Predictors of cardiac arrest in severe accidental hypothermia.

STUDY OBJECTIVE: To indicate predictors of witnessed hypothermic cardiac arrest. METHODS: We conducted a retrospective analysis of 182 patients with severe accidental hypothermia (i.e., with core body temperature of ≤28 °C) who presented with preserved spontaneous circulation at first contact with medical services. We divided the study population into two groups: patients who suffered hypothermic cardiac arrest (HCA) at any time between encounter with medical service and restoration of normothermia, and those who did not sustain HCA. The analyzed outcome was the occurrence of cardiac arrest prior to achieving normothermia. Hemodynamic and biochemical parameters were analyzed with regard to their association with the outcome. RESULTS: Fifty-two (29%) patients suffered HCA. In a univariable analysis, four variables were significantly associated with the outcome, namely heart rate (p < 0.001), systolic blood pressure (p = 0.03), ventricular arrhythmia (p = 0.001), and arterial oxygen partial pressure (p = 0.002). In the multivariable logistic regression the best model predicting HCA included heart rate, PaO2, and Base Excess (AUROC = 0.78). In prehospital settings, when blood gas analysis is not available, other multivariable model including heart rate and occurrence of ventricular arrhythmia (AUROC = 0.74) can be used. In this study population, threshold values of heart rate of 43/min, temperature-corrected PaO2 of 72 mmHg, and uncorrected PaO2 of 109 mmHg, presented satisfactory sensitivity and specificity for HCA prediction. CONCLUSIONS: In patients with severe accidental hypothermia, the occurrence of HCA is associated with a lower heart rate, hypoxemia, ventricular arrhythmia, lower BE, and lower blood pressure. These parameters can be helpful in the early selection of high-risk patients and their allocation to extracorporeal rewarming facilities.

Survival in a Collapsed Stable for 37 Days After Avalanche Burial in 1755.

In 1755 in Bergemoletto, Italy, an avalanche buried 4 people (2 women, a girl, and a boy) and several animals in a stable. After 37 d in a pitch-dark confined space, 3 of the 4 people were rescued alive. The 3 survivors had only goat milk, a few chestnuts, a few kg of raw kid meat, and meltwater for nutrition. We describe the longest-known survival in an avalanche burial and discuss the medical and psychological problems of the survivors. The boy died. When they were extricated, all 3 survivors were exhausted, cachectic, and unable to stand or walk. They were severely malnourished and were experiencing tingling, tremors, and weakness in the legs; constipation; changes in taste; and amenorrhea. One of the women had persistent eye problems and developed symptoms consistent with post-traumatic stress disorder. The survivors were given slow refeeding. It took from 1 to 6 wk before they could walk. We compare this case to other long-duration burials, especially mining accidents, and describe the rescue and patient care after long-duration burials. This case demonstrates that people can overcome extremely adverse conditions and survive.

Prehospital Use of Ultrathin Reflective Foils.

Ultrathin reflective foils (URFs) are widely used to protect patients from heat loss, but there is no clear evidence that they are effective. We review the physics of thermal insulation by URFs and discuss their clinical applications. A conventional view is that the high reflectivity of the metallic side of the URF is responsible for thermal protection. In most circumstances, the heat radiated from a well-clothed body is minimal and the reflecting properties of a URF are relatively insignificant. The reflection of radiant heat can be impaired by condensation and freezing of the moisture on the inner surface and by a tight fit of the URF against the outermost layer of insulation. The protection by thermal insulating materials depends mostly on the ability to trap air and increases with the number of covering layers. A URF as a single layer may be useful in low wind conditions and moderate ambient temperature, but in cold and windy conditions a URF probably best serves as a waterproof outer covering. When a URF is used to protect against hypothermia in a wilderness emergency, it does not matter whether the gold or silver side is facing outward.

The efficiency of continuous renal replacement therapy for rewarming of patients in accidental hypothermia--An experimental study.

