What is the treatment for hyperthermia in the Intensive Care Unit (ICU)?

Treatment of Hyperthermia in the ICU

The treatment of hyperthermia in the ICU depends critically on the underlying etiology: for malignant hyperthermia, immediately stop trigger agents and administer dantrolene 2-3 mg/kg IV while actively cooling; for heatstroke, rapidly cool to <38.5°C using external cooling methods combined with hemodynamic support; for post-cardiac arrest or neurological injury, maintain targeted temperature management at normothermia (36-37.5°C) and treat any fever >37.6°C with antipyretics and active cooling. 1

Immediate Assessment and Etiology-Specific Management

Malignant Hyperthermia Crisis

If malignant hyperthermia is suspected (unexplained progressive rise in ETCO2, muscle rigidity, rapid temperature elevation during anesthesia):

• Stop all trigger agents immediately (volatile anesthetics, succinylcholine) and hyperventilate with 100% oxygen at 2-3 times normal minute volume 1
• Administer dantrolene 2-3 mg/kg IV as initial dose, then 1 mg/kg every 5 minutes until ETCO2 <6 kPa with normal minute ventilation and core temperature <38.5°C 1
• Active cooling measures: infuse 2000-3000 mL chilled (4°C) 0.9% saline IV, apply wet cold sheets with fans, place ice packs in axillae and groin, stop cooling once temperature <38.5°C 1
• Monitor for at least 24 hours in ICU/HDU as recrudescence can occur 1

Critical pitfall: Do not waste time changing the anesthetic circuit or machine—disconnect the vaporizer and proceed with treatment. At least 36-50 ampoules of dantrolene may be needed for an adult, so obtain additional supplies immediately. 1

Heatstroke

For classic or exertional heatstroke (core temperature >40°C with CNS dysfunction):

• Rapid cooling is the primary treatment—the degree and duration of hyperthermia directly determines mortality and neurologic morbidity 1, 2
• External cooling methods: immersion in cold water, cold packs/ice slush over body, cooling blankets, or wetting body surface while continually fanning 1
• Hemodynamic support: treat distributive shock with fluid resuscitation (crystalloids), as circulatory failure results from relative/absolute hypovolemia and peripheral vasodilation 1
• No specific endpoint temperature for safe cessation of cooling has been established, but aim for rapid reduction below 40°C 1

Critical pitfall: Myocardial failure is rare in heatstroke—the shock is primarily distributive, so aggressive fluid resuscitation is appropriate. 1

Post-Cardiac Arrest Hyperpyrexia

For fever following return of spontaneous circulation (ROSC):

• Treat hyperthermia (≥37.6°C) with antipyretics and consider active cooling in unconscious patients, as post-arrest pyrexia is associated with poor neurological outcomes 1
• Rebound hyperthermia after targeted temperature management is particularly harmful and associated with increased mortality 1
• Maintain blood glucose ≤10 mmol/L (180 mg/dL) but avoid strict glucose control due to hypoglycemia risk 1

Neurological Injury (TBI, Stroke, ICH, SAH)

For hyperthermia in brain-injured patients:

• Maintain targeted temperature management at normothermia (36-37.5°C) 1
• Treat fever aggressively as hyperthermia worsens neurological outcomes in traumatic brain injury, stroke, and intracranial hemorrhage 1, 3
• Use antipyretics routinely, though evidence for impact on neurological outcome is limited 1
• Consider active cooling for persistent fever, particularly in comatose patients 1

Critical pitfall: Do not use therapeutic hypothermia (32-34°C) routinely for traumatic brain injury—the Eurotherm study showed worse neurological outcomes at 6 months (OR 1.53 for unfavorable outcome). 1 Hypothermia below 35°C increases infection risk and provides no additional benefit for ICP control. 1

General Cooling Techniques and Monitoring

Active Cooling Methods (in order of typical application):

• Pharmacologic: antipyretics (acetaminophen, NSAIDs) for all causes except malignant hyperthermia where dantrolene is specific 1, 4
• Surface cooling: cold/wet sheets with fans, ice packs to axillae/groin, cooling blankets 1, 5
• Intravascular cooling: chilled IV saline (2-3 L at 4°C), intravascular cooling catheters if available 1, 5
• Evaporative cooling: wetting body surface with continuous fanning maximizes heat dissipation 1

Essential Monitoring During Cooling:

• Continuous core temperature monitoring (rectal, esophageal, or bladder) 1, 5
• Cardiac monitoring for arrhythmias (treat tachyarrhythmias with amiodarone 300 mg IV or beta-blockers) 1
• Electrolytes, particularly potassium (treat hyperkalemia with dextrose/insulin, calcium chloride) 1
• Creatine kinase and myoglobin for rhabdomyolysis 1
• Urine output >2 mL/kg/h (use furosemide 0.5-1 mg/kg or mannitol 1 g/kg if needed) 1
• Arterial blood gases, glucose, coagulation studies 1, 5

Complications to Anticipate:

• Rhabdomyolysis and acute kidney injury: maintain high urine output, consider sodium bicarbonate for urine alkalinization 1
• Compartment syndrome: monitor limbs for swelling and measure compartmental pressures if suspected; fasciotomy may be required 1
• Disseminated intravascular coagulopathy: treat empirically with platelets, FFP, and cryoprecipitate if it develops 1
• Infections: hypothermia increases infection risk proportional to duration and depth of cooling 1, 5
• Electrolyte disturbances: particularly hypokalemia during rewarming 5

Critical pitfall: Fever occurs in 47% of neurosurgical ICU patients and in >90% of those staying >14 days. Despite antipyretic therapy in 86% of episodes, 57% of fevers last >4 hours. 3 This suggests that passive antipyretic therapy alone is often insufficient and active cooling should be considered earlier.