Accidental Hypothermia

The Birth of the Mammalian Sleep

Simple Summary

Mammals evolved from reptiles as a consequence of an evolutionary bottleneck. Some diurnal reptiles extended their activity, first to twilight and then to the entire dark time. This forced the change of the visual system. Pursuing maximal sensitivity, they abandoned the filters protecting the eyes against the dangerous diurnal light, which, in turn, forced immobility in lightproof burrows during light time. This was the birth of the mammalian sleep. Then, the Cretacic-Paleogene extinction of dinosaurs leaved free the diurnal niche and allowed the expansion of a few early mammals to diurnal life and the high variability of sleep traits. On the other hand, we propose that the idling rest is a state showing homeostatic regulation. Therefore, the difference between behavioral rest and wakeful idling is rather low: both show quiescence, raised sensory thresholds, reversibility, specific sleeping-resting sites and body positions, it is a pleasing state, and both are dependent of circadian and homeostatic regulation. Indeed, the most important difference is the unconsciousness of sleep and the consciousness of wakeful idling. Thus, we propose that sleep is a mere upgrade of the wakeful rest, and both may have the same function: guaranteeing rest during a part of the daily cycle.

Abstract

Mammals evolved from small-sized reptiles that developed endothermic metabolism. This allowed filling the nocturnal niche. They traded-off visual acuity for sensitivity but became defenseless against the dangerous daylight. To avoid such danger, they rested with closed eyes in lightproof burrows during light-time. This was the birth of the mammalian sleep, the main finding of this report. Improved audition and olfaction counterweighed the visual impairments and facilitated the cortical development. This process is called “The Nocturnal Evolutionary Bottleneck”. Pre-mammals were nocturnal until the Cretacic-Paleogene extinction of dinosaurs. Some early mammals returned to diurnal activity, and this allowed the high variability in sleeping patterns observed today. The traits of Waking Idleness are almost identical to those of behavioral sleep, including homeostatic regulation. This is another important finding of this report. In summary, behavioral sleep seems to be an upgrade of Waking Idleness Indeed, the trait that never fails to show is quiescence. We conclude that the main function of sleep consists in guaranteeing it during a part of the daily cycle.

A Rare Case of Hypothermia-Induced ST Segment Elevation

Prompt recognition of ST segment elevation myocardial infarction (STEMI) is critical as it has significant management and outcome implications, often leading to emergent cardiac catheterization for revascularization. However, other conditions such as pulmonary embolism, myocarditis, hyperkalemia, hypercalcemia, hypothermia, drug overdose, septic shock, left bundle branch block, left ventricular aneurysm, pericarditis, Brugada syndrome, and Takotsubo cardiomyopathy can mimic this presentation on electrocardiography (EKG) and need to be recognized to avoid unnecessary procedures and improve treatment outcomes. We report a case of prominent Osborn waves on EKG from significant hypothermia incorrectly labeled as STEMI. We also provide a literature review on EKG manifestations of hypothermia and the mechanism of those changes, the differential diagnoses of ST segment elevation and their management.

Management of accidental hypothermia: A narrative review

A narrative review is presented on the diagnosis, treatment and management of accidental hypothermia. Although all these processes form a continuum, for descriptive purposes in this manuscript the recommendations are organized into the prehospital and in-hospital settings. At prehospital level, it is advised to: a) perform high-quality cardiopulmonary resuscitation for cardiac arrest patients, regardless of body temperature; b) establish measures to minimize further cooling; c) initiate rewarming; d) prevent rescue collapse and continued cooling (afterdrop); and (e) select the appropriate hospital based on the clinical and hemodynamic situation of the patient. Extracorporeal life support has revolutionized rewarming of the hemodynamically unstable victim or patients suffering cardiac arrest, with survival rates of up to 100%. The new evidences indicate that the management of accidental hypothermia has evolved favorably, with substantial improvement of the final outcomes.

