Post Arrest Hypothermia

So, your cardiac arrest patient now has a pulse. Great work! Now what? The new AHA guidelines really stress post-resuscitative care. Induction of "therapeutic hypothermia" immediately after return of spontaneous circulation has been clinically proven to preserve brain function. This is due to the decreased metabolic demands on the brain in the hypothermic patient. The criteria for this is essentially any patient post arrest who is comatose, and not septic. The studies were done on post-arrest patients that had been in ventricular fibrillation, but patients with a history of PEA or asystole are also candidates for therapy. The goal is to induce low body temperature for the first 12-24 hours post-arrest. The goal temperature is 32-34 Celsius (about 90-93 Fahrenheit.) This can be accomplished with ice packs to the armpits and groin, but that takes a while. A faster way is to begin chilled saline boluses. Fridge temperature saline is fine. If given at around 100ml per minute IV, (via a pressure bag,) each 100ml is expected to drop body temperature around 1 degree Celsius every 10 minutes. A 500ml bolus may well be sufficient, as the average adult body temperature is 37 Celsius. So, rechecking a temperature in 30 minutes should reveal a temp of about 34 Celsius. To maintain this temp for 12-24 hours, automatic cooling blankets are best. They often are placed under and over the patient. These utilize a temperature probe (esophageal probe, or bladder probe) connected to the device to maintain the temperature of the patient within the desired range. There are medications that are also commonly used to assist in maintaining the temperature. A Fentanyl drip can be useful here, as it decreases the body's shivering response (shivering will raise temperature) as well as keeping the patient sedated. A non-sedated patient may have increased brain activity, which is counter- productive. Tylenol via suppository is also useful to blunt the body's hypothalamic (temperature control) response. The patient does not necessarily need to be paralyzed. Some would say don't paralyze the patient, as the non-sedated, or poorly sedated paralyzed patient will surely have increased brain activity which will not be recognized. Potential complications include coagulopathy- hypothermia can cause bleeding. Another problem is that hypothermia causes a decreased immune response, so it is not really indicated for septic patients. Frequent blood sugar checks are Again, the non-comatose patient who achieves return of spontaneous circulation is not a candidate for this therapy. Cessation of therapeutic hypothermia generally consists of ceasing cooling measures, and allowing the body temperature to come up naturally.