Multicenter hypothermia survey

Impact of prehospital hypothermia on transfusion requirements and outcomes

BACKGROUND

Prehospital hypothermia (PH) is known to increase mortality following traumatic injury. PH relationship with transfusion requirements has not been documented. The purpose of this investigation was to analyze the impact of PH on blood product requirements and subsequent outcomes.

METHODS

The Los Angeles County Trauma System Database was queried for all patients admitted between 2005 and 2009. Demographics, physiologic parameters, and transfusion requirements were obtained and dichotomized by admission temperatures with a core temperature of less than 36.5 °C considered hypothermic. Multivariate analysis was performed to determine factors contributing to transfusion requirements and to derive adjusted odds ratios (AORs) for mortality and rates of adult respiratory distress syndrome and pneumonia.

RESULTS

A total of 21,023 patients were analyzed in our study with 44.6% presenting with PH. Hypothermic patients required 26% more fluid resuscitation (p < 0.001) in the emergency department and 17% more total blood products (p < 0.001) than those who were admitted with a normal temperature. There was a trend toward an increase in emergency department transfusion (8%, p = 0.06). PH was independently associated with the need for a transfusion (AOR, 1.1; p = 0.047), increased mortality (AOR, 2.0; p < 0.01), as well as incidence of adult respiratory distress syndrome (AOR, 1.8; p < 0.05) and pneumonia (AOR, 2.6; p < 0.01).

CONCLUSION

PH is associated with increased transfusion and fluid requirements and subsequently worse outcomes. Interventions that correct hypothermia may decrease transfusion requirements and improve outcomes. Prospective studies investigating correction of hypothermia in trauma patients are warranted.

LEVEL OF EVIDENCE

Prognostic/epidemiologic study, level III.

Resuscitation of avalanche victims: Evidence-based guidelines of the international commission for mountain emergency medicine (ICAR MEDCOM): intended for physicians and other advanced life support personnel

BACKGROUND

In North America and Europe ∼150 persons are killed by avalanches every year.

METHODS

The International Commission for Mountain Emergency Medicine (ICAR MEDCOM) systematically developed evidence-based guidelines and an algorithm for the management of avalanche victims using a worksheet of 27 Population Intervention Comparator Outcome questions. Classification of recommendations and level of evidence are ranked using the American Heart Association system.

RESULTS AND CONCLUSIONS

If lethal injuries are excluded and the body is not frozen, the rescue strategy is governed by the duration of snow burial and, if not available, by the victim's core-temperature. If burial time ≤35 min (or core-temperature ≥32 °C) rapid extrication and standard ALS is important. If burial time >35 min and core-temperature <32 °C, treatment of hypothermia including gentle extrication, full body insulation, ECG and core-temperature monitoring is recommended, and advanced airway management if appropriate. Unresponsive patients presenting with vital signs should be transported to a hospital capable of active external and minimally invasive rewarming such as forced air rewarming. Patients with cardiac instability or in cardiac arrest (with a patent airway) should be transported to a hospital for extracorporeal membrane oxygenation or cardiopulmonary bypass rewarming. Patients in cardiac arrest should receive uninterrupted CPR; with asystole, CPR may be terminated (or withheld) if a patient is lethally injured or completely frozen, the airway is blocked and duration of burial >35 min, serum potassium >12 mmol L(-1), risk to the rescuers is unacceptably high or a valid do-not-resuscitate order exists. Management should include spinal precautions and other trauma care as indicated.

Successful resuscitation after multiple injuries in the wilderness

BACKGROUND

Survival of blunt trauma associated with hypothermic and hemorrhagic cardiac arrest in wilderness areas is extremely rare.

CASE REPORT

We describe a case of a 19-year-old female college sophomore who, while glissading down Mt. Adams, had a 400-pound boulder strike her back and left pelvis, propelling her 40 feet down the mountain to land face down in the snow at 7000 feet. It took 4 h from the time of injury until the arrival of the helicopter at our Emergency Department and Trauma Center. The patient lost vital signs en route and had no CO(2) production. A cardiothoracic surgeon was the trauma surgeon on call. The patient was taken directly from the helipad to the operating room, where cutdowns enabled initial intravenous access, median sternotomy and pericardiotomy open heart massage, massive transfusion, chest and abdominal cavity irrigations with warm saline, correction of acid base imbalances and coagulopathies, and epicardial pacing that led to a successful reanimation of the patient. The patient was rewarmed without extracorporeal membrane oxygenation or heat exchangers. The ensuing multiple organ failures (heart, lungs, kidneys, intestines, brain, and immune system) and rhabdomyolysis led to a 2-month intensive care unit stay. She received over 120 units of blood and blood products. The patient regained cognitive function, mobility, and overcame multiple organ failure.

CONCLUSION

This report is presented to increase awareness of the potential survivability in hypothermia, and to recognize the heroic efforts of the emergency services personnel whose efforts saved the patient's life.

Damage control in severely injured trauma patients - A ten-year experience

BACKGROUND

This study reviews our 10-year institutional experience with damage control management and investigates risk factors for early mortality.

