Le MARCHE en ambiance grand froid

 

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Réchauffement cutané acif: Attention

Treatment of accidental hypothermia: Impact of insulation placement above or below an active external rewarming device on temperature and burn risk

 

Mydske S et Al.J Therm Biol. 2025 Apr:129:104126. doi: 10.1016/j.jtherbio.2025.104126

 

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Le risque de brûlures en raport avec l'emploi de moyens de réchauffement cutané actif est connu dès lors que la température cutanée dépasse 43°C, surtout quand le temps de contact est long comme cela peut arriver quand une medevac dure . La plupart des fabriquants recommande de ne pas les appliquer directement au contatc de la peau. Cette étude, qui compare 3 types de RCA dans 9 scenarios,  confirme le risque de dépassement de cette température. Surtout qu'il s'agisse de moyens chimique ou électrique le même risque s'observe. Il est donc fondamental de placer un dispositif isolant entre la peau du blessé et le dispositif de réchauffement cutané actif

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Introduction:

Prehospital treatment of accidental hypothermia typically involves using active external rewarming, usually either with chemical or electrical heating pads. Active external rewarming is a recommended treatment method, but carries the risk of burn injury, which can occur if tissue temperature exceeds 43 ◦C. Some device manufacturers discourage direct skin contact; however, there are no recommendations regarding type or amount of insulating material that should be placed between the patient and the device. We aimed to describe the impact of different insulating materials above and below various devices on the temperature at the contact area.

Methods:

Three different active external rewarming devices were suspended above a thermal imaging camera capable of recording the peak and average temperature of a surface area. Nine different scenarios with varying layers of insulation above and below the device, were tested over a 20-min period. The devices included an electric resistive heat pad, an oxygen-activated chemical heating blanket, and a sodium acetate chemical heat pack. Peak surface temperature was recorded every 30 s, and average surface temperature was calculated after
each test.

Results:

Nine scenarios for three different devices were tested, resulting in 27 experiments. Development of peak surface temperature varied between devices. The electric device reached a highest average temperature of 42.9 ◦C and a peak temperature of 51.4 ◦C. The oxygen-reactive chemical heating device reached a highest average temperature of 27.2 ◦C, with a peak temperature of 57.5 ◦C. The sodium acetate chemical heat pack reached a highest average temperature of 50.4 ◦C and a peak temperature of 56.2 ◦C.

Conclusions:

The devices demonstrated different temperature development characteristics depending on amount and relative placement of insulation, and all had the potential to exceed the threshold of potential thermal injury to the skin. Rescuers need to be aware of both the benefits and risks associated with the rewarming devices they use. 

Hypothermie: Plutôt un blessé au sec dès que possible que mouillé

Effect of wet clothing removal on skin temperature in subjects exposed to cold and wrapped in a vapor barrier: a human, randomized, crossover field study
Hagen LT et Al. BMC Emergency Medicine volume 24, Article number: 18 (2024) 

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La présence de vêtements humides chez un blessé pris en charge dans un contexte tactique ne permet pas le plus souvent de remplacer ceux ci par des effets secs. Cela est tout à fait acceptable si la prévention de l'hypothermie fait appel à un emballage avec plusieurs couches dont une faisance office de barrière contre la vapeur (1). L'idéal est quand même de remplacer ceux ci au plus tôt par des effets secs car alors la prise en charge de cette hypthermie sera de bien meilleure qualité 

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Background
Prehospital care for cold-stressed and hypothermic patients focuses on effective insulation and rewarming. When encountering patients wearing wet clothing, rescuers can either remove the wet clothing before isolating the patient or isolate the patient using a vapor barrier. Wet clothing removal increases skin exposure but avoids the need to heat the wet clothing during rewarming. Leaving wet clothing on will avoid skin exposure but is likely to increase heat loss during rewarming. This study aimed to evaluate the effect of wet clothing removal compared to containing the moisture using a vapor barrier on skin temperature in a prehospital setting.

