAL •

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difference and developed a protocol based on their study.21 In this study, 60 participants with temperatures lower than 35.4° C (95.7° F) in a surgical ICU were assigned randomly to one of three warming methods: • warmed cotton blankets, • fluid-filled warm circulating blankets, or • forced-air warming devices. Patients underwent a variety of surgical procedures, and there were no reported differences among the groups in gender, weight, age, admission temperature, or use of ventilator. The mean rewarmResearchers in one ing times for the forcedair warming device (ie, study were 195 minutes) and fluidfilled warm circulating concerned with blanket (ie, 220 minutes) were not significantly the weight of different, but both were significantly different from fluid-filled the mean rewarming time for warmed cotton blankets blankets (ie, 295 minutes). In the absence of (ie, 6 lbs) statistical support, the compared to the authors concluded that the forced-air warming device was the most weight of effective. They did not report the power calculaforced-air tion in the study, and warming blankets perhaps with a larger sample, this time differ(ie, 1 oz). ence may have been significant.21 In another study comparing forced-air warming devices to fluid-filled warm circulating blankets, however, patient’s undergoing forced-air warming achieved normothermia significantly faster (P < .001).22 Data were collected on only 32 patients admitted to the PACU with temperatures lower than 34.7° C (94.46° F). Furthermore, the researchers were

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concerned with the weight of the fluidfilled blankets (ie, 6 lbs) compared to the weight of the forced-air warming device (ie, 1 oz). INCREASED PATIENT COMFORT. Compared to the use of warm blankets, forced-air warming also has been associated with increased patient comfort, higher hemoglobin oxygen saturation in the blood, and decreased incidence of shivering.23 In a two-group experimental study, 91 adult patients were randomly assigned to either an experimental group that was warmed with circulated air or a control group that was provided with warmed cotton blankets that were replaced as needed. Each patient was admitted to the PACU with a temperature lower than 36° C (96.8° F). Core and surface body temperatures, hemoglobin oxygen saturation, and blood pressure measurements were obtained from each patient at 15-minute intervals until discharge from the PACU. In addition, patients were asked to rate their level of comfort. Results from this study indicated that there was a significant difference between the effects of the two warming measures on surface temperature (F = 15.36, P < .001), hemoglobin saturation (F = 2.95, P = .013), and perceived comfort (F = 5.26, P = .024). In this study, the differences between the two warming methods on blood pressure and core temperature were not found to be significant.23

A THEORETICAL MODEL NURSING PRACTICE

FOR

Roy’s Adaptation Model for Nursing24 provides an organized framework for planning nursing care for a patient with hypothermia during the perioperative period. In this model, the recipient of nursing care (ie, the patient) is viewed as an adaptive system. The patient receives input, or “stimuli,” from the external environment as well as from the internal environment (ie, himself or herself). The

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Figure 3 • Hypothermia as a behavioral response in Roy’s Adaptation Model.

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Stimuli (eg, cold OR, cold IV fluids, exposed body cavities)

person has four adaptive modes: physiological, selfconcept, role function, and interdependence. The outputs from the system Physiological are termed either adaptive mode or ineffective responses (Figure 3). Adaptive responses are those that promote integrity of the individual (eg, pain experienced after an acute injury, such as an ankle sprain, keeps the person Adaptive (eg, shivering, piloerection) or from further injuring the ineffective (eg, temperature < 36º C [96.8º F], arrythmias) joint), whereas ineffective behavioral responses responses do not contribute to the goals of the individual (eg, chronic pain, such as regional sympathetic dys- tate adaptation, stress may be placed on trophy, that is not protective and does other body systems (eg, shivering is an not serve any physiological purpose). adaptive response to raise body temperBoth responses provide additional ature, but it increases metabolic defeedback for the person as a system. mands, increases oxygen consumption, According to Roy, it is the nurse’s and causes discomfort), therefore, the responsibility to modify various stim- nursing process, although described as uli that could interfere with an individ- steps, in reality, occurs in a circular, ual’s successful adaptation to a given simultaneous manner.24 situation.24 As an adaptive system, the patient The patient, as an adaptive being, is responds to the environment to maintain faced with the challenge of recovering a normal temperature. Temperature regufrom surgery. This recovery becomes lation is affected by both external and more difficult in the presence of hypo- internal stimuli. Ineffective maintenance thermia, but nurses are able to modify of normal body temperature occurs when stimuli so that the patient is able to the magnitude of external and internal achieve a normal body temperature. stimuli are greater than the body’s ability Roy’s model outlines a six-step nursing to maintain a state of equilibrium. This is process to identify appropriate nursing an appropriate time for nursing interveninterventions, incorporating the clinical tion. By assessing and manipulating the practice guidelines (Figure 4). These six influencing stimuli as they relate to steps include hypothermia, nurses can help the patient achieve a temperature level necessary for • assessing behavior, normal physiological functioning. As a • assessing stimuli, establishing a nursing diagnosis, result, the patient’s cellular activity and • setting goals, body metabolism performs at a more • optimal level.24 • providing an intervention, and the results of the interASSESSING BEHAVIOR AND STIMULI. Using this • evaluating vention.24 framework to plan care for a patient with It is possible that in an effort to facili- hypothermia in surgery or returning AORN JOURNAL •

