Saturday, February 12, 2011

complications during rewarming

Therapeutic rewarming is being used widely in patients after a cardiac arrest (irrespective of type of cardiac arrest). Earlier the patient is cooled ..better the neurological outcome. Usually we keep them under hypothermia for 24 hours. Then comes the period of rewarming, which can be safely done by reducing the body temperature by 0.3 - 0.5 C /hr...and the aim is to normalise body temparature by 8 hours after starting to rewarm. Hemodynamic instability /electrolyte derangements/ arrhythmias can occur during this period...and should be addressed sooner than later.
Medications During Rewarming
Maintain sedation until a temperature of 35° C (95° F) is reached.
- If a neuromuscular blocking agent is infusing solely  to prevent shivering, discontinue the neuromuscular blocking agent before the sedative/analgesic agents.
- Do not discontinue the sedative/analgesic until the patient is moving or until the neuromuscular blocking agent has been discontinued for at least 3 to 5 half lives of the paralytic.

Monitor patient for hypotension. This is secondary to peripheral vasodilatation induced by rewarming. Gentle i.v fluids helps with this issue. Its physiologically reasonable ..not to use Ringer Lactate in this situation, as the hypothermic liver would not be able to metabolise lactate. Try to avoid vasopressors like dopamine during this period..due to the cardiac excitability from these drugs. Again ...physiologically phenylephrine would make more sense as it does not have a beta activity..and only has alpha atction.

Discontinue potassium infusions during rewarming as potassium moves out of cells into the extracellular space.
Acetaminophen and external cooling p.r.n. to keep temperature less than 37.5° C (99.5° F) for 48 hours after  warming.