# Emergency Department Management of Acute Heatstroke: A Retrospective Analysis from Phoenix, Arizona

## TL;DR

This study examines how emergency departments in Phoenix manage acute heatstroke, finding that many patients survive with treatments like cold water immersion.

## Contribution

The study provides insights into the clinical presentation and outcomes of acute heatstroke in a region with extreme heat.

## Key findings

- Most heatstroke patients were male, middle-aged, and presented via emergency medical services.
- Cold water immersion and other treatments led to a high survival rate with neurological recovery.
- Substance use, particularly methamphetamines and fentanyl, was common among heatstroke patients.

## Abstract

The global incidence and severity of severe heat illness is on the rise. The increasing number of summer heatwaves in Phoenix, Arizona, gave us a distinctive opportunity to better understand the impact on the clinical presentation and management of acute heatstroke. Our primary objective in this study was to describe the prehospital and emergency department (ED) clinical presentation, treatment, and outcomes of patients with acute heatstroke at a single hospital system during the summers of 2021 and 2022 in Phoenix.

This was a descriptive, retrospective observational study of heatstroke-associated adult ED presentations occurring from June 1 – August 31, 2021 and June 1 – August 31, 2022, to a single hospital system in Maricopa County.

We identified 60 ED heatstroke encounters. The median environmental daily maximum (Tmax) and minimum (Tmin) were 106.0° Fahrenheit (interquartile range [IQR]) 102.0 – 109.0°F) and 84.0°F (IQR 79.0 – 88.0°F), respectively. The patients were commonly male (42, 70.0%, 95% CI 56.8 – 81.2%), White (26, 43.3%, 95% CI 30.6 – 56.8%), middle-aged (mean 52.7 years, 95% CI 48.4 – 56.9), Medicaid-insured (37, 61.7%, 95% CI 48.2 – 73.9%), and presenting via emergency medical services (60, 100%). Patients were commonly of high acuity (median Emergency Severity Index 1, IQR 1.0 – 2.0), and intubated (45, 75.0%, 95% CI 62.1–85.3%). Forty-seven (78.3%, 95% CI 65.8 – 87.9%) patients were found unresponsive outside with associated substance use (methamphetamines 22, 46.8%, 95% CI 32.1 – 61.9%; and fentanyl 14, 29.8%, 95% CI 17.3 – 44.9%). The average patient Tmax at ED presentation was 41.9°C (IQR 41.1 – 42.2). Forty-one patients (68.3%, 95% CI 55.0 – 79.7%) survived to hospital discharge or transfer, of whom 32 (82.1%, 95% CI 66.5 – 92.5%) were neurologically intact.

During the summers of 2021 and 2022, a significant number of heatstroke presentations were treated in a single healthcare system in Maricopa County, Arizona. A substantial number were successfully treated with cold water immersion and discharged neurologically intact. In this urban population, extreme weather exposure and associated substance use appeared to play significant roles.