MATERIALS AND METHODS

The trauma registry of our level I trauma centre was utilized to identify all patients from 01/96 through 12/05 who underwent initial damage control procedures. Demographics, clinical and physiological parameters, and outcomes were abstracted. Patients were categorized as either early survivors (surviving the first 72 hours after admission) or early deaths.

RESULTS

During the study period, 319 patients underwent damage control management. Overall, 52 patients (16.3%) died (early deaths) and 267 patients (83.7%) survived the first 72 hours (early survivors). Early deaths showed significantly deranged serum lactate (5.81±0.55 vs. 3.46±0.13 mmol/L; P<0.001), base deficit (10.10±0.95 vs. 4.90±0.28 mmol/L; P<0.001) and pH (7.16±0.03 vs. 7.29±0.01; P<0.001) levels compared to early survivors on hospital admission. An International Normalized Ratio >1.2, base deficit >3 mmol/L, head Abbreviated Injury Scale ≥3, body temperature <35°C, serum lactate >6 mmol/L, and hemoglobin <7 g/dL proved to be independent risk factors for early mortality on hospital admission.

CONCLUSIONS

Several risk factors for early mortality such as severe head injury and the lethal triad (coagulopathy, acidosis and hypothermia) in patients undergoing damage control procedures were identified and should trigger the trauma surgeon to maintain aggressive resuscitation in the intensive care unit.

Risk factors for onset of hypothermia in trauma victims: the HypoTraum study

Introduction

Hypothermia is common in trauma victims and is associated with an increase in mortality. Its causes are not well understood. Our objective was to identify the factors influencing the onset of hypothermia during pre-hospital care of trauma victims.

Methods

This was a multicenter, prospective, open, observational study in a pre-hospital setting.

The subjects were trauma victims, over 18 years old, receiving care from emergency medical services (EMS) and transported to hospital in a medically staffed mobile unit.

Study variables included: demographics and morphological traits, nature and circumstances of the accident, victim's presentation (trapped, seated or lying down, on the ground, unclothed, wet or covered by a blanket), environmental conditions (wind, rain, ground temperature and air temperature on site and in the mobile unit), clinical factors, Revised Trauma Score (RTS), tympanic temperature, care provided (including warming, drugs administered, infusion fluid temperature and volume), and EMS and hospital arrival times.

Results

A total of 448 patients were included. Hypothermia (<35°C) on hospital arrival was present in 64/448 patients (14%). Significant factors associated with the absence of hypothermia in a multivariate analysis were no intubation: Odds Ratio: 4.23 (95% confidence interval 1.62 to 1.02); RTS: 1.68 (1.29 to 2.20); mobile unit temperature: 1.20 (1.04 to 1.38); infusion fluid temperature: 1.17 (1.05 to 1.30); patient not unclothed: 0.40 (0.18 to 0.90); and no head injury: 0.36 (0.16 to 0.83).

Conclusions

The key risk factor for the onset of hypothermia was the severity of injury but environmental conditions and the medical care provided by EMS were also significant factors. Changes in practice could help reduce the impact of factors such as infusion fluid temperature and mobile unit temperature.

Accidental hypothermia

Accidental hypothermia has produced many cases of intact survival even after prolonged cardiac arrest, but it is also often fatal. In recent years, alterations in resuscitation care that sometimes confused or discouraged resuscitation teams have largely been supplanted by an emphasis on safe, rapid, effective rewarming. Rewarming decisions and even the simple recognition of hypothermia remain challenging. This review seeks to update and demystify some of these challenges.

Early use of hemodialysis for active rewarming in severe hypothermia: a case report and review of literature

Deep accidental hypothermia (body temperature below 28°C) is rare. Even with modern supportive care of active external and internal rewarming techniques it is associated with a high mortality rate. We report the early and successful use of hemodialysis (HD) for active rewarming of a middle-aged alcoholic man with severe deep accidental hypothermia after failure of initial efforts of rewarming using conventional strategies. This case report and review of the literature highlights the advantages and the challenges of using HD in this setting and suggests a potential role for HD in the routine management of severe hypothermia in the absence of circulatory arrest.

Active intravascular rewarming for hypothermia associated with traumatic injury: early experience with a new technique

Hypothermia is a significant contributor to mortality in severely injured patients. Rewarming is an enormous challenge, especially in those who require operative or angiographic intervention. In this patient population, external warming methods are only capable of reducing further heat loss, whereas active rewarming adds heat to the body's core but is invasive. This article analyzes our initial experience with a minimally invasive, continuous, automated, and easily portable intravascular rewarming technique using the Alsius Corporation's CoolGard system. The records of 11 hypothermic critically injured patients presenting to our level 1 trauma center over a 6-month period were reviewed. The patients' mean age was 39 +/- 22 years, 7 (64%) were male, and 7 (64%) had blunt mechanisms of injury. The mean injury severity score was 40 +/- 16, and the mean initial systolic blood pressure was 91 +/- 60 mm Hg. The mean core temperature at the initiation of rewarming was 33.6 +/- 1.0 degrees C, and the mean rewarming rate was 1.5 +/- 1.0 degrees C/h. Six patients died (55%), two of acute exsanguination and four of unsurvivable traumatic brain injuries. One patient developed a deep vein thrombosis at the femoral catheter site and experienced a nonfatal pulmonary embolus. Our experience demonstrates that active intravascular balloon-catheter rewarming represents a practical, automated technique for the immediate and continuous treatment of hypothermia in all phases of the acute care of trauma patients.

