Therapeutic Hypothermia

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OVERVIEW

• the currently preferred term for therapeutic hypothermia is targeted temperature management (TTM)
• induced hypothermia successfully used in cardiac surgery -> protects against global cerebral ischaemia (deep hypothermic arrest)
• described since the 1950s in various clinical settings it has remained an unproven therapy
• recently there have been animal and human studies demonstrating benefit (improved survival and neurological outcome) in cardiac arrest victims.

CLINICAL USES

Cardiac Arrest

• See Targeted temperature management after cardiac arrest

Traumatic Brain Injury

 Lack of Effect of Induction of Hypothermia after Acute Brain Injury (NEJM, 2001)

• MRCT, US, 9 centers
• n = 392
  -> improves ICP but no reduction in mortality
  -> patients older than 45 do worse with induced hypothermia
  -> if they arrive hypothermic -> do not warm to 37 C (poorer outcome)
  -> if you have a low temperature on arrival you have a more significant TBI

HYPHIT Study

• hypothermia in paediatric TBI (Canadian)
• MCRCT
  -> lack benefit

Systematic Review (2007)

• 12 trials
• n = 1100
• overall benefit if cooled to 32-34 C in severe TBI
• need to cool for > 48 hrs (5-7 days: length of maximal elevated ICP and oedema)
• get cool within 4-8 hrs
• fever in TBI is bad

AREAS UNDER INVESTIGATION

• stroke patients
• perinatal asphyxia
• nyocardial ischemia

PRACTICAL ISSUES

• difficulty achieving hypothermia rapidly
• shivering + relaxants -> delay neurological assessment and mask seizures
• hypothermia can cause diuresis -> electrolyte disorders
• arrhythmia risk
• infection risk
• bleeding risk
• immunosuppression

References and Links

LITFL

• CCC — Targeted temperature management after cardiac arrest