MIXED VENOUS OXYGENATION IN CRITICALLY ILL NEONATES

Objective: To describe the typical ranges for central venous oxygen sa turation and Po-2 in a group of critically ill neonates and the relati onship of these measurements to measurements of arterial oxygenation a nd indicators of oxygen supply and demand, Design: Survey. Setting: Ne wborn intensive care unit (ICU) in a children's hospital. Patients: Ei ghteen newborn infants (1 to 3 days old) who required mechanical venti lation for respiratory diseases, but who were hemodynamically stable a nd in acid-base balance. Interventions: Umbilical artery and right atr ial catheterization were performed, allowing simultaneous blood gas sa mpling. Measurements and Main Results: Simultaneous umbilical arterial and right atrial blood gas measurements were analyzed (n = 100). Mean mixed venous oxygen saturation was 83.3% and mixed venous oxygen tens ion 37.8 torr (5.1 kPa). The mixed venous oxygen saturation correlated well with the arterial-venous oxygen content difference (C[a-(v) over bar]o(2)) and fractional oxygen extraction, r = -.77 (r(2) = .59) and -.85 (r(2) = .72), respectively (p <.0005). Poor correlation was foun d between the mixed venous oxygen saturation and arterial oxygen satur ation values. Two cases are presented in which measurements of mixed v enous oxygenation led to recognition of apparent tissue hypoxia earlie r than did measurements of arterial oxygenation. Conclusions: We concl ude that measurement of central venous oxygenation in ill. neonates ma y reflect more accurately the oxygen supply and demand status of the n eonate than measurement of arterial oxygenation alone.