Hypothermia Prevention

#### HYPOTHERMIA PREVENTION & MANAGEMENT

J Trauma Acute Care Surg. 2019 Mar;86(3):458-463

# The impact of hypothermia on outcomes in massively transfused patients.

Lester E, Fox E, Holcomb J, Brasel K, Bulger E, Cohen M, Cotton B, Fabian T, Kerby J, OʼKeefe T, Rizoli S, Scalea T, Schreiber M, Inaba K; PROPPR study group.

BACKGROUND: Hypothermia is associated with poor outcomes after injury. The relationship between hypothermia during contemporary large volume resuscitation and blood product consumption is unknown. We evaluated this association, and the predictive value of hypothermia on mortality.

METHODS: Patients predicted to receive massive transfusion at 12 level 1 trauma centers were randomized in the Pragmatic Randomized Optimal Platelet and Plasma Ratios (PROPPR) trial and were grouped into those who were hypothermic (<36°C) or normothermic (36-38.5°C) within the first 6 hours of emergency department arrival. The impact of hypothermia or normothermia on the volume of blood product required during the first 24 hours was determined via negative binomial regression, adjusting for treatment arm, injury severity score, mechanism, demographics, pre-emergency department fluid volume, blood administered before becoming hypothermic, pulse and systolic blood pressure on arrival, and the time exposed to hypothermic or normothermic temperatures.

RESULTS: Of 680 patients, 590 had a temperature measured during the first 6 hours in hospital, and 399 experienced hypothermia. The mean number of red blood cell (RBC) units given to all patients in the first 24 hours of admission was 8.8 (95% confidence interval [CI], 7.9-9.6). In multivariable analysis, every 1°C decrease in temperature below 36.0°C was associated with a 10% increase (incidence rate ratio, 0.90; 95% CI, 0.89-0.92; p < 0.00) in consumption of RBCs during the first 24 hours of admission. There was no association between RBC administration and a temperature above 36°C. Hypothermia on arrival was an independent predictor of mortality, with an adjusted odds ratio of 2.7 (95% CI, 1.7-4.5; p < 0.00) for 24-hour mortality and 1.8 (95% CI, 1.3-2.4; p < 0.00) for 30-day mortality.

CONCLUSION: Hypothermia is associated with increase in blood product consumption and mortality. These findings support the maintenance of normothermia in trauma patients and suggest that further investigation on the impact of cooling or rewarming during massive transfusion is warranted.

LEVEL OF EVIDENCE: Prognostic, level III.

Wilderness Environ Med. 2019 Jun;30(2):163-176

Human Responses to 5 Heated Hypothermia Wrap Systems in a Cold Environment.

Dutta R, Kulkarni K, Steinman A, Gardiner P, McDonald G, Giesbrecht G

INTRODUCTION: We compared the effectiveness of 5 heated hypothermia wrap systems.

METHODS: Physiologic and subjective responses were determined in 5 normothermic subjects (1 female) for 5 heated hypothermia wraps (with vapor barrier and chemical heat sources) during 60 min of exposure to a temperature of -22°C. The 5 systems were 1) user-assembled; 2) Doctor Down Rescue Wrap; 3) hypothermia prevention and management kit (HPMK); 4) MARSARS Hypothermia Stabilizer Bag; and 5) Wiggy's Victims Casualty Hypothermia Bag. Core and skin temperature, metabolic heat production, skin heat loss, and body net heat gain were determined. Subjective responses were also evaluated for whole body cold discomfort, overall shivering rating, overall temperature rating, and preferential ranking.

RESULTS: The Doctor Down and user-assembled systems were generally more effective, with higher skin temperatures and lower metabolic heat production; they allowed less heat loss, resulting in higher net heat gain (P<0.05). HPMK had the lowest skin temperature and highest shivering heat production and scored worse than the other 4 systems for the "whole body cold discomfort" and "overall temperature" ratings (P<0.05).

CONCLUSIONS: The user-assembled and Doctor Down systems were most effective, and subjects were coldest with the HPMK system. However, it is likely that any of the tested systems would be viable options for wilderness responders, and the choice would depend on considerations of cost; volume, as it relates to available space; and weight, as it relates to ability to carry or transport the system to the patient.

J Trauma Acute Care Surg. 2019 Mar;86(3):458-463

The impact of hypothermia on outcomes in massively transfused patients.

Lester E, Fox E, Holcomb J, Brasel K, Bulger E, Cohen M, Cotton B, Fabian T, Kerby J, OʼKeefe T, Rizoli S, Scalea T, Schreiber M, Inaba K; PROPPR study group.

BACKGROUND: Hypothermia is associated with poor outcomes after injury. The relationship between hypothermia during contemporary large volume resuscitation and blood product consumption is unknown. We evaluated this association, and the predictive value of hypothermia on mortality.

METHODS: Patients predicted to receive massive transfusion at 12 level 1 trauma centers were randomized in the Pragmatic Randomized Optimal Platelet and Plasma Ratios (PROPPR) trial and were grouped into those who were hypothermic (<36°C) or normothermic (36-38.5°C) within the first 6 hours of emergency department arrival. The impact of hypothermia or normothermia on the volume of blood product required during the first 24 hours was determined via negative binomial regression, adjusting for treatment arm, injury severity score, mechanism, demographics, pre-emergency department fluid volume, blood administered before becoming hypothermic, pulse and systolic blood pressure on arrival, and the time exposed to hypothermic or normothermic temperatures.