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Assess behavior (ie, signs of hypothermia)

Assess stimuli

Evaluate

(ie, environmental causes)

(eg, environment, signs of hypothermia)

Intervene

Diagnose

(eg, active/preventive treatments, guidelines)

(ie, temperature < 36º C [96.8º F])

Set goal (ie, temperature > 36.5º C [97.7º F])

Figure 4 • Roy’s six-step nursing process applied to a patient with postoperative hypothermia.

from surgery, the nurse first must identify how the patient is reacting to the decrease in body temperature. Assessment of behavior involves observation and measurement. An abnormally low temperature can result in what Roy terms behavioral manifestations such as an increased heart rate, increased blood pressure, cardiac arrhythmias, and shivering. When considering the stimuli that contributed to the state of hypothermia, the nurse must remember the physiological changes that occur with general anesthesia. In addition to anesthetic-induced impairment of the hypothalamic thermostat and decreased metabolic rate, the patient is exposed to a cold OR environment.25 DIAGNOSING HYPOTHERMIA, SETTING GOALS, AND INTERVENING. When the diagnosis of hypothermia is established, the goal or expected outcome becomes normothermia. Nursing interventions to warm the patient are cited in the guidelines and include warming the temperature of the room, limiting exposure by covering the patient with blankets, and using forcedair warming devices.18 Throughout the warming process, nurses continuously

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evaluate the patient’s improvement in temperature and tolerance to the warming measures. EVALUATING. The nurse continuously evaluates the behavioral adaptations of the patient to environmental stimuli and to interventions, which also are stimuli. Furthermore, nurses can administer medications (ie, stimuli) to inhibit shivering that will decrease metabolic demands and improve patient comfort.

SUMMARY It is not uncommon for patients undergoing surgery to become hypothermic because of anesthetic-induced impairment of thermoregulatory control and exposure to a cool OR environment. Although there are occasions when hypothermia is iatrogenic and induced for the purpose of the surgical procedure, more often hypothermia is an unintended consequence of the surgical experience. Hypothermia generally will persist for several hours unless warming measures are initiated. Research has demonstrated that postoperative hypothermia may result in several physiological alterations. Clinical practice guidelines have

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been developed that support frequent monitoring of the patient’s temperature during surgery and the postoperative period and provide specific interventions to prevent and treat hypothermia. Providing comfort measures always has been an integral part of nursing care. As the research has demonstrated, initiating warming measures for patients with hypothermia intraoperatively and postoperatively not only enhances their level of comfort, but also improves physiological outcomes. Prompt nursing interventions are warranted because of the potential complications of hypothermia. Forced-air warming has been demonstrated to be effective at restoring normothermia and for its ability to enhance patient comfort during the recovery process. Roy’s Adaptation Model provides nurses with a theoretical basis for caring for the perioperative patient with hypothermia. ❖ Kelly K. Good, RN, MSN, CRNA, is a nurse anesthetist at Anesthesiology Consultants Exchange, Chattanooga, Tenn. Jill A. Verble, RN, BSN, is a graduate nursing student in the anesthesia program at the University of Tennessee School of Nursing, Chattanooga, Tenn. Janet Secrest, RN, PhD, is an associate professor at the University of Tennessee School of Nursing, Chattanooga, Tenn. Barbara R. Norwood, RN, EdD, is an associate professor at the University of Tennessee School of Nursing, Chattanooga, Tenn.

NOTES 1. R Stoelting, “Autonomic nervous system,” in Pharmacology and Physiology in Anesthetic Practice (Philadelphia: Lippincott Williams & Wilkins, 1999) 619-627.

