* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Hypothermia in Trauma Running head: HYPOTHERMIA IN TRAUMA PATIENTS Hypothermia in Trauma Patients: Incidence, Pathology, Prevention & Treatment Frederick D. Watters University of Pennsylvania 1 Hypothermia in Trauma Abstract The purpose of the review is to examine the challenges of critically injured patients with co-existing or secondary hypothermia and the research published in the past decade addressing these issues. Using the search terms ‘trauma’ and ‘hypothermia,’ computerized searches of the MEDLINE, CINAHL, and Pre-MEDLINE databases were conducted. The primary research concerning hypothermia in trauma patients was organized into three general categories for the purpose of analysis: 1) Incidence, 2) Pathology, 3) Prevention and Treatment. The body of evidence is lacking in three main areas: 1) sample size, location, and continuity of care; 2) variability of injury severity and measurement; and 3) temperature measurement variations. Future research should focused on hypothermia during trauma resuscitation and nurses’ roles in initial recognition and treatment. The nursing literature must be updated to reflect the clinical research understanding of pathology and recommendations for practice. 2 Hypothermia in Trauma 3 Hypothermia in Trauma Patients: Incidence, Pathology, Prevention & Treatment In the late 1980’s and early 1990’s, the US healthcare system saw an unprecedented surge in severe trauma, primarily related to the incidence of penetrating injuries reaching epidemic proportions. The creation of a nationwide trauma system ushered in the concept of “the golden hour,” the critical timeframe for transport to definitive hospital care. This short window of opportunity has driven the evolution of advances in trauma resuscitation. Patients who would have died at the scene in years past are now arriving in the emergency room alive. Patients who would have died in the emergency room are surviving into the operating room. These advances in care have been accompanied by new problems that need to be addressed. One of these clinical challenges is hypothermia The late 1980’s saw a surge of research investigating the incidence of hypothermia in these trauma patients. Anecdotal evidence grew into an understanding of an insidious cycle of hypothermia, acidosis, and coagulopathy that was killing many patients despite their quick transport and care in the hands of highly trained medical professionals. By 1991, research studies in urban trauma centers had shown as many as 50% of major trauma victims will develop some degree of hypothermia, with 10% to 15% experiencing severe hypothermia (Gentilello & Jurkovich, 1996). Nursing care is essential to addressing the particular challenges of trauma hypothermia; critical care nurses must have an intimate knowledge of the pathology of this population as well as the skills to recognize, prevent, and treat these patients. Defining the Problem In its most general terms, hypothermia is defined as a core body temperature below 35°C. The traditional research literature and protocols have broken the designation down further into: mild hypothermia 35°C to 32°C; moderate 32°C to 28°C; and severe below 28°C (Tisherman, Hypothermia in Trauma 2002). Normally the human body is able to maintain its temperature in a very narrow range regardless of environment. Heat loss occurs through radiation, conduction, convection, and evaporation. A person under some type of cold stress may increase their physical activity, shiver, and increase food intake in an effort to create endogenously the heat necessary to maintain homeostasis. A severely injured patient is often unable to do any of these (Tisherman, 2002). During mild hypothermia, changes are subtle; however, as core temperature decreases, profound and far-reaching effects are seen in all major body systems. The body initially tries to conserve body heat by increasing metabolic activity and shivering, resulting in metabolic acidosis (Tisherman, 2002). As cooling progressing, breathing slows, level of consciousness drops, and with severe hypothermia, cardiac arrhythmias develop (Tisherman, 2002). In her synopsis of nursing knowledge necessary to face this challenge, Sedlack (1995) states, “Overall hypothermia complicates trauma care by interfering with ventilation and oxygenation; by causing vasoconstriction, which obscures arterial assessment and hampers venous access; by producing coagulopathy and increased blood loss; and by slowing hepatic metabolism and elimination of drugs” (p. 20-21). Hypothermia decreases kidney ability to reabsorb fluid and electrolytes resulting in “cold diuresis,” further complicating the clinical picture (Tisherman, 2002). Similar to shock, the process is progressive, starting as a protective function that rapidly progresses to major organ dysfunction and eventual death. Sedlack (1995), Tisherman (2002), and Gentilello & Jurkovich (1996) all suggest there are predisposing conditions, certain injuries, and iatrogenic causes of trauma hypothermia. Young, elderly, and alcohol-impaired patients are predisposed to hypothermia. Large wounds such as burns, significant abrasions, and open cavities as well as central nervous system injuries 4 Hypothermia in Trauma predispose patients to hypothermia. Additionally, hypothermia may results from the interventions commonly used to resuscitate a traumatic patient. Administration of medications can suppress the body’s ability to maintain heat production metabolically (Tisherman, 2002; Gentilello & Jurkovich, 1996; Sedlack, 1995). Use of unwarmed intravenous fluids, irrigations, and lavages as well as the stripping of clothing during assessment can cause hypothermia and significantly lower the temperature of an already hypothermic patient (Tisherman, 2002; Gentilello & Jurkovich, 1996; Sedlack, 1995). Review Process The purpose of the review is to examine the particular challenges of a critically