Mechanistic insights into hypothermic ventricular fibrillation: the role of temperature and tissue size

AIMS

Hypothermia is well known to be pro-arrhythmic, yet it has beneficial effects as a resuscitation therapy and valuable during intracardiac surgeries. Therefore, we aim to study the mechanisms that induce fibrillation during hypothermia. A better understanding of the complex spatiotemporal dynamics of heart tissue as a function of temperature will be useful in managing the benefits and risks of hypothermia.

METHODS AND RESULTS

We perform two-dimensional numerical simulations by using a minimal model of cardiac action potential propagation fine-tuned on experimental measurements. The model includes thermal factors acting on the ionic currents and the gating variables to correctly reproduce experimentally recorded restitution curves at different temperatures. Simulations are implemented using WebGL, which allows long simulations to be performed as they run close to real time. We describe (i) why fibrillation is easier to induce at low temperatures, (ii) that there is a minimum size required for fibrillation that depends on temperature, (iii) why the frequency of fibrillation decreases with decreasing temperature, and (iv) that regional cooling may be an anti-arrhythmic therapy for small tissue sizes however it may be pro-arrhythmic for large tissue sizes.

CONCLUSION

Using a mathematical cardiac cell model, we are able to reproduce experimental observations, quantitative experimental results, and discuss possible mechanisms and implications of electrophysiological changes during hypothermia.

Accidental cold-related injury leading to hospitalization in northern Sweden: an eight-year retrospective analysis

BACKGROUND

Cold injuries are rare but important causes of hospitalization. We aimed to identify the magnitude of cold injury hospitalization, and assess causes, associated factors and treatment routines in a subarctic region.

METHODS

In this retrospective analysis of hospital records from the 4 northernmost counties in Sweden, cases from 2000-2007 were identified from the hospital registry by diagnosis codes for accidental hypothermia, frostbite, and cold-water drowning. Results were analyzed for pre-hospital site events, clinical events in-hospital, and complications observed with mild (temperature 34.9 - 32°C), moderate (31.9 - 28°C) and severe (<28°C), hypothermia as well as for frostbite and cold-water drowning.

RESULTS

From the 362 cases, average annual incidences for hypothermia, frostbite, and cold-water drowning were estimated to be 3.4/100,000, 1.5/100,000, and 0.8/100,000 inhabitants, respectively. Annual frequencies for hypothermia hospitalizations increased by approximately 3 cases/year during the study period. Twenty percent of the hypothermia cases were mild, 40% moderate, and 24% severe. For 12%, the lowest documented core temperature was 35°C or higher, for 4% there was no temperature documented. Body core temperature was seldom measured in pre-hospital locations. Of 362 cold injury admissions, 17 (5%) died in hospital related to their injuries. Associated co-factors and co-morbidities included ethanol consumption, dementia, and psychiatric diagnosis.

CONCLUSIONS

The incidence of accidental hypothermia seems to be increasing in this studied sub-arctic region. Likely associated factors are recognized (ethanol intake, dementia, and psychiatric diagnosis).

Effect of warmed irrigation solution on core body temperature during hip arthroscopy for femoroacetabular impingement

PURPOSE

To determine the effect of warming arthroscopic irrigation solution on core body temperature during hip arthroscopic surgery in patients with femoroacetabular impingement.

METHODS

An analytical, prospective, observational study was performed in a cohort of 166 consecutive patients. All patients underwent hip arthroscopy for treatment of femoroacetabular impingement. Two groups were studied: patients operated on with arthroscopic irrigation solution warmed up to 32°C ± 2°C (89.6°F ± 3.6°F) and a control group comprising patients operated on with irrigation solution used at room temperature. Relevant information was collected regarding the patients (age, sex, body mass index, and blood pressure) and the procedure (volume and temperature of saline solution, pressure of fluid pump, surgery time, and room temperature). Corresponding statistical analysis was performed with STATA 11.0 (StataCorp, College Station, TX), by use of descriptive statistics, parametric and nonparametric tests, and a generalized estimating equation model for repeated measurements.