Severe accidental hypothermia carries high mortality and morbidity and is often treated with invasive extracorporeal methods. Continuous veno-venous hemodiafiltration (CVVHDF) is widely available in intensive care units. We sought to provide theoretical basis for CVVHDF use in rewarming of hypothermic patients. CVVHDF system was used in the laboratory setting. Heat balance and transferred heat units were evaluated for the system without using blood. We used 5L of crystalloid solution at the temperature of approximately 25°C, placed in a thermally insulated tank (representing the "central compartment" of a hypothermic patient). Time of warming the central compartment from 24.9 to 30.0°C was assessed with different flow combinations: "blood" (central compartment fluid) 50 or 100 or 150 mL/min, dialysate solution 100 or 1500 mL/h, and substitution fluid 0 or 500 mL/h. The total circulation time was 1535 minutes. There were no differences between heat gain values on the filter depending on blood flow (P = .53) or dialysate flow (P = .2). The mean heating time for "blood" flow rates 50, 100, and 150 mL/min was 113.7 minutes (95% CI, 104.9-122.6 minutes), 83.3 minutes (95% CI, 76.2-90.3 minutes), and 74.7 minutes (95% CI, 62.6-86.9 minutes), respectively (P < .01). The respective median rewarming rate for different "blood" flows was 3.6°C/h (IQR, 3.0-4.2°C/h), 4.8 (IQR, 4.2-5.4°C/h), and 5.4 (IQR, 4.8-6.0°C/h), respectively (P < .01). The dialysate flow did not affect the warming rate. Based on our experimental model, CVVHDF may be used for extracorporeal rewarming, with the rewarming rates increasing achieved with higher blood flow rates.

Outcomes of patients suffering unwitnessed hypothermic cardiac arrest rewarmed with extracorporeal life support: A systematic review.

Prolonged cardiac arrest (CA) may lead to neurologic deficit in survivors. Good outcome is especially rare when CA was unwitnessed. However, accidental hypothermia is a very specific cause of CA. Our goal was to describe the outcomes of patients who suffered from unwitnessed hypothermic cardiac arrest (UHCA) supported with Extracorporeal Life Support (ECLS). We included consecutive patients' cohorts identified by systematic literature review concerning patients suffering from UHCA and rewarmed with ECLS. Patients were divided into four subgroups regarding the mechanism of cooling, namely: air exposure; immersion; submersion; and avalanche. A statistical analysis was performed in order to identify the clinical parameters associated with good outcome (survival and absence of neurologic impairment). A total of 221 patients were included into the study. The overall survival rate was 27%. Most of the survivors (83%), had no neurologic deficit. Asystole was the presenting CA rhythm in 48% survivors, of which 79% survived with good neurologic outcome. Variables associated with survival included the following: female gender (P < .001); low core temperature (P = .005); non-asphyxia-related mechanism of cooling (P < .001); pulseless electrical activity as an initial rhythm (P < .001); high blood pH (P < .001); low lactate levels (P = .003); low serum potassium concentration (P < .001); and short resuscitation duration (P = .004). Severely hypothermic patients with unwitnessed CA may survive with good neurologic outcome, including those presenting as asystole. The initial blood pH, potassium, and lactate concentration may help predict outcome in hypothermic CA.

Artifacts in fluoroscopy and changes in radiation dose caused by heating blankets and insulating covers during simulated endovascular treatment.

PURPOSE: We aimed to assess whether insulating covers and warming systems cause artifacts in fluoroscopy, and whether they alter the radiation dose. METHODS: Eight insulating and warming systems were wrapped around the phantom in order to obtain images in fluoroscopy, and to measure the absorbed and scattered radiation dose. A dosimeter, endovascular catheters, and stents were placed into a phantom. The other dosimeter was placed outside of a C-arm table, at the operator's and anesthesiologist's locations. RESULTS: Most of the insulating covers did not cause artifacts in the fluoroscopy and led to a significant decrease in both the absorbed and scattered radiation dose. The highest decrease in the absorbed dose was observed with metalized foil (- 2.09%; p = 0.001) and in the scattered dose with Helios cover (- 55%; p < 0.001). Only one heating system (Ready Heat combined with Hypothermia Prevention and Management Kit cover) caused significant artifacts and increased radiation up to 99% (p < 0.001). CONCLUSION: Thermal insulation may be maintained during X-ray-guided emergency endovascular procedures in trauma victims. Self-heating blankets should be replaced with another warming system.

Resuscitation of an Unconscious Victim of Accidental Hypothermia in 1805.

