Neonatal polycythemia: I. Criteria for diagnosis and treatment

In order to better define criteria for diagnosis and treatment of neonatal polycythemia, 74 neonates with peripheral venous hematocrit levels greater than or equal to 65% were studied. The hematocrit levels of capillary (Cap Hct), peripheral venous (PV Hct), and umbilical venous (UV Hct) blood was measured. Viscosity of umbilical venous blood (UV eta) was determined. Mean +/- SE Cap Hct (75 +/- 0.5%) was significantly higher than PV Hct (71 +/- 1.0%, P less than .001) and PV Hct was higher than mean UV Hct (63 +/- 0.6%, P less than .001). Cap Hct correlated with neither PV Hct nor UV Hct, but PV Hct and UV Hct correlated moderately (r = .54, P less than .001). Of the neonates with UV Hct greater than or equal to 63%, 80% and UV eta in excess of 3 SD above the normal mean (in excess of 14.6 cps at shear rate 11.5 sec(-1)), whereas 94% of the neonates with UV Hct less than 63% had UV eta within normal range. Neonates with hyperviscosity were seen with two or more clinical symptoms more often than their peers with normal viscosity (P less than .04). Partial exchange transfusion in 21 neonates reduced mean UV Hct from 61 +/- 1.1% to 50 +/- 1.0% (P less than .001) and mean UV eta from 13.0 +/- 0.64 cps to 8.6 +/- 0.54 cps (P less than .001). These data suggest that Cap Hct and PV Hct may be used to screen neonates for polycythemia, but that the final diagnosis and therapeutic decisions should be based on UV Hct or even preferably on UV eta. They further suggest that UV Hct greater than or equal to 63% is strongly indicative of hyperviscosity and should be treated by partial exchange transfusion.