injured patient with co-existing or secondary hypothermia. Using the search terms ‘trauma’ and ‘hypothermia,’ computerized searches of the MEDLINE, CINAHL, and Pre-MEDLINE databases were conducted. The hypothermia search was focused to include all of the possible sub-headings. The terms were combined and limited to research since 1992, conducted on human subjects, and published in the English language. This produced 61 articles. Accidental hypothermia, therapeutic hypothermia, military, pediatric, and laboratory studies were omitted. With these limits applied, along with the dropping of letters, opinions, and anecdotal case studies, 41 studies remained to be examined. Twenty-five of these studies were review articles. Twelve of these studies were primary research. After cross-referencing the reference lists of all 41 studies, as well as texts with chapters addressing hypothermia such as Tomaszewski (2001) and Tisherman (2002), an additional 3 studies were included in the review. In order to create a clear picture of research relating specifically to hypothermia prevention and treatment in trauma patients, several limits were used to omit research from this review that may have confounded resulting recommendations. Studies that exclusively 5 Hypothermia in Trauma 6 addressed what is termed ‘accidental hypothermia,’ or hypothermia primarily from environmental exposure, were excluded due to the fact that cold temperatures may be protective in an otherwise non-injured patient. This creates very different research modalities which do not apply to a massively injured, exsanguinating patient. Similarly, there has also been a lot of research, particularly in head trauma, concerning the use of therapeutic hypothermia. Again, this is a separate research category and falls outside the scope of research concerned with a traumatically injured patient in critical need of resuscitation, stabilization, and definitive surgical intervention. Researchers in therapeutic hypothermia have stated more research is needed before rapid rewarming and aggression treatment is withheld from this population (Tisherman, 2002; Kirkpatrick, Chun, Brown, & Simons, 1999; Tisherman, Rodriguez, & Safar, 1999). Military studies were omitted due to the different wounds sustained by this population (landmine injuries, shrapnel injuries, high velocity gunshot wounds, severe burns, etc.) compared to civilian trauma patients as well as the distinctive prehospital treatment and transport of military personnel. Pediatric studies were omitted due to different physiologic needs of children compared to adults. Laboratory studies and human ‘model’ studies were omitted due to their inability to reproduce the dynamic environment of trauma resuscitation and the endpoint of failed rewarming, death. A significant amount of research relating to the best method of temperature measurement has been conducted; this research was omitted as being beyond the scope of this paper (Fallis, 2002; Clemence, 2001; Giuliano, Scott, Elliot & Giuliano, 1999). These related areas of research show that there exists a large body of literature related to this subject; in order to understand temperature homeostasis in various patient populations, these areas should be examined separately. Hypothermia in Trauma 7 Discussion of the Literature The primary research concerning hypothermia in trauma patients was organized into three general categories for the purpose of analysis: 1) Incidence, 2) Pathology, 3) Prevention and Treatment. Table 1 includes detailed analysis of each study including objective, design, methods, sample, setting variables analyzed, results, conclusions, and implications. A series of meta-analyses, evidence-based practice programs, and state of the science papers will be used to both comment on the primary research and to synthesize implications of the entire body of knowledge. Incidence Hypothermia can begin to affect patients from the moment of injury; a study in Austria found that 80 out of 100 patients with minor injuries were hypothermic at the scene when initially treated by emergency crews (Kober et al., 2001). In order to examine trends in the incidence, prevention and treatment of hypothermia, several epidemiologic studies were conducted in the past decade. Three research studies retrospectively analyzed trauma center records to determine the frequency of hypothermia. Studies varied in size but tended to have samples representative of the general trauma population. The majority of patients were male, most received blunt and penetrating injuries, and many were in motor vehicle crashes. Mize, Koziol-McLain, & Lowenstein (1993) found that only 77% of the patients in their study had temperature assessed during trauma resuscitation, 10% of which were hypothermic. More importantly, they found that the more severely injured a patient, the less likely they were to have their temperature measured. Five years later a smaller study showed similar results; only 40% of patients had temperature measurement in the emergency department, 33.3% of which were hypothermic (Shreve, 1998). Both of these studies found a negative correlation between injury Hypothermia in Trauma 8 severity and temperature and a clear association between hypothermia and mortality. The absence of temperature measurement affects research as demonstrated by Shreve (1998), who was unable to show a statistical relationship between morality and temperature because none of the mortalities had a temperature measurement recorded. Hypothermia is a continuing issue beyond the resuscitation phase. Watts et al. (1999) found approximately 65% of their patients to be hypothermic on admission to the emergency department (ED); and lower temperatures correlated with longer ICU and total hospital stays. On arrival in the intensive care unit (ICU); 52.7% of trauma patients were shown to have a temperature less than 35°C (Rutherford et al., 1998). Furthermore, this study showed that spinal