Therapeutic hypothermia

Background

• Determination of Neurologic Prognosis is unreliable before at least 72 hours after ROSC. Do not neuroprognosticate until 72 hours post rewarming.
• Greatest benefit in out-of-hospital V-fib, though evidence suggests hypothermia helps in other dysrhythmias
• Two most likely mechanisms of action:
  • Reduces cerebral metabolism by 6-8% per degree C
  • Reduces oxygen free radical production and lipid peroxidation

Exclusion/Contraindications

• >12hrs since ROSC
• Glasgow Motor score >5
• Minimal pre-morbid cognitive status
• Unable to maintain SBP > 90 mmHg, with or without pressors, after CPR
• Other reason for coma
  • intracranial pathology (i.e. intracranial hemorrhage, ischemic stroke)
  • subarachnoid hemorrhage
  • sedation
• Sepsis as etiology for arrest
• DNR/DNI status
• Uncontrollable bleeding or known bleeding diathesis with active bleeding
• Significant trauma (especially intra-abdominal)

Sedation and Paralytics

Should administer one or more of the following:

• Fentanyl Injection 50 mcg IV every hour as needed for pain.
• Fentanyl IV infusion NSS
• Propofol IV infusion
• Lorazepam IV infusion
• Lorazepam Injection 1 mg IV every 2 hours as needed for agitation.
• Pancuronium IV infusion
  • Initiate before initiating cooling. Dosing recommendations: 0.1 mg/kg loading dose followed by a continuous infusion of 0.33-2 mcg/kg/minute.
  • Do not use in patients with renal and/or hepatic insufficiency.

Prevention of shivering is important to avoid warming and needless oxygen consumption

• May require train of four monitor with goal of 1-2/4 twitches with neuromuscular blockade
• Lower doses of NMB work against shivering
• Higher doses of NMB used to paralyze the diaphragm in these scenarios:
  • Need to decrease O2 consumption
  • Decrease plateau pressures
  • Hypoxemia is present

Management

• Consider head CT
• Head of bed at 30 degrees
• Goal MAP > 80 mmHg
  • Titrate with norepinephrine (start 2-4 mcg/min) if EF > 50%
  • Titrate with dobutamine (start 2.5-20 mcg/kg/min) if EF < 50%
• If life-threatening dysrhythmia/hemodynamic instability/bleeding develops, rewarm pt
• Check skin q2-6 hrs for cold injury
• Common ECG findings during cooling - Osborne wave, HR < 40 bpm not concerning in absence of hemodynamic instability
• Consider continuous EEG within 6 hrs, no later than 12 hrs after onset of cooling
• Monitor for acute adrenal insuffiency, and consider stress dose steroids

Cooling

• Cool to 32-34º C as soon as possible (within 4 hours)
• Initiate rewarming 24 hrs after target temperature was reached
• Cooling methods
  • 2 cooling blankets to sandwich the pt, with sheets covering the blankets to protect skin
  • Alternatively, use heat exchange device, per manufacturer's recs
  • Ice packs to groin, sides of chest, axillae, sides of neck until 34º C reached, and maintain with cooling blankets or heat exchange device

Disposition

• ICU admission

See Also

• Post Cardiac Arrest
• Hypothermia

Source

• University of Pennsylvania Targeted Temperature Management Protocol
• eMedicine - Adler, Jonathan et Al. Therapeutic Hypothermia.