Exertional Heat Injury: Effects of Adding Cold (4°C) Intravenous Saline to Prehospital Protocol

Association between normal saline infusion volume in the emergency department and acute kidney injury in heat stroke patients: a multicenter retrospective study

BACKGROUND

Previous studies have shown that intravenous normal saline (NS) may be associated with the incidence of acute kidney injury (AKI). This study aimed to evaluate the association between the volume of NS infusion and AKI in heat stroke (HS) patients.

METHODS

This multicenter retrospective cohort study included 138 patients with HS. The primary outcome was the incidence of AKI. Secondary outcomes included the need for continuous renal replacement therapy (CRRT), admission to the intensive care unit (ICU), length of stay in the ICU and hospital, and in-hospital mortality. Multivariate regression models, random forest imputation, and genetic and propensity score matching were used to explore the relationship between NS infusion and outcomes.

RESULTS

The mean volume of NS infusion in the emergency department (ED) was 3.02 ± 1.45 L. During hospitalization, 33 patients (23.91%) suffered from AKI. In the multivariate model, as a continuous variable (per 1 L), the volume of NS infusion was associated with the incidence of AKI (OR, 2.51; 95% CI, 1.43-4.40; p = .001), admission to the ICU (OR, 3.46; 95% CI 1.58-7.54; p = .002), and length of stay in the ICU (β, 1.00 days; 95% CI, 0.44-1.56; p < .001) and hospital (β, 1.41 days; 95% CI, 0.37-2.45; p = .008). These relationships also existed in the forest imputation cohort and matching cohort. There were no differences in the use of CRRT or in-hospital mortality.

CONCLUSIONS

The volume of NS infusion was associated with a significant increase in the incidence of AKI, admission to the ICU, and length of stay in the ICU and hospital among patients with HS.

Management of Heat-Related Illness and Injury in the ICU: A Concise Definitive Review

OBJECTIVES

The increasing frequency of extreme heat events has led to a growing number of heat-related injuries and illnesses in ICUs. The objective of this review was to summarize and critically appraise evidence for the management of heat-related illnesses and injuries for critical care multiprofessionals.

DATA SOURCES

Ovid Medline, Embase, Cochrane Clinical Trials Register, Cumulative Index to Nursing and Allied Health Literature, and ClinicalTrials.gov databases were searched from inception through August 2023 for studies reporting on heat-related injury and illness in the setting of the ICU.

STUDY SELECTION

English-language systematic reviews, narrative reviews, meta-analyses, randomized clinical trials, and observational studies were prioritized for review. Bibliographies from retrieved articles were scanned for articles that may have been missed.

DATA EXTRACTION

Data regarding study methodology, patient population, management strategy, and clinical outcomes were qualitatively assessed.

DATA SYNTHESIS

Several risk factors and prognostic indicators for patients diagnosed with heat-related illness and injury have been identified and reported in the literature. Effective management of these patients has included various cooling methods and fluid replenishment. Drug therapy is not effective. Multiple organ dysfunction, neurologic injury, and disseminated intravascular coagulation are common complications of heat stroke and must be managed accordingly. Burn injury from contact with hot surfaces or pavement can occur, requiring careful evaluation and possible excision and grafting in severe cases.

CONCLUSIONS

The prevalence of heat-related illness and injury is increasing, and rapid initiation of appropriate therapies is necessary to optimize outcomes. Additional research is needed to identify effective methods and strategies to achieve rapid cooling, the role of immunomodulators and anticoagulant medications, the use of biomarkers to identify organ failure, and the role of artificial intelligence and precision medicine.

Whole-body cooling effectiveness of cold intravenous saline following exercise hyperthermia: a randomized trial

INTRODUCTION

In some athletic, occupational, military and emergency settings, cold intravenous (IV) fluids are used to facilitate whole-body cooling in an effort to treat heat illness. This treatment has anecdotal support, but currently lacks evidence supporting it as a whole-body cooling modality. Other modalities may offer superior cooling rates, and thus, patient outcomes following treatment. We sought to evaluate cooling rates of cold-IV normal saline immediately following exercise-induced hyperthermia.