RESULTS

Both groups were comparable in terms of age, sex, systolic and diastolic blood pressure, body mass index, volume of irrigation solution used, and room temperature. The mean age of the cohort was 33 years (range, 14 to 60 years); mean body mass index, 23.7 kg/m(2) (range, 17.2 to 34 kg/m(2)); mean volume of irrigation solution, 26 L (range, 12 to 39 L); mean systolic blood pressure, 97 mm Hg; mean diastolic blood pressure, 51 mm Hg; and mean surgical time, 110 minutes. A decrease in core body temperature by 0.5°C (0.9°F) or greater occurred during the course of surgery in 66% of patients in the control group versus 28% in the warmed-solution group (P < .001). At least 1 core body temperature measurement of less than 36°C (96.8°F) was recorded in 48% of patients in the control group versus 14% in the warmed-solution group (P < .001). The trend toward a decrease in core body temperature was 4 times greater in the control group than in the warmed-solution group (P < .001).

CONCLUSIONS

Use of arthroscopic irrigation solution warmed up to 32°C (89.6°F) reduces the risk of a decrease in core body temperature during hip arthroscopy in patients with femoroacetabular impingement.

LEVEL OF EVIDENCE

Level II, analytical, prospective, comparative study in a cohort of consecutive patients.

Hip arthroscopy and hypothermia

PURPOSE

To determine the incidence of and factors that contribute to the development of hypothermia during hip arthroscopic surgery.

METHODS

An analytic observational study was carried out in a cohort of 73 consecutive patients. All patients underwent hip arthroscopy for the treatment of femoroacetabular impingement. The patients' core temperature (esophageal) was measured throughout the surgery. Relevant information was collected on the patients (age, gender, body mass index, blood pressure) and on the procedure (volume and temperature of saline solution, pressure of fluid pump, surgery time, room temperature). The corresponding statistical analysis was performed with Stata 10.0 (StataCorp, College Station, TX), by use of a repeated-measures generalized estimating equations model.

RESULTS

The patients' mean age was 33 years, and there were 39 female and 34 male patients. The mean body mass index was 23.9; systolic blood pressure, 97.5 mm Hg; and diastolic blood pressure, 52.2 mm Hg. The incidence of hypothermia below 35°C (95°F) was 2.7%. The multivariate statistical analysis of the results showed a direct relation between hypothermia and surgery time of more than 120 minutes (P < .001). There was an inverse relation between core body temperature and surgery time (P < .001), with a drop of 0.19°C/h (32.342°F/h). Of the patients, 68.22% had a decrease in temperature of more than 0.5°C (32.9°F) until the end of surgery. There was also a direct relation between core body temperature and saline solution temperature (P < .001), body mass index (P < .01), and diastolic blood pressure (P < .03).

CONCLUSIONS

The incidence of hypothermia below 35°C (95°F) in patients who underwent hip arthroscopy for the treatment of femoroacetabular impingement is 2.7%. The factors that contribute toward the development of hypothermia during hip arthroscopic surgery are prolonged surgery time, low body mass index, low blood pressure during the procedure, and low temperature of the arthroscopic irrigation fluid.

Hypothermia and rapid rewarming is associated with worse outcome following traumatic brain injury

PURPOSE

The purpose of the present study was to determine (1) the prevalence and degree of hypothermia in patients on emergency department admission and (2) the effect of hypothermia and rate of rewarming on patient outcomes.

METHODS

Secondary data analysis was conducted on patients admitted to a level I trauma center following severe traumatic brain injury (n = 147). Patients were grouped according to temperature on admission according to hypothermia status and rate of rewarming (rapid or slow). Regression analyses were performed.

