Patients are routinely cooled before surgical procedures that involve stopping the heart. But so-called therapeutic hypothermia has never been tried in patients when the injury has already occurred, and until now doctors have never tried to replace a patient’s blood entirely with cold saltwater.
In their trial, funded by the Department of Defense, doctors at the University of Pittsburgh Medical Center will be performing the procedure only on patients who arrive at the E.R. with “catastrophic penetrating trauma” and who have lost so much blood that they have gone into cardiac arrest.
At normal body temperatures, surgeons typically have less than five minutes to restore blood flow before brain damage occurs.
“In these situations, less than one in 10 survive,” said Dr. Samuel A. Tisherman, the lead researcher of the study. “We want to give people better odds.”
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.
Dr. Tisherman and his colleagues plan to try the technique on 10 subjects, then review the data, consider changes in their approach, and enroll another 10. For every patient who has the operation, there will be a control subject for comparison.
The experiment officially began in April and the surgeons predict they will see about one qualifying patient a month.
It may take a couple of years to complete the study. Citing the preliminary nature of the research, Dr. Tisherman declined to say whether he and his colleagues had already operated on a patient.