Effect of intentional hemodilution on platelet survival in secondary pulmonary hypertension.

Platelet regeneration time was assessed in 13 young adults with pulmonary hypertension and polycythemia secondary to congenital heart defects who underwent isovolemic hemodilution to improve clinical status and coagulation defects. The estimated platelet half-life in patients with Eisenmenger's complex was significantly shortened in comparison with normal subjects (3.8 +/- 1.9 vs 4.8 +/- 1.0 days, p less than 0.05). Hemodilution was carried out with no adverse effects, using low molecular weight dextran solutions. Lowering hematocrit from 61 to 50 percent resulted in a significant increase in platelet half-life from 3.8 +/- 1.9 to 5.7 +/- 1.8 days (p less than 0.02), which was followed by a marked rise in platelet count from 149 +/- 31 to 209 +/- 47 x 10(9) platelets/L (p less than 0.003). Arterial oxygen tension did not change significantly. These observations indicate that high hematocrit levels may have accounted for the shortened platelet survival and thrombocytopenia in these patients. Significant hemodilution may lead to a marked improvement in platelet abnormalities in patients with Eisenmenger's complex.