"Killing a Patient to Save His Life": Therapeutic hypothermia in trauma cases (from The New York Times)

Freezing food helps to preserve the food by preventing the growth of bacteria that can degrade and contaminate the food. In a somewhat similar process cooling or even freezing living organsism slows down damaging processes potentially preserving them. In theory, it is then possible to restore them to life by thawing (i.e. cryonics).

In the lab, scientists freeze individual cells (i.e. cell lines) all the time. It is done is an aqueous solution spiked with glycerol to prevent ice crystals from forming (which can damage delicate structures like the cell membrane). However, it is a major challenge to freeze more complex multicellular organisms. For example, no one has frozen and then revived any mammal.

However, it is known that people can survive for long periods of time when kept at a cold temperature. Children who have fallen through the ice have survived as long as 40 minutes submerged beneath the water and then resuscitated. The critical organ is the brain which is very sensitive to oxygen deprivation. Neurons (brain cells) can survive longer without oxygen if they are chilled; the metabolic processes are slowed reducing injurious physical, chemical, and biological reactions:

"Submerged in a frozen lake or stowed away in the wheel well of a jumbo jet at 38,000 feet, people can survive for hours with little or no oxygen if their bodies are kept cold."

Indeed, doctors have taken notice of this fact and have begun to explore "therapeutic hypothermia"as a medical procedure for cases in which the heart is stopped and blood may not reach the brain:

"In the 1960s, surgeons in Siberia began putting babies in snow banks before heart surgery to improve their chances of survival. Patients are routinely cooled before surgical procedures that involve stopping the heart."

Last week, The New York Times reported on a proposed extreme form of therapeutic hypothermia for those who have suffered massive blood loss (preventing sufficient oxygen from reaching vital organs like the brain). The idea is to chill the body by replacing the blood in a patient with cold saline solution:

"Trauma patients arriving at an emergency room here after sustaining a gunshot or knife wound may find themselves enrolled in a startling medical experiment. Surgeons will drain their blood and replace it with freezing saltwater. Without heartbeat and brain activity, the patients will be clinically dead."

The rationale is that at normal body temperatures the brain cells will die rapidly after 5 minutes or so without blood flow to maintain oxygenation. At the lower temperature the brain can last as long as an hour without adequate oxygen.  The basic mechanics involve the following:

"Dr. Tisherman and his team will insert a tube called a cannula into the patient’s aorta, flushing the circulatory system with a cold saline solution until body temperature falls to 50 degrees Fahrenheit. As the patient enters a sort of suspended animation, without vital signs, the surgeons will have perhaps one hour to repair the injuries before brain damage occurs. 

After the operation, the team will use a heart-lung bypass machine with a heat exchanger to return blood to the patient. The blood will warm the body gradually, which should circumvent injuries that can happen when tissue is suddenly subjected to oxygen after a period of deprivation.

If the procedure works, the patient’s heart should resume beating when body temperature reaches 85 to 90 degrees. But regaining consciousness may take several hours or several days."

Before the therapeutic hypothermia begins, the patient would have both brain and heart activity i.e. is alive. Then the replacement of blood with cold saline solution would result in the heart and brain stopping. Technically the patient would be dead, and hence the title of the article: "Killing a Patient to Save His Life". The patient would be saved when the traumatic wound is repaired so that blood could be restored without any life-threatening leaks. The chilling gives surgeons more time to repair the wound.

As you imagine there are great risks when you attempt to restore life to someone who is technically dead (albeit well-preserved for a short period of time):

“If this works, what they’ve done is suspended people when they are dead and then brought them back to life,” said Dr. Arthur L. Caplan, a medical ethicist at New York University. “There’s a grave risk that they won’t bring the person back to cognitive life but in a vegetative state.” But researchers at a number of institutions say they have perfected the technique, known as Emergency Preservation and Resuscitation, or E.P.R., in experimental surgeries on hundreds of dogs and pigs over the last decade. As many as 90 percent of the animals have survived in recent studies, most without discernible cognitive impairment — after the procedure, the dogs and pigs remembered old tricks and were able to learn new ones."

It is somewhat reassuring news that the procedure has worked on dogs and pigs, but humans of course are much more complicated especially in terms of neural functioning. One possible analogy is thinking of this procedure as rebooting a computer. In theory you should be able to turn your computer on and off without harm, but in practice you always hold your breath when you press the reboot button (Figure 1).

Regardless it is an exciting experimental technique to add to the growing arsenal of trauma doctors. Other possible procedures include much faster repair of the traumatic wound and/or the use of replacement synthetic blood (that can carry oxygen) in case of massive blood loss.

Figure 1. I always hesitate before I press OK.