Peripheral blood flow and oxygen extraction in the sick, newborn very low birth weight infant shortly after birth

Abstract

This study examined the relationship between blood pressure, peripheral blood flow (PBF), and peripheral fractional oxygen extraction (FOE). Variables that may influence PBF and peripheral FOE were also measured. Measurements of PBF by near infrared spectroscopy and fractional shortening by echocardiography were made within 12 h of birth in 24 infants less than 32 wk gestation. Blood gases, Hb, temperature, and blood pressure were also measured. PBF was significantly correlated with fractional shortening (r = 0.56, p = 0.005), Po2 (r = -0.5, p = 0.01), and peripheral temperature (r = 0.52, p = 0.01). Peripheral FOE was significantly correlated with fractional shortening (r = -0.48, p = 0.02), Po2 (r = 0.52, p = 0.02), and Pco2 (r = -0.53, p = 0.008), but not with peripheral temperature. There was no significant correlation between blood pressure and either PBF or peripheral FOE. These results indicate the importance of several physiologic variables, but not blood pressure, in determining peripheral tissue oxygen delivery in sick preterm infants receiving intensive care. It adds weight to the idea that blood pressure should not be considered a surrogate for peripheral blood flow and oxygen delivery.