Objective. We previously demonstrated that acidosis (pH <7.15) predicts poor motor outcome in very low birth weight (VLBW) infants. The present study was undertaken to examine the association between acidosis and developmental outcome in more detail and to better understand the interrelationship of acidosis with related factors such as hypoxemia and hypotension.

Methods. The nursery records of 191 infants enrolled in our VLBW follow-up study were reviewed to identify the type of acidosis (metabolic or respiratory) present, measure the duration of single and cumulative episodes, and examine the interaction of acidosis with hypoxemia and hypotension. The Bayley Scales of Infant Development and a detailed neurologic examination were performed at 6 (n = 158) and 24 (n = 106) months corrected age.

Results. At 6 months, both respiratory and metabolic acidosis as well as the total duration and longest single episode of acidosis were significantly correlated with cognitive, motor, and neurologic outcome (P < .0001). By 24 months, only the association of the metabolic component of acidosis with all three outcome measures remained significant. Duration of hypotension independently correlated with outcome at both testing periods (P <.002) but isolated hypoxemia did not. The metabolic component of acidosis and isolated hypotension contributed significantly to the variance in all three outcome measures (P < .05). Duration of hypoxemia, but not hypotension, contributed significantly (53%) to the variance in the metabolic component of acidosis.

Conclusion. We conclude that it is the metabolic component of acidosis that is important in predicting poor developmental outcome in VLBW infants. The detrimental effect of hypoxemia appears to be closely related to the occurrence of metabolic acidosis while hypotension has an independent effect on outcome.

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