Methods
This randomized crossover experimental field study was conducted in a snow cave in Hemsedal, Norway. After an initial cooling phase of 30 min while wearing wet clothes, the participants were subjected to one of two rewarming scenarios: (1) wet clothing removal and wrapping in a vapor barrier, insulating blankets, and windproof outer shell (dry group) or (2) wrapping in a vapor barrier, insulating blankets, and windproof outer shell (wet group). The mean skin temperature was the primary outcome whereas subjective scores for both thermal comfort and degree of shivering were secondary outcomes. Primary outcome data were analyzed using the analysis of covariance (ANCOVA).

Results
After an initial decrease in temperature during the exposure phase, the dry group had a higher mean skin temperature compared to the wet group after only 2 min. The skin-rewarming rate was highest in the initial rewarming stages for both groups, but increased in the dry group as compared to the wet group in the first 10 min.

 

 

Return to baseline temperature occurred significantly faster in the dry group (mean 12.5 min [dry] vs. 28.1 min [wet]). No intergroup differences in the subjective thermal comfort or shivering were observed.

Conclusion
Removal of wet clothing in combination with a vapor barrier increases skin rewarming rate compared to encasing the wet clothing in a vapor barrier, in mild cold and environments without wind.

Réchauffer les perfusions ++++++

Changes in temperature in preheated crystalloids at ambient temperatures relevant to a prehospital setting: an experimental simulation study with the application of prehospital treatment of trauma patients suffering from accidental hypothermia

Jensen E. et Al. BMC Emerg Med 24, 59 (2024)

 

Background

Accidental hypothermia is common in all trauma patients and contributes to the lethal diamond, increasing both morbidity and mortality. In hypotensive shock, fluid resuscitation is recommended using fluids with a temperature of 37–42°, as fluid temperature can decrease the patient’s body temperature. In Sweden, virtually all prehospital services use preheated fluids. The aim of the present study was to investigate how the temperature of preheated infusion fluids is affected by the ambient temperatures and flow rates relevant for prehospital emergency care.

Methods

In this experimental simulation study, temperature changes in crystalloids preheated to 39 °C were evaluated. The fluid temperature changes were measured both in the infusion bag and at the patient end of the infusion system. Measurements were conducted in conditions relevant to prehospital emergency care, with ambient temperatures varying between − 4 and 28 °C and flow rates of 1000 ml/h and 6000 ml/h, through an uninsulated infusion set at a length of 175 cm.

Results

The flow rate and ambient temperature affected the temperature in the infusion fluid both in the infusion bag and at the patient end of the system.

A lower ambient temperature and lower flow rate were both associated with a greater temperature loss in the infusion fluid.

Conclusion

This study shows that both a high infusion rate and a high ambient temperature are needed if an infusion fluid preheated to 39 °C is to remain above 37 °C when it reaches the patient using a 175-cm-long uninsulated infusion set. It is apparent that the lower the ambient temperature, the higher the flow rate needs to be to limit temperature loss of the fluid.

 

Hypothermia: Up to Date

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Hypothermie: On doit mieux faire

Hypothermia in trauma victims at first arrival of ambulance personnel: an observational study with assessment of risk factors.

Lapostolle F et Al. Scand J Trauma Resusc Emerg Med. 2017 Apr 24;25(1):43.

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Malgré les diverses recommandations portant sur le réchauffement préhospitalier, cette mesure de prévention de l'hypothermie demeure insuffisament prise en compte. Ce travail, dans lequel seul 50%es patients pris en charge bénéficient d'un réchauffement préhospitalier, le rappelle.

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BACKGROUND:

Hypothermia is common in trauma victims and is associated with increased mortality, however its causes are little known. The objective of this study was to identify the risk factors associated with hypothermia in prehospital management of trauma victims.

METHODS:

This was an ancillary analysis of data recorded in the HypoTraum study, a prospective multicenter study conducted by the emergency medical services (EMS) of 8 hospitals in France. Inclusion criteria were: trauma victim, age over 18 years, and victim receiving prehospital care from an EMS team and transported to hospital by the EMS team in a medically equipped mobile intensive care unit. The following data were recorded: victim demographics, circumstances of the trauma, environmental factors, patient presentation, clinical data and time from accident to EMS arrival. Independent risk factors for hypothermia were analyzed in a multivariate logistic regression model.