FINDINGS

Hypothermic patients were more likely to have lower postresuscitation Glasgow Coma Scale scores and a higher initial injury severity score. Hypothermia on admission was correlated with longer intensive care unit stays, a lower Glasgow Coma Scale score at discharge, higher mortality rate, and lower Glasgow outcome score-extended scores up to 6 months postinjury (P < .05). When controlling for other factors, rewarming rates more than 0.25°C/h were associated with lower Glasgow Coma Scale scores at discharge, longer intensive care unit length of stay, and higher mortality rate than patients rewarmed more slowly although these did not reach statistical significance.

CONCLUSION

Hypothermia on admission is correlated with worse outcomes in brain-injured patients. Patients with traumatic brain injury who are rapidly rewarmed may be more likely to have worse outcomes. Trauma protocols may need to be reexamined to include controlled rewarming at rates 0.25°C/h or less.

The Osborn wave in accidental hypothermia

Hypothermia is generally defined as a core body temperature less than 35 degrees C (95 degrees F), and is one of the most common environmental emergencies encountered by emergency physicians. A 32-year-old male hunter was admitted to the hospital with altered mental status. He remained unconscious, Glasgow Coma Scale (GCS) score was recorded as 5/15, and pupils were dilated and unreactive. His vital signs showed a heart rate of 48 beats/min, respiratory rate of 10 breaths/min, blood pressure of 95/50 mm Hg, and rectal temperature of 31 degrees C. An electrocardiogram (ECG) was obtained and showed marked sinus bradycardia and J waves. His finger-stick glucose was 85. He was intubated. After 3 h of active rewarming, his temperature was 34 degrees C, and the repeat ECG showed near-complete resolution of the J waves and acceleration of the sinus rate to 68 beats/min. At the same time, emergency head computed tomography (CT) scan showed subarachnoid hemorrhage (SAH) and subdural hemorrhage. The patient died on the third day of admission. In this case we want to indicate that J waves and obtunded state could be due to either SAH or hypothermia, and SAH could have been missed if initial obvious hypothermia had been believed to cause all symptoms.

Kardiopulmonale Reanimation nach Heroinintoxikation und Hypothermie

We present the case of a 21-year-old female drug addict with severe accidental hypothermia (core body temperature 27.5 degrees C) and cardiorespiratory arrest. After successful cardiopulmonary resuscitation the patient was actively internally rewarmed without the use of extracorporal circulation. Although at the first clinical presentation the patient appeared to be dead, an excellent neurological outcome was achieved. This case report reviews the epidemiology, pathophysiology, prognostic markers and the therapeutic approaches of severe hypothermia.

Akzidentelle urbane Unterkühlung

In emergency medicine accidental hypothermia (<35 degrees C) is a common epiphenomenon of many medical conditions. In contrast, severe hypothermia (<28 degrees C) occurs very seldom and presents a difficult medical situation. Here we present a female patient with severe urban hypothermia (core temperature of 20.7 degrees C) and circulatory arrest. An overview of the emergency treatment, rewarming strategy with extracorporeal circulation and the clinical course will be given. The survival of the patient and the favorable neurological outcome will be discussed considering the current literature. Due to the paucity of treatment guidelines or clear prognostic criteria of withholding or withdrawing treatment in severe hypothermia, the decision of prolonged resuscitation and rewarming strategy is solely dependent on the individual judgement and medical experience of the physician. The positive clinical outcome which can be gleaned from case reports or single retrospective studies should encourage the emergency physician to selectively rewarm a severe hypothermic patient with extracorporeal circulation under prolonged CPR.

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.

Pancytopenia induced by hypothermia

Hypothermia has been demonstrated to induce pancytopenia in animals, but whether this association exists in humans is unknown. The authors report the case of an 8-year-old girl in whom hypothermia (temperature 33 degrees C-35 degrees C) is the cause of pancytopenia. The patient developed thermoregulatory dysfunction subsequent to surgical resection of a craniopharyngioma. Her recurrent cytopenias could not be explained by any etiology except chronic hypothermia. The pancytopenia improved upon rewarming the patient to a temperature of 36 degrees C. This association between hypothermia and pancytopenia has rarely been reported in humans and may be underdiagnosed especially in cases of transient or milder presentations. The authors recommend careful hematologic monitoring of patients with thermoregulatory dysfunction.

