A coma can be induced through hypothermia. Image: Shutterstock
An induced coma gives the brain the rest necessary to recover.
Medically induced coma requires an extreme type of general anesthesia that essentially deactivates the brain; this prevents the patients from being revived or reacting on their own. During an induced coma, cardiac rhythm, blood pressure and breathing are maintained mechanically or with the use of drugs.
A patient can be put in a medically induced coma with the administration of barbiturate drugs or by lowering the body temperature to 32-34° C. The purpose of an induced coma is to allow the brain to rest after an injury, such as those that deprive it of oxygen (a blood clot, a blow to the head that caused pressure in the brain to increase, or a chemical imbalance in the nerve cells resulting from a drug overdose). Doctors can bring the patient out of a coma by discontinuing the treatment.
Often a patient lapses into a coma after a severe accident because the brain needs to recover. As with induced comas, it’s in the patient’s best interest to remain unconscious because the brain must use a lot of energy responding to sense impressions, conscious thoughts and muscle movement when awake. A new Australian study suggests that brain-injury patients who were put into an induced coma at the scene of the accident have a better chance of recovery than those who were put into a coma at the hospital.
The controlled administration of mild hypothermia is one way to induce a coma. These are the steps that are usually followed:
1. The patient is anesthetised to prevent shivers during hypothermia. A respirator lets the patient breathe.
2. A drip of salt water with a temperature of 3.9 degrees cools the patient from within. Typically, two quarts are given over a 30-minute period.
3. Two cooling blankets with a temperature of 3.9 degrees, and ice bags on the most exposed places, cool the body from the outside.
4. The body temperature is regularly measured in the bladder, a major artery or the oesophagus. When the body temperature is between 32.8 and 33.9 degrees, the ice bags are removed and the cooling blanket is set to 32.8 degrees. During the cooling, the patient’s vital functions are constantly measured and monitored.
5. When the cooling is complete, the patient is warmed back up. The cooling blanket temperature is slowly increased over the course of 10 hours. The anesthetisation is discontinued once the body temperature exceeds 35 degrees, and when the body reaches 36 degrees, the blanket is removed.