METHODS

Eight healthy participants (3 females; 25 ± 2y; 72.9 ± 10.9 kg) completed 2 trials in random order. Prior to exercise, participants provided a small urine sample to confirm hydration status via urine specific gravity. Wet bulb globe temperature (WBGT) was assessed throughout trials. In both trials, participants exercised outdoors until rectal temperature (Tre) reached ∼38.9 °C, or volitional exhaustion, and then were cooled. In cooling, participants received either cold-IV (∼5 °C 0.9% NaCl fluids) or no treatment (sat in the shade; passive). Throughout exercise and treatment, Tre and heart rate (HR) were monitored. During exercise and every 10 min throughout cooling, participants were asked to assess thermal sensation.

RESULTS

Hydration status (P = .847) was not significantly different prior to exercise between trials. WBGT throughout was not different between trials (P = .426). Maximum Tre reached was not different between cold-IV (38.88 ± 0.30 °C) and passive cooling (38.76 ± 0.28 °C) trials (P = .184). Mean cooling rate for cold-IV (0.039 ± 0.005 °C·min-1) was significantly greater than for passive cooling (0.028 ± 0.005 °C·min-1; P = .002). Tre throughout cooling was not different between trials (P = .707), but did decrease throughout (P = .008), regardless of trial. HR was decreased over time (P < .001), but cold-IV and passive cooling were not different throughout HR recovery (P = .141). Thermal sensation decreased throughout cooling (P < .001), but was not different between trials (p = .278).

CONCLUSION

Emergency medical personnel should adopt treatment protocols that employ documented effective treatments for exertional heat stroke. In isolation, our data casts significant doubt for the use of cold-IV saline infusion for whole-body cooling of hyperthermic individuals.

General Medical Emergencies in Athletes

This article focuses on the management of the most common on-field medical emergencies. As with any discipline in medicine, a well-defined plan and systematic approach is the cornerstone of quality health care delivery. In addition, the team-based collaboration is necessary for the safety of the athlete and the success of the treatment plan.

Cooling Modality Effectiveness and Mortality Associate With Prehospital Care of Exertional Heat Stroke Casualities

BACKGROUND

Cold-water immersion is the gold standard for field treatment of an exertional heat stroke (EHS) casualty. Practical limitations may preclude this method and ice sheets (bed linens soaked in ice water) have emerged as a viable alternative. Laboratory studies suggest that this is an inferior method; however, the magnitude of hyperthermia is limited and may underestimate the cooling rate in EHS casualties.

OBJECTIVE

Our aim was to determine the prehospital core cooling rate, need for continued cooling on arrival to the emergency department, and mortality rate associated with ice sheet use.

METHODS

De-identified retrospective data were obtained from emergency medical services (EMS) and included presence or absence of altered mental status, cooling measures applied prior to EMS arrival, and time and core temperature (T_c; rectal) on-scene and on hospital arrival. Cooling rate was calculated from time and temperature data. Mortality data were obtained from the U.S. Army Combat Readiness Center.

RESULTS

There were 462 casualties that met inclusion criteria. The cooling rate for the entire sample was 0.07°C ± 0.08°C · min^-1. EHS casualties with an observed initial T_c < 39°C had an en route cooling rate of 0.03°C ± 0.04°C · min^-1 vs. initial T_c ≥ 39°C cooling rate of 0.16°C ± 0.08°C · min^-1. There was one fatality due to EHS, for a mortality rate of 0.20% (95% CI 0.01-1.20%).

CONCLUSIONS

The cooling rate in EHS casualties with initial T_c ≥ 39°C was approximately double that reported in laboratory studies. The observed mortality rate was comparable with casualties treated with cold-water immersion. Our data suggest that ice sheets provide a viable alternative when practical constraints preclude cold-water immersion.