cord injuries were associated with high risk for hypothermia and hypothermia was associated with greater length stay and resource use. The incidence of hypothermia was independent of month of admission. Other research studies conducted in the past ten years, but not specifically designed to investigate incidence, offer very similar findings. Bernabei, Levinson & Bender (1992) found that 46% of trauma laparotomy patients arrived in the operating room (OR) with temperatures less than 36°C. Watts et al. (1998) found 38% of their patients to have temperature under 36°C. These studies, in addition to studies with similar design and purpose published in the decades prior, clearly show that hypothermia continues to be a major issue for trauma patients and needs to be better addressed by nurses and physicians in their initial stabilization and continuing treatment of severely injured individuals. Pathology Is the low temperature of severely injured patients who eventually succumb to their injuries simply a sign of the death process as their metabolism progressively fails? Studies controlling for injury severity have shown that blood loss, fluid requirements, and the presence Hypothermia in Trauma 9 of shock are higher in hypothermic patients (Gentilello & Jurkovich, 1996). Similar to the studies investigating hypothermia incidence, those addressing the pathology of hypothermia in trauma patients were conducted in a variety of settings, including emergency departments, operating rooms, and intensive care units. Primarily these studies address a concept referred to by Rotondo & Zonies (1997), as the “trauma triad of death,” or by Moore (1996) as “the bloody vicious cycle.” Active hemorrhage, iatrogenic factors, cellular shock, tissue injury, massive transfusions, and pre-existing diseases all combine with hypothermia, acidosis, and coagulopathy to form a lethal physiological state (Moore, 1996). During the early nineties, studies proved this lethality of hypothermia in trauma laparotomy with as many as 90% of deaths occurring in the coldest patients, with a four-fold increase in blood loss, and a significant correlation between hypotension and hypothermia (Bernabei et al., 1992). There has been a large shift in the understanding of hypothermia over the past decade; the abbreviated laparotomy and damage control approach have been developed to address this issue specifically (Moore, 1996). It was hypothesized that the coagulopathies associated with trauma hypothermia are related to blood transfusions as well as the breakdown in the normal clotting process. Research shows that standard coagulation assays conducted at 37°C do not adequately reflect the clotting dysfunction in a hypothermic critically ill patient; and correction of hypothermia alone can correct the coagulopathies (Gubler, Gentilello, Hassantash, & Maier, 1994). This finding supports the damage control approach of early transfer to the ICU for aggressive rewarming prior to definitive surgical closure. In an attempt to determine which patients should receive the abbreviated laparotomy with damage control approach and aggressive rewarming treatments, Cosgriff et al. (1997) strove to create a formula for predicting life-threatening coagulopathies in trauma patients receiving Hypothermia in Trauma 10 transfusions. They found a systolic blood pressure less than 70mmHg, a pH less that 7.10, a temperature less that 34°C, and ISS greater than 25 was associated with a 100% mortality rate (Cosgriff et al., 1997). These life-threatening coagulopathies were investigated in a similar study with larger sample; patients with temperature below 34°C have significant alterations in platelet and clotting enzyme function, lower blood pressures and heart rates, and increased mortality (Watts et al., 1998). Severe trauma is invariably associated with large amounts of tissue damage, resulting in the release of thromboplastin, leading to hypercoagulation and tissue hypoxia; “…while hypothermia does affect coagulation, the hypercoagulability that is the result of severe trauma seems to allow the body to compensate for some of this hypothermic alteration” (Watts et al., 1998, p. 853). Watts et al. (1998) found that their coldest patients’ blood was able to clot but at a much slower rate. When controlling for injury severity, Watts et al. (1998) found that hemorrhage may well lead to hypothermia but clinically hypothermia seems related to shock rather than merely volume loss. These findings are limited, however, by the fact that only prehospital fluid requirements were included in the study and the very short transport times for all included patients. Despite this limitation or others in individual studies, the mortality rates associated with hypothermia in trauma prompted Gentilello & Jurkovich (1996) to suggest a very different severity definition for guidance of treatment: mild hypothermia 36°C to 34°C; moderate hypothermia 33.9°C to 32°C; and severe hypothermia below 32°C. This change has not been adopted by the entire research or practice literature but does reflect a valid point; declining temperature in a critically injured patient in a major warning sign of impending complications. Aggressive treatment is needed. All of the authors urge the conduction of large, multi-center Hypothermia in Trauma 11 studies to continue to better understand these key physiological variables; this will help nurses and physicians predict which patients will suffer “the bloody vicious cycle.” Another frontier of understanding the pathology of hypothermia in trauma patients is the relationship between hypothermia and cellular levels of adenosine triphosphate (ATP). Seekamp, von Griensven, Hildebrandt, Wahlers, & Tscherne (1999) compared trauma patients, 55% of whom were hypothermic, to patients undergoing voluntary coronary bypass and knee surgery. Therapeutic hypothermia in elective surgery preserves ATP storage and maintains aerobic metabolism thus reducing