By Jesse Marx
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Orders for blood have been trickling in since morning rush hour. Five pack cells of red, 10 units of plasma. By noon, the Memorial Blood Center's fax machine sounds like the ticker tape in an off-track betting office. The numbers look normal, routine, no alarming spikes that might indicate a pile-up on the freeway, a plane down, a ruptured aneurysm on the surgical table--any of the infinite scenarios that would require extra blood and throw off last week's calculations enough to wipe out the inventory reserves. Human bodies are, after all, unpredictable things; they crash into railings, they fall from the sky, they break and leak and come apart in all kinds of ways.
At nonprofit banks like Memorial in south Minneapolis, where Connie Adams manages the blood supply for nearly the whole of Hennepin County and several hospitals upstate, the quantity of blood needed to put bodies back together is always a guess. When she took the job two years ago, Adams says trying to divine the demand for blood was like looking into a crystal ball--a foggy one. It still is. All you need is a single catastrophe out there. A single round of gunshots. A single speedboat running head-on into another, out there where all the intricate calculations she and her lab technicians and donor recruiters made last week come down to mathematics and, finally, best guessing.
The margin of error in those guesses is designed to be thin. Delivered blood components, like milk, have a limited shelf life, even with a round of anticoagulants and stabilizers added--42 days is the common figure for red pack cells, and less than a week for platelets, after which they spoil. Draw too many and the surplus goes to waste; too few, and a patient runs out of blood. Last year, the bank moved over 80,000 pack cells from hundreds of bodies to hundreds of others, each tracked by computer from the moment a donor rolled up his sleeve in the Mall of America parking lot, the corporate lunchroom, or the union hall to the moment it was transfused on the operating table, the paramedic's stretcher, the hemophiliac's couch.
"But what happens to our attempts at precision between point A and point B," says Adams, "is that so much can go wrong. For one, every time you transport units, you run the risk of losing them." Maybe the shipment gets loaded onto the wrong airplane and ends up at point C, in Cleveland; it could take a couple days until anybody realizes the mistake, and by then the optimum temperature range has been topped and it's lost. Or a box gets dropped. Or it's 30 below and the insulating blanket wrapped around a shipment slips off in transit. Or it's 90 above, and the blood's been accidentally left out in the sun. "So there's those kinds of errors. And then there's just plain expiration. The shelf life runs out. Time's up. That's more rare." Usually, she says, they get it right.
"Getting it right" means that the blood the bank draws gets used and, more crucially, that it doesn't run out. It means estimating the demand accurately, recruiting enough donors, and moving enough units from station to station to stay in that narrow margin--a five-day inventory at most hospitals--without wasting components as surplus. But even this is difficult, Adams adds. Hospitals have limited storage space, and smaller ones may have stricter budgets that don't allow for much state-of-the-art refrigeration in which to keep extra pack cells on hand.
Some, especially those with oncology facilities and busy trauma centers, go through blood products so fast they often order out twice, three times on a fast day. And at some sites, blood is purposely overstocked, up in Sandstone or Ely or Moose Lake, say--remote posts an hour or two from Duluth, where staffers figure travel time for emergencies into their equations; blood that goes unused, in a calm month, circulates back to busier metro hospitals in a kind of recycling operation.
Of course the best-case scenario for any blood bank is a world in which every "bleed" is predictable, a closed-circuit system of prophesy and delivery. And it does sometimes happen--not decisively, but with enough regularity to give them what Adams calls "an occasional cushion of security in an otherwise tricky business." On the one hand, there are the anticipated cyclical peaks: early summer weekends before people get their sea legs on boats or the hang of their motorcycles again; full moons, during which both anecdotal and scientific evidence point to an unusual number of freak accidents; elective surgeries postponed until after the holidays. All of which call for extra blood, and can be stocked for in advance. On the other hand, there are the valleys: namely February in Minnesota, when non-emergency operations are put off while physicians and surgeons conference in Cancun, and donors, too, head south, taking their blood along with them.
These seasonal trends figure into the numbers when the bank gears up for a drive, or as some in the blood trade put it, a "harvest." In regard to those drives, it's almost unheard of to pay donors for whole blood anymore. The tactical change came, according to Memorial's associate medical director, Elizabeth Perry, back in the early 1980s, when the HIV epidemic was just beginning to break and its modus operandi understood.