Beating Heart CadaversLast year we had a terminal (non-recovery) fish practical which required fresh

Beating Heart CadaversLast year we had a terminal (non-recovery) fish practical which required fresh cadavers. The fish were humanely euthanised with an anaesthetic overdose. As an added precaution, the gill arches were then cut (causing them to bleed out and preventing respiration) and the spinal cord transected (obstructing electrical signals from the brain). Despite these measures, the fish hearts continued to beat for several minutes. Even once removed from the rest of the body, they continued to beat. As you can imagine, it was quite disconcerting, but we were all reassured that the fish were, in fact, dead and unable to feel any pain. I hadn’t given it another thought until I came across this video yesterday and my curiosity got the better of me. So I did what any ex-vet student would do - RESEARCH!The heart continues to beat because, unlike most muscles in the body, the heart doesn’t rely on electrical impulses from the brain, but instead generates its own electrical impulses from specialised cells within the heart. These cells can continue to fire as long as they have sufficient ATP (energy). Apparently this phenomenon can (and does) occur in humans too.So then I started thinking about the process of dying, how “death” is defined, and what criteria are used to determine death. Is a patient dead when the heart stops beating, or when respiration ceases? Are they dead when there is no longer conscious thought, no response to stimulus, or an absence of electrical activity in the brain (“brain dead”)? Or a combination? It’s clearly a controversial question because death isn’t a single event, it’s a process! Cells, tissues and organs die at different rates.While I was reading, I came across the term “beating heart cadaver” which I hadn’t heard of before. A beating heart cadaver is a body that is pronounced dead (by the brain dead definition), yet retains functioning organs and a pulse. Because the brain stem is dead and can’t control ventilation, the body is connected to a medical ventilator which keeps the blood oxygenated. This blood is circulated around the body by the heart, which continues to beat independently. Beating heart cadavers are known to “survive” for up to 20 years! These cadavers are even capable of maintaining pregnancies! Fascinating right?In the vet industry we routinely determine whether an animal is alive or not simply by feeling for a pulse and using a stethoscope to auscultate the heart. I suppose if the heart ISN’T beating, the animal is definitely dead. And with pharmacological euthanasia, the cardiovascular system is likely to be the last to go (after nervous and respiratory systems). Even so, assessing cardiovascular function now seems an over-simplified means for determining death in veterinary patients. I will certainly be giving more thought to my death criteria from now on.If you’re as fascinated by this topic as I apparently am, I found this interesting BBC article which is worth a read: http://www.bbc.com/future/story/20161103-the-macabre-fate-of-beating-heart-corpsesCheck out the videos of my fish practical here: https://www.instagram.com/p/BtaeSQKnW-a/ -- source link

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