[Physiologic effects of hypothermia]

Therapeutic use of hypothermia has come to the frontline in the past decade again in the prevention and in mitigation of neurologic impairment. The application of hypothermia is considered as a successful therapeutic measure not just in neuro- or cardiac surgery, but also in states causing brain injury or damage. According to our present knowledge this is the only proven therapeutic tool, which improves the neurologic outcome after cardiac arrest, decreasing the oxygen demand of the brain. Besides influencing the nervous system, hypothermia influences the function of the whole organ system. Beside its beneficial effects, it has many side-effects, which may be harmful to the patient. Before using it for a therapeutic purpose, it is very important to be familiar with the physiology and complications of hypothermia, to know, how to prevent and treat its side-effects. The purpose of this article is to summarize the physiologic and pathophysiologic effects of hypothermia.

Successful resuscitation from cardiopulmonary arrest due to profound hypothermia using noninvasive techniques

Profound hypothermia is defined as a core body temperature of 20.0 °C or less. Successful resuscitation from this degree of hypothermia is rare. We present a case of successful resuscitation in a 2-year-old boy found in cardiac arrest due to profound hypothermia. Invasive techniques such as cavity lavage, extracorporeal membrane oxygenation, and cardiopulmonary bypass were not used.

Prognostic factors in avalanche resuscitation: a systematic review

OBJECTIVE

Avalanche resuscitation will save lives if focussed on victims that have the potential to survive. The purpose of this systematic review was to examine 4 critical prognostic factors for burial victims in cardiac arrest.

METHODS

Time of burial, airway patency, core temperature and serum potassium level were analyzed as PICO (Patient/population, Intervention, Comparator, Outcome) questions within the 2010 Consensus on Science process of the International Liaison Committee on Resuscitation. The electronic databases of Medline via PubMed, EMBASE via OVID and the Cochrane Database of Systematic Reviews were searched using combinations of the search terms "avalanche", "air pocket", "hypothermia" and "serum potassium".

RESULTS

Of 1910 publications that were identified 30 were found relevant. The predictive value for survival of a short time of burial or a patent airway after 35 min of burial is supported by 10 retrospective case-control studies, 4 case series and 2 experimental studies, while no studies are neutral or opposed. A core temperature of less than 32 degrees C with a patent airway is supported by 2 retrospective case-control studies and 3 case series, while 10 studies are neutral. Serum potassium level is supported by 6 retrospective case-control studies and 3 case reports, while 3 retrospective case-control studies and 1 animal model are neutral.

CONCLUSION

After 35 min of burial, or where the core temperature is less than 32 degrees C, a patent airway is associated with survival to hospital discharge. A serum potassium of less than 7 mmol/L may be a valuable indicator for survival when other indicators are unclear. These findings should modify the current avalanche resuscitation scheme.

Treatment of severe accidental hypothermia with intermittent hemodialysis

The optimal management of moderate-to-severe hypothermia with hemodynamic instability remains unclear. Although cardiopulmonary bypass offers the most rapid rate of rewarming and has been suggested as the method of choice in the presence of circulatory arrest, there is no evidence to support the use of this highly invasive technique over other rewarming modalities in the absence of circulatory collapse. We report the successful treatment of hemodynamically unstable hypothermia with conventional hemodialysis in a patient with normal renal function, after initial efforts of rewarming using conventional strategies had failed. This case report and review of the literature highlights the advantages and the challenges of using hemodialysis in this setting, and suggests a potential role for hemodialysis in the routine management of moderate-to-severe hypothermia in the absence of circulatory arrest.

Thrombelastography is better than PT, aPTT, and activated clotting time in detecting clinically relevant clotting abnormalities after hypothermia, hemorrhagic shock and resuscitation in pigs

BACKGROUND

Hypothermia and hemorrhagic shock contribute to coagulopathy after trauma. In this study, we investigated the independent and combined effects of hypothermia and hemorrhage with resuscitation on coagulation in swine and evaluated clinically relevant tests of coagulation.

METHODS

Pigs (n = 24) were randomized into four groups of six animals each: sham control, hypothermia, hemorrhage with resuscitation, and hypothermia, hemorrhage with resuscitation combined. Hypothermia to 32 degrees C was induced with a cold blanket. Hemorrhage was induced by bleeding 35% of total blood volume followed by resuscitation with lactated Ringer's solution. Coagulation was assessed by thrombin generation, prothrombin time (PT), activated partial thromboplastin time (aPTT), activated clotting time (ACT), and thrombelastography (TEG) from blood samples taken at baseline and 4 hour after hypothermia and/or hemorrhage with resuscitation. Data were compared with analysis of variance.