ischemia; however, hypothermia in trauma patients is caused by insufficient heat production due to depletion of ATP stores under anaerobic conditions (Seekamp et al., 1999). This study found that low plasma levels of ATP combined with hypothermia predispose patients to severe complications, specifically multiple organ dysfunctions. The implications of this study and other animal studies investigating the same process could eventually result in the administration of ATP-MgCl2 during trauma resuscitation in order to reverse cellular dysfunction; Seekamp et al. (1999) suggest the need for considerable research before this is added to the treatment options presently available. Prevention & Treatment Prevention and treatment of hypothermic trauma patients depend on the severity of injury, severity of hypothermia, and resources available at the scene and receiving hospital. Treatment options can be classified as: 1) passive external rewarming; 2) active external rewarming; and 3) active core rewarming. The three categories are not exclusive but rather build upon each other as hypothermia becomes more severe; all three levels of rewarming are necessary. Nurses and physicians who care for trauma victims not only need an understanding of Hypothermia in Trauma 12 the pathology of hypothermia, they need to understand the basis and underlying logic for choosing prevention and treatment methods in different situations. Passive External Rewarming All trauma patient should receive hypothermia prevention and treatment starting in the field and continuing until they are fully rewarmed (Tisherman, 2002). Passive external rewarming refers to several basic measures: wet clothing removal; reducing airflow over the body to reduce heat loss due to convection; raising transport unit, trauma resuscitation, and emergency room temperatures; covering the head, and wrapping in warm blankets (Peng & Bongard, 1999). There has been little research into the merits of blankets, room temperature, and convection alone; however, there have been various studies of their effectiveness on patients in surgery under general anesthesia (Goodlock, 1995). This is a very different population and findings may not fully apply to the specific difficulties faced by trauma patients. Intraoperative studies have demonstrated the equal effectiveness of warm cotton blankets and metallic plastic blankets (Goodlock, 1995); however, the aluminum ‘space blankets’ do not conform well to body surfaces resulting in convective and conductive heat loss (Gentilello & Jurkovich, 1996). Passive external rewarming relies on the patient’s own rewarming mechanisms to generate heat; this requires tremendous energy and oxygen consumption, which an injured patient often does not have to spare (Gentilello & Jurkovich, 1996). Specifically, passive rewarming of a patient with intact thermoregulation may result in anaerobic metabolism, lactic acidosis, and significant cardiopulmonary stress; anesthetic and neuromuscular blocking agents can minimize this process but do not treat the clotting and cardiac issues that also occur in hypothermia (Gentilello, 1995). Passive rewarming is still the easiest and least expensive method available. Active External Rewarming Hypothermia in Trauma 13 Active external rewarming refers to the use of heating blankets, convective air blankets, and radiant warmers. In addition to increased rewarming rates with active external rewarming, Kober et al. (2001) showed that ‘resistive heating,’ their term for active rewarming, during prehospital transport increases thermal comfort, reduces pain and anxiety, and improves patient satisfaction with care. Their study only addressed patients with minor injuries; however, the patients supplied with an electric and cotton blanket showed oral temperature increases of 0.8°C per hour compared to the patients covered in blankets alone who cooled 0.4°C per hour during transport. Kober et al. (2001) found that even these patients with minor injuries were at risk for hypothermia if not actively rewarmed; the mean core temperature of the 100 patients was 35.5°C upon admission to the hospital. Much of the research on efficacy of different heating methods such as fluid-filled blankets and radiant warmers took place more than ten years ago. Synopses of the results of these studies are available in many different state of the science papers as well as critical care texts. Watts et al. (1999) strove to examine the efficiency of rewarming methods that have been used by prehospital crews for years with or without research proving their usefulness. Although two of their treatment groups included active internal rewarming with warmed intravenous fluids, this study actually found that patients receiving hot packs under the axilla, behind the head, and on the abdomen, retained more heat. Watts et al. (1999) suggest that this simple active rewarming method is one of the least used interventions in prehospital and resuscitation studies despite its effectiveness. Convective air warmers, otherwise known as forced-air rewarming blankets, are in use in many emergency departments throughout the country. These devices use a disposable plastic or paper blanket with slits on the patient side to create a warm air space around the patient. Hypothermia in Trauma 14 Properly creating a 43°C microenvironment around the patients, the temperature necessary to actively stop heat loss, requires a substantial portion of the body surface be covered, limiting access to the patient (Gentilello & Jurkovich, 1996). A recent nursing-centered study by Cohen, Hayes, Tordella, & Puente (2002) found this limitation to be a major drawback of this method of rewarming. Their patients received one of three interventions: 3 pre-warmed (105°C) cotton blankets; a reflective blanket with head covering over 1 pre-warmed cotton blanket; or a forcedwarm-air inflatable blanket. Cohen et al. (2002) found no significant difference in rewarming rates between