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2. K Panagiotis et al, “Is postanesthesia care unit length of stay increased in hypothermic patients?” AORN Journal 81 (February 2005) 379-392. 3. C Roe et al, “The influence of body temperature on early postoperative oxygen consumption,” Surgery 60 (July 1966) 85-92. 4. G J Slotman, E H Jed, K W Burchard, “Adverse effects of hypothermia in postoperative patients,” American Journal of Surgery 149 (April 1985) 495-501. 5. J Zwischenberger et al, “Suppression of shivering decreases oxygen consumption and improves hemodynamic stability during postoperative rewarming,” Annals of Thoracic Surgery 43 (April 1987) 428-431. 6. M Vaughan, R Vaughan, R Cork, “Postoperative hypothermia in adults: Relationship of age, anesthesia, and shivering to rewarming,” Anesthesia and Analgesia 60 (October 1981) 746-751. 7. S Frank et al, “Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial,” JAMA 277 (April 9, 1997) 1127-1134. 8. C Mahoney, J Odom, “Maintaining intraoperative normothermia: A metaanalysis of outcomes with costs,” The Journal of the American Association of Nurse Anesthetists 67 (April 1999) 155-163. 9. M Rohrer, A Natalie, “Effect of hypothermia on the coagulation cascade,” Critical Care Medicine 20 (October 1992) 1402-1405. 10. T Heier et al, “Mild intraoperative hypothermia increases duration of action and spontaneous recovery of vecuronium blockade during nitrous oxide-isoflurane anesthesia in humans,” Anesthesiology 74 (May 1991) 815-819. 11. K Leslie et al, “Mild hypothermia alters propofol pharmacokinetics and increases the duration of action of atracurium,” Anesthesia and Analgesia 80 (May 1995) 1007-1014. 12. RU Boelhouwer, H A Bruining, G L Ong, “Correlations of serum potassium fluctuations with body temperature after major surgery,” Critical Care Medicine 15 (April 1987) 310-312. 13. S M Frank et al, “Unintentional hypothermia is associated with postoperative myocardial ischemia. The Perioperative Ischemia Randomized Anesthesia Trial Study Group,” Anesthesiology 78 (March 1993) 468-476. 14. S M Frank et al, “Perioperative maintenance of normothermia reduces the incidence of morbid cardiac events. A randomized clinical trial,” JAMA 277 AORN JOURNAL •

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(April 9, 1997) 1127-1134. 15. S Frank et al, “The catecholamine, cortisol, and hemodynamic responses to mild perioperative hypothermia. A randomized clinical trial,” Anesthesiology 82 (January 1995) 83-93. 16. B Beilin et al, “Effects of mild perioperative hypothermia on cellular immune responses,” Anesthesiology 89 (November 1998) 1133-1140. 17. A Kurz, D I Sessler, R Lenhardt, “Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group,” The New England Journal of Medicine 334 (May 9, 1996) 1209-1215. 18. American Society of PeriAnesthesia Nurses, “Clinical guideline for the prevention of unplanned perioperative hypothermia,” Journal of PeriAnesthesia Nursing 16 (October 2001) 305-313. Also available at http://www .aspan.org/PDFfiles/HYPOTHERMIA_GUIDE LINE10-02.pdf (accessed 7 March 2006). 19. A Taguchi et al, “Negative pressure rewarming vs forced air warming in hypothermic postanesthetic volunteers,” Anesthesia and Analgesia 92 (January 2001) 261-266.

20. M Giuffre et al, “Rewarming postoperative patients: Lights, blankets, or forced warm air,” Journal of PeriAnesthesia Nursing 6 (December 1991) 387-393. 21. S Summers et al, “The effects of two warming methods on core and surface temperatures, hemoglobin oxygen saturation, blood pressure, and perceived comfort of hypothermic postanesthesia patients,” Journal of PeriAnesthesia Nursing 5 (October 1990) 354-364. 22. S Grossman, C Bautista, L Sullivan, “Using evidence-based practice to develop a protocol for postoperative surgical intensive care unit patients,” Dimensions of Critical Care Nursing 21 (September/ October 2002) 206-214. 23. D Ciufo, S Dice, C Coles, “Rewarming hypothermic postanesthesia patients: A comparison between a water coil warming blanket and a forced-air warming blanket,” Journal of Postanesthesia Nursing 10 (June 1995) 155-158. 24. C Roy, H A Andrews, The Roy Adaptation Model, second ed (Englewood Cliffs, NJ: Prentice Hall, Inc, 1999). 25. C Roy, S Roberts, In Theory Construction in Nursing: An Adaptation Model (Englewood Cliffs, NJ: Prentice-Hall, Inc, 1981).

Data Not Being Used to Improve Quality of Patient Care

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lthough the majority of US hospitals collect data on their patients’ race, ethnicity, and language preference, few are using the information to improve the quality of health care for their patients, according to a Feb 9, 2006, news release from the National Public Health and Hospital Institute. A study that surveyed the information-collection processes of 500 US nonfederal acute care hospitals found that more than three-quarters of hospitals gather data on patient race, and approximately half gather data on patient ethnicity and language. Researchers found that few of the hospitals that collect these data are using them to improve the quality of care for their patients. Less than 20% of the hospitals surveyed use the information to evaluate quality of care, use of health services, health outcomes, or patient satisfaction across different patient populations. The study also revealed that more than half of the hospitals that do not collect these patient data believe there is no need to do so. Those

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hospitals were likely to identify technology, funding, and legal limitations as barriers to information gathering. Researchers suggest that hospital staff members need to be educated on the importance of collecting these patient data and the effect that putting the data to use can have on the quality of care patients receive at their facility. In addition, the researchers also recommend that efforts be made to standardize race and ethnicity categories so facilities can accurately evaluate the quality of health care being provided to all patients. Researchers suggest that using data collected on race, ethnicity, and language is essential in working toward the elimination of racial and ethnic disparities wherever they may exist. New Study Indicates Majority of Hospitals Collect Patients’ Race, Ethnicity and Language Data; Yet Few Hospitals Use the Data to Improve Quality of Care (news release, Washington, DC: National Public Health and Hospital Institute, Feb 9, 2006).