RESULTS

Baseline values were similar among groups. There were no changes in any measurements in the control group. Compared with baseline values, hemorrhage with resuscitation increased lactate to 140% +/- 15% (p < 0.05). Hypothermia decreased platelets to 73% +/- 3% (p < 0.05) with no effect on fibrinogen. Hemorrhage with resuscitation reduced platelets to 72% +/- 4% and fibrinogen to 71% +/- 3% (both p < 0.05), with similar decreases in platelets and fibrinogen observed in the combined group. Thrombin generation was decreased to 75% +/- 4% in hypothermia, 67% +/- 6% in hemorrhage with resuscitation, and 75% +/- 10% in the combined group (all p < 0.05). There were no significant changes in PT or aPTT by hemorrhage or hypothermia. ACT was prolonged to 122% +/- 1% in hypothermia, 111% +/- 4% in hemorrhage with resuscitation, and 127% +/- 3% in the combined group (all p < 0.05). Hypothermia prolonged the initial clotting time (R) and clot formation time (K), and decreased clotting rapidity (alpha) (all p < 0.05). Hemorrhage with resuscitation only decreased clot strength (maximum amplitude [MA], p < 0.05). TEG parameters in the combined group reflected the abnormal R, K, MA, and alpha observed in the other groups.

CONCLUSION

Hypothermia inhibited clotting times and clotting rate, whereas hemorrhage impaired clot strength. Combining hypothermia with hemorrhage impaired all these clotting parameters. PT, aPTT were not sensitive whereas ACT was not specific in detecting these coagulation defects. Only TEG differentiated mechanism related to clotting abnormalities, and thus may allow focused treatment of clotting alterations associated with hypothermia and hemorrhagic shock.

In vitro effect of activated recombinant factor VII (rFVIIa) on coagulation properties of human blood at hypothermic temperatures

BACKGROUND

Recombinant activated factor VII (rFVIIa) is currently administered off-label to control diffuse coagulopathic bleeding of patients with traumatic injuries. These patients are often cold, acidotic, and coagulopathic upon arrival and each responds differently to rFVIIa therapy. This study investigated the effects of hypothermia on clotting and the potential benefit of rFVIIa administration on blood coagulation at different hypothermic temperatures.

METHOD

Citrated blood samples were collected from eight healthy volunteers (20-45 years old) and incubated at 37 degrees C, 34 degrees C, 31 degrees C, and 28 degrees C for 30 minutes. rFVIIa (1.26 microg/mL equivalent to 90 microg/kg in vivo dose) or vehicle solution (saline) was added to each blood sample, incubated (10 minutes), and analyzed at the respective temperatures by standard coagulation tests and thrombelastography.

RESULTS

The clot reaction time of blood samples, measured as prothrombin time, activated partial thromboplastin time, and R time (thrombelastography analysis), was significantly prolonged at 31 degrees C or below compared with at 37 degrees C. The clot formation rate ([alpha] angle, maximum clotting velocity [Vmax]) was decreased at all cold temperatures. Maximum clot strength (maximum amplitude) was only affected (reduced) at 28 degrees C. Addition of rFVIIa shortened the prothrombin time, activated partial thromboplastin time, and R times at every temperature, surpassing the normal (37 degrees C) temperature values in 31 degrees C and 34 degrees C cold samples. Similarly, clot formation rate parameters (clotting time, [alpha] angle, Vmax) were also improved by rFVIIa addition and normothermic values were restored in 31 degrees C and 34 degrees C cold blood samples. rFVIIa did not affect maximum amplitude at any temperature.

CONCLUSIONS

Mild to moderate hypothermia delayed the initial clot reaction and reduced clot formation rate without affecting ultimate clot strength. FVIIa effectively compensated for the adverse effects of hypothermia except in severe cases. These results suggest that administration of FVIIa should be beneficial in enhancing hemostasis in hypothermic trauma patients without the need for prior correction of the patient's body temperature.

[Management of accidental hypothermia]

Patients with hypothermia are frequently encountered in emergency medicine. Particularly trauma patients, but also other predisposed persons, can be expected to suffer from hypothermia at any time of the year. Therapy focuses not only on symptom-oriented intensive care to stabilize and secure vital functions, but also on rewarming. Even in cases of severe hypothermia with circulatory arrest, therapy can produce excellent results. This paper first gives a brief overview of the typical clinical symptoms of hypothermia, before giving a detailed description of the preclinical and in-hospital management of the hypothermia patient. The various rewarming strategies are the subject of special attention and critical evaluation.

Perioperative management of the patient with hematologic disorders

Bleeding at the time of surgery has the potential to become a serious complication. Careful patient assessment and review of history are of the utmost importance if this situation is to be avoided on the operating table. Unfortunately, many patients, particularly younger individuals with little to no previous exposure to surgery, are unaware of underlying bleeding disorders that they may have. Understanding the basic pathophysiology and management of these conditions becomes critical for the treating surgeon. For patients who have known conditions, close interconsultation with the treating hematologists and careful observation of preoperative, intraoperative, and postoperative established protocols reduces the risk of complications for patients and makes the possibility of success a reality for these individuals.

An Experimental Study of Warming Intravenous Fluid in a Cold Environment☆

OBJECTIVE

Numerous studies support the use of warmed intravenous fluids in hypothermic patients. The most effective method to accomplish this goal in a cold prehospital, wilderness, or combat setting is unknown. We evaluated various methods of warming intravenous fluids for a bolus infusion in a cold remote environment.

