Exertional Heat Stroke, Modality Cooling Rate, and Survival Outcomes: A Systematic Review

Abstract

Background and Objectives: The purpose of this systematic review is to synthesize the influence cooling modality has on survival with and without medical complications from exertional heat stroke (EHS) in sport and military populations. Methods and Materials: All peer-reviewed case reports or series involving EHS patients were searched in the following online databases: PubMed, Scopus, SPORTDiscus, Medline, CINAHL, Academic Search Premier, and the Cochrane Library: Central Registry of Clinical Trials. Cooling methods were subdivided into “adequate” (>0.15 °C/min) versus “insufficient” (<0.15 °C/min) based on previously published literature on EHS cooling rates. Results: 613 articles were assessed for quality and inclusion in the review. Thirty-two case reports representing 521 EHS patients met the inclusion criteria. Four hundred ninety-eight (498) patients survived EHS (95.58%) and 23 (4.41%) patients succumbed to complications. Fischer’s Exact test on 2 × 2 contingency tables and relative risk ratios were calculated to determine if modality cooling rate was associated with patient outcomes. EHS patients that survived who were cooled with an insufficient cooling rate had a 4.57 times risk of medical complications compared to patients who were treated by adequate cooling methods, regardless of setting (RR = 4.57 (95%CI: 3.42, 6.28)). Conclusions: This is the largest EHS dataset yet compiled that analyzes the influence of cooling rate on patient outcomes. Zero patients died (0/521, 0.00%) when treatment included a modality with an adequate cooling rate. Conversely, 23 patients died (23/521, 4.41%) with insufficient cooling. One hundred seventeen patients (117/521, 22.46%) survived with medical complications when treatment involved an insufficient cooling rate, whereas, only four patients had complications (4/521, 0.77%) despite adequate cooling. Cooling rates >0.15 °C/min for EHS patients were significantly associated with surviving EHS without medical complications. In order to provide the best standard of care for EHS patients, an aggressive cooling rate >0.15 °C/min can maximize survival without medical complications after exercise-induced hyperthermia.

Exertional Heat Stroke Knowledge and Management among Emergency Medical Service Providers

“…Heat-related illnesses are more frequently encountered by EMS agencies during the summer months of May to September, between 11:00 am and 7:00 pm, and can occur in any geographic region [ 14 , 29 ]. Exertional heat stroke is 100% survivable when recognized and treated promptly and effectively [ 24 , 25 ].…”

“…These statements agree an accurate core body temperature via rectal thermometry must be obtained as soon as possible and continuously monitored during the treatment process to accurately diagnose EHS [ 2 , 3 , 17 , 19 , 20 ]. Frequently used alternative methods of temperature assessment (oral, temporal, aural thermometry) are too inaccurate to be used to detect heat illness, putting patient lives at risk [ 19 , 20 , 21 , 22 ].The gold standard treatment for EHS is cold-water immersion or a similar method achieving a cooling rate of >0.15 °C per minute [ 2 , 3 , 23 , 24 ]. Cooling of the patient should occur on-site prior to transport until the patient’s core body temperature reaches 38.9 °C (102 °F).…”

“…The patient should then be transported to the nearest emergency department via emergency medical services (EMS), eliciting the mantra “cool first, transport second”. Exertional heat stroke is 100% survivable when promptly recognized and proper cooling techniques are implemented [ 24 , 25 ]. A recent survey of EMS medical directors revealed that approximately 15% did not have a protocol specific to the management of EHS and most performed patient cooling en-route to the hospital as opposed to cooling on-site [ 26 ].…”

Gait instability and estimated core temperature predict exertional heat stroke

“…Reducing the time Tcr is at very high temperatures is critical to minimising organ damage and overall prognosis 5. Survival of EHS without medical complications is dependent on the rapid recognition, rapid cooling and rapid advanced treatment 7…”

Heat Acclimatization, Cooling Strategies, and Hydration during an Ultra-Trail in Warm and Humid Conditions

“…Hot and humid ambient conditions impair prolonged exercise capacity and may favor exertional heat illness (EHI) [ 1 , 2 ]. Its most severe form, exertional heat stroke (EHS), is characterized by a core body temperature above 40.5 °C associated with central nervous system dysfunction (delirium, convulsions, coma) [ 3 , 4 ].…”