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.

Field management of avalanche victims

The median annual mortality from snow avalanches registered in Europe and North America 1981-1998 was 146 (range 82-226); trend stable in Alpine countries (r=-0.29; P=0.24), increasing in North America (r=0.68; P=0.002). Swiss data over the same period document 1886 avalanche victims, with an overall mortality rate of 52.4% in completely-buried, versus 4.2% in partially-, or non-buried, persons. Survival probability in completely-buried victims in open areas (n=638) plummets from 91% 18 min after burial to 34% at 35 min, then remains fairly constant until a second drop after 90 min. Likewise, survival probability for completely-buried victims in buildings or on roads (n=97) decreases rapidly following burial initially, but as from 35 min it is significantly higher than that for victims in open areas, with a maximum difference in respective survival probability (31% versus 7%) from 130 to 190 min (P<0.001). Standardised guidelines are introduced for the field management of avalanche victims. Strategy by rescuers confronted with the triad hypoxia, hypercapnia and hypothermia is primarily governed by the length of snow burial and victim's core temperature, in the absence of obviously fatal injuries. With a burial time < or =35 min survival depends on preventing asphyxia by rapid extrication and immediate airway management; cardiopulmonary resuscitation for unconscious victims without spontaneous respiration. With a burial time >35 min combating hypothermia becomes of paramount importance. Thus, gentle extrication, ECG and core temperature monitoring and body insulation are mandatory; unresponsive victims should be intubated and pulseless victims with core temperature <32 degrees C (89.6 degrees F) (prerequisites being an air pocket and free airways) transported with continuous cardiopulmonary resuscitation to a specialist hospital for extracorporeal re-warming.

Q-T and JT dispersion in the elderly with urban hypothermia

Twenty elderly patients (12 females and 8 males, aged 65-88 years) were treated because of hypothermia: 11 suffered from moderate (35-32 degrees C) and nine from severe hypothermia (<32 degrees C). The control group consisted of 20 age and sex-matched healthy elderly persons. Twelve-channel electrocardiograms were recorded on admission and during hospitalization. In patients with moderate hypothermia Osborn wave was present in eight of 11, and minimal Osborn wave in three of 11; in severe hypothermia Osborn wave was seen in seven of nine, and minimal in two of nine. The corrected Q-T interval (Q-Tc) was analyzed according to the formula of Bazett: measured Q-T(s)/ radical R-R(s). The JT and the corrected JT interval (JTc) were measured according to the formula: JT=Q-T-QRS. The Q-T interval index (Q-TI) was measured according to the formula: (Q-TI:656)x(HR+100); and the JT interval index JTI: (JT:518)x(HR+100). The dispersion of the Q-Tc (JTc) was defined as the difference between maximum and minimum measured Q-Tc interval (JTc). The Q-Tc interval in the group with hypothermia was 651.41+/-130.06 ms, while in the control group it was 398.14+/-76.21 ms (P<0.001). The Q-Tc dispersion in the group with hypothermia was 91.39+/-51.98, and in the control group 33.21+/-10.25 ms (P<0.001). The Q-TcI in the group with hypothermia was 89.91+/-21.44, and in the control group 39.56+/-9.41 ms ((P<0.001). The JTc in the group with hypothermia was 542.66+/-132.74, in the control group: 328.06+/-76.92 (P<0.001). The JTc dispersion in the group with hypothermia was 79.35+/-46.22, and in the control group 28.53+/-7.99 (P<0.0001). The JTcI in the group with hypothermia was 93.06+/-17.38, in the control group it was 40.23+/-7.59 (P<0.001). The mean values of the Q-TcI were greater than Q-TI, and the mean values of the JTcI were greater than JTI, but the difference was not significant (P>0.10). The mean values of the JTcI were greater than Q-TcI, but the difference was not significant as well (P>0.05). There was no correlation between rectal temperature and dispersion of Q-T, Q-Tc, JT, JTc, and Osborn wave. The maximum Osborn wave and the maximum Q-T interval were registered in anteroseptal leads (V(2)-V(3)). The dispersion of the Q-Tc and of the JTc lasted more than Osborn wave. There was no correlation between rectal temperature and PR interval, RR interval and QRS duration. The prolonged dispersion of the Q-Tc (and JTc) last 24-48 h longer than Osborn wave.