In 1805, W.D., a 16-y-old boy, became hypothermic after he was left alone on a grounded boat in Leith Harbour, near Edinburgh, Scotland. He was brought to his own house and resuscitated with warm blankets, smelling salts, and massage by Dr. George Kellie. W.D. made an uneventful recovery. We discuss the pathophysiology and treatment of accidental hypothermia, contrasting treatment in 1805 with treatment today. W.D. was hypothermic when found by passersby. Although he appeared dead, he was rewarmed with help from Dr. Kellie and his assistants over 200 y ago using simple methods. One concept that has not changed is the critical importance of attempting resuscitation, even if it seems to be futile. Don't give up!

Prognostic Factors for Nonasphyxia-Related Cardiac Arrest Patients Undergoing Extracorporeal Rewarming - HELP Registry Study.

OBJECTIVE: Extracorporeal rewarming is the treatment of choice for patients who had hypothermic cardiac arrest, allowing for best neurologic outcome. The authors' goal was to identify factors associated with survival in nonasphyxia-related hypothermic cardiac arrest patients undergoing extracorporeal rewarming. DESIGN: All 38 cardiac surgery departments in Poland were encouraged to report consecutive hypothermic cardiac arrest patients treated with extracorporeal life support. All variables collected were analyzed in order to compare survivor and nonsurvivor groups. The parameters available at the initiation of extracorporeal rewarming were considered as potential predictors of survival in a logistic regression model. The primary outcome was survival to discharge from the intensive care unit. The secondary outcome was neurologic status. SETTING: Multicenter retrospective study. PARTICIPANTS: Ninety-eight cases in the final analysis. INTERVENTIONS: All patients in nonasphyxia-related hypothermic cardiac arrest rewarmed with extracorporeal life support. MEASUREMENTS AND MAIN RESULTS: The survival rate was 53.1%, and 94.2% of survivors had favorable neurologic outcome. The lowest reported core temperature with cerebral performance category scale 1 was 11.8°C. A univariate analysis identified 3 variables associated with survival, namely: age, initial arterial pH, and lactate concentration. In a multivariate analysis, 2 independent predictors of survival were age (0.957; 95% confidence interval [CI] 0.924-0.991) and lactates (0.871; 95% CI 0.789-0.961). The area under the receiver operating characteristics curve for this fitted model was 0.71; 95% CI 0.602-0.817. CONCLUSIONS: Favorable survival with good neurologic outcome in nonasphyxiated hypothermic patients treated with extracorporeal life support was reported. Age and initial lactate level are independently associated with survival.

Efficacy of warming systems in mountain rescue: an experimental manikin study.

Mountain accident casualties are often exposed to cold and windy weather. This may induce post-traumatic hypothermia which increases mortality. The aim of this study was to assess the ability of warming systems to compensate for the victim's estimated heat loss in a simulated mountain rescue operation. We used thermal manikins and developed a thermodynamic model of a virtual patient. Manikins were placed on a mountain rescue stretcher and exposed to wind chill indices of 0 °C and - 20 °C in a climatic chamber. We calculated the heat balance for two simulated clinical scenarios with both a shivering and non-shivering victim and measured the heat gain from gel, electrical, and chemical warming systems for 3.5 h. The heat balance in the simulated shivering patient was positive. In the non-shivering patient, we found a negative heat balance for both simulated weather conditions (- 429.53 kJ at 0 °C and - 1469.78 kJ at - 20 °C). Each warming system delivered about 300 kJ. The efficacy of the gel and electrical systems was higher within the first hour than later (p < 0.001). We conclude that none of the tested warming systems is able to compensate for heat loss in a simulated model of a non-shivering patient whose physiological heat production is impaired during a prolonged mountain evacuation. Additional thermal insulation seems to be required in these settings.

Successful Defibrillation at a Core Temperature of 18.2 Degrees Celsius.

Both the temperature at which defibrillation can be effectively used and how often it should be repeated in severe accidental hypothermia have not been definitely established. Current recommendations are based mainly on expert opinion and suggest withholding defibrillation after 3 shocks when the core temperature is below 30°C (86°F). However, growing evidence supports the effectiveness of defibrillation in patients with a core temperature below 30°C (86°F). We present a case of successful defibrillation of a 54-y-old, severely hypothermic patient with a core temperature of 18.2°C (64.8°F). The shock was delivered automatically by an implanted cardioverter-defibrillator shortly after the implementation of extracorporeal rewarming. The patient survived and was discharged from the hospital neurologically intact. It might be reasonable to consider defibrillation attempts in severely hypothermic patients despite current guidelines to the contrary. Increasing coronary perfusion using extracorporeal circulation may result in a better response to defibrillation.