the three methods. More important for nursing staff was the finding that the forced-warm-air blanket was difficult to work around during resuscitation; this method received the worst scores on ease of use, convenience, and access. Nurses also reported that heated cotton blankets needed frequent changing and reflective blankets with head coverings could not be used if the patient was on a backboard. Cohen et al. (2002) suggest that since each rewarming method shows similar results, nurses should use the intervention most readily available and most effective for the particular patient and setting. For example, Peng & Bongard (1999) suggest that in trauma patients with alcohol intoxication, forced-air rewarming may be more effective due to peripheral vasodilation, but in shock may be no more efficient than cotton blankets due to peripheral vasoconstriction. Active Core Rewarming Aggressive active external rewarming should not be used as the sole intervention in severe hypothermia due to afterdrop and aftershock. Afterdrop refers to a core temperature drop of 2° to 3°C during the first 30 minutes of external only rewarming which has been associated with ventricular fibrillation; cold, acidotic, blood, returning to the heart can cause cardiac collapse (Sedlack, 1995). During hypothermia, intravascular fluid is shifted into the core; the Hypothermia in Trauma 15 kidneys respond by excreting an excess of fluid, a process known as “cold diuresis” (Sedlack, 1995). When surface tissues are rewarmed first, they vasodilate, creating a relative hypovolemia; this results in hypotension (Sedlack, 1995). Therefore, passive rewarming and active external rewarming must serve as adjuncts to care when a clinician is faced with a severely hypothermic trauma patient. The core of the body must be warmed first. Leben, Tryba, Bading, & Heuer (1996) confirmed this when they found infusing trauma patients with a fluid warmer and warming with convective blankets prevented afterdrop, reduced length of intubation, and length of stay in the intensive care unit. Active core rewarming refers to methods including airway rewarming; heated peritoneal or pleural lavage; infusion of warmed intravenous fluids and blood products; and extracorporeal circulatory rewarming. Airway rewarming is considered a means of preventing respiratory heat loss, not a method of core rewarming; it has shown little efficiency when used alone (Gentilello & Jurkovich, 1996). No studies have been conducted in recent years comparing peritoneal or pleural lavage to other methods; however, both are used extensively to rewarm trauma patients, especially with moderate or severe hypothermia (Gentilello & Jurkovich, 1996). Warmed intravenous (IV) and blood products are not only an excellent way to prevent heat loss; they actively warm a hypothermic patient. As mentioned above, Leben et al. (1996) reconfirmed this already accepted method. The length of tubing and infusion rate can have significant effects on the actual delivered temperature of fluid. Handrigan, Wright, Becker, Linakis, & Jay (1997) showed that adequately warmed fluids for IV or lavage is achievable by: 1) preheating fluid to 60°C when using long segments of tubing; 2) preheating fluid to 40°C when using short segments of tubing; and 3) administering fluids in rapid boluses rather than continuous drips. Hypothermia in Trauma 16 The use of warm IV fluids as a warming technique; however, is limited by the fluid requirements of the patient (Gentilello & Jurkovich, 1996). In their early investigation or extracorporeal rewarming, Gentilello, Cobean, Soderberg, & Jurkovich (1992) were able to warm hypothermic patients to 35°C in an average of 39 minutes rather than 3.23 hours from the same start point. In addition, they found that this rapid reversal of hypothermia reduced organ failure, fluid requirements, ICU stay, and increased survival significantly. Gentilello et al. (1992) had developed the used of Continuous Arteriovenous Rewarming (CAVR); this method is similar to arteriovenous hemofiltration with the addition of a fluid-warmer in the circuit. Gentilello, Jurkovich, Stark, Hassantash, & O’Keefe (1997) expanded on these findings by comparing hypothermic trauma patients treated with CAVR to patients receiving warm IV fluids, airway rewarming, convective air blankets, and head covering. They were able to show that the patients rapidly rewarmed with CAVR had less fluid requirements, a much lower risk of early mortality, fewer organ failures, and lower oxygen requirements. Gentilello et al. (1997) did find a higher incidence of acute respiratory distress syndrome and longer intensive care unit stay in CAVR patients; however, they felt this was because more of the CAVR patients survived initial resuscitation and later succumbed to their injuries. Most importantly, this method warms the core blood supply without the dangers of afterdrop or aftershock. Extracorporeal rewarming using cardiopulmonary bypass has been the standard of treatment for severely hypothermic patients for some time; however, this method requires a degree of anticoagulation that is often ill advised for a patient already faced the trauma triad of death (Lapointe & Von Rueden, 2002). Despite this, in patients with deep hypothermia and cardiac arrest, it is still the treatment of choice and does not seem to cause long-term effects (Walpoth et al. (1997). Patients who require these aggressive active internal rewarming methods Hypothermia in Trauma 17 are at the greatest risk for developing severe cardiac arrhythmias and the coagulopathies associated with acidosis and hypothermia; this level of care requires highly trained, extremely vigilant nursing at all times. Nurses in all clinical areas have the ability to recognize hypothermia and begin measures to prevent heat loss; passive external, active external, and active internal rewarming methods should all be familiar in order to treat the particular challenges of