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.

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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.

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

Lapostolle F et Al. 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.

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

Weatherall A. et Al. 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.

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.

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.

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.

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

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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

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

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.

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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

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

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

Prise en charge d’un malade en hypothermie accidentelle

Briot R et all. Réanimation (2010) 19, 607—615

ATTENTION le réchauffement préhospitalier a pour objectif de limiter l'hypothermie.

ATTENTION un réchauffement actif préhospitalier n'est pas indiqué si l'hypothermie est profonde

ATTENTION le réchauffement actif préhospitalier est d'autant plus efficace si la conscience et le frisson persistent

ici la procédure du SAMU 38

The effect of active warming in prehospital trauma care during road and air ambulance transportation - a clinical randomized trial.

Lundgren P. et all Scand J Trauma Resusc Emerg Med. 2011 Oct 21;19:59.

La prévention de l'hypothermie fait appel à des moyens de réchauffement cutanés passifs ( couverture renforcée type Rothco ou la couverture triple couche type blizzard blanket ) ou actifs (couverture ready-heat). Mais comment choisir ?

Le travail présenté ici démontre qu'en présence d'une hypothermie modérée supérieures à 35°C il n'est pas utile d'avoir recours à un moyen actif en terme de limitation de l'hypothermie dès lors que le frisson est conservé. Le seul gain porte sur un confort thermique accru.