Accidental hypothermia in a child

We report a case of severe accidental hypothermia (24.8 degrees C) in a seven-year-old child due to prolonged exposure to low temperatures and temporary contact with river water. When the patient was seen in hospital, bradycardia (30.min-1), bradypnoea (5. min-1), scarcely reacting pupils, and Glasgow Coma Scale=3 were noted. For rewarming minimally invasive techniques (humidified warmed gases and intravenous solutions at 40 degrees C) were employed with a very successful outcome.

Forced air surface rewarming in patients with severe accidental hypothermia

Methods of rewarming patients with severe accidental hypothermia remain controversial. This paper reports our experience with the use of forced air rewarming in patients with severe accidental hypothermia and a body core temperature below 30 degrees C. Fifteen hypothermic patients (body core temperature 24-30 degrees C) were successfully treated with forced air rewarming to a body core temperature above 35 degrees C (mean rewarming rate 1.7 degrees C/h, range from 0.7 to 3.4 degrees C/h). An afterdrop phenomenon was not observed in any of the patients. Nine hypothermic patients (group 1) had no prehospital cardiac arrest, all nine were long-term survivors and made a full recovery. Six patients (group 2) had prehospital cardio circulatory arrest with restoration of spontaneous circulation. None of the group 2 patients survived long-term. Group 1 and group 2 patients did not differ in core temperature (26.6+/-1.6 degrees C group 1 and 27.0+/-1.8 degrees C group 2). Group 2 patients needed catecholamine support during rewarming more frequently (83 versus 22%) and had higher lactate levels and lower pH values at all points of observation. In conclusion our preliminary data indicate that forced air rewarming is an efficient and safe method of managing patients with severe accidental hypothermia. The poor outcome of patients with a history of prehospital cardiopulmonary resuscitation is probably due to irreversible ischaemic brain damage in primarily asphyxiated avalanche and near-drowning victims, rather than the consequence of the rewarming method used.

Accidental hypothermia

Individuals at extremes of age and those who have certain underlying medical conditions are at greatest risk for hypothermia. Hypothermia may occur during any season of the year and in any climate. Prompt recognition of hypothermia and early institution of the rewarming techniques are imperative for a successful outcome with minimal complications. Several rewarming techniques are available and the decision to use any of them depends on the degree of hypothermia, the condition of the patient, and the rewarming rate possible with the technique chosen.

[Hypothermia in traumatology]

Basing on the experience of the Chamonix hospital team which managed in six years 89 cases of hypothermia in trauma patients, this article reviewed the literature concerning the association hypothermia-trauma. Shock is a major triggering factor. The deleterious effects of hypothermia on the outcome is due to inadequate cardiorespiratory adaptation to shock and to increased bleeding. Although a few articles reported a beneficial effect of hypothermia in head trauma, further studies are required to assess the value of deliberate hypothermia in such patients. Restoration of a satisfactory haemodynamic activity is a priority and most often requires surgery. The rewarming manoeuvres should be initiated early and always be preventive. They are active, internal and rapid in case of haemodynamic instability and when the central temperature is below 32 degrees C. It can be more progressive and less invasive in other cases. During recovery from anaesthesia the patient must be closely monitored. In spite of a possible protecting effect, hypothermia remains an aggravating factor in traumatology and must therefore be either prevented or amended.