individual patients. Conclusions The research addressing hypothermia in traumatically injured patients offers a successful example of research and practice integration with continuous improvement of techniques over time. As trauma incidence has increased, clinical practitioners and researchers have responded. Studies showing high levels of mortality in hypothermic trauma patients resulted in investigation of the intricacies of the pathology of hypothermia, comparison of the utility of various prevention and treatment methods, and development of completely new forms of rapid core rewarming. The basic premises of how and why the body reacts to hypothermia are fairly well understood; and the methods of rewarming are approaching the physiological limits of the patients. The body of evidence is most lacking in three main areas: 1) sample size, location, and continuity of care; 2) variability of injury severity and measurement; and 3) temperature measurement variations. Although several large, multi-center studies are referenced in the literature, they were conducted more than 15 years ago. Almost all of the studies in this review had sample sizes smaller than 100 and most fewer than 15 per treatment group. Larger samples are needed to give statistical power and clinical significance to the research. Also, considering the evidence given by Mize et al. (1993) that many trauma patients are not having their temperatures assessed Hypothermia in Trauma 18 despite severe injuries and hypothermia, updated multi-centered research investigating the progress in addressing this issue is needed. Moreover, almost none of the studies published concerning trauma hypothermia specifically focuses on the nursing-centered care of hypothermia prevention and treatments during trauma resuscitation. To synthesize data from the entire body of research one must make conclusions based on the temperatures of patients when transferred to the operating room or intensive care unit. In addition to a lack of studies focusing specifically on trauma resuscitation, few studies sought, within their design, to track the temperature management of patients from the field through their entire treatment process. To aid in clinical and policy decisions concerning hypothermia prevention, the areas of greatest danger must be identified and best means of addressing temperature loss in that arena delineated. Although not a research study, Aragon (1999) offers an excellent example of this process. Specific results have yet to be published; however, in a major facility investigation and improvement program in Orlando, Florida, a team was created to study every area of care where hypothermia can be recognized and treated from the prehospital teams, through the emergency rooms, radiology suites, operating rooms, and critical care units (Aragon, 1999). New protocols were written and measures were taken to insure they were followed, such as posters reminding staff of hypothermia issues. Specifically this study recommended the creation of critical checklists, including documentation of temperature along with other vital signs at every point in a trauma patients care (Aragon, 1999). In addition to location variation among research studies, the samples in this review had wide ranges and methods of measuring injury severity, thus limiting the application of findings to the creation of protocols for use with all patients. Two studies used the APACHE II scoring system; however, this system only accounts for the lowest temperature in a 24-hour period and Hypothermia in Trauma 19 therefore does not measure progressive heat loss or gain in the resuscitation phase (Rutherford et al., 1998; Gubler et al., 1994). Most studies used the Injury Severity Score (ISS), a system assigning each anatomical injury an abbreviated injury score (AIS), that when combined provides an overall score for patients with multiple injuries. Its weaknesses are that any error in AIS scoring increases the ISS error, many different injury patterns can yield the same ISS score and injuries to different body regions are not weighted. Also, as a full description of patient injuries is not known prior to full investigation & operation, the ISS (along with other anatomical scoring systems) is not useful as a triage tool. (Baker, S. P. et al., 1974, as referenced by Trauma Scoring) In addition to these internal weaknesses, the mean ISS score varied widely among the studies in this review from 8.9±9.6 to 32±8.3 (see Table 1 for details). The studies focusing on pathology tended to address patients with higher ISS scores than the studies addressing prevention and treatment. Temperature was found to correlate negatively with ISS (Mize et al., 1993; Shreve, 1998); and when stratified by ISS, hypothermic patients have significantly higher mortality rates than patients with the same ISS who remain warm (Gentilello, 1995). Additionally, Watts (1998) found the Glasgow Coma Score (GCS) and Revised Trauma Score (RTS) also correlate to hypothermia. ISS is a measure of anatomic injury; Revised Trauma Score is a measure of physiologic derangement; Bernabei, et al., (1992) found trauma score to be a much better predictor of hypothermia than ISS. Since all levels of ISS score found deleterious effects of hypothermia, it would be useful to take the research literature closer to clinical reality and use the Trauma Score-Injury Severity Score (TRISS) system as a measure consistently. The TRISS system integrates ISS, GCS, and blood pressure (Trauma Scoring); this would allow for clearer comparisons between research study designs, samples, and settings. Hypothermia in Trauma 20 The initial recognition of hypothermia is likely to be made by nurses during the assessment of vital signs. Research has shown significant problems with consistent measurement practices ranging from complete omission to varying results from different measurement techniques. The reviewed research studies used oral, rectal, airway, tympanic, and