RESULTS:

A total of 461 trauma patients were included in the study. Road traffic accidents (N = 261; 57%) and falls (N = 65; 14%) were the main causes of trauma. Hypothermia (<35 °C) was present in 136/461 cases (29%). Independent factors significantly associated with the presence of hypothermia were: a low GCS (Odds Ratio (OR) = 0,87 ([0,81-0,92]; p < 0.0001), a low air temperature (OR = 0,93 [0,91-0,96]; p < 0.0001) and a wet patient (OR = 2,08 [1,08-4,00]; p = 0.03).

CONCLUSION:

The incidence of hypothermia was high on EMS arrival at the scene. Body temperature measurement and immediate thermal protection should be routine, and special attention should be given to patients who are wet.

Easywarm: Une autre couverture chauffante

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Réchauffeur: M Warmer, the best ?

Comparison of portable blood-warming devices under simulated pre-hospital conditions: a randomised in-vitro blood circuit study.

Weatherall  A. et Al. Anaesthesia. 2019 May 7. doi: 10.1111/anae.14680

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Lire aussi cet article qui met en avant la performance du Qiflow warmer

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Pre-hospital transfusion of blood products is a vital component of many advanced pre-hospital systems. Portable fluid warmers may be utilised to help prevent hypothermia, but the limits defined by manufacturers often do not reflect their clinical use. The primary aim of this randomised in-vitro study was to assess the warming performance of four portable blood warming devices (Thermal Angel, Hypotherm X LG, °M Warmer, Buddy Lite) against control at different clinically-relevant flow rates. The secondary aim was to assess haemolysis rates between devices at different flow rates. We assessed each of the four devices and the control, at flow rates of 50 ml.min^-1 , 100 ml.min^-1 and 200 ml.min^-1 , using a controlled perfusion circuit with multisite temperature monitoring. Free haemoglobin concentration, a marker of haemolysis, was measured at multiple points during each initial study run with spectrophotometry. At all flow rates, the four devices provided superior warming performance compared with the control (p < 0.001). Only the °M Warmer provided a substantial change in temperature at all flow rates (mean (95%CI) temperature change of 21.1 (19.8-22.4) °C, 20.4 (19.1-21.8) °C and 19.4 (17.7-21.1) °C at 50 ml.min^-1 , 100 ml.min^-1 and 200 ml.min^-1 , respectively).

 

There was no association between warming and haemolysis with any device (p = 0.949) or flow rate (p = 0.169). Practical issues, which may be relevant to clinical use, also emerged during testing. Our results suggest that there were significant differences in the performance of portable blood warming devices used at flow rates encountered in clinical practice.

Hypothermie profonde: Pourquoi pas ?

Deep and profound hypothermia in haemorrhagic shock, friend or foe? A systematic review

Moffatt ES. et Al. J R Army Med Corps. 2017 May 11. pii: jramc-2016-000723.

Introduction

Survival in exsanguinating cardiac arrest patients is poor, as is neurological outcome in survivors. Hypothermia has traditionally been seen as harmful to trauma patients and associated with increased mortality; however, there has been speculation that cooling to very low temperatures (≤20°C) could be used to treat haemorrhagic trauma patients by the induction of a suspended animation period through extreme cooling, which improves survival and preserves neurological function. This has been termed emergency preservation and resuscitation (EPR).

Methods

A systematic review of the literature was used to examine the evidence base behind the use of deep and profound hypothermia in haemorrhagic shock (HS). It included original research articles (human or animal) with cooling to ≤20°C after HS or an experimental model replicating it. Normovolaemic cardiac arrest, central nervous system injury and non-HS models were excluded.

Results

Twenty articles using 456 animal subjects were included, in which 327 were cooled to ≤20°C. All studies describing good survival rates were possible using EPR and 19/20 demonstrated that EPR can preserve neurological function after prolonged periods of circulatory arrest or minimal circulatory flow. This additional period can be used for surgical intervention to arrest haemorrhage in HS that would otherwise be lethal.

Conclusions The outcomes of this review have significant implications for application to human patients and the ongoing human clinical trial (EPR for Cardiac Arrest from Trauma). Current evidence suggests that hypothermia ≤20°C used in the form of EPR could be beneficial to the HS patient.

