Table 1. Differential diagnosis of exertional collapse - signs, symptoms, and initial treatment.

CNS: central nervous system; EMS: emergency medical services; CPR: cardiopulmonary resuscitation; AED: automated external defibrillator; IV: intravenous; POC: point-of-care; O2: oxygen; WNL: within normal limits; TTP: tender to palpation; U/A: urinalysis; RBC: red blood cell; TACO: tarp-assisted cooling oscillation; CHAMP: Consortium for Health and Military Performance; WHEC: Warrior Heat and Exertion-Related Events Collaborative

Notes:

1. HE is distinguished from EHS by the absence of CNS and end-organ damage. Temperatures >41°C (105.8°F) should initially be considered as EHS given the possibility of a lucid interval, and that proteins denature at temperatures >41°C (105.8°F), thus resulting in end-organ damage.

2. Simple cooling: ice packs, ice towels/sheets, fan, forearm immersion, etc.

3. Active cooling: ice water immersion, Quantico method, TACO, ice sheets with ice packs.

4. Exercise-associated collapse is also identified as exercise-associated postural hypotension (EAPH).

Source: Ref [29]. Permission for use and reprint obtained from the CHAMP/WHEC Medical Director.

Condition	Core Temp	CNS Dysfunction	Timing	Muscles	Urine	Shortness of Breath	Initial Treatment
Sudden Cardiac Arrest (SCA)	Variable	Abrupt loss of consciousness	Variable	Flaccid or seizing	N/A	Apneic or agonal breathing	Activate EMS, CPR, early AED
Exertional Heat Exhaustion (HE)	≥38°C (100.5°F), ≤41°C (105.8°F). See note 1	No	Late	May have exercise-associated muscle cramps (EAMC)	Often dehydrated	Possible	Remove excess clothing, oral fluids (+/– IV fluids), simple cooling, rest. See note 2
Exertional Heat Stroke (EHS)	≥40°C (104.0°F)	Yes (may be intermittent or subtle)	Late	May have EAMC	Possibly dehydrated	Possible	COOL FIRST, COOL FAST, COOL on site +/– IV fluids. See note 3
Exercise-Associated Hyponatremia (EAH)	Usually <39°C (102°F)	Yes, if severe. Often headache, confusion, and/or repeated emesis	Usually late	N/A	Urination may be increased or decreased	No	Oral sodium solution, POC testing, and administer 3% saline if CNS dysfunction or cannot swallow
Exertional Collapse Associated with Sickle Cell Trait (ECAST)	Usually <39°C (102°F). If >40°C (104°F), must treat as EHS	Typically, intact CNS function, “conscious collapse”	Often early	Typically, flaccid lower extremity muscle groups, global pain	May be dark/bloody	Possible, may be severe	O2, AED, IV fluids, activate EMS
Exertional Rhabdomyolysis (ER)	WNL	No	Late	May be stiff and swollen; TTP; pain with active motion	May be dark, “cola-colored” U/A + blood, but no RBCs	No	Rest, oral vs IV fluids
Exercise-Induced Hypoglycemia	WNL	Yes	Late	WNL	Variable	No	Glucose
Exercise-Associated Collapse (EAC). See note 4	WNL	+/– CNS dysfunction that recovers quickly (<15 min)	Late, typically end of event	WNL	Variable	No	• Rule out other causes • Place patient supine with legs elevated 12–24” above the heart • If not rapidly better, re-check for other causes