The new AHA guidelines really stress post-resuscitative care, and have a true post-arrest algorithm. 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. Most 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 24 hours post-arrest. There is a widening of the range with the 2015 guidelines for target temperature. The goal temperature is 32-36 Celsius (about 90-96 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 1000ml is expected to drop body temperature around 1 degree Celsius every 10 minutes. A 500ml bolus may even 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.
The one caveat here is that the patient should be maintained at a CONSTANT temperature after cooling measures for the 24 hour time period. One thing that can not be done is cooling the patient to say 32, then letting them warm to 36, then cooling again. Constant temperature is desired! If cooling ceases at 36, that is where the patient stays for 24 hours, with tight control.
To maintain this temp for 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, perhaps a rectal temp 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. Remember, the goal is to literally and figuratively make the patient "chill out!"
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 also important. 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. As patients can rebound to hyperthermia, there is increased attention being paid to this now, and worry that rebound hyperthermia may increase morbidity. Stay tuned!