However, people who fall into icy water have been resuscitated up to 30 minutes after their heart stopped beating. This is because cell functions slow, and nearly stop at low temperatures, and the need for oxygen is drastically reduced.
Heart and brain surgery can involve using ice-packs to cool the body externally, while the blood is rerouted through an artificial circulation system to cool it. This gives surgeons more time. But this is a slow process.
If the heart has stopped beating, there are just a few minutes to spare. Ditto for massive blood loss. EPR could come into play here. The inspiration for EPR goes back to studies during the Vietnam War. Military surgeons noted that one leading cause of death was blood loss in the first 5-20 minutes after an injury, even for soldiers who had wounds that could have been treated.
In the early 2000s, researchers at the University of Arizona started experimenting on pigs, replacing their blood with cold saline solutions after inflicting serious wounds. They discovered that the animals could be resuscitated up to three hours later, with no apparent ill-effects, after treatment.
Now, the School of Medicine at the University of Maryland (Baltimore) has received permission to use EPR techniques on emergency cases where the victim has a very low chance of survival. According to reports, EPR has already been used on at least one patient.
EPR involves replacing all the blood in the body with ice-cold saline solutions. It takes about 15 minutes for the temperature to drop to 10°C. At this point there is no blood in the body, the patient is not breathing, and there is no brain activity.
This clinically dead patient is then disconnected from the machinery, and surgery or other emergency medical procedures can then be performed. After that, the saline is replaced with blood, which heats the body slowly. Researchers estimate that EPR could give doctors
a window of about two hours for treatment, instead of mere minutes, in working with near-fatal injuries.
It isn’t clear how long an EPR procedure can last without lasting damage. Nor are the parameters for “reboots” clear. During the “warmup” period, chemical reactions restart at the cellular level. This can cause damage — “reperfusion” injuries may be caused when oxygen supply returns to cells. The reperfusion process is not fully understood, and there could eventually be drugs developed to minimise this damage and thus, allow for longer EPR times.
The EPR trials in Baltimore will initially involve 10 EPR subjects and 10 controls. All will be trauma victims brought into the Emergency Room of the University of Maryland Hospital with near-fatal injuries. This is legally awkward because the subjects and controls may be incapable of giving consent.
The US Food and Drug Administration has waived the consent requirements for this important experiment. The logic is, this procedure will only be performed on subjects with very serious injuries, where there is no alternative treatment, and the chances of survival are very low.
The EPR technique will be tested on 10 people, and the outcome compared with 10 controls. The technique will be refined, then tested on another 10, etc. The EPR trials will continue through 2020. This is a long way from the SF scenario, where people in suspended animation are taken on century-long spaceflights. But it could be a powerful new tool for emergency medicine.