Hypothermic Cardiac Arrest
Management of cardiac arrest in the severely hypothermic patient can be difficult.
Brain function
At 18oC, the brain can tolerate circulatory arrest up to 10 times as long as the normothermic brain, so resuscitative efforts need to be prolonged.
Heart activity
The patient in VF should be defibrillated. If VF persists, two further shocks should be given. If a total of three shocks have been given and the patient remains in VF, further defibrillation attempts should be withheld until the core temperature is above 30oC.
Distinguishing between VF and asystole can be challenging, particularly in the prehospital setting.
Certain stable arrhythmias, such as atrial arrythmias, will respond to rewarming measures only and antiarrythmics should be avoided.
The use of antiarrythmic medications in the hypothermic patient is controversial and in the small studies done so far, only bretylium has been shown to be of any benefit.
Drug administration
Drug metabolism is slowed, causing toxic accumulation.
Current guidelines advise that drugs are avoided below 30oC. Above 30oC, the interval between drug administration should be doubled.
Deciding when to end resuscitative efforts depends on clinical judgement, but the patient should be rewarmed before this decision is made.
CPR
The hypothermic chest wall and myocardium are stiffer and less compliant.
CPR should continue until the patient is rewarmed to 30oC, at which point renewed attempts at defibrillation and resuscitation with Advanced Life Support medications are undertaken [5].