Abstract
Objective Anemia causes blood flow redistribution and altered tissue metabolic behavior to
sustain homeostatic oxygen consumption. We hypothesized that anemia severity would
correlate with increased regional fractional tissue oxygen extraction among premature
neonates.
Study Design Regional oxygen extraction was calculated using pulse oximetry and near-infrared
spectroscopy data among neonates <1,250 g during their first 10 postnatal days. Oxygen
extraction was assessed for correlations with raw hematocrit levels and following
grouping into hematocrit quartiles.
Results Twenty-seven neonates with gestational age 27 ± 2 weeks and birth weight 966 ± 181 g
underwent 116 hematocrit determinations. Cerebral and flank oxygen extraction inversely
correlated with hematocrit (cerebral r = −0.527, p = 0.005; flank r = −0.485, p = 0.01). Increased cerebral oxygen extraction was observed for the lowest three hematocrit
quartiles (Q1 0.26 ± 0.08, p = 0.004; Q2 0.24 ± 0.09, p = 0.01; Q3 0.25 ± 0.09, p = 0.03; all compared with Q4 0.18 ± 0.10). Increased flank oxygen extraction occurred
for the lowest two quartiles (Q1 0.36 ± 0.12, p < 0.001; Q2 0.35 ± 0.11, p < 0.001; compared with Q4 0.22 ± 0.13). Splanchnic oxygen extraction demonstrated
no similar correlations.
Conclusion Increases in tissue oxygen extraction may indicate early pathophysiologic responses
to nascent anemia in premature neonates.
Keywords
anemia - hematocrit - neonate - near-infrared spectroscopy - oxygen extraction - regional
oxygenation
