SUSPENDED ANIMATION COULD BECOME A LIFE-SAVING TECHNIQUE
NEW ORLEANS -- The ability to actually bring back patients from death after severe trauma or a heart arrest looms in the not-too-distant future, according to one of the nation's foremost experts in resuscitation medicine.
As part of a panel on resuscitation at the annual meeting of the American Society of Anesthesiologists, Peter Safar, M.D., from the University of Pittsburgh will present the latest information on new possibilities for saving patients following two types of emergencies: sudden heart arrest that does not respond to current resuscitation techniques and severe blood loss. Heart arrest, which results in no blood flow, differs from a heart attack in which some blood continues to flow through the heart.
Dr. Safar and fellow researchers are testing a technique that could one day save heart-arrest victims who cannot be resuscitated. In the laboratory, they have successfully produced a state of "suspended animation for delayed resuscitation" by rapidly flushing cold saline (salt water) into the aorta (the main artery) of lab animals. The technique quickly cools the brain, heart and organs to five to 10 degrees centigrade, producing profound hypothermia (lowered body temperature). A similar technique is being tested as well to help victims of severe blood loss, or hemorrhage, possibly due to trauma or a vehicle accident, with the heart continuing to beat, by purposely lowering the person's body temperature slightly while they are being transported to the hospital and resuscitated.
When hypothermia occurs under uncontrolled circumstances -- from exposure to cold weather, for example -- it can kill. Produced in a controlled, deliberate manner, however, it could save lives, according to Dr. Safar, who is Distinguished Professor of Resuscitation Medicine at the University of Pittsburgh's Safar Center for Resuscitation Research.
There are a number of reported cases where victims who have drowned in frozen lakes and ponds have been revived after having been pulled from the water after as long as 60 minutes. In recent nonclinical studies, however, the University of Pittsburgh team has successfully revived laboratory animals after two hours of death.
Rapid, severe chilling of the body that produces a state of suspended animation could one day buy doctors the critical additional time they need to transport and resuscitate patients in whom blood flow has not merely slowed, such as during a heart attack or shock, but stopped when the heart fully arrests, Dr. Safar said.
"Hypothermia preserves the viability of organs deprived of oxygen," Dr. Safar said.
The technique offers the possibility of delayed resuscitation in heart-arrest patients who could not be revived with cardiopulmonary resuscitation (CPR) or other emergency techniques, he said. It could one day also save the lives of combat casualties or civilian patients suffering severe hemorrhaging and victims of sudden injury.
The researchers hope to conduct clinical trials on "pulseless" trauma patients who otherwise would not survive. First, however, they must develop a procedure to gain rapid access to the aorta within the first five minutes after the heart arrests to flush in cold fluid. Often this must occur even before the patient reaches the hospital. The procedure to do this, called a thoracotomy (opening of the chest), is used in emergency rooms, but a new method has to be found for doing the procedure "in the field," Dr. Safar said.
For severe hemorrhagic shock (low blood flow), many attempts to develop techniques to resuscitate patients have met with disappointment, Dr. Safar said. However, "hypothermic strategies" for resuscitation have generated renewed scientific interest over the past 15 years, he said.
Dr. Safar also presented the results of research under way at the Safar Center to extend the "golden hour" of shock tolerance -- the window of time during which blood volume must be restored to prevent multiple-organ failure and death.
"We've shown in laboratory studies that lowering whole body temperature two to three degrees during severe hemorrhagic shock can double the survival time and rate. The technique would involve producing mild hypothermia by undressing patients or using any of a variety of blood-cooling methods. This could provide valuable extra time to transport and resuscitate them," Dr. Safar said.
The hypothermic techniques presented by Dr. Safar also involve giving a special anti-oxidant drug plus administering small amounts of hypertonic solution, a liquid containing a high concentration of salt. The solution draws fluid into the blood stream, improving blood flow, he said.
Hypothermic strategies challenge some traditional medical practices, Dr. Safar noted. Physicians have long believed that they must warm patients in shock, not cool them. They have also known that hypothermia can increase blood loss by interfering with blood clotting. According to studies at the Safar Center, however, the controlled lowering of body temperature by only two to three degrees does not significantly hamper blood clotting.
"There is a big difference between uncontrolled, spontaneous, moderate-to-severe hypothermia and controlled, mild hypothermia," Dr. Safar said.
Uncontrolled hypothermia also can lead to shivering, a potentially dangerous complication. Controlled, mild cooling circumvents this dangerous problem, he added.
Anesthesiologists from the University of Pennsylvania, University of Maryland and the University of Texas Medical Branch in Galveston also participated in the panel.
###
During the meeting a press room will be set up in the Morial Convention Center, room 283-284. The press room will be open from 8 a.m. to 5 p.m. Saturday, October 13, through Wednesday, October 17. The media can call the press room during the dates of the annual meeting at (504) 670-6512. Before the meeting, ASA staff members can be contacted by e-mail, [email protected] or by calling (847) 825-5586. Phil Weintraub, [email protected].
This news release is protected by copyright. American Society of Anesthesiologists attribution is required.
Copyright 2001American Society of AnesthesiologistsAll Rights Reserved
RSS