Heat-Related Illness in Emergency and Critical Care: Recommendations for Recognition and Management with Medico-Legal Considerations

Hyperthermia is an internal body temperature increase above 40.5 °C; normally internal body temperature is kept constant through natural homeostatic mechanisms. Heat-related illnesses occur due to exposure to high environmental temperatures in conditions in which an organism is unable to maintain adequate homeostasis. This can happen, for example, when the organism is unable to dissipate heat adequately. Heat dissipation occurs through evaporation, conduction, convection, and radiation. Heat disease exhibits a continuum of signs and symptoms ranging from minor to major clinical pictures. Minor clinical pictures include cramps, syncope, edema, tetany, and exhaustion. Major clinical pictures include heatstroke and life-threatening heat stroke and typically are expressed in the presence of an extremely high body temperature. There are also some categories of people at greater risk of developing these diseases, due to exposure in particular geographic areas (e.g., hot humid environments), to unchangeable predisposing conditions (e.g., advanced age, young age (i.e., children), diabetes, skin disease with reduced sweating), to modifiable risk factors (e.g., alcoholism, excessive exercise, infections), to partially modifiable risk factors (obesity), to certain types of professional activity (e.g., athletes, military personnel, and outdoor laborers) or to the effects of drug treatment (e.g., beta-blockers, anticholinergics, diuretics). Heat-related illness is largely preventable.

Exertional heat stroke: An evidence based approach to clinical assessment and management

NEW FINDINGS

What is the topic of this review? The treatment of exertional heat stress, from initial field care through the return-to-activity decision, is reviewed. What advances does it highlight? Clinical assessment during field care using AVPU and vital signs to gauge recovery Approaches to field cooling and end of active cooling Shared clinical decision making for return to activity recommendations ABSTRACT: Exertional heat stroke (EHS) is a potentially fatal condition characterized by central nervous system dysfunction and body temperature often but not always >40°C that occurs in the context of physical work in warm or hot environments. In this paper, we review the continuum of care, from initial recognition and field care to transport and hospital care, and finally return to duty considerations. Morbidity and mortality can be greatly reduced if not eliminated with prompt recognition and aggressive cooling. If medical personnel are not present at point of collapse during or immediately following exercise, EHS should be the presumptive diagnosis until a formal diagnosis can be determined by qualified medical staff. EHS is the rare medical situation where initial treatment (cooling) takes precedence over transport to a medical facility, where advanced medical care may be required for severe EHS casualties. Recovery from EHS and return to activity is usually straightforward and unremarkable provided the casualty is rapidly cooled at time of collapse and adequate time is allowed for body healing. However, evidence-based data to guide return to activity following EHS is limited. Current research suggests that most individuals recover completely within a few weeks though some individuals may suffer prolonged sequalae and additional evaluation may be warranted, including heat tolerance testing. Several aspects of the care of the EHS casualty are based on best practices derived from personal experience and continued research is necessary to optimize evaluation and management. This article is protected by copyright. All rights reserved.

Classic and exertional heatstroke

In the past two decades, record-breaking heatwaves have caused an increasing number of heat-related deaths, including heatstroke, globally. Heatstroke is a heat illness characterized by the rapid rise of core body temperature above 40 °C and central nervous system dysfunction. It is categorized as classic when it results from passive exposure to extreme environmental heat and as exertional when it develops during strenuous exercise. Classic heatstroke occurs in epidemic form and contributes to 9-37% of heat-related fatalities during heatwaves. Exertional heatstroke sporadically affects predominantly young and healthy individuals. Under intensive care, mortality reaches 26.5% and 63.2% in exertional and classic heatstroke, respectively. Pathological studies disclose endothelial cell injury, inflammation, widespread thrombosis and bleeding in most organs. Survivors of heatstroke may experience long-term neurological and cardiovascular complications with a persistent risk of death. No specific therapy other than rapid cooling is available. Physiological and morphological factors contribute to the susceptibility to heatstroke. Future research should identify genetic factors that further describe individual heat illness risk and form the basis of precision-based public health response. Prioritizing research towards fundamental mechanism and diagnostic biomarker discovery is crucial for the design of specific management approaches.

