Methods of preparing a unit of whole blood for centrifugation
A quality assurance officer within a network of donor collection centers reports that their leadership is looking to standardize blood component preparation SOPs across their entire system. At present, each of that network's individual sites has been able to maintain its own set of SOPs, but now they are attempting to standardize SOPs according to best practices. One question that has come up pertains to the practice of how best to prepare a unit of whole blood to be centrifuged, so that it can be manufactured into component parts. Some of the network sites gently mix the whole blood unit several times before placing the bag into the centrifuge, while other sites shake the unit vigorously before centrifugation. She laments that she cannot find a "good" reference as to whether this shaking is best done gently or vigorously. The blood bag's package insert states only to "... mix several times...", without further guidance. She wonders what others do to prepare the whole blood unit for centrifugation, and upon what scientific evidence is that practice based.
The following comments have been received.
ADDENDA June 11, 2004
- The Technical Director of a Blood Bank in Northern California suggests that it is generally best to consult the manufacturer for help in these areas, in addition to reading the Manufacturers' bag package inserts. Manufacturers will usually have a Technical Services department that can be phoned, and knowledgable individuals who can make recommendations based on the properties of the bag under discussion. The Northern California colleague would be concerned with vigorous shaking of a unit of whole blood prior to its centrifugation, for fear that shear forces could compromise the RBCs.
ADDENDA June 12, 2004
- A colleague from Spain reports that following manufacturer's instructions, they shake blood bags precisely 9 times up and down, vigorously. Their QC results are good, and they report having observed no increase in hemolysis. Shaking blood bags before component preparation is a simple but key issue, because in their experience, one needs to homogenize blood thoroughly to achieve a good separation. This is particularly critical if blood bags have been stored overnight at cold temperature, because viscosity increases. By shaking, cellular components mix uniformly with plasma and form a good buffy coat after centrifugation. He adds that this is even more important when they prepare platelet concentrates using buffy coat techniques. To minimize blood bag breakage inside the centrifuge, they stack satellite bags carefully, gather the tubing, put it upon the satellite bags, and on top of them place the blood bag. They insert this package carefully in the centrifuge bucket, with the blood bag touching the inner part of the bucket. The Spaniard cautions that if the buckets have two compartments, blood bags should face each other. The blood bags should not bulge over the brim of the bucket. The next step is to precisely balance the buckets. For this they use bits of discarded satellite bags (or rubber bands, or strips of kitchen gloves) to balance the buckets. He adds that if their blood bags have an odd number, they use a 500mL saline plastic bag or fill a discarded blood bag with water. Finally, he suggests that based on his experience and long practice, they do not try to prepare components inmediately after collection, but let the blood 'rest' at least two hours.
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