Effect of Thermal Insulation on Image Quality and Radiation Dose in Polytrauma Computed Tomography.

PURPOSE: Unintentional drop in body temperature in trauma victims is an independent risk factor for mortality. We aimed to assess the impact of thermal insulation on image quality and radiation dose in polytrauma computed tomography (CT). METHODS: Thirteen different insulating covers were used to wrap CT phantoms. Images were assessed subjectively at a radiological workstation and analyzed digitally with dedicated software evaluating the noise intensity, spatial resolution, and image homogeneity. The radiation dose was measured using a dosimeter. RESULTS: Most materials did not cause significant artifacts apart from 2 heating pads. Although the radiation dose was increased by the majority of insulating covers (up to 64.66%), certain covers decreased the absorbed radiation (up to -7.35%). CONCLUSIONS: The majority of insulating systems do not cause artifacts in CT scans. When using covers with self-heating warmers, removing the heating pad is suggested due to the risk of considerable artifacts appearing. Certain insulating covers may increase or decrease the radiation dose.

Body temperature measurement in ambulance: a challenge of 21-st century?

BACKGROUND: Some crucial decisions in treatment of hypothermic patients are closely linked to core body temperature. They concern modification of resuscitation algorithms and choosing the target hospital. Under- as well as over-estimation of a patient's temperature may limit his chances for survival. Only thermometers designed for core temperature measurement can serve as a guide in such decision making. The aim of the study was to assess whether ambulance teams are equipped properly to measure core temperature. METHODS: A survey study was conducted in collaboration with the Health Ministry in April 2018. Questionnaires regarding the model, number, and year of production of thermometers were sent to each pre-hospital unit of the National Emergency Medical System in Poland. RESULTS: A total of 1523 ground ambulances are equipped with 1582 thermometers. 53.57% are infrared-based ear thermometers, 23.02% are infrared-based surface thermometers, and 20.13% are conventional medical thermometers. Only 3.28% of devices are able to measure core body temperature. Most of analyzed thermometers (91.4%) are not allowed to operate in ambient temperature below 10 °C. CONCLUSIONS: There are only 3.28% of ground ambulances that are able to follow precisely international guidelines regarding a patient's core body temperature. A light, reliable thermometer designed to measure core temperature in pre-hospital conditions is needed.

Is an emergency department a safer place for hypothermic victims than an ambulance? A comparison of the knowledge of medical personnel concerning hypothermia.

OBJECTIVE: Introduction: Improper initial management of a victim in severe hypothermia is associated with a risk of cardiac arrest. At the same time, an uncontrolled drop in core body temperature in trauma victims is an independent risk factor for mortality. Medical personnel require a thorough understanding of the pathophysiology and treatment of hypothermia. Gaps in this understanding can lead to serious complications for patients. The aim: To compare knowledge concerning hypothermia between medical personnel working in emergency departments (ED) and emergency medical services (EMS). PATIENTS AND METHODS: Materials and methods: A total of 5,362 participants were included in the study. In this study, EMS and ED personnel were encouraged to participate in an e-learning course on hypothermia. Subsequently, the scores of a pre-test, lesson tests and post-test completed by participants of this course were compared. RESULTS: Results: Pre-test scores were significantly higher among personnel working in EMS compared with those working in EDs. Nurses employed in EDs had significantly more failures in completing the course than EMS nurses. The most difficult topics for all practitioners were post-traumatic hypothermia and hypothermia-related clotting disorders. CONCLUSION: Conclusions: EMS personnel have a higher level of knowledge of hypothermia than ED personnel. Moreover, an e-learning course is an effective tool for improving medical personnel's knowledge of hypothermia.

Ten-year follow-up after combined coronary artery bypass grafting and transmyocardial laser revascularization in patients with disseminated coronary atherosclerosis.