METHODS

One liter and 500 mL bags of intravenous fluid at 5 degrees C were heated using various methods in a 5 degrees C cold room. Methods included attachment of 3 types of chemical heat packs and heating the fluid in a pot on a camping stove. For all methods, fluids were run at a wide-open rate through an intravenous line with an 18-gauge catheter attached to the end to simulate a bolus infusion. The temperature of the fluid at the end of the intravenous line was measured. Each method was tested twice. Equipment weight and setup times are reported. Mean infusion temperatures for the various methods are compared.

RESULTS

Equipment weights ranged from 19 to 665 gm. Setup times ranged from 5 to 11 minutes. The 2 methods which achieved the desired mean infusion temperature of 35 to 42 degrees C without excessive maximum temperatures were 1) 2 Meal Ready to Eat hot packs attached to a 500 mL bag of fluid for 10 minutes prior to infusion, and 2) a camping stove heating the surface of a 500 mL bag of fluid to 75 degrees C prior to infusion. Other methods, including the use of commonly available heat packs and a commercially available IV fluid warmer were ineffective, with mean infusion temperatures ranging from 7 to 12 degrees C.

CONCLUSIONS

Heating of cold intravenous fluids in a cold environment is possible using either Meal Ready to Eat heat packs or a camping stove. Further study is needed to evaluate the ability of either method to consistently produce an appropriate fluid temperature given various ambient and initial fluid temperatures.

Trauma and aggressive homeostasis management

Three important issues concerning homeostasis in the acute care of trauma patients that are related directly to the stress response are hyperglycemia, lactic acidosis, and hypothermia. Recently, there has been a resurgence of interest in investigating the effects of aggressive thermal and glucose concentration and volume resuscitation on outcomes in critically ill and trauma patients. Significant reason exists to question the "conventional wisdom" relating to current approaches to restoring homeostasis in this patient population.

Environmental Cold-Induced Injury

More than 650 deaths from hypothermia occur each year in the United States. Even minor deviation from normal temperature leads to important symptoms and disability. The most significant risk factors are advanced age, mental impairment, substance abuse, and injury. This article examines the incidence of hypothermia, its detrimental effect on trauma patients, and methods of rewarming the hypothermic patient. It also looks at the controversial protective role hypothermia might play in shock, organ transplantation, cardiac arrest, and brain injury. Finally, it examines cold injuries, including frostbite, chilblain, and trench foot, and makes recommendations for their treatment.

Rewarming rates in urban patients with hypothermia: prediction of underlying infection

BACKGROUND

In the urban setting, hypothermia is commonly associated with illness or intoxication, with death often secondary to infection.

OBJECTIVES

To evaluate factors that affect the rewarming rate (RWR) and the ability of the RWR and other clinical markers to predict the presence or absence of underlying infection in an adult urban population.

METHODS

This was a prospective observational study of hypothermic patient visits to a large emergency department. Serial temperatures were obtained during rewarming to construct rewarming curves. Rewarming modalities selected by emergency physicians were correlated with admission temperatures. Univariate associates of RWR and infection were assessed.

RESULTS

The authors identified 96 patient visits. The median temperature was 89.5 degrees F (31.9 degrees C; range, 73.0 degrees F to 95.0 degrees F [22.8 degrees C to 35.0 degrees C]). Thirteen patients had temperatures of < 80.0 degrees F (26.0 degrees C). Seven died within 14 hours of presentation; six, of infection. No patient experienced ventricular fibrillation. Potential candidate predictors of infection from a multivariate analysis were a RWR of < 1.80 degrees F (1.0 degrees C) per hour and a serum albumin of < 2.7 g/dL. Rapid rewarming was associated with the absence of infection and a temperature below 86.0 degrees F (30.0 degrees C). In patients without significant underlying illness, rewarming rates appeared to be independent of the modality of rewarming.

CONCLUSIONS

Rewarming rates reflect intrinsic capacity for thermogenesis. Increased RWRs were associated with the absence of infection. The achievement of normothermia did not prevent death in infected patients. Initiation of invasive rewarming in urban patients with hypothermia who have not had hypothermic cardiac arrest may be unwarranted. Management of this population should emphasize support, detection, and treatment of underlying illness.

Rewarming from severe accidental hypothermia with circulatory arrest

This case report demonstrates successful cardiopulmonary and cerebral resuscitation (CPCR) of a young male explored 15 hours following a suicide attempt (carbamazepine intoxication) in deep hypothermia (19 degrees C) with circulatory arrest. An extracorporeal circuit was used to rewarm the patient's blood. Weaning from extracorporeal circulation (ECC) was successful and without complications as was recovery from multiorgan dysfunction, severe rhabdomyolysis and carbamazepine intoxication. An excellent outcome was achieved without any neurological deficit at the time of discharge from the hospital.

