Treatment of moderate-to-severe hypothermia in an urban setting

Effects of ethanol on systemic hemodynamics in a porcine model of accidental hypothermia

OBJECTIVES

Accidental hypothermia is frequently associated with ethanol intoxication. Each has independent effects on systemic hemodynamics, but their combined effects are poorly understood. We aimed to describe the hemodynamic effects of ethanol intoxication in a model of severe hypothermia and rewarming.

METHODS

Anesthetized pigs was assigned to control (n=8) or ethanol groups (ETOH) (n=7, 3 mg/kg of ethanol via an orogastric tube). Subjects were cooled to 25°C using ice packs and then warmed to baseline core temperature with passive external and active core rewarming.

RESULTS

In the ETOH group, peak serum ethanol concentration was 202 mg/dL at 25°C. Ethanol had no effect on time of cooling or rewarming. In both the control and ETOH, there were similar maximal decreases in mean arterial pressure (from 94±24 to 50±15 mm Hg and 100±27 to 31±12 mm Hg, respectively), ventricular contractility (rate of maximal left ventricular pressure rise from 5731±1462 to 2610±596 mm Hg/s and 6832±1384 to 1937±437 mm Hg/s, respectively), and cardiac output (from 2.14±0.8 to 0.53±0.3 L/min and 2.93±0.9, to 0.44±0.2 L/min, respectively; all P<.001). After rewarming, only in the ETOH group were persistent decreases in mean arterial pressure (59±14 mm Hg), contractility (3982±1573 mm Hg/s), and cardiac output (1.6±0.9 L/min, all P<.03) observed.

CONCLUSIONS

Hypothermia caused significant adverse effects on cardiac function and systemic hemodynamics, which returned to baseline with rewarming. Ethanol intoxication had no additional effects on systemic hemodynamics during cooling; however, it caused more prolonged depression of cardiac function and adverse effects on systemic hemodynamics during rewarming. These data may have implications for resuscitation of ethanol-intoxicated victims of accidental hypothermia.

Database of post-mortem rectal cooling cases under strictly controlled conditions: a useful tool in death time estimation

The most common method used in determining the estimated time since death in the early post-mortem phase is back-calculation based on rectal temperature decrease. Cooling experiments are essential for model generation and validation. Post-mortem temperature models are necessary to perform back-calculations. Thus far, cooling experiments have not been performed under controlled environmental conditions. The present study provides data on 84 post-mortem cooling experiments under strictly controlled environmental conditions. For a period of 5 years, starting in 2003, deceased persons with a known time of death and known environmental conditions at the death scene were transferred to a climatic chamber for the process of body cooling. The environmental temperature was programmed to the death scene temperature and kept constant throughout the process of body cooling. Rectal and ambient temperatures were measured every minute. Relevant case-specific information was summarized in a FileMaker database. The database serves as a reference tool for the comparison of real cases in forensic routine and to check the plausibility of model-derived estimates.

Accidental hypothermia

Hypothermia is a life threatening condition, and management can be challenging, with little robust evidence to support the various treatments. This article should help doctors to understand the condition better

Hypothermia and localized cold injuries

Hypothermia and localized cold injuries are largely preventable with proper preparation for activities in cold environments. Proficient field management is crucial to the final outcome in terms of function and viability because proper care is vital to preventing exacerbation of the initial exposure and injury. Rapid rewarming is optimal when further cold exposure can be avoided reliably. Repetitive freeze-thaw cycles are associated with increased morbidity and tissue loss caused by progressive microvascular injury and thrombosis. The subsequent care is largely supportive and consists of wound care and physical and hydrotherapy to promote optimal functional recovery.

Cardiopulmonary bypass resuscitation for accidental hypothermia

Many victims of accidental hypothermia have been successfully resuscitated with cardiopulmonary bypass, but questions remain regarding treatment indications and efficacy. To assess the role of cardiopulmonary bypass in resuscitation from hypothermia, a collective literature review was performed. Data on 68 hypothermic patients resuscitated with cardiopulmonary bypass were analyzed. Impairment from alcohol, drug abuse, or mental illness was the most common predisposing factor for accidental hypothermia. Mean initial core temperature was 21 degrees C. Sixty-one patients (90%) were in cardiac arrest. Femoral-femoral bypass was used in 72% of patients. Overall survival was 60%. Eighty percent of survivors returned to their previous level of function. Sixty-seven percent of nonsurvivors died because of inability to establish a cardiac rhythm or wean from bypass. Patient age, type of cardiopulmonary bypass (femoral-femoral or atrial-aortic), and initial core temperature were not significant prognostic indicators. There were no survivors among the 6 patients with a core temperature less than 15 degrees C. Patients in cardiac arrest had a higher mortality than patients who were not (p = 0.02). Climbing and avalanche victims had a higher mortality than other hypothermic patients (p = 0.003). The possibility of publication bias must be considered before firm conclusions can be drawn from this collective literature review. Controlled studies comparing the efficacy of cardiopulmonary bypass and alternative warming techniques have not been done. Nevertheless, cardiopulmonary bypass has several advantages over other warming methods for profoundly hypothermic patients. Tissue perfusion and oxygenation are maintained while rapid warming occurs. Cardiopulmonary bypass resuscitation is recommended for hypothermic patients in arrest and for patients with core temperatures lower than 25 degrees C, irrespective of rhythm. Patients in stable condition with temperatures between 25 degrees and 28 degrees C can be treated with cardiopulmonary bypass or conventional warming methods.

Controlled trial of an intravenous fluid warmer

INTRODUCTION

In critically ill patients (e.g., trauma victims) prevention of hypothermia is an important goal. Infusion of warm fluids has been addressed in the hospital setting, but not in the air medical transport setting.

PURPOSE

The purpose of this study was to test the efficacy of an intravenous (IV) fluid warming device that is well-suited for the air medical transport environment.

METHOD

The warmer studied was used with IV fluid heated to approximately 38 degrees C (100 degrees F) and evaluated in environmental temperatures of -16 degrees C (3 degrees F), 2 degrees C (36 degrees F), and 22 degrees C (72 degrees F). The warmer group was compared to a control group of similarly treated IV fluids without a warming device. Temperatures were measured at baseline, 15, 30 and 60 minutes.

RESULTS

The 30- and 60-minute fluid temperatures were higher in the warmer than in the control group for all three environmental temperature settings. At 15 minutes, fluid temperatures were higher in the warmer group for the 2 degrees C and -16 degrees C, but not the 22 degrees C, environments. There was no significant drop in temperature in the warmer group in the 22 degrees C and 2 degrees C settings, but a decrease was noted in the -16 degrees C environment. There was a significant drop in the control group at all temperatures tested.

CONCLUSION

The IV fluid warmer tested effectively maintains the temperature of warmed IV fluids in temperatures above 2 degrees C. At -16 degrees C there was significant heat loss, but the loss was significantly less when compared to the control group.