Differences in the thermal properties and surface temperature of prehospital antihypothermia devices: an in vitro study

Dvir, Erez; Epstein, Danny; Berzon, Baruch; Raz, Aeyal; Lehavi, Amit

doi:10.1136/emermed-2020-211057

Emerg Med J

2021

DOI: 10.1136/emermed-2020-211057

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Differences in the thermal properties and surface temperature of prehospital antihypothermia devices: an in vitro study

Erez Dvir

Danny Epstein

Baruch Berzon

et al.

Abstract: BackgroundPreventing and treating hypothermia in prehospital settings is crucial. Several products have been developed to prevent heat loss and actively warm patients in prehospital settings. We compared the efficacy and the surface temperature of different antihypothermia products, using a fluid-based model at two ambient temperatures.MethodsWe tested five active (Blizzard Heat with active pads, Ready-Heat, Ready-Heat-II, Hypothermia Prevention and Management Kit (HPMK), Bair Hugger) and five passive (Blizzar… Show more

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Cited by 4 publications

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Seasonal Association With Hypothermia in Combat Trauma

Eisenhauer,

April,

Rizzo

et al. 2023

Military Medicine

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Introduction Hypothermia increases mortality in trauma populations and frequently occurs in military casualties due to the nature of combat environments. The association between hypothermia and the time of year when injured remains unclear. We sought to determine the association between seasonal changes in temperature and hypothermia among combat casualties. Materials and Methods This observational study was a secondary analysis of a previously described Department of Defense Trauma Registry dataset which included U.S. military and Coalition casualties who received prehospital care from January 2007 to March 2020 in Afghanistan and Iraq. We tested for associations between hypothermia (<36.2°C) and seasonal ambient temperatures by constructing multivariable logistic regression models. Summer was defined as June through August and winter as December through February. We assumed that the combat operations occurred in the area near the point of first contact with the deployed military treatment facilities. This study was determined to be exempt from Institutional Review Board oversight. Results There were 5,821 that met inclusion for this study. Within the multivariable logistic regression model, we adjusted for injury severity score, mechanism of injury, and imputed transport time, finding that combat casualties were 2.28 (odds ratio, 95% confidence interval 1.93-2.69) times more likely to develop hypothermia in the winter versus summer. When using temperature as a continuous outcome, casualties had a lower emergency department temperature during the winter (parameter estimate −0.133°C, P < 0.001) after adjusting for confounders. In casualties experiencing hypothermia, mortality was higher (4% versus 1%, P < 0.001), and composite median injury severity score values were higher (10 versus 5, P < 0.001). Among hypothermic casualties, serious injuries were significantly more common (all P < 0.001) to the head (15% versus 7%), thorax (15% versus 7%), abdomen (9% versus 6%), extremities (35% versus 22%), and skin (4% versus 2%). Conclusions We found a seasonal variation in the occurrence of hypothermia in a large cohort of trauma casualties. Despite adjustment for multiple known confounders, our findings substantiate probable ambient temperature variations to trauma-induced hypothermia. Furthermore, our findings, when taken in the context of other studies on the efficacy of current hypothermia prevention and treatment strategies, support the need for better methods to mitigate hypothermia in future cold-weather operations.

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Seasonal Association With Hypothermia in Combat Trauma

Eisenhauer,

April,

Rizzo

et al. 2023

Military Medicine

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Skin heating during simulated hemorrhage lowers arterial blood pressure but not tolerance following exercise in a cold environment

