Evaluation of a centrifugal blood cell processor for washing platelet concentrates

A semiautomated saline wash procedure using a blood cell processor was evaluated as a technique for removing plasma from platelet concentrates. In vitro studies demonstrated 92 to 99.6 percent (mean, 96%) removal of total plasma protein (n = 30) with 84 to 97 percent (mean, 90.8%) platelet recovery (n = 28) in post-wash units. Post-wash pH values changed by +0.2 to -0.86 (mean, -0.47) (n = 30); the level of recovery from hypotonic shock was 69 to 97 percent (mean, 86%) (n = 11) of pre-wash units; weighted morphology scores decreased from a mean of 248 to 223 (n = 9). Aggregation response to arachidonic acid, collagen, and adenosine diphosphate plus epinephrine showed essentially no change following the wash procedure, and electron microscopy demonstrated slight morphologic alteration. Autologous platelets labeled with indium-111 demonstrated 43 +/- 20 percent recovery (n = 11) for washed units, compared to 41 +/- 10 percent for control unwashed units (n = 5); mean survivals were 140 +/- 41 hours (n = 11) for washed platelets and 185 +/- 28 hours for unwashed units (n = 5). Thirteen alloimmunized patients receiving 55 washed platelet concentrates demonstrated a mean 1- to 4-hour corrected count increment of 3.99 X 10(3) per microliter, compared to 3.02 X 10(3) per microliter for 77 unwashed platelet units given to the same patients. This study documents that platelet concentrates maintain viability and efficacy following a semiautomated saline wash method using the Cobe 2991 Blood Cell Processor, a technique that may be helpful for patients who require plasma-depleted platelet transfusions.