Cooling Baths in the Hospital: Emergency Department Protocol for Heat Stroke

Field teams increasingly start cold water immersion before the patient ever reaches the hospital, and that shift has saved lives. But the handoff from prehospital care to the emergency department is not the end of the cooling protocol, it is a checkpoint where the ED must confirm the job is actually finished. A hospital cooling bath and a clear ED protocol around it remain essential, not optional.

Why ED cooling protocols still matter after field cooling

Prehospital cooling is often incomplete by the time a patient arrives. Transport time, a partial water supply at the scene, ice availability, or simply the severity of the case can mean core temperature is still above the safe threshold on arrival. Relying on the assumption that "cooling was started in the field" without confirming where core temperature actually stands is a common and dangerous gap. The ED needs to treat every incoming exertional heat stroke (EHS) case as if cooling status is unknown until measured, not assumed.

Rapid triage recognition on arrival

Heat stroke can be missed at triage when it presents alongside other complaints, or when a patient arrives already partially cooled and looking clinically better than their organ status suggests. Triage staff should flag:

History of exertion, heat exposure, or a sporting/occupational event, combined with altered mental status.
Any prehospital report mentioning hyperthermia, collapse, or field cooling attempts, even brief ones.
Rectal temperature, not oral, ear, or forehead, as the only reliable measurement to confirm or rule out ongoing hyperthermia at triage. Peripheral measurements systematically underestimate core temperature in EHS and should not be used to clear a patient.

Maintaining or resuming immersion in the ED

If core temperature on arrival is still above the target threshold, the ED should resume or continue whole-body cold water immersion without delay, using its own equipment rather than waiting for the patient to be routed elsewhere in the hospital. This is why an ED having a deployable cooling bath of its own matters: a delay spent locating or improvising cooling equipment inside the department costs exactly the minutes the prehospital team worked to save.

Whole-body cold water immersion remains the reference method in-hospital as in the field, with cooling rates up to 0.35°C per minute (Casa et al. 2007), compared with 0.03 to 0.08°C per minute for ice packs, ice sheets, fans, or misting. A rate above 0.15°C per minute is considered adequate. If the ED's only cooling option is a cart of ice packs and a fan, it is working well below what the evidence supports as sufficient.

Core temperature monitoring targets

Measure rectal temperature continuously or at minimum every 5 minutes during active cooling.
Target: maintain immersion until core temperature falls below 38.6°C.
Document each reading. A clear temperature trend is what tells the team whether cooling is working or whether the patient needs escalation.

When to stop cooling

Cooling should stop once core temperature reaches the target threshold, not before, and not significantly after. Stopping too early risks rebound hyperthermia, since a patient's own residual muscle heat and impaired thermoregulation can drive temperature back up after immersion ends. Continuing well past the threshold risks overshoot into hypothermia, particularly in patients who have also received IV fluids. Regular monitoring during and immediately after immersion is what keeps the team inside the correct window in both directions.

Post-cooling monitoring for rhabdomyolysis, AKI, and coagulopathy

Reaching target temperature is not the end of the case. EHS patients need monitoring for delayed complications that can appear hours after apparent recovery:

Rhabdomyolysis: monitor creatine kinase, myoglobinuria, and urine output.
Acute kidney injury (AKI): track renal function markers and urine output over the following hours, not just at the point cooling stops.
Coagulopathy: watch for signs of disseminated intravascular coagulation, which can develop even after the patient appears clinically stable.

A patient who looks recovered immediately after cooling should still be admitted for observation given how these complications present with a delay.

Why EDs should have their own deployable cooling bath

Relying solely on prehospital equipment creates a structural gap: EMS units carry their cooling tub back into service once they hand off a patient, and a department without its own unit is left improvising with ice packs and towels for the next case, or worse, for a patient whose field cooling was incomplete. A hospital-owned cooling bath, sized for whole-body immersion and, ideally, built to support up to 2 people in simultaneous immersion for mass-casualty heat events, closes that gap. It also means the ED is not dependent on ambulance turnaround timing to have cooling capacity ready for the next walk-in or transferred case.