Injury-associated hypothermia: an analysis of the 2004 National Trauma Data Bank

Severe injury and shock are frequently associated with abnormalities in patient body temperature. Substantial increases in mortality have been associated with profound hypothermia, especially below 35 degrees C. The purpose of this study was to further characterize the impact of hypothermia in a large dataset of trauma patients. This study was a retrospective analysis of the 2004 version of the National Trauma Data Bank (NTDB), which contains approximately 1.1 million patients from over 400 trauma centers. Admission temperature was analyzed with respect to mortality, injury severity score (ISS), base deficit (BD), Glasgow Coma Score (GCS), and hospital outcomes. The NTDB contained 701,491 patients with temperatures recorded upon trauma center admission. Of these, 11,026 patients had admission temperatures <35 degrees C, and 802 had temperatures <32 degrees C. Comparison of core temperature versus mortality revealed that as temperature decreased, the mortality rate increased, reaching approximately 39% at 32 degrees C, and remained constant at lower temperatures. Surprisingly, 477 patients (59.5%) survived with temperatures <32 degrees C. Similarly, BD increased as hypothermia worsened until body temperature reached 31 degrees C, below which there was little further increase. Patients with admission temperatures less than 35 degrees C had significantly greater mortality (25.5% vs. 3.0%, P < 0.001) and BD (7.8 vs. 3.7, P < 0.001) when compared with patients with temperatures >or=35 degrees C. In survivors, average ventilator days and intensive care unit (ICU) days were 14.4 and 12.8, respectively, for patients with temperatures <35 degrees C as opposed to more normothermic patients who demonstrated an average of 9.5 ventilator days and 9.1 ICU days (P < 0.001). When grouped by individual ISS, BD level, and GCS motor score, mortality was significantly greater when admission temperature was below 35 degrees C (ISS mean difference = 11.4%, BD mean difference = 22.8%, and GCS motor mean difference = 9.85%). Logistic regression revealed that hypothermia remains an independent determinant of mortality after correction for confounding variables (odds ratio = 1.54, 95% confidence interval 1.40-1.71). Admission hypothermia is associated with greater mortality, increased injury severity, more profound acidosis, and prolonged ICU/ventilator courses. However, although mortality at <32 degrees C is high, patients with temperatures this low do survive. As temperatures drop below 32 degrees C, mortality rates remain constant, which may indicate a threshold below which physiologic mechanisms are unable to correct body temperature regardless of injury severity. Although shock severity is highly indicative of outcome, hypothermia independently contributes to the substantial mortality associated with severe injury.

The Impact of Global Warming on Health and Mortality

Initial concern about the possible effects of global warming on infections has declined with the realization that the spread of tropical diseases is likely to be limited and controllable. However, the direct effects of heat already cause substantial numbers of deaths among vulnerable people in the summer. Action to prevent these deaths from rising is the most obvious medical challenge presented by a global rise in temperature. Strategies to prevent such deaths are in place to some extent, and they differ between the United States and Europe. Air conditioning has reduced them in the United States, and older technologies such as fans, shade, and buildings designed to keep cool on hot days have generally done so in Europe. Since the energy requirements of air conditioning accelerate global warming, a combination of the older methods, backed up by use of air conditioning when necessary, can provide the ideal solution. Despite the availability of these technologies, occasional record high temperatures still cause sharp rises in heat-related deaths as the climate warms. The most important single piece of advice at the time a heat wave strikes is that people having dangerous heat stress need immediate cooling, eg, by a cool bath. Such action at home can be more effective than transporting the patient to hospital. Meanwhile, it must not be forgotten that cold weather in winter causes-many more deaths than heat in summer, even in most subtropical regions, and measures to control cold-related deaths need to continue.

A Systematic Evaluation of the Effect of Temperature on Coagulation Enzyme Activity and Platelet Function

BACKGROUND

Hypothermia is associated with an increased risk of bleeding and is a significant contributing factor to the morbidity and mortality of trauma and complicated surgical procedures. A core temperature of 33 degrees C is associated with a significantly increased risk of death after trauma compared with 37 degrees C. Hypothermia-associated bleeding has been hypothesized to result from dysregulation of enzymatic function, reduced platelet activity, and/or altered fibrinolysis.

METHODS

We systematically evaluated the effects of temperature on isolated pro- and anticoagulant enzyme processes and platelet activation and adhesion. We also evaluated the effects of temperature on complete coagulation systems (activated partial thromboplastin time and an in vitro, cell-based model of coagulation).

RESULTS

Enzyme activities were only slightly reduced at 33 degrees C versus 37 degrees C, and this reduction was not statistically significant (p > 0.05). Platelet activation was also not significantly reduced at 33 degrees C versus 37 degrees C. Conversely, platelet aggregation and adhesion were significantly reduced at 33 degrees C compared with 37 degrees C (p < 0.05). Below 33 degrees C, however, both enzyme activity and platelet function were significantly reduced.

CONCLUSION

Our results suggest that bleeding observed at mildly reduced temperatures (33 degrees - 37 degrees C) results primarily from a platelet adhesion defect, and not reduced enzyme activity or platelet activation. However, at temperatures below 33 degrees C, both reduced platelet function and enzyme activity likely contribute to the coagulopathy.

Severe traumatic head injury in adults: which patients are at risk of early hyperthermia?

OBJECTIVE

Prevention of secondary insults, such as hyperthermia, is a major goal after traumatic brain injury. The aim of our study was to identify risk factors for early hyperthermia in severe head-injured patients.

DESIGN

Retrospective cohort study.

SETTING

A 17-bed multidisciplinary ICU of a 700-bed teaching hospital.

PATIENTS

A total of 101 adult patients admitted from January 1999 to December 2001 requiring continuous monitoring of intracranial pressure according to international guidelines.

