Introduction
Exertional heat stroke (EHS) is defined as a core body temperature greater than 40°C (104°F) with associated central nervous system dysfunction. EHS is a leading cause of morbidity among competitive athletes, with untreated mortality rates up to 71%, though individual risk and severity are modulated by intrinsic and extrinsic factors.Reference Hifumi, Kondo, Shimizu and Miyake 1 , Reference Breslow, Shrestha, Feroe, Katz, Troyanos and Collins 2 Fortunately, prompt identification and rapid cooling dramatically improve clinical outcomes, with survival approaching 100% with on-site cold-water immersion (CWI).Reference Sorensen and Hess 3 , Reference Nowak, Kennelley, Krabak, Roberts, Tenforde and Tenforde 4 Here, the clinical presentation, emergency department (ED) management, and outcomes of seven patients transported with a diagnosis of EHS to a single hospital emergency department following unseasonably warm half marathon are described.
Setting
The Cambridge Half Marathon took place on November 6, 2022, in Cambridge, Massachusetts. A race day high temperature of 76°F with wet bulb globe temperature of 74°F exceeded historical average temperatures for date and location of 54.9°F and record high of 73°F. 5 In total, 4,039 runners started the race and 3,959 finished. Medical personnel including spotters, roaming utility vehicles, and bike teams were positioned along the course. Basic medical aid stations were spaced along the route with dedicated emergency medical services (EMS) transport services available on standby. The finish line medical tent had advanced life support (ALS) and CWI capabilities; CWI was not available elsewhere along the course.
Methods
A retrospective review was performed of athletes transported by EMS to a single academic level 1 trauma center with an annual ED visit volume of over 110,000 patients annually; notably, this was the closest ED to most of the racecourse. In total, 10 runners were transported to local area hospitals, of whom 7 were transported to the study facility (Table 1). An additional 25 athletes were treated in the finish line medical tent and 80 patients (2% of field) did not finish the race. The Mass General Brigham institutional review board deemed this study exempt from human subject research review.
Summary of patient presentations to the ED for exertional heat stroke
Abbreviations: ED = emergency department; NA = data element not available; CWI = cold water immersion; ICU = intensive care unit; AMS = Altered mental state; Unk = Unknown.
Patient 1: A 24-year-old male transported from Mile 12 with syncope. Initial ED vital signs were HR 157, BP 115/53, SpO2 98% and temperature 106.9°F. In the ED, he was cooled with ice packs and was placed into an ice-filled body bag. Testing revealed an elevated creatinine (2.23 mg/dL), lactic acid (6.2 mmol/L), creatine kinase (453 U/L), and high-sensitivity troponin (141 ng/L). He received 2 liters of intravenous (IV) crystalloid, 1 mg of lorazepam for agitation, and was admitted to the intensive care unit (ICU). His mental status improved, and he was discharged on hospital day four.
Patient 2: A 26-year-old male transported from Mile 11 with syncope. On scene, his temperature was 106°F. Initial ED vital signs were HR 171, BP 184/96, SpO2 99%, and temperature 103.1°F. He was cooled with misting, fans, and ice packs. Testing revealed an elevated lactic acid (5.4 mmol/L), sodium (146 mmol/L), and creatinine (2.03 mg/dL), and a low blood sugar (53 mg/dL). He received 25 g of dextrose and 1 L of IV crystalloid and was admitted to the ICU. He developed transient rhabdomyolysis (peak creatine kinase 1638 U/L), acute tubular necrosis, transaminitis, and thrombocytopenia, all of which resolved with supportive care. He was discharged on hospital day five.
Patient 3: A 34-year-old male transported from the finish line with syncope and agitation. Initial ED vital signs were HR 188, BP 125/55, SpO2 91%, and temperature 106.3°F. He was placed in an ice-filled body bag. Testing revealed an elevated creatinine (2.01 mg/dL), lactic acid (14.0 mmol/L), and troponin (94 ng/L). He received 30 mg of haloperidol for agitation and was placed on a dexmedetomidine infusion. He developed transient hypotension treated with norepinephrine, rhabdomyolysis (peak creatine kinase of 14,750 U/L), and volume overload treated with IV furosemide. His symptoms resolved and he was discharged on hospital day nine.
Patient 4: A 23-year-old female transported from the finish line with syncope and a core temperature of 107°F. She underwent CWI prior to transport. Initial ED vital signs were HR 100, BP 115/58, SpO2 99%, and temperature 95.1°F. Testing revealed an elevated creatinine (1.53 mg/dL), troponin (41 ng/mL), and lactic acid (3.5 mmol/L). She was treated with 1 L of IV crystalloid and discharged from the ED.
Patient 5: A 22-year-old female transported from the finish line with weakness, chest pain, and a core temperature of 105°F. She underwent CWI prior to transport. Initial ED vitals were HR 120, BP 124/56, SpO2 98%, and temperature 97.1°F. Testing revealed an elevated troponin (85 ng/mL), and a computed tomography angiograph showed no evidence of a pulmonary embolism. She was treated with 2L IV crystalloid and discharged from the ED.