pulmonary artery temperatures; these variations in the literature make substantive conclusions somewhat difficult. An entire separate body of evidence exists concerning the best method of temperature assessment (Fallis, 2002; Clemence, 2001; Giuliano, Scott, Elliot & Giuliano, 1999); however, during the initial stages of trauma resuscitation oral, rectal, and tympanic temperatures are most often used (Peng & Bongard, 1999). Only research conducted in the operating room or ICU usually has the luxury of the ‘gold-standard’ pulmonary artery temperature. The variations across the body of research also become a challenge when one seeks to create clinical protocols relating to treatment and prevention at various temperature ranges. Some of the research defines a temperature less than 36°C as hypothermic, some less than 35°C. Most of the literature considers temperatures over 32°C mild hypothermia. Gentilello & Jurkovich (1996) and Gentilello (1995) suggest narrowing the ranges for treatment modalities significantly to 36° to 34°C as mild, 33.9°C to 32°C as moderate, and below 32°C as severe. The lethal reactions to temperatures below 32°C have been clearly delineated in the trauma hypothermia research. These recommendations are not reflected throughout the research literature, especially research designed specifically for consumption by nurses (Lapointe & Von Rueden, 2002; Cochrane, 2001; Fritsch, 1995). As research is focused on trauma resuscitation and nurses’ roles in initial recognition and treatment of hypothermia, the nursing literature must be updated to reflect the most current understanding of pathology and recommendations of researchers and clinicians. Hypothermia in Trauma 21 This integration of research with practice can be seen in the Hospital of the University of Pennsylvania Trauma Center protocols for hypothermia treatment; this policy insists that all trauma patients must have temperature assessed within 30 minutes of arrival to the trauma bay (Reilly, Gracias, Fitzpatrick, 1999). The policy has clear and specific recommendations for each level of hypothermia severity including aggressive prevention measures for all patients, active external warming for temperatures less than 36°C, active internal warming for temperatures less than 35°C, and external veno-venous rewarming for temperatures less than 34°C (Reilly, Gracias, Fitzpatrick, 1999). In keeping with the recommendations of the research literature, this policy also has specific recommendations for measures in each phase of care from trauma bay, to radiology, to OR, and ICU (Reilly, Gracias, Fitzpatrick, 1999). The currently accepted standard of care is to prevent and treat hypothermia from the initial scene, through the primary assessment during trauma resuscitation, and beyond into stabilization. The advanced trauma life support (ATLS) guidelines from the Committee on Trauma of the American College of Surgeons continually urge the importance of temperature control and aggressive efforts to avoid and treat hypothermia, including the specific trauma hypothermia temperature range definitions suggested by the research literature (Committee on Trauma, American College of Surgeons, 1997). The Society of Trauma Nurses also trains nurses to begin prevention and treatment of hypothermia as soon as the primary assessment is completed (Society of Trauma Nurses, 2003). They offer warming strategies by department and, in the hemorrhagic shock chapter, specifically address the pathophysiologic consequences of hypothermia. The research literature, the policies of leading hospitals, and the recommendations of trauma surgeon and nursing organizations all stress the importance of prevention and treatment, early and continually, throughout patient care. Hypothermia in Trauma 22 Hypothermia has been clearly associated with coagulopathies, hypotension, acidosis, and high mortality. More remains to be understood about the effects of hypothermia in trauma on the physiology of patients; the future may see the use of therapeutic hypothermia for head trauma, ATP treatment to reverse adverse effects, and aggressive rewarming taking place early in resuscitation. Trauma care clinicians, especially nurses, will continue to be at the forefront of prevention, recognition, treatment, and research in hypothermia, thus pushing back the definition of survivable injury. Hypothermia in Trauma 23 References Aragon, D. (1999). Temperature management in trauma patients across the continuum of care: The TEMP group. AACN Clinical Issues, 10(1), 113-123. Bernabei, A. F., Levinson, M. A., & Bender, J. S. (1992). The effects of hypothermia and injury severity on blood loss during trauma laparotomy. The Journal of Trauma, 33(6), 835-839. Clemence, B. (2001). Back to basics: Monitoring trauma patients for hypothermia induced by treatment in the emergency department. Journal of Emergency Nursing, 27(6), 610-611. Cochrane, D. A. (2001). Hypothermia: A cold influence on trauma. International Journal of Trauma Nursing, 7(1), 8-13. Cohen, S., Hayes, J. S., Tordella, T., Puente, I. (2002). Thermal efficiency of prewarmed cotton, reflective, and forced-warm-air inflatable blankets in trauma patients. International Journal of Trauma Nursing, 8(1), 4-8. Committee on Trauma, American College of Surgeons. Advanced trauma life support for doctors. Student course manual. Chicago: American College of Surgeons, 1997. Cosgriff, N., Moore, E. E., Sauaia, A., Kenny-Moynihan, M., Burch, J. M., & Galloway, B. (1997). Predicting life-threatening coagulopathy in the massively transfused trauma patient: Hypothermia and acidosis revisited. The Journal of Trauma: Injury, Infection and Critical Care, 42(5), 857-862. Fallis, W. M. (2002). Monitoring temperature in trauma patients: New research and new technologies. Journal of Emergency Nursing, 28(5), 471-472. Fritsch, D. E. (1995). Hypothermia in the trauma patient. AACN Clinical Issues, 6(2), 196-211. Hypothermia in