MEASUREMENT AND RESULTS

Forty-four patients experienced early hyperthermia (at least one episode of body temperature >38.5 degrees C within the first 2 days). On univariate analysis five variables were associated with early hyperthermia: sex; body temperature; white blood cell count on admission; prophylactic use of acetaminophen; and diabetes insipidus within 2 days. On multivariate analysis, white blood cell count >14.5 x 10(9)/l on admission (odds ratio, 7.1; 95% confidence interval, 2.4-20.5; p=0.001) and a body temperature on admission >36 degrees C (odds ratio, 6.7; 95% confidence interval, 2.3-20.1) were strong risk factors of early hyperthermia. Prophylactic use of acetaminophen was negatively associated with early hyperthermia (odds ratio, 0.1; 95% confidence interval, 0.02-0.4). Patients who experienced early hyperthermia were less prone to have good recovery (GOS=5; p=0.03). More patients with severe or moderate disability (GOS=3 or 4) experienced early hyperthermia ( p=0.01).

CONCLUSION

We identified a subgroup of patients at high risk of early hyperthermia, which is common in severe head-injured patients. These results could have clinical implications for prevention of hyperthermia after traumatic brain injury in adults.

Hypothermia in the trauma patient

Hypothermia is a common finding in severely injured patients. Historically described as a consequence of wartime casualties where cold exposure was common, this topic has resurfaced in the trauma literature because of the increasing recognition of the morbidity and mortality associated with hypothermia. Hypothermia, along with acidosis and coagulopathy, has been identified as a component of the "lethal triad" in injured patients, and has been shown to contribute to increased mortality in these patients. Decreases in core temperature during the course of initial evaluation and resuscitation are common, and can contribute to poor outcomes in the injured patient. As induced hypothermia has been shown to be beneficial in some clinical situations, recent animal studies have attempted to investigate whether hypothermia in the trauma patient has any beneficial effects. This review examines the incidence and pathophysiology of hypothermia, and discusses mechanisms of heat loss and rewarming techniques that can be utilized in the trauma patient.

The effect of temperature and pH on the activity of factor VIIa: implications for the efficacy of high-dose factor VIIa in hypothermic and acidotic patients

BACKGROUND

Recombinant coagulation factor VIIa (FVIIa) is approved for treating hemophiliacs with inhibitors. High-dose FVIIa has also been used off-label to manage hemorrhage in trauma and surgical patients, many of whom also develop hypothermia and acidosis.

METHODS

We examined the activity of FVIIa on phospholipid vesicles in the presence and absence of tissue factor (TF) and on platelets as a function of temperature and pH.

RESULTS

FVIIa activity on phospholipids and platelets was not reduced at 33 degrees C compared with 37 degrees C. The activity of FVIIa/TF was reduced by 20% at 33 degrees C compared with 37 degrees C. A pH decrease from 7.4 to 7.0 reduced the activity of FVIIa by over 90% and FVIIa/TF by over 60%.

CONCLUSION

FVIIa should be effective in enhancing hemostasis in hypothermic patients. However, because the activity of FVIIa is so dramatically affected by pH, its efficacy may be reduced in acidotic patients.

Outcome from severe accidental hypothermia in Southern Finland—a 10-year review

The charts of all adult patients with accidental hypothermia who were admitted to a single academic hospital during a 10 year period were retrospectively retrieved. The aim was to identify factors associated with survival of those with hypothermic cardiac arrest. Of 75 admitted patients, 44 were found to be haemodynamically stable and not to require invasive rewarming measures. Of the remaining 31 patients, 23 were in refractory cardiac arrest due to primary hypothermia and rewarmed using cardiopulmonary bypass (CPB). The aetiology of hypothermia was immersion in cold water in 48%, exposure to cold environment in 39% and submersion in 13% of these patients. Their median age was 50 years, and 83% were males. The patients received a total of 70 min of conventional CPR before institution of CPB. Fourteen of these patients (61%) survived to discharge from hospital. Factors associated with survival were age (P=0.015), arterial pH (P=0.011), PaCO2 (P=0.003), and serum potassium (P=0.007). Logistic regression analysis showed that of the 23 patients, 22 could be correctly classified as survivor or nonsurvivor based on the level of serum potassium and arterial pCO2. It is concluded that patients with cardiac arrest due to primary hypothermia tolerate long periods of conventional CPR before institution of CPB. The possible predictive role of serum potassium and arterial pCO2 needs further evaluation.

Surgical management and strategies in the treatment of hypothermia and cold injury

Increased participation in outdoor activities and the epidemic of homelessness have caused the incidence of cold injuries in the civilian population to rise dramatically over the last 20 years. Knowledge of the treatment is crucial for emergency physicians in rural and urban areas. Recent developments have significantly advanced the understanding of the pathophysiology of hypothermic and frostbite injuries. Together with improved rewarming techniques and use of radiological assessment of tissue viability, future advancements should allow for a more aggressive and active approach to the management of these injuries.