Patient 6: A 25-year-old male transported from Mile 6 with altered mental status and cooling with ice packs initiated prior to transport. Initial ED vital signs were HR 130, BP 89/51, SpO2 100%, and temperature 104°F. Testing revealed elevated troponin (225 ng/mL), creatinine (2.14 mg/dL), and lactic acid (3.5 mmol/L). He was treated with 3 L IV crystalloid and discharged from the ED.
Patient 7: A 27-year-old male transported from the course with altered mental status. Initial ED vital signs were HR 157, BP 125/58, SpO2 97%, and temperature 103.1°F. He was cooled with mist, fans, wet towels, and ice packs. Labs showed an elevated lactic acid (8.9 mmol/L). He received 3 L of IV crystalloid and was discharged from the ED.
Discussion
This experience with patients transported to a single ED following an unseasonably warm half-marathon highlights several lessons learned in the management of EHS. Although environmental conditions are the primary predisposing factor to EHS, exercise intensity, age, race distance, and heat acclimatization also play an important role,Reference Nichols 6 , Reference Leyk, Hoitz, Becker, Glitz, Nestler and Piekarski 7 as do chronic medical conditions and certain medications that may predispose to EHS. The faster pace of shorter distance races, as compared to marathons or races of longer distance, may lead to higher metabolic heat production.Reference DeMartini, Casa and Belval 8 The EHS rate at the 2022 Cambridge Half Marathon was approximately 2 per 1000 athletes, consistent with rates of EHS at other shorter races run in warmer weather,Reference Stearns, Hosokawa and Belval 9 while rates at longer distance races including marathons are as low as 3 per 10,000 athletes.Reference Roberts 10 This suggests that athlete metabolic demands in this particular event were atypical and at odds with planning assumptions. Further, lack of athlete acclimatization to record-setting race day temperatures likely contributed to high patient presentation rates.
This review highlights the critical importance of prompt recognition and treatment of EHS. All runners in this case series who received prompt CWI on course were later discharged from the ED, while 3 of 4 patients with delayed cooling required admission, supporting recommendations for immediate on-site cooling in cases of exertional heat illness.Reference Hosokawa, Adams and Belval 11 –Reference McDermott, Casa and Ganio 13 Unfortunately, protocols directing on-site care of EHS vary widely.Reference Monseau, Hurlburt, Balcik, Oppenlander, Chill and Martin 14 , Reference Hosokawa, Nagata and Hasegawa 15 In the study region at the time of this event, EMS protocols required transport of all patients to the nearest hospital ED, despite CWI being readily available at the finish line. Based in part on lessons learned from this event, regional EMS protocols now allow for patients to be transported from the course to the closest ALS-equipped medical facility with CWI capabilities, which may be the race finish line. Race directors and public health agencies should carefully evaluate protocols pertaining to both race and EMS medical management, prioritizing rapid on-site cooling of patients with EHS. For shorter distance or loop courses, this may be the finish line. For longer distance or point-to-point races, consideration should be given to staged CWI capabilities along the course route.
While the study hospital ED is equipped to manage patients with EHS, the race day in question saw record-high temperatures, leading to an unexpected patient surge. The department’s resources for tub-based CWI were soon overwhelmed and required supplementation with alternative, and potentially less effective, methods. The study facility has since focused on improved communication and coordination before and during possible mass casualty events, especially in unexpected inclement weather. Additional tubs for CWI are now kept on site and can be quickly deployed in the event of an unexpected patient surge. Additionally, race planning has included more detailed considerations of potential impacts to local area hospitals.
Finally, while the study hospital was the closest by proximity to the event finish line, several additional nearby hospitals were also available to accept patients. Specifically, while the hospital ED was capable of caring for multiple ill athletes, an influx of seven EHS patients requiring intensive care significantly strained ED resources on an otherwise busy shift. Distributing patients to avoid overwhelming any single site is a previously described principle of effective mass casualty response.Reference Biddinger, Baggish and Harrington 16 Improved regional pre-planning and real-time communication may have resulted in improved patient distribution.
Conclusions
This case series highlights the variable presentation of EHS during a half marathon, exacerbated by unseasonable environmental conditions. With the ever-worsening impacts of climate change, medical providers must be vigilant in identifying and rapidly treating EHS. Sufficient race resources including adequate medical personnel and access to on-site CWI are critical. A comprehensive communication plan coordinating race personnel, public safety, EMS agencies, and hospitals can help mitigate downstream impacts to patients and healthcare entities. While the overall response to this incident was successful, we hope that lessons learned from this experience will improve preparedness for future events.
Author contribution
LVW and SAG conceived of the study. PDB supported data collection. LVW and GL drafted the manuscript, and all authors contributed substantially to its revision. LVW takes responsibility for the manuscript as a whole.
Funding
None
Competing interests
None
