How, after a cerebrovascular accident (CVA), a heart attack or a respiratory arrest, to protect the cells and the organs from the harmful effects related to the deprivation of oxygen and its reintroduction? In the issue of the scientific journal Nature released August 3, teams from the Yale Faculty of Medicine (Connecticut, USA) describe an infusion system called OrganEx which allows oxygen to be recirculated throughout the body of a pig. This system “restored circulation and repaired damaged cells in the bodies of pigs that had been dead for an hour,” said Brendan Parent, director of ethics and transplant policy at New York University, who was not involved in the study.
The group behind this breakthrough had already, in 2019, developed a technique called BrainEx, which restored a certain degree of metabolic activity in pig brain cells, four to six hours after oxygen deprivation. However, the authors insisted, if the cells were active, the brains showed no signs of consciousness or perception. This strategy involved a specialized fluid, a cryoprotectant perfusate, pumped through the blood vessels of the animal’s brain. This perfusate contained a synthetic form of hemoglobin (the protein that carries oxygen in red blood cells) as well as a cocktail of protective molecules, in particular to prevent blood clots.
In the current study, the authors optimized this fluid by adapting it for whole-body infusion. To test their system, they caused cardiac arrest in pigs. An hour after they died, this modified fluid was infused using a computer-controlled system that kept the perfusate molecules at stable levels. The authors then compared the effectiveness of OrganEx to that of an extracorporeal respiratory assistance system, extracorporeal membrane oxygenation (ECMO), a device used in the event of severe circulatory or respiratory failure and in patients suffering from a severe form of Covid-19.
Results, “after six hours of infusion, OrganEx was much more effective than ECMO in getting fluids back to flow through arteries and organs,” summarizes Brendan Parent. The ECMO, in fact, did not allow a correct perfusion of all the organs, many small blood vessels having collapsed. “In contrast, the OrganEx system provided complete reperfusion and stable oxygen uptake,” emphasizes Robert Porte of the University of Groningen (Netherlands), in an article putting the study into perspective.
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