Where is the line between life and death?


A group of doctors in the US have recently induced human patients with a state of suspended animation for the first time.

When a person suffers a traumatic injury such as a stab or gunshot wound, their likelihood of survival is less than 5%. Suspended animation, however, immediately preserves the body in unnatural conditions post-trauma, giving surgeons extra time to operate and save a patient when otherwise their injury would result in death.

The first step is for the patient to be rapidly cooled to 10°C by their blood being replaced with ice-cold saline solution. At 10°C the brain activity of the patient is reduced to an almost standstill, but can revert back to a normal state once the body temperature is increased again.

The patient’s body is cooled to 10°C by replacing their blood with ice-cold saline solution

Officially, this process is called emergency preservation and resuscitation (EPR) and is being trialled on patients at the University of Maryland in Baltimore, US. The aim is to find out whether the hour or so bought by rapidly cooling the trauma patient can save a life otherwise lost. So far, Dr Samuel Tisherman, involved in the trial, has revealed that at least one person has undergone the treatment but has not yet elaborated on whether they survived or not.

EPR works by pumping the saline solution into the heart which distributes it around the body. Once the patient is cooled and all their blood replaced with saline they can be removed from the cooling system and taken to the operating theatre. At this point the patient could be classified as dead. Then the surgeons have around two hours to operate before the patient is warmed back up and resuscitated.

At least one person has undergone animated suspension treatment

But how does it all work? Normal body temperature is 37°C, which is needed for chemical reactions and processes like cell survival. For cells to survive they need a constant oxygen supply which is provided through the blood and the heart pumping blood constantly around the body. So, when the heart stops beating and no oxygenated blood is supplied to the cells, cells start to die. Within five minutes of oxygen deprivation, irreversible brain damage can be caused. But reducing the body temperature from 37°C to a hypothermic 10°C means that chemical reactions run a lot slower requiring a lot less energy. This means cells have a lower oxygen demand and the brain can survive on massively reduced oxygen levels. Thus in EPR, patient brain and cellular function can continue at a lower rate at 10°C and the patient can be resuscitated following surgery.

The trial in Maryland is planning to involve 10 trauma patients undergoing EPR who will be compared to 10 trauma patients who didn’t have the treatment due to the correct team not being present when they were admitted to hospital. Approved by the US Food and Drug Administration (FDA), the trial does not require consent due to patients admitted being in conditions where injuries are fatal and there are no other options. However, there is a website where people can opt-out of the EPR treatment.

Animated suspension could change how trauma patients are treated

Previous animal experiments conducted on pigs, showed that the animals could be placed in animated suspension for three hours and survive the resuscitation.

But is it really that simple? When a person is warmed up from animated suspension a series of chemical reactions triggered can damage cells which can be exaggerated by a longer time spent without oxygen. These processes are called cell reperfusion injuries and may cause different levels of damage depending on the patient and time spent in EPR. Tisherman and his team are looking into different drug cocktails that can help mitigate this issue however have yet to fully elucidate the causes of cell reperfusion.

The US space agency and NASA have considered suspended animation-esque methods of sending astronauts into space in a hibernated state. However, Tisherman’s aim here is not for interstellar travel but to gain more time to save lives and prevent irreversible brain damage that often occurs if trauma patients survive without EPR.

At the moment the trial is ongoing and results are set to be published in late 2020. If successful, this research could pioneer new methods into treating and saving the lives of trauma patients.

Image by Zdenko Zivkovic via Flickr and Creative Commons.

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