Extreme marginal donor: severe hypothermia as a rare preservation condition for explantable organs--a case report

The progressive increase in patients with end stage liver disease has lengthend the waiting- list for liver transplantation. Unfortunately this has not been followed by a suitable increase in the number of donors. The expanding "donor pool" has required use of "marginal" donors (ICU stay > 10 days, sepsi; steatosis > 30-40%, hypernatremia > 155 mmol/L, inotropic drugs). We report the case of a skier who remained for more than 1 hour in cardio-respiratory arrest under the snow; the 49-year-old women was extracted from the snow after 1 hour and 12 minutes and found to be asystolic, fixed pupils and deep hypothermia (27.2 degrees C). After cardiopulmonary resuscitation, partial cardio-respiratory activity was re-established. In the ICU severe hypothermia (26.7 degrees C) was treated with extracorporeal circulation until a re-establishment of satisfactory cardio-circulatory conditions was obtained. Unfortunately cerebral anoxic cerebral death was established and multiorgan procurement performed 3 days later. After liver transplantation into a 59 year-old patient with PNC-C was performed. The course was uneventful and the patient was discharged on the 19th postoperative day.

CONCLUSIONS

Organ procurement from donors involved in accidental traumatic events with cardio-respiratory arrest and hypothermia, is similar to the non-heart-beating donor (NHBD) condition. Correct cardiopulmonary resuscitation and the use of extracorporeal circulation for gradual restoration of body temperature are necessary for optimal organ perfusion. In the present case the anoxic insult induced by the cessation of the cardio-respiratory function, was probably mitigated (if not even annulled) by the hypothermia.

Severe accidental hypothermia treated in an ICU: prognosis and outcome

STUDY OBJECTIVES

To assess the characteristics and outcomes of patients admitted to an ICU for severe accidental hypothermia, and to identify risk factors for mortality.

METHODS

All consecutive patients admitted to an ICU between January 1, 1979, and July 31, 1998, with a temperature of < or = 32 degrees C were retrospectively analyzed. Rewarming was always conducted passively with survival blankets and conventional covers. Prognostic factors were studied by means of univariate analysis (Mann-Whitney U and chi(2) tests) and multivariate analysis (logistic regression).

RESULTS

Forty-seven patients were enrolled (mean +/- SD age, 61.7 +/- 16 years). Five patients had a cardiac arrest before ICU admission. Patient characteristics at ICU admission were as follows: temperature, 28.8 +/- 2.5 degrees C; systolic BP, 85 +/- 23 mm Hg; heart rate, 60 +/- 24 beats/min; Glasgow Coma Scale, 10.4 +/- 3.7; and simplified acute physiology score (SAPS) II, 50.9 +/- 27. Mechanical ventilation was necessary in 23 cases, and 22 patients in shock received vasoactive drugs. The mean length of stay in the ICU was 6.7 +/- 9 days. Eighteen patients (38%) died, but ventricular arrhythmia was never the cause. Univariate analysis identified several prognostic factors (p < 0.05): age (57 +/- 16 years vs 69 +/- 14 years), systolic arterial BP (93 +/- 20 mm Hg vs 71 +/- 21 mm Hg), blood bicarbonate level (23.5 +/- 5.2 mmol/L vs 16.6 +/- 6.2 mmol/L), SAPS II score (35.3 +/- 19.5 vs 72 +/- 21), mechanical ventilation (34% vs 81%), vasopressor agents (42% vs 82%), rewarming time (11.5 +/- 7.2 h vs 17.2 +/- 7 h), and discovery of the patient at home (2.3% vs 54.5%). The initial temperature did not influence vital outcome (28.9 +/- 2.6 degrees C vs 28.6 +/- 2.2 degrees C). Only the use of vasoactive drugs (odds ratio, 9; 95% confidence interval, 1.6 to 50.1) was identified as a prognostic factor in the multivariate analysis.

CONCLUSION

Severe accidental hypothermia is a rare cause of ICU admission in an urban area. Its mortality remains high, but there is no overmortality according to the SAPS II-derived prediction of death. Shock, requiring treatment with vasoactive drugs, is an independent risk factor for mortality, while initial core temperature is not. It remains to be determined whether aggressive rather than passive rewarming procedures are better.

Hypothermia deaths in Jefferson County, Alabama

INTRODUCTION

Some reported characteristics associated with hypothermia mortality include older age, alcohol consumption, male sex, and black race. The purpose of this paper is to present the epidemiology of hypothermia deaths in Jefferson County, Alabama.

METHODS

Autopsy reports maintained by the county coroner's office were abstracted for all cases with primary or underlying causes of death listed as "hypothermia" or "exposure to cold" between January 1983 and July 1999.

RESULTS

Sixty three hypothermia deaths occurred in Jefferson County during the study period. The mean age among cases was 68 years, 63.9% were male and 70% were of black race. Rates of hypothermia death were highest among black males, followed by black females, particularly blacks aged 80 years or older. Deaths occurring indoors were more common among older persons and outdoor deaths more common among younger persons. Thirty per cent of decedents tested positive for alcohol, 75% of whom were found outdoors. Nine decedents tested positive for drugs or medications. Approximately 90% of decedents were identified as having one or more chronic medical conditions. Excluding alcoholics, 52% of decedents had one or more chronic medical conditions.

CONCLUSIONS

Hypothermia in Jefferson County, Alabama is a cause of death primarily affecting two distinct groups of individuals, elderly persons who develop hypothermia inside a dwelling and middle aged males who develop hypothermia out of doors and have consumed alcohol.