Successful treatment of severe hypothermia and prolonged cardiac arrest with closed thoracic cavity lavage

This case report describes the resuscitation of a 19-year-old man who had been immersed in ice water for 14 h and presented with a rectal temperature of 22 degrees C and no pulses. It reports the successful use of prolonged cardiac massage (3.5 h) and closed thoracic cavity lavage in the treatment of severe hypothermia. It also confirms that victims of severe hypothermia can be effectively treated in peripheral hospitals not equipped for cardiopulmonary bypass.

Hypothermia

Hypothermia in the hospitalized adult may be a primary process, as in exposure, or a result of a multitude of disease processes or iatrogenic factors. The condition affects virtually every metabolic process in the body. A thorough understanding of the pathophysiology of hypothermia enables the clinician to differentiate between the hypothermic syndrome and underlying illness and can assist in the detection and management of clinical sequelae. A reliable patient history is the most helpful diagnostic tool, but careful physical examination and laboratory studies are also important for detection of primary or secondary illness.

Factors and methodology in achieving ideal delivery temperatures for intravenous and lavage fluid in hypothermia

A study was undertaken to determine the relationship between temperature and delivery rate of warmed intravenous fluid using standard intravenous infusion equipment and tubing. One-liter bags of 0.9% NaCl were warmed to 60 degrees C and run through standard microdrip tubing for 1 hour at rates of 1,000, 800, 600, and 400 mL/h. Thermistor probes were placed into the bag and into the tubing at 0, 100, 180, 230, and 280 cm from the intravenous bag. Separate fluid bags were also warmed to 39.3 degrees and 75 degrees C, and the fluid was run through the same apparatus at 1,000 mL/h and 200 mL/h, respectively. Temperatures were recorded at each site at the start of the infusion and every 10 minutes thereafter for 1 hour, Subsequently, 60-mL syringes of fluid warmed to 39.5 degrees C were eluted through 50 cm tubing over 10 minutes at 300 mL/h and 360 mL/h. Mean delivery temperature over each 10-minute infusion was determined. Fluid preheated to 39.3 degrees C approached room temperature at delivery even at a flow rate of 1,000 mL/h and tubing lengths as short as 100 cm. Fluid preheated to 60 degrees C was delivered at near 37 degrees C using tubing lengths as long as 280 cm when eluted at 1,000 mL/h. Fluid preheated to 39 degrees C in 60-mL syringes and eluted through 50 cm of tubing over a period of 10 minutes at 300 mL/h or 360 mL/h was delivered near a mean temperature of 37 degrees C. These results show that warmed fluid can be delivered through standard intravenous tubing at or near 37 degrees C if the fluid is preheated to 60 degrees C and eluted through long tubing (280 cm) at high flow rates (1,000 mL/h). Alternatively, fluid warmed to 37 degrees C to 42 degrees C can be delivered at or near 37 degrees C via intermittent bolus through short tubing (50 cm) either by hand or syringe pump. The latter approach would be particularly beneficial in the pediatric population, in whom it is not advisable to administer fluid at flow rates as high as 1,000 mL/h.

The rapid reversal of profound hypothermia using peritoneal dialysis

Severe hypothermia is associated with serious patient morbidity and mortality. The groups most frequently affected are the elderly, the very young and substance abusers. We describe three such cases which were successfully treated using warmed peritoneal dialysis. Two patients recovered completely and were left with no long term deficits. The third patient recovered from the acute event, but succumbed later to an underlying medical condition. Warmed peritoneal lavage is an efficient, cost effective approach which is easily performed without specialist equipment, and involves minimal risk to the patient.