Réchauffer une perfusion: La tubulure +++

An Analysis of the Temperature Change in Warmed Intravenous Fluids during Administration in a Cold Environment at Temperatures of Less than 0

2016 Critical Care Transport Medicine Conference Scientific Forum

SIngleton W et Al. Air Medical Journal 35 (2016) 205-207

 

Objective: This is a non-human simulation study determining the decrease in temperature that occurred to 1L bags of Normal Saline in an austere environment. The bags were warmed to 38°C (100°F), administered through standard intravenous tubing at a set flow rate, while in an environment with ambient temperatures of less than 0°C (32°F). The goal was to determine if there was a significant decrease in fluid temperature from the IV bag through the tubing to the IV catheter administration site.

Methods/Materials: Three trials were run at four different temperatures, 0°C (32°F), -7 °C (20°F), -12°C (10°F ) and 33°C (72°F control ). Each bag of normal saline was warmed to the same temperature 38°C (100°F) utilizing the Soft Sack IV Fluid Warmer. Three of the bags were then placed in a cold austere environment (freezer) at each of the specified temperatures. The remaining bag was kept in the ambient temperature 33°C (72°F control). The fluid was administered through standard intravenous tubing (18 gauge catheter, 20 drop set, 211 cm in length) at a flow rate of 999ml/hr in temperatures less than 0°C (32°F). Fluid was collected in a glass container outside the austere environment with the temperature being recorded at 5 minute intervals.

Results: The results demonstrated a statistically significant (p> 0.05) change in temperature between the IV bag and the administration site. The most rapid change occurred within the first 5 minutes. The temperature change was more significant with the colder ambient temperatures, with an average of 50° difference at -7°C (20°F) and -12°C (10°F ). This is compared to a 27° difference at 0°C and the control temperature of 33°C (72°F control). The temperature of the fluid remaining within the IV bag also decreased an average of 15°C at the control temperature of 33°C (72°F control) and 0°C (32°F), which is statistically significant. The temperature in the bag decreased an average of 35°C at -7°C (20°F) and -12°C (10°F), which was statistically significant (p>0.05).

Conclusion: Based on these results, it appears that the most significant heat loss occurs through the IV tubing itself, the loss occurs rapidly, and is more pronounced at colder ambient air temperatures. Therefore, it may be beneficial to insulate the tubing on a trauma patient receiving warmed IV fluids in a cold environment of less than 0°C (32°F) to help prevent hypothermia.

Gelures

Cold Exposure Injuries to the Extremities

Golant A. et AL. J Am Acad Orthop Surg 2008;16:704- 715

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Un document un peu ancien, mais bien fait notamment une physiopathologie clairement présentée.

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Cold exposure injuries comprise nonfreezing injuries that include chilblain (aka pernio) and trench, or immersion, foot, as well as freezing injuries that affect core body tissues resulting in hypothermia of peripheral tissues, causing frostnip or frostbite. Frostbite, the most serious peripheral injury, results in tissue necrosis from direct cellular damage and indirect damage secondary to vasospasm and arterial thromboses. The risk of frostbite is influenced by host factors, particularly alcohol use and smoking, and environmental factors, including ambient temperature, duration of exposure, altitude, and wind speed. Rewarming for frostbite should not begin until definitive medical care can be provided to avoid repeated freeze-thaw cycles, as these cause additional tissue necrosis. Rewarming should be rapid and for an affected limb should be performed by submersion in warm water at 104° to 107.6°F (40° to 42°C) for 15 to 30 minutes. Débridement of necrotic tissues is generally delayed until there is a clear demarcation from viable tissues, a process that usually takes from 1 to 3 months from the time of initial exposure. Immediate escharotomy and/or fasciotomy is necessary when circulation is compromised. In addition to the acute injury, frostbite is associated with late sequelae that include altered vasomotor function, neuropathies, joint articular cartilage changes, and, in children, growth defects caused by epiphyseal plate damage.

Hyporthermie: Il faut envelopper !

Protection Against Cold in Prehospital Care: Wet Clothing Removal or Addition of a Vapor Barrier

Henriksson O. et All. Prehosp Disaster Med. 2012 Feb;27(1):53-8

Objective.

