Capillary-venous hematocrit differences in newborn infants

Abstract

Venous and capillary hematocrit, acid base values, and circulatory parameters were measured simultaneously in 92 newborn infants within six hours of birth. Gestational age ranged from 26 to 41 weeks. The capillary/venous hematocrit ratio (Hctc/Hctv) was greater than 1.00 in 89 infants. We found significant inverse correlations between Hctc/Hctv and several parameters, such as pH (r = -0.82), standard bicarbonate (r = -0.73), systolic blood pressure (r = -0.51), and peripheral blood flow (r = -0.70). Most of the infants with a Hctc/Hctv of 1.20 and above had red cell mass values of less than 35 ml/kg. However, blood volume apparently did not influence the Hctc/Hctv. Gestational age appeared to affect Hctc/Hctv only before 30 weeks, when compared with the Hctc/Hctv of term infants. Our results indicate that disturbed circulation, and in particular, disturbed microcirculation is involved in the development of high Hctc/Hctv ratios. We strongly advise that hematocrits obtained by skin prick from a sick newborn infant should not be relied on as they may give misleading information on oxygen carrying capacity to vital organs.

Venous and Skin puncture blood counts compared

“…In such situations clinically important findings may be missed. Similar conclusions were drawn from a study of newborn infants where high skin puncture : venous haematocrit ratios were found in acidotic, anaemic infants with poor peripheral circulation (Linderkamp et al 1977).…”

Umbilical cord blood as a replacement source for admission complete blood count in premature infants

“…22–25 Moreover, the difference in capillary and venous hematocrit is more pronounced for premature infants. 24,26 We report no difference between hemoglobin from cord blood and admission blood obtained from a UVC, UAC or radial artery. These results are consistent with previously published studies, which reported unpaired cord blood hemoglobin values within normal neonatal reference values.…”

Neonatal polycythaemia: critical review and a consensus statement of the Israeli Neonatology Association

“…Capillary HCT is generally higher than venous HCT (16) which in turn is higher than 'central' HCT (from umbilical vein) (17). Capillary HCT from warmed heels correlates well with venous HCT (18), but there is only a loose correlation between capillary blood from unwarmed heel sticks and umbilical vein HCT (16).…”