Advanced Cardiac Life Support

In brief Changes in the advanced car-brief diac life support guidelines in-elude a new classification system for interventions, training in the use of automated defibrillators, and required early defibrillation for ventricular fibrillation. The algorithms for treating ventricular fibrillation and pulseless ventricular tachycardia, pulseless electrical activity, and asystole are reviewed. Cardiac arrest caused by special circumstances-hypothermia, near drowning, trauma, and electrical injuries-presents additional treatment considerations.

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.

Successful resuscitation of a severely hypothermic neonate

A profoundly hypothermic 5-hour-old infant in cardiac arrest was brought to the emergency department by paramedics. The infant was found wrapped in a garbage bag inside a freezer. She had been in the freezer for approximately four hours. Her initial rectal temperature was 16.2 degrees C. Active external and core warming modalities, including warm blanket, radiant heat lamp, warm humidified air, heated gastric lavage, and heated bladder lavage, were used to rewarm the infant. Her temperature rose to 30.5 degrees C in three hours (4.8 degrees C/hr). The infant converted from a slow idioventricular rhythm to sinus bradycardia at 49 minutes (20.4 degrees C) into the resuscitation. At 53 minutes (21.5 degrees C), the infant moved both upper extremities. At the time of discharge from the hospital, she had no significant physical or neurologic problems. Neurologic examination at 4 months was normal. This report supports prior recommendations to aggressively rewarm severely hypothermic infants in cardiac arrest.

Portable cardiopulmonary bypass: resuscitation from prolonged ice-water submersion and asystole

Accidental hypothermia associated with near-drowning and cardiac arrest has a high mortality, especially in the adult. We report the resuscitation of a 31-year-old man who suffered extended ice-water submersion, severe hypothermia (23 degrees C), and prolonged (> or = 78 minutes) cardiac asystole. A modified portable cardiopulmonary bypass system and femoral-femoral cannulation in the Emergency Department permitted the rapid institution of core rewarming, oxygenation, and controlled reperfusion, with a successful outcome. Rapid initiation of cardiopulmonary bypass outside the operating room can be an initial treatment option in this unique clinical situation.

Environment-dependent sports emergencies

As more individuals participate in sports and outdoor activities, the frequency of environmentally related illnesses will increase. Participants in sporting events of long duration and those requiring particularly inclement weather and adverse conditions are especially prone to developing injury. Hypothermia, heat-related illnesses, and high-altitude illnesses are multisystem emergencies that require immediate, specific therapeutic maneuvers. Physicians must be able to recognize the signs and symptoms of these medical emergencies and institute definitive care. Rapid core rewarming, airway control, and prolonged cardiopulmonary resuscitation are the key factors in managing the hypothermic patient. Adequate cooling and volume resuscitation provide the basis for treating the hyperthermic patient. The patient with high altitude-related illness should be returned to a lower elevation and given supplemental oxygen. Specific intervention depends on the patient's presentation. Environmental illnesses cause severe morbidity and mortality and are frequently within the control of the sport participant. Thus physicians must educate their patients on basic preventive measures if they are going to participate in outdoor sporting activities.

[Severe accidental hypothermia]

Two cases of severe accidental hypothermia (core temperature below 25 degrees C) are reported. Both occurred in an urban area during the same winter period. Both patients had the same age and similar clinical symptoms. In the first patient, the EEG, the echocardiography and the blood gases were in favour of a good tolerance of hypothermia, which led to choice a non aggressive rewarming method. The latter included the rewarming of inhaled gas mixture as well as i.v. fluids and gastro-intestinal lavage fluid. The outcome was uneventful. In the second patient, the visceral and biological consequences were more important (pH: 6.80, blood glucose concentration: 1.48 mmol.L-1, major coagulation disorders). Therefore a rapid rewarming via a cardiopulmonary bypass was preferred. The patient died from a prolonged shock with disseminated intravascular coagulation. The use of cardiopulmonary bypass which is essential in case of cardiac arrest rhythm, is controversial in case of severe hypothermia with a still beating heart.