Heart and Blood

From my school days, I remember a chapter on the man who did the first heart transplant: Christiaan Barnard. Bill Bryson’s excellent book, The Body: A Guide for Occupants, brings up an interesting point that was instrumental in why a doctor in South Africa got there first, as opposed to the regular haunts of Europe and America. It had to do with (hold your breath) the definition of death in Europe and the US!

“A person could not be declared dead until his heart had been stopped for a specified period, but that was all but certain to render the heart unusable for transplant. To remove a beating heart, no matter how far gone the owner was in all other respects, was to risk prosecution for murder.”

But in South Africa, the definition of death was based on brain inactivity, which meant the heart could still be active. And that, apart from his skills, was key to why Dr.Barnard from South Africa was the first man to do a heart transplant. Not surprisingly then, after Barnard’s success, many nations changed their criteria to be brain death and voila – “Heart transplants were being attempted all over”.

 

Since we are on the heart, remember what the heart does? Yes, it pumps blood. And what does that blood carry? Most of think the answer is oxygen (and carbon dioxide). But it carries so many other things around the body, says Bryson. From hormones to waste, signalling our emotions (as in blushing), and helping regulate blood temperature. Since it does so many different things, blood has “four thousand different types of molecules”. In turn, that explains something:

“That’s why doctors are so fond of blood tests: your blood is positively packed with information.”

 

Talk of blood, and we think of blood groups. Those were discovered due to the weird behavior wherein some blood transfusions worked, whereas others seemed to trigger violent reactions, even death. Karl Landsteiner noticed that when blood from different people was mixed, “sometimes it clumped and sometimes it did not”. He thus found 3 groups that he called A, B and 0. We read the last one as the letter O, but Landsteiner had meant it as zero, because it didn’t clump at all. The fourth group, AB, was discovered shortly afterwards and the Rh (positive or negative) factor 40 years later by Landsteiner again.

 

Well, that discovery certainly helped solve the blood transfusion problem. But blood is a living tissue, and when we take it from a person and store it, it starts to degrade. Which is why blood banks have an expiry date. With the advent of AIDS, doctors were more cautious of transfusing blood but strangely, lesser transfusions sometimes produced better results! What was going on? Turns out blood contains nitric oxide, which serves as a signalling molecule for the body to gauge status. When we transfuse someone else’s blood, it “confuses the signalling system”. Which is why less/no transfusion can sometimes be a better choice!

 

It’s all so endlessly informative and fascinating.