Coronary artery disease involving heavily calcified lesions has been associated with worse short- and long-term outcomes including increased mortality. This paper aims to evaluate long-term survival benefit when CABG + transmyocardial laser revascularization (TMLR) are performed on the hearts of patients with disseminated coronary atherosclerosis (DCA). This novel retrospective study was conducted between 1997 and 2002 and followed 86 patients with ischemic heart disease and severe DCA who underwent TMLR using a Holmium:YAG laser and/or CABG. There were 46 patients who had CABG plus TMLR on at least one heart wall ("combined therapy group") and 40 patients who had CABG or TMLR separately on at least one heart wall ("single therapy group"). For the whole group, actuarial survival at 10 years was 78.3% in the combined group compared to 72.5% in the single therapy group (p = 0.535). Ten-year survival in the combined vs. single therapy group for the anterior heart walls was 100 vs. 72.2% (p = 0.027). For the lateral and posterior heart walls were 73.7 vs. 73.3% (p = 0.97) and 84.2 vs. 72% (p = 0.27), respectively. Kaplan-Meier survival analysis showed benefit only for the anterior heart wall (F Cox test, p = 0.103). Single therapy procedures on all heart walls (odds ratio 1.736, p = 0.264) or on the anterior heart wall only (odds ratio 3.286, p = 0.279) were found to be predictors of 10-year late mortality. Combined therapy (TMLR + CABG) provides benefit for perioperative mortality and long-term survival only when provided on the anterior heart wall. For patients with disseminated coronary atherosclerosis, cardiac mortality was found to be increased when followed up 6 years later, regardless of the therapy applied.

[Hypothermia - e-learning course dedicated to lifeguards, border guards and policemen].

OBJECTIVE: Introduction: The paper covers the problem of pre-hospital hypothermia recognition and management among lifeguards, board guards and policemen, who took part in e-learning course Academy of Hypothermia. PATIENTS AND METHODS: Materials and methods: The subject of analysis were the results of pre-test, post-test and lesson revision tests of Academy of Hypothermia e-learning course, taken by lifeguards (WOPR), board guards (SG) and policemen (POL). RESULTS: Results: 221 participants were enrolled in a study. Lifeguards were significantly younger than other groups (mean age respectively: 34,13 years SG; 32,95 years POL and 23,31 years WOPR; p< 0,001) and median work experience (respectively: 10 years SG, 8 years POL and 2 years WOPR; p< 0,001). Pre-test analysis showed significant difference in results of board guards and lifeguards (median and q1-q3 values respectively: 61%; 43%-92% for SG and 53%; 46%-69% for WOPR, p = 0,02). Post-test analysis proved significantly better results of board guards (median and q1-q3 values: 92%; 77%-100%) in comparison to policemen (median and q1-q3 values: 85%; 69%-92%) and lifeguards (median and q1-q3 values: 85%; 69%-92%). Extra analysis was performed for lesson revision tests. The least correct answers were noted in lessons covering the topic of post trauma hypothermia and the algorithm of hypothermia casualty management. CONCLUSION: Conclusions: Lifeguards have least knowledge on accidental hypothermia than board guards and policemen. E-learning course is an effective tool for improving knowledge of hypothermia recognition and treatment.

Measuring core temperature using the proprietary application and thermo-smartphone adapter.

Fast and accurate measurement of core body temperature is crucial for accidental hypothermia treatment. We have developed a novel light and small adapter to the headset jack of a mobile phone based on Android. It has been applied to measure temperature and set up automatic notifications (e.g. Global Positioning System coordinates to emergency services dispatcher, ECMO coordinator). Its validity was confirmed in comparison with Vital Signs Monitor Spacelabs Healthcare Elance 93300 as a reference method, in a series of 260 measurements in the temperature range of 10-42 °C. Measurement repeatability was verified in a battery of 600 measurements (i.e. 100 readings at three points of 10, 25, 42 °C for both esophageal and tympanic catheters). Inter-method difference of ≤0.5 °C was found for 98.5% for esophageal catheter and 100% for tympanic catheter measurements, with concordance correlation coefficient of 0.99 for both. The readings were almost completely repeatable with water bath measurements (difference of ≤0.5 °C in 10 °C: 100% for both catheters; in 25 °C: 99% for esophageal catheter and 100% tympanic catheter; in 42 °C: 100% for both catheters). This lightweight adapter attached to smartphone and standard disposable probes is a promising tool to be applied on-site for temperature measurement in patients at risk of hypothermia.