Diagnosis and treatment of patients with heat-related illnesses

Heat stress disorders or heat-related illnesses are a kind of physiological damage that occurs when the body cannot dissipate enough heat due to its thermoregulatory dysfunction. This paper aims to summarize the latest information on the diagnosis and treatment of heat-related illnesses. Heat stress disorders come in a variety of forms including heat edema, heat rash, heat cramps, heat syncope, heat tetany, severe heat exhaustion, and life-threatening heatstroke. Major risk factors may include excessive exercise, continuous exposure to high temperatures or humid environments, lack of acclimation, excessive clothing or protective equipment, obesity, and dehydration. Additional risk factors may include the patientʼs existing medical condition, environmental and personal factors, and the use of various drugs. Mild heat-related illnesses can be treated only by supportive care such as moving patients to a cool place and laying them in a supine position while elevating their legs and loosening their clothes. However, in the case of heatstroke, quickly lowering the body temperature is an essential in reducing the mortality rate. The most effective cooling method is to immerse the entire body in ice cold water.

Low Incidence of Death and Renal Failure in United States Military Service Members Hospitalized with Exertional Heat Stroke: A Retrospective Cohort Study

INTRODUCTION

The goal of the current study was to characterize the rate and estimate associated mortality and morbidity of exertional heat stroke (EHS) in U.S. military service members.

MATERIALS AND METHODS

The current study was a retrospective cohort medical chart review study of all active-duty U.S. military service members, hospitalized with EHS at any MTF in the world between January1, 2007 and July 1, 2014. Enrolled patients were identified by altered mental status and elevated temperatures associated with physical exercise.

RESULTS

Out of 607 service members with an International Classification of Disease code indicating any type of heat injury, 48 service members met inclusion criteria for EHS. Core temperature was M = 105.8°F (41°C), standard deviation = 1.43, 90% were diagnosed with EHS prior to hospitalization, and 71% received prehospital cooling. Meantime to normothermia post-hospitalization was 56 minutes (standard deviation = 79.28). Acute kidney injury was diagnosed in 40% of patients although none developed hyperkalemia or required dialysis. Disseminated intravascular coagulation was rare (4%, n = 2) and overall observed mortality was very low (2%, n = 1).

CONCLUSION

EHS is aggressively identified and treated in U.S. Military Treatment Facilities. Mortality and morbidity were strikingly low.

Successful Management of Severe Exertional Heat Stroke with Endovascular Cooling After Failure of Standard Cooling Measures

BACKGROUND

Exertional heat stroke (EHS) is a potentially life-threatening emergency requiring rapid reduction in core body temperature. Methods of cooling include cold water immersion, ice packs, cold water lavage, and chilled saline, among others. We report a case of EHS successfully cooled using an endovascular cooling device after traditional cooling methods failed to reduce core body temperature.

CASE REPORT

A 24-year old soldier collapsed during a 12-mile foot march while training in southern Georgia. His initial rectal temperature was 43.1°C (109.6°F). External cooling measures (ice sheet application) were initiated on site and Emergency Medical Services were called to transport to the hospital. Paramedics obtained a repeat rectal temperature of 42.4°C (108.4°F). Ice sheet application and chilled saline infusion were continued throughout transport to the Emergency Department (ED). Total prehospital treatment time was 50 min. Upon ED arrival, the patient's rectal temperature was 41.2°C (106.2°F). He was intubated due to a Glasgow Coma Scale score of 4, and endovascular cooling was initiated. Less than 45 minutes later his core body temperature was 37.55°C (99.6°F). He was admitted to the intensive care unit, where his mental status rapidly improved. He was found to have rising liver enzymes, and there was concern for his developing disseminated intravascular coagulation, prompting transfer to a tertiary care center. He was subsequently discharged from the hospital 14 days after his initial injury without any persistent sequelae. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The primary treatment for EHS is rapid reduction of core body temperature. When external cooling methods fail, endovascular cooling can be used to rapidly decrease core body temperature.