How It Works: Putting Humans In Suspended Animation

A new human trial will chill gunshot victims to keep them alive

“Suspended animation” — literally putting life on hold — has long been a medical dream. (The preferred scientific term for the procedure is emergency preservation and resuscitation [ EPR ].) Dr. Sam Tisherman and a team of surgeons at UPMC Presbyterian Hospital in Pittsburgh, Pennsylvania, have recently started human trials for a practical application of EPR. This surgical technique replaces all of a patient’s blood with a solution to cool the body down and buy time for doctors to fix injuries without losing patients to blood loss.

Dr. Peter Rhee at the University of Arizona in Tucson first started researching suspended animation when asked by the military to find a way of preserving wounded victims before they reached the hospital, and together with his colleagues developed a technique through experimenting on pigs. Dr. Tisherman of the University of Pittsburgh and his team developed another method, which is what will be tested in the new human trials.

Hypothermia — an abnormally low body temperature — dramatically decreases the human body’s need for oxygen. This is similar to how animals hibernate. In EPR, doctors will induce hypothermia in patients by swapping their blood with very cold salt water to cool the entire body down to 10°C (50°F) in 15 minutes. Normally, we can’t survive with our blood missing — it carries the oxygen that cells need to make energy. However, when the body temperature is very low, cellular activity stops and cells survive without oxygen, thus preventing further damage to tissues and organs. It’s also important to cool the body down quickly when trauma patients are losing blood rapidly. If they don’t have any blood flow to the brain for 4 to 5 minutes, while the body is at normal temperature, there could be irreversible damage.

Here’s how this particular suspended animation technique will work.

  1. Patients qualifying for this human trial must be victims of penetrating wounds — which means gunshot wounds and stab wounds — who suffer cardiac arrest and have lost their pulse. Statistically, these patients have only a 7 percent chance of being resuscitated. Theoretically, they’ll have lost their pulse and about 50 percent of their blood already. Their chest will likely already be open, following attempts to perform open-chest CPR, standard procedure for trauma patients with cardiac arrest.
  2. A large tube is placed directly in the aorta.
  3. Cold saline solution is pumped through the heart and towards the brain first, since the brain is the most vulnerable organ and can only survive 4 to 5 minutes without oxygen.
  4. The solution is then pumped to the rest of the body, thus emptying the remaining blood volume of the patient. The patient now has no blood and no brain activity.
  5. The current technique allows doctors around two hours to repair the trauma injuries. Then the saline solution is replaced with blood again. If the patient’s heart does not start on its own after blood is pumped, doctors will resuscitate the patient with a heart-lung bypass machine.

No humans have yet undergone this procedure, as Dr. Tisherman and his team are still waiting for the right patients to come in. The human trial will go on until there are enough data to analyze, which could take up to a year. Dr. Tisherman anticipates that enrollment will begin as summer approaches. Hopefully in the near future, suspended animation can be extended to other trauma conditions to save lives.

Dr. Tisherman answers frequently asked questions in the video below.