The purpose of this study was to evaluate the effect of wet clothing removal or the addition of a vapor barrier in shivering subjects exposed to a cold environment with only limited insulation available.

Methods.

Volunteer subjects (n ¼ 8) wearing wet clothing were positioned on a spineboard in a climatic chamber (–18.51C) and subjected to an initial 20 minutes of cooling followed by 30 minutes of 4 different insulation interventions in a crossover design: 1) 1 woolen blanket; 2) vapor barrier plus 1 woolen blanket; 3) wet clothing removal plus 1 woolen blanket; or 4) 2 woolen blankets. Metabolic rate, core body temperature, skin temperature, and heart rate were continuously monitored, and cold discomfort was evaluated at 5-minute intervals.

Results.

Wet clothing removal or the addition of a vapor barrier significantly reduced metabolic rate (mean difference
SE; 14
4.7 W/m2 ) and increased skin temperature rewarming (1.01
0.21C). Increasing the insulation rendered a similar effect. There were, however, no significant differences in core body temperature or heart rate among any of the conditions. Cold discomfort (median; interquartile range) was significantly lower with the addition of a vapor barrier (4; 2–4.75) and with 2 woolen blankets (3.5; 1.5–4) compared with 1 woolen blanket alone (5; 3.25–6).

Conclusions. 

In protracted rescue scenarios in cold environments with only limited insulation available, wet clothing removal or the use of a vapor barrier is advocated to limit the need for shivering thermogenesis and improve the patient’s condition on admission to the emergency department

Gelures: Le guidelines de la WMS

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Hypothermie et vêtements humides

Dry and wet heat transfert through clothing dependent on the clothing properties under cold conditions

Richards GM et Al. Int J Occup Saf Ergon. 2008;14(1):69-76.

Il est recommandé  lors de la prise en charge de blessés hypothermes de remplacer leurs vêtements humides par de vêtements secs. Ceci permettrait d'éviter l'aggravation de l'hypothermie secondaire à un transfert accru de châleur par conduction et par évaporation. Ceci est loin d'être toujours réalisable. Il convient dès lors de réaliser un isolement particulier du blessé basé sur latechnique de Hibler et dont la couche externe doit être ETANCHE à l'air. Ceci est connu depuis longtemps (ref ici). Le document proposé explique cela.

Une couche externe ETANCHE réduit les pertes thermiques évaporatives.

Lire la a fiche mémento

Hypothermie et trauma: Un point 2013

Clinical and translational aspects of hypothermia in major trauma patients: From pathophysiology to prevention, prognosis and potential preservation

http://dx.doi.org/10.1016/j.injury.2012.12.027

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Un revue très synthétique à lire, notamment le paragraphe portant sur le recours à une hypothermie induite en cas de traumatisme sévère.

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Generally, hypothermia is defined as a core temperature <35°C. In elective surgery, induced hypothermia has beneficial effects. It is recommended to diminish complications attributable to ischemia reperfusion injury. Experimental studies have shown that hypothermia during hemorrhagic shock has beneficial effects on outcome. In contrast, clinical experience with hypothermia in trauma patients has shown accidental hypothermia to be a cause of posttraumatic complications. The different etiology of hypothermia might be one reason for this disparity because induced therapeutic hypothermia, with induction of poikilothermia and shivering prevention, is quite different from accidental hypothermia, which results in physiological stress. Other studies have shown evidence that this contradictory effect is related to the plasma concentration of high-energy phosphates (e.g., adenosine triphosphate [ATP]). Induced hypothermia preserves ATP storage, whereas accidental hypothermia causes depletion. Hypothermia also has an impact on the immunologic response after trauma and elective surgery by decreasing the inflammatory response. This might have a beneficial effect on outcome. Nevertheless, posttraumatic infectious complications may be higher because of an immunosuppressive profile. Further studies are needed to investigate the impact of induced hypothermia on outcome in trauma patients.

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Quatre plaques pour une lecture rapide

Hypothermie: Quelle isolation ? Plusieurs couches et étanches à l'air

Protection against cold in prehospital care

Henriksson O. 

