Protein and colloid osmotic pressure changes with albumin and/or saline replacement during plasma exchange

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Abstract
Colloid osmotic pressure (COP) was used as a predictor of fluid egress from the vascular space and edema development in the lungs and elsewhere. The relative safety, as predicted by the COP, of 5% albumin plus saline and 5% albumin alone as replacement fluids during plasma exchange was investigated. Fifty-three one and one-half plasma volume exchanges were performed in 15 patients with a variety of diagnoses using intermittent flow cell separators. On specimens obtained, before, during, and after each plasma exchange, the COP was measured directly with a membrane oncometer, and total protein, albumin and protein electrophoresis were determined using standard biochemical techniques. COP dropped significantly with 1-1 5% albumin replacement but even more with 1/2 5% albumin and 1/2 saline replacement during the exchange. COP did not fall below 12.5 torr at the end of the plasma exchange, even with 1/2 saline replacement, compared to the 10-12 torr level at which pulmonary edema might be expected. The fall in COP during exchange when saline was given first did approach this range but rapidly reversed itself with albumin administration. Clinically, no evidence of tissue or pulmonary edema was observed. Recovery in total protein and COP between plasma exchanges was significant.