By Banda Chisomo, King Edward IV Five Ways School, Birmingham
Picture this: a patient has a large gunshot wound to their lower abdomen and they had excessive haemorrhaging before suffering from myocardial infarction and flatlining. They are rushed to the accident and emergency ward where the doctors assess the extent of the damage and they agree that under traditional care the patient has a 7% chance of survival. However, with the use of suspended animation, the survival rate of this particular patient (and plenty other trauma patients) could be vastly increased.
The technical term for this process is emergency preservation and resuscitation (EPR). This idea has appeared plenty of times in movies but it is often more extreme, resembling something like cryogenic preservation whereby patients are thawed after “x” amount of time. This type of suspended animation actually involves the doctors inducing a state of hypothermia in the patient. Their blood is replaced with a very cold, saline solution (10°C/50°F) in about 15 minutes. This is quite strange to imagine because we require blood to transport oxygen around the body for vital life processes. However, when the body temperature is this low, cellular activity is significantly reduced and often grinds to a halt enabling cells to survive without oxygen. This prevents further damage to tissue and organs. One mustn’t forget the brain, which can suffer irreversible damage without blood flow for 4-5 minutes at normal temperature, so cooling is the main priority. The exact process is as follows:
1. Insert a cannula directly into the aorta
2. Pump cold, saline solution in through the heart and towards the brain first (the most vulnerable organ to oxygen deprivation)
3. Pump solution to the rest of the body which empties the remaining blood volume of the patient. At this point the patient should have no blood and no brain activity.
4. After the surgical repairs, replace the saline solution with blood again. The patient will then be resuscitated using a heart-lung bypass machine, should the heart not start again independently.
This is where the major discrepancy between this technique and cryogenic freezing lies. It allows surgeons around two hours to treat and repair the trauma injuries, which is plenty more than they would have using traditional treatment. Effectively it’s like pressing a pause button whilst surgeons get to work. Quite obviously this is different to freezing a patient for many years and bringing them back to life.
Dr Sam Tisherman and a team of surgeons at UPMC Presbyterian Hospital in Pittsburgh, Pennsylvania, started human trials for a practical application of EPR back in 2014. Dr Peter Rhee at the University of Arizona in Tucson also began research on this much before Tisherman after being approached by the military and developed a technique through experimenting on pigs. Dr Rhee’s work was more focused on the re-warming of trauma victims to find the optimum rate of re-warming. He inflicted a lethal wound on 40 test pigs to simulate real-world trauma scenarios and some pigs were cooled down using a very similar method. He had ten control pigs which were not cooled down and they all died due to excessive haemorrhage while their core temperature was maintained at 36°C-37°C. The surgeons were able to save seventeen other pigs and they were split into groups. A group of 10 had their bodies re-warmed at a rate of 0.25°C/minute (slow), another group of ten had their bodies re-warmed at a rate of 0.5°C/minute (medium) and the final group of ten had their bodies re-warmed at a rate of 1°C/minute (fast). Of the ten re-warmed slowly, 50% survived; of the 10 re-warmed at a medium rate, 90% survived and of the 10 re-warmed quickly, 30% survived. To quote the research “after discontinuation of cardiopulmonary bypass, the animals were recovered and monitored for six weeks for neurological deficits, cognitive function and organ dysfunction. All the surviving animals were neurologically intact, displayed normal learning capacity, and had no long-term organ dysfunction.” This research is integral because it shows that long-term survival is heavily influenced by the rate of reversal of hypothermia.
EPR seems revolutionary and it should become normal practice in the coming years. This will not only save more lives but reduce the amount of stress in the lives of trauma surgeons.