Ce travail suédois compare l'efficacité de diverses méthodes d'isolation thermique en fonction des conditions de vent. Le document proposé fait la synthèse de 4 publication par la même équipe:

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Lundgren P, Henriksson O, Widfeldt N, Vikström T. Insulated Spine Boardsfor Prehospital Trauma Care in a Cold Environment. International Journal of Disaster Medicine 2004;2:33–37.

Henriksson O, Lundgren P, Kuklane K, Holmér I, Björnstig U. Protection Against Cold in Prehospital Care – Thermal Insulation Properties of Blankets and Rescue Bags in Different Wind Conditions. Prehosp Disaster Med. 2009;24(5):408–415.

Henriksson O, Lundgren P, Kuklane K, Holmér I, Naredi P, Bjornstig U. Protection Against Cold in Prehospital Care: Evaporative Heat Loss Reduction by Wet Clothing Removal or the Addition of a Vapor Barrier – A Thermal Manikin Study. Prehosp Disaster Med 2012;26(6):1–6. 2009;24(5):408–415

Henriksson O, Lundgren P, Kuklane K, Holmér I, Giesbrecht G, Naredi P, Björnstig U. Protection Against Cold in Prehospital Care – The Effect on Thermoregulation by Wet Clothing Removal or Addition of a Vapour Barrier in Shivering Subjects. Manuscript.

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On utilise souvent une couverure aluminisée comme moyen deprévention de l'hypothermie? Cette façon de faire est peu efficace et doit être remise en questoin surtout en présence de vent, ce qui est habituel lors d'EVASAN Hélico. Il est alors fondamental d'avoir recours à des protections étanches non compressibles par le vent ambiant. Le retrait des vêtemenst humides n'apparaît pas être nécessaire si ces conditions sont obtenues.

 

La thermorégulation par N. Deye IAR IDF

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Hypothermie: Toujours une réalité!

Evaluation of military trauma system practices related to damage-control resuscitation

Palm K et All. J Trauma Acute Care Surg. 2012;73: S459YS464.

 

Patients admitted with documented temperature less than 96.8-F (36-C) January 2002 to December 2011 Operation Enduring Freedom and Operation Iraqi Freedom/Operation New Dawn combined.

La prévention d'une hypothermie est un des enjeux de la prise en charge du combattant blessé. Dans ce texte les auteurs rapportent l'évolution de la température à la prise en charge hospitalière sur une période de plus de 10 ans. Malgré l'introduction en 2006 d'une procédure de mise en place en 2006 d'une procédure spécifique,  On note la réapparition de ce problème en 2010 notamment sur le théâtre afghan (contexte climatique, moindre adéquation à la procédure ??). 

On rappelle l'importance de la qualité de la mise en oeuvre des moyens disponibles dont le principe global est l'isolation la plus parfaite possible du blessé aux effets de l'environnement (froid, vent, humidité) notamment par la technique de l'oignon (technique de hibbler). La mise en oeuvr d'une protection thermique nécessite donc un entraînement spécifique.

La fiche mémento sur l'hypothermie est accessible ici

 

 

 

Secours en milieu froid

 http://www.cosafe.eu/PDF/ENG_booklet_casualty_workers%20(... 

Un document intéressant qui fait le point sur les principes de la mise en condition des blessés en milieu froid

Réchauffer les perfusions

An experimental study of warming intravenous fluid in a cold environment.

Platts-Mills TF et all. Wilderness Environ Med. 2007 Fall;18(3):177-85.

Il existe des moyens artisanaux pour réchauffer les perfusions, notamment l'emploi de pack de réchauffe de rations alimentaires.

Cette manière de faire n'est pas toujours efficace et dans certains cas réchauffe de manière trop importante les solutés qui dépasse alors la température maximum généralement admise à laquelle ces derniers peuvent être perfusés: 42°c

 

Il peut être proposé d'attendre une dizaine de minutes avant de'adminstrer ces perfusions. 

http://www.fresno.ucsf.edu/em/posters/2006_IVF_warming.pdf

Bien sur il existe des dispositifs électriques mais aussi des packs chimiques spécifiques