Last week, if you’d said the words ‘suspended animation’ to me, I’d have thought of Han Solo being frozen in carbonite. Now I’d think of the pioneering surgical technique that could be used to save the lives of people with fatal gunshot wounds.
The technique used by Professor Samuel Tisherman and his colleagues at UPMC Presbyterian Hospital in Pittsburgh is, of course, rather a lot different to the one used by Darth Vader. It involves draining the patient’s blood and replacing it with a cold saline solution so that body temperature drops to 10°C. At this point, the patient will be clinically dead and doctors will have hours instead of minutes to stop blood loss and perform surgery. Inducing clinical death sounds counterintuitive as part of a life-saving surgical procedure, but the human body has some pretty amazing tricks up its sleeve, and it isn’t going to be beaten by a bit of cold.
When the body is in hypothermia, chemical reactions in the cells slow down, and they require less oxygen. Since just five minutes of oxygen starvation can lead to permanent brain damage, patients suffering massive blood loss are unlikely to survive. Cooling the body until these vital chemical reactions have virtually stopped causes them to use anaerobic glycolysis (the same system used during bursts of intense exercise) rather than oxygen to produce energy. Cold saline is pumped into the aorta, and a clamp placed on the lower part of the heart causes the saline to flow to the brain. Once the heart and brain (the organs most susceptible to the damaging effects of low oxygen) have started to cool, the heart is unclamped and saline is pumped through the rest of the body. After about 15 minutes, the patient will not be breathing and there will be no brain activity – not alive, but not dead either.
As anyone who’s ever run for a bus can tell you, anaerobic glycolysis is by no means a sustainable method of energy production. After a couple of minutes you’re likely to be feeling the burn as lactic acid builds up in your muscles. However, during hypothermia, anaerobic glycolysis can sustain cells for around two hours.
It’s during these hours that surgeons can operate to try and save the patient. After surgery, new blood is used to replace the saline, and the body gradually reheats and the heart restarts.
The technique has successfully been demonstrated in pigs, and will now be tested in 10 humans. The trial has raised some ethical problems however. Due to the severity of the patients’ injuries and the lack of an alternative treatment, the surgeons don’t have to get consent to perform the technique. Instead, they had to place adverts describing the trial in local newspapers and allow people to opt-out online. So far, nobody has opted-out, suggesting that the people of Pittsburgh trust Professor Tisherman and his science fiction-esque technique to save them if they’re unlucky enough to need it.
Photo reference: http://www.flickr.com/photos/piero/311703408/