Tracy,

Hill,

Liester

et al. 2024

Journal of Applied Physiology

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Skin heating helps avoid hypothermia in trauma victims but may influence systolic (SBP) and mean arterial blood pressures (MAP) helping guide resuscitation. We examined the effect of skin heating upon tolerance and arterial blood pressure during lower body negative pressure (LBNP) across four trials. Nine participants completed 15 exercise intervals (60 sec 88% PPO and 60 sec 10% PPO) in a cold environment (0°C, 70% RH) lowering mean skin temperature (Tsk) before undergoing LBNP to pre syncope where Tsk remained low (Cold Trial: 27.6 ± 1.1°C) or was increased via water perfused suit sixty seconds into LBNP to 32.3 ± 0.7°C (Normothermic Trial), 34.8 ± 0.4°C (Warm Trial) or 36.1 ± 0.8°C (Hot Trial). Tsk was different between trials (P = 0.001). Core temperature was not different between trials, increasing with exercise (36.9 ± 0.3°C to: 37.9 ± 0.4°C) and remaining elevated during LBNP (37.7 ± 0.4°C). During LBNP, MAP was greatest in the Cold (88 ± 7 mmHg) and relatively lowered in Normothermic (83 ± 5mmHg), Warm (82 ± 5mmHg) and Hot Trials (79 ± 7mmHg, all P ≤ 0.017 vs. Cold). SBP was greatest in Cold (111 ± 9mmHg) and Normothermic trials (110 ± 10mmHg) and relatively lowered in Warm (105 ± 7mmHg) and Hot trials (103 ± 11mmHg, both P ≤ 0.037). LBNP tolerance was not different between trials (P = 0.746). Following exercise in a cold environment, skin heating during simulated hemorrhage lowers arterial blood pressures and has implications for prehospital care of trauma victims.

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What is the best way to keep the patient warm during technical rescue? Results from two prospective randomised controlled studies with healthy volunteers

et al. 2023

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Background Accidental hypothermia is a manifest problem during the rescue of entrapped victims and results in different subsequent problems as coagulopathy and wound infection. Different warming methods are available for the preclinicial use. However, their effectiveness has hardly been evaluated. Methods In a first step a survey among German fire brigades was performed with questions about the most used warming methods. In a second step two crossover studies were conducted. In each study two different warming method were compared with forced air warming – which is the most frequently used and highly effective warming method in operation rooms (Study A: halogen floodlight vs. forced air warming; Study B: forced air warming vs. fleece blanket). In both studies healthy volunteers (Study A: 30 volunteers, Study B: 32 volunteers) were sitting 60 min in a cold store. In the first 21 min there was no subject warming. Afterwards the different warming methods were initiated. Every 3 min parameters like skin temperature, core body temperature and cold perception on a 10-point numeric rating scale were recorded. Linear mixed models were fitted for each parameter to check for differences in temperature trajectories and cold perception with regard to the different warming methods. Results One hundred fifty-one German fire brigades responded to the survey. The most frequently used warming methods were different rescue blankets (gold/silver, wool) and work light (halogen floodlights). Both studies (A and B) showed significantly (p < 0.05) higher values in mean skin temperature, mean body temperature and total body heat for the forced air warming methods compared to halogen floodlight respectively fleece blanket shortly after warming initiation. In contrast, values for the cold perception were significantly lower (less unpleasant cold perception) during the phase the forced air warming methods were used, compared to the fleece blanket or the halogen floodlight was used. Conclusion Forced air warming methods used under the standardised experimental setting are an effective method to keep patients warm during technical rescue. Halogen floodlight has an insufficient effect on the patient’s heat preservation. In healthy subjects, fleece blankets will stop heat loss but will not correct heat that has already been lost. Trial registration The studies were registered retrospectively on 14/02/2022 on the German Clinical Trials registry (DRKS) with the number DRKS00028079.

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Differences in the thermal properties and surface temperature of prehospital antihypothermia devices: an in vitro study

Cited by 4 publications

References 17 publications

Seasonal Association With Hypothermia in Combat Trauma

Seasonal Association With Hypothermia in Combat Trauma

Skin heating during simulated hemorrhage lowers arterial blood pressure but not tolerance following exercise in a cold environment

What is the best way to keep the patient warm during technical rescue? Results from two prospective randomised controlled studies with healthy volunteers

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