RESULTS: Of 680 patients, 590 had a temperature measured during the first 6 hours in hospital, and 399 experienced hypothermia. The mean number of red blood cell (RBC) units given to all patients in the first 24 hours of admission was 8.8 (95% confidence interval [CI], 7.9-9.6). In multivariable analysis, every 1°C decrease in temperature below 36.0°C was associated with a 10% increase (incidence rate ratio, 0.90; 95% CI, 0.89-0.92; p < 0.00) in consumption of RBCs during the first 24 hours of admission. There was no association between RBC administration and a temperature above 36°C. Hypothermia on arrival was an independent predictor of mortality, with an adjusted odds ratio of 2.7 (95% CI, 1.7-4.5; p < 0.00) for 24-hour mortality and 1.8 (95% CI, 1.3-2.4; p < 0.00) for 30-day mortality.

CONCLUSION: Hypothermia is associated with increase in blood product consumption and mortality. These findings support the maintenance of normothermia in trauma patients and suggest that further investigation on the impact of cooling or rewarming during massive transfusion is warranted.

LEVEL OF EVIDENCE: Prognostic, level III.

Wilderness Environ Med. 2019 Sep 28;Epub ahead of print

Risk of Burns During Active External Rewarming for Accidental Hypothermia.

Giesbrecht G, Walpoth B

This article describes 3 incidents in which therapeutic or experimental warming of cold individuals caused first- to third-degree burns to the skin. Mechanisms for these injuries are considered. We conclude that active external rewarming of the trunk of a cold patient in the field can be administered safely and burn risk reduced if 1) manufacturer instructions are followed; 2) insulation is placed between the skin the and heat source; and 3) caregivers make regular efforts to observe heated skin for possible pending burn injury. Direct inspection is mandatory for the skin of areas that are on top of a heat source when the patient is lying on the heat source.

J Int Med Res. 2019 Aug;47(8):3559-3568

Effect of hypothermia on haemostasis and bleeding risk: a narrative review.

Kander T, Schött U

It must be remembered that clinically important haemostasis occurs in vivo and not in a tube, and that variables such as the number of bleeding events and bleeding volume are more robust measures of bleeding risk than the results of analyses.

In this narrative review, we highlight trauma, surgery, and mild induced hypothermia as three clinically important situations in which the effects of hypothermia on haemostasis are important. In observational studies of trauma, hypothermia (body temperature <35°C) has demonstrated an association with mortality and morbidity, perhaps owing to its effect on haemostatic functions. Randomised trials have shown that hypothermia causes increased bleeding during surgery. Although causality between hypothermia and bleeding risk has not been well established, there is a clear association between hypothermia and negative outcomes in connection with trauma, surgery, and accidental hypothermia; thus, it is crucial to rewarm patients in these clinical situations without delay. Mild induced hypothermia to ≥33°C for 24 hours does not seem to be associated with either decreased total haemostasis or increased bleeding risk.

Burns. 2019 Aug 1. pii: S0305-4179(19)30194-9

Early hypothermia as risk factor in severely burned patients: A retrospective outcome study.

Ziegler B, Kenngott T, Fischer S, Hundeshagen G, Hartmann B, Horter J, Münzberg M, Kneser U, Hirche C

INTRODUCTION: Burn trauma-related hypothermia is a frequent observation but risk factors and impact on patient related outcome are ambiguously reported. It is expected that hypothermia is associated with increased mortality and reduced overall outcome in severely burned patients, but available evidence is limited.

METHODS: This retrospective single-center-study reviewed preclinical service protocols and medical records of patients sustaining a burn with a total body surface area (TBSA) ≥15% from 2008 to 2012. General patient and burn specific characteristics, outcome parameters as well as body temperature at admission measured via urine catheter or nasal temperature probe were recorded and statistically analyzed comparing normothermic (≥36 °C), mild hypothermic (<36 °C) and severely hypothermic (<34.5 °C) patients. Chi-square test was performed to demonstrate impact of hypothermia on primary outcome parameters and to reveal risk factors for developing hypothermia. To assess independent influences on mortality, a multivariate logistic regression analysis was performed.

RESULTS: Out of 300 patients matching inclusion criteria, a sufficient record of temperature was found in 144 patients (48%). Out of 141 eligible patients with an average burn extent (SD) of 33.38% (24.5%) TBSA, 31.9% (n = 45) suffered from severe hypothermia (<34.5 °C) and 28.4% (n = 40) showed mild hypothermia. Total burn extent, presence of full thickness burns, presence of inhalation injury, preclinical mechanical ventilation and administration of sedative drugs were risk factors for developing hypothermia. Patients' age, total burn extent and presence of full thickness burns could be identified as independent factor for mortality. Although a trend towards an independent positive influence of normothermia at admission on mortality was seen, it was not statistically significant.

CONCLUSION: Incidental hypothermia of burned patients is associated with an increased mortality and needs to be addressed by emergency health care providers and immediately at the burn center. Especially patients with extensive burns, full-thickness burns, inhalation injury or patients undergoing preclinical intubation are at risk for hypothermia and benefit from any measures for temperature preserving.