Platelets

So what are platelets?

Platelets are one of the major components of your blood. When they’re sailing around your bloodstream, platelets look like little saucers – sort of streamlined little brothers of red blood cells.

When there’s a break in a blood vessel, platelets become “activated.” Activated platelets look like a aliens from a 1950s sci-fi movie. They’re full of what appear to be tentacles, which help them bind together and encourage other blood-clotting components to join in, in most cases plugging an opening in an artery or vein.

Platelets were first described by the British scientist George Gulliver in 1841, observed under one of the earliest microscopes.

Who needs platelets?

People who have traumatic injuries need platelets beyond what their bodies can produce. People who are undergoing cancer treatments need platelets, because the treatments can reduce the amount of platelets their bodies produce. And people who are receiving transplants often need them as well.

How do you collect platelets?

There are two typical ways to collect platelets.

If you donate whole blood, after your donation is done, we use a system that separates the platelets from the red blood cells and the plasma, the liquid that carries the platelets and red cells through the bloodstream. To make a unit large enough to raise an adult’s platelet count, we need to combine four to six of these separate donations.

You also can donate just platelets using a process called apheresis. Your blood goes through a machine that separates the platelets and returns the rest of the components to your body. This produces one to three units large enough to affect an adult patient’s platelet count.

Why should I donate platelets?

Essentially, two reasons.

First, they’re in high demand, especially for cancer patients. Second, they have a short shelf life, typically five days or less. The problem is that they become sticky very easily, so they can’t be refrigerated and they have to be agitated constantly.

Other blood components can be refrigerated and/or stored frozen for longer periods of time. But not platelets.

How long does it take to donate platelets?

An average donation takes about two hours, or the length of “Frozen.”

How often can I donate platelets?

You can donate about every seven to 10 days, up to 24 times in a year.

What are the requirements?

You have to be at least 16 years old, have had one successful blood donation (or more), and submit a parental consent form. Also, your body needs to have a certain platelet count – which we’ll measure – to see if you are able to donate.

Ever been pregnant? Check out the latest research concerning donation post pregnancy

How many platelets do I give? 

The typical platelets-only donation – called apheresis or single-donor platelets – collects between 300 billion and 600 billion platelets, less than a quarter of all the platelets in your bloodstream.

But don’t worry. Your bone marrow makes about 100 billion platelets a day, and in the typical 10-day period, all the platelets in your body are replaced anyway.

How many platelets are collected in a year?

There were 2.2 million units of platelets collected in the United States in 2013, according to the American Association of Blood Banks.

So how does my body make platelets?

Platelets actually are fragments of bone marrow cells called megakaryocytes. The megakaryocytes are too big to get into the bloodstream, but portions of them break off and are small enough to enter the bloodstream. Those broken-off pieces are platelets. A typical megakaryocyte produces about 1,000 platelets.

How big are platelets?

An unactivated platelet is between 2 and 4 micrometers (a micrometer is a millionth of a meter) in diameter.

If you have a difficult time thinking in terms either than small or that metric, here’s a different perspective: If you lined up 6,500 platelets, they would stretch from the knuckle of your thumb to the tip.

On the other hand, if you lined up all the platelets your body made in a day, it would be a very odd-looking line – and would stretch from San Antonio to the southern suburbs of Dallas. Yes, 400 billion micrometers is just about 250 miles. Ain’t math grand?

And even though there are lots of them, platelets make up less than 1 percent of the total volume of your bloodstream.

What do I need to do to get ready to donate?

Don’t take any aspirin or ibuprofen for at least 48 hours before your appointment, since they alter the way platelets work and make them pretty much ineffective. If you need something for aches and pains, use acetaminophen. If figuring out what acetaminophen is makes your head hurt, take two. (It’s the active ingredient in Tylenol.)

Is it going to hurt?

The process is very similar to giving blood, with just the slight pinch of a needle and passing soreness in your arm. Side effects are pretty much the same as well, including minor tingling of the hands or mouth or a slight chill.

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