Trauma 24 Gentilello, L. M., Cobean, R. A., Offner, P. J., Soderberg, R. W., & Jurkovich, G. J. (1992). Continuous arteriovenous rewarming: Rapid reversal of hypothermia in critically ill patients. The Journal of Trauma, 32(3), 316-327. Gentilello, L. M. (1995). Advances in the management of hypothermia. Surgical Clinics of North America, 75(2), 243-255. Gentilello, L. M., Jurkovich, G. J. (1996). Hypothermia. In R. R. Ivatory & C. G. Cayten (Eds.), The Textbook of Penetrating Trauma (pp. 995-1006). Baltimore: Williams & Williams. Gentilello, L. M., Jurkovich, G. J., Stark, M. S., Hassantash, S. A., & O’Keefe, G. E. (1997). Is hypothermia in the victim of major trauma protective or harmful? Annals of Surgery, 226(4), 439-449. Goodlock, J. L. (1995). Methods of rewarming the hypothermic patient in the accident and emergency department. Accident and Emergency Nursing, 3, 114-117. Gubler, K. D., Gentilello, L. M., Hassantash, S. A., & Maier, R. V. (1994). The impact of hypothermia on dilutional coagulopathy. The Journal of Trauma, 36(6), 847-851. Giuliano, K. K., Scott, S. S., Elliot, S., Giuliano, A. J. (1999). Temperature measurement in critically ill orally Intubated adults: A comparison of pulmonary artery, core, tympanic, and oral methods. Critical Care Medicine, 27(10), 2188-2193. Handrigan, M. T., Wright, R. O., Becker, B. M., Linakis, J. G., & Jay, G. D. (1997). Factors and methodology in achieving ideal delivery temperatures for intravenous and lavage fluid in hypothermia. American Journal of Emergency Medicine, 15(4), 350-353. Kober, A., Scheck, T., Fulesdi, B., Lieba, F., Vlach, W., Friedman, A., & Sessler, D. (2001). Effectiveness of resistive heating compared with passive warming in treating Hypothermia in Trauma 25 hypothermia associated with minor trauma: A randomized trial. Mayo Clinical Procedures, 76, 369-375. Kirkpatrick, A. W., Chun, R., Brown, R. & Simons, R. K. (1999). Hypothermia and the trauma patient. Canadian Journal of Surgery, 42(5), 333-343. Lapointe, L. A. & Von Rueden, K. T. (2002). Coagulopathies in trauma patients. AACN Clinical Issues, 13(2), 192-203. Leben, J., Tryba, M., Bading, B., & Heuer, L. (1996). Clinical consequences of hypothermia in trauma patients. Acta Anaesthesiologica Scandinavica Supplementum, 109, 39-41. Mize, J., Koziol-McLain, J., & Lowenstein, S. R. (1993). The forgotten vital sign: Temperature patterns and associations in 642 trauma patients at an urban level I trauma center. Journal of Emergency Nursing, 19(4), 303-305. Moore, E. (1996). Laparotomy for the hypothermia, acidosis, and coagulopathy syndrome. American Journal of Surgery, 172, 405-410. Peng, R. Y., Bongard, F. S. (1999). Hypothermia in trauma patients. Journal of the American College of Surgeons, 188(6), 685-696. Reilly, P. M., Gracias, V. H., Fitzpatrick, M. K. (1999). Hypothermia. [Clinical Policy]. (Available from Division of Traumatology and Surgical Critical Care University of Pennsylvania Health System, 3440 Market Street, First Floor, Philadelphia, PA, 19104). Rotondo, M. F., & Zonies, D. H. (1997). The damage control sequence and underlying logic. Surgical Clinics of North America, 77, 761-777. Rutherford, E. J., Fusco, M. A., Nunn, C. R., Bass, J. G., Eddy, V. A., & Morris, J. A., Jr. (1998). Hypothermia in critically ill trauma patients. Injury, 29(8), 605-608. Hypothermia in Trauma 26 Seekamp, A., van Griensven, M., Hildebrandt, F., Wahlers, T., & Tscherne, H. (1999). Adenosine-triphosphate in trauma-related and elective hypothermia. The Journal of Trauma: Injury, Infection and Critical Care, 47(4), 673-683. Sedlack, S. K. (1995). Hypothermia in trauma: The nurse’s role in recognition, prevention, and management. International Journal of Trauma Nursing, 1(1), 19-26. Shreve, W. S. (1998). Adherence to standards of care and implications of body temperature measurement in trauma patients. Journal of Trauma Nursing, 5(4), 85-91. Society of Trauma Nurses. (2003). Advanced Trauma Care for Nurses. Provider Manual. Hotz, H., Henn, R., Lush, S., Hollingsworth-Fridlund, P. (Eds.). Santa Fe, NM: Society for Trauma Nurses. Tisherman, S. A. (2002). Hypothermia, cold injury, and drowning. In A. B. Peitzman, M. Rhodes, C. W. Schwab, D. M. Yealy, & T. C. Fabian (Eds.), The Trauma Manual: Second Edition (pp. 404-410). Philadelphia: Lippincott Tisherman, S. A., Rodriguez, A., & Safar, P. (1999). Therapeutic hypothermia in traumatology. Surgical Clinics of North America, 79(6), 1269-1289. Tomaszewski, C. (2001). Hypothermia. In R. F. Sing & P. M. Reilly (Eds.), Initial Management of Injuries (pp. 217-224). London: BMJ Books. Trauma Scoring. (n.d.). Retrieved March 26, 2003, from http://www.trauma.org/scores/index.html Walpoth, B. H., Walpoth-Aslan, B. N., Mattle, H. P., Radanov, B. P., Schroth, G., Schaeffler, L., et al. (1997). Outcome of survivors of accidental deep hypothermia and circulatory arrest treated with extracorporeal blood warming. The New England Journal of Medicine, 337(21), 1500-1504. Hypothermia in Trauma 27 Watts, D. D., Trask, A., Soeken, K., Perdue, P., Dols, S., & Kaufman, C. (1998). Hypothermic coagulopathy in trauma: Effect of varying levels of hypothermia on enzyme speed, platelet function, and fibrinolytic activity. The Journal of Trauma: Injury, Infection and Critical Care, 44(5), 846-854. Watts, D. D., Roche, M., Tricarico, R., Poole, F., Brown, J. J., Jr., Colson, G. B., Trask, A. L., & Fakhry, S. M. (1999). The utility of traditional prehospital interventions in maintaining thermostasis. Prehospital Emergency Care, 3(2), 115-122. Hypothermia in Trauma 28 Author’s Note Frederick D. Watters, BSN student, School of Nursing, University of Pennsylvania. The author would like to thank Dr. Therese Richmond, Associate Professor of Trauma & Critical Care Nursing, at the University of Pennsylvania School of Nursing, who served as faculty advisor to the project, guided the topic selection, and gave editorial and content advice in the process of writing.