Hypotension and Adverse Outcomes in Prematurity: Comparing Definitions

Abstract

Background: In the premature neonate, there is no consensus regarding normal blood pressure (BP). The most common definition used is a mean arterial BP (MAP) less than the gestational age (GA); however, studies indicate that the neuroprotective mechanism of autoregulation is lost below a MAP of 30 mm Hg. Objective: To determine whether hypotension defined as MAP <30 mm Hg or MAP less than the infant's GA better predicts adverse outcomes of intraventricular hemorrhage (IVH) and death. Study Design: For this retrospective study, demographic, clinical, and BP data in epochs of 12 h were collