Five Quarts_ A Personal and Natural History of Blood - Bill Hayes [91]
In the interim, he steered me to an adjoining room, a kind of platelet pantry. On floor-to-ceiling shelves, small bags of the straw-colored cells lay like flat pillows on undulating metal racks, the rocking movement driven by grinding motors. “Platelets are very fragile,” he said in a raised voice, “not hale and hearty like red cells.” But they’re very eager to clump, which is their pivotal role in the coagulation cascade. Once clumped, though, they don’t unclump. “So,” Richard concluded, “you have to keep them in constant motion.” You also have to keep them exactly at room temperature, a fact I found quite odd. Ironically, once removed from the 98.6 degrees Fahrenheit of the human body, platelets no longer thrive at that temperature. He picked up one of the bags for me to peer at, holding it up to the ceiling light. The platelets were just a swirl in a shallow bath of plasma.
These cells remain functional for only five days, Richard said. They’re the shortest-lived products produced at the center, and biting into that time is the thirty-six-hour wait for test results. I quickly did the math in my head. Subtract the day it takes to process the blood, minus the day and a half for testing: “So half their shelf life is spent here on the shelf,” I observed.
“You got it,” Richard said with a nod. “Which is why we always, always need new donors.”
Red cells, he went on to say, can last forty-two days if refrigerated and years if frozen. Plasma is more finicky. If not frozen within six hours, the essential clotting factors “will disintegrate” or break down. Frozen plasma will keep for no more than twelve months.
Back at the centrifuge, Richard gently withdrew a spun bag of blood, now displaying neat layers of amber, white, and burgundy. We took a giant step to the right, at the same time moving from high tech to low. At this workstation each bag of separated blood is hung by its edges to the “plasma expresser.” Anyone who’s worked an old-fashioned orange juicer could handle this device. Pulling down a simple lever applies pressure to the lower portion of the bag, thus squeezing the plasma at the top through the tubing and into the second collection bag. The only trick is knowing when to stop pulling.
On the other side of this counter, an IV stand held several fat red pouches of plasma-less blood that were now being stripped of white cells, a slow process that appeared to depend mostly on gravity. Blood snaked down a length of narrow tubing, passed through a white-cell-catching filter about the size of an ant trap, and pooled in a bag near the floor. The white cells would be discarded. Watching this procedure brought up a question that’s nagged at me for many years: If a healthy person’s immunity is largely contained in his or her white cells, couldn’t an ill person benefit from them? Or, coming at it another way, why throw them out? Wouldn’t transfusing them be useful?
“No, almost never,” Richard answered. “White cells are not a good thing, and you want to remove them.” Beneath his blanket statement were a number of powerful reasons. For starters, too great a risk exists of transmitting an infectious disease for which testing isn’t done, such as the cytomegalovirus (CMV), which may be present in white cells even if the donor has never manifested symptoms. Further, contrary to my layman’s thinking, white cells rarely see another person’s white cells as allies. Instead, they go on the attack. The recipient may, as a result, suffer a high fever or a life-threatening reaction. “There are very few indications for white cell transfusions,” Richard concluded, “one or two a year, if that.” Thankfully, for the vast majority of patients a far safer and more effective alternative exists in antibiotics.
Okay, that all made sense, but