MIXED VENOUS OXYGENATION IN CRITICALLY ILL NEONATES

Objective: To describe the typical ranges for central venous oxygen saturation and Po-2 in a group of critically ill neonates and the relationship of these measurements to measurements of arterial oxygenation and indicators of oxygen supply and demand, Design: Survey. Setting: Newborn intensive care unit (ICU) in a children's hospital. Patients: Eighteen newborn infants (1 to 3 days old) who required mechanical ventilation for respiratory diseases, but who were hemodynamically stable and in acid-base balance. Interventions: Umbilical artery and right atrial catheterization were performed, allowing simultaneous blood gas sampling. 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 tension 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 found between the mixed venous oxygen saturation and arterial oxygen saturation values. Two cases are presented in which measurements of mixed venous oxygenation led to recognition of apparent tissue hypoxia earlier than did measurements of arterial oxygenation. Conclusions: We conclude that measurement of central venous oxygenation in ill. neonates may reflect more accurately the oxygen supply and demand status of the neonate than measurement of arterial oxygenation alone.