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Weekend Engineering: Blood Donation

June 14, 2011 at 10:52 am


By Phillip King, long-time Stanford Blood Center platelet donor

Above, Phillip is donating platelets after being the very first donor to try out our new software system for the registration process.

Today’s entry is one of those gimmicky pieces where the writing of the entry is intimately connected with the topic being written about. Yup, as I sit here (at Stanford Blood Center) typing this, I am hooked up to a Gambro BCT blood separation machine which is pulling blood out of my left arm, extracting the desired components (in this case platelets), and putting the bulk material back into my arm.

The fact that I can write this at all is a tribute to evolving medical technology. When I first started doing platelet apheresis in 1992, the machines used separate extraction and return needles, so I had to sit with both elbows extended and unbending, a needle in each arm. This pretty well limited what I could do during the 80 – 120 minute period of the donation to watching a movie. One time I had an itch on my nose that just wouldn’t go away. I finally told one of the blood center staff, and she took a piece of gauze in a pair of tongs and used it to scratch my nose for me. When the single needle machines were first put into use, I didn’t like them as well as the two needle process, and I continued to request the two needle machines for several years. Eventually, though, the single needle machines got better, and now that is all they use, except for white cell donations.

Although the donation takes longer, donating platelets is (I have been told) less physiologically stressful than giving a pint of whole blood. Donating whole blood is essentially bleeding out 7-14% of your entire blood mass, and you can only do it once every 56 days in the U.S. Platelet donations, on the other hand takes almost no red blood cells, and instead just platelets suspended in a few hundred milliliters of plasma. Because the human body replaces lost platelets in about three days, donors are eligible to do apheresis as often as once a week, and in an emergency, as often as every four days. There are a few other limits that the FDA puts on apheresis. You can only donate a maximum of 24 times in any one year period, and they limit your total plasma loss in any one year period to 12 liters if you weigh between 110 and 175 pounds, or 14.4 liters if you are over 175 pounds.

Right now I am donating a “double,” or two sets of platelets, which are actually going into two separate bags. In total, they will take out 710 billion platelets, and about 415 ml of plasma, plus the tubes of whole blood removed at the beginning of the process for testing. Every blood donation is tested for a variety of diseases, including HIV, hepatitis, and West Nile virus, which is why they extract those additional samples. Sometimes the test samples are also used for research.

In order to keep my blood liquid while they are running it through the machine, they introduce an anticoagulant. The anticoagulant combines with calcium in the blood, creating a temporary calcium deficiency during the period of the donation. One side effect of this is a tingling in my lips, and mild muscle cramps in my jaw. To counteract this, the staff provide Tums antacid for me to suck on, which gives me back calcium. The tingling and other effects disappear as soon as the donation ends, and my body quickly metabolizes any remaining anticoagulant.

So why do this? Well, for one thing, someone has to. Platelets are used in the treatment of a lot of things, particularly for cancer patients undergoing chemotherapy. Currently only about 3% of the medically eligible population donates blood or blood products. Many people have asked me if I get paid for donating. The answer is no. Tax laws let me deduct the mileage to drive to the Center, and the Stanford Blood Center gives me cookies and occasionally coupons for free movie tickets or Baskin Robbins ice cream, but I don’t get paid. And really, if you were in the hospital and needed blood products, would you want them to come from someone that donated because he or she needed the money?

And, like so many things, this began in part due to a dare. When I was in college in the late 80s and early 90s, my best friend, who had been giving blood since high school, mocked me mercilessly because I wouldn’t give blood along with her. So finally, during my senior year, I stopped in at the Stanford bloodmobile one afternoon when it was parked in front of my university residence. I mentioned to them that I was doing it in part to confront my discomfort with needles. “Well if you REALLY want to confront needles,” they said, “you should try apheresis! You get two needles!” And here I am, 18 years later…

And the needle just came out, so it is time to go eat cookies and then go to work!

Click here to be taken to the original piece on Phillip’s blog, Weekend Engineering.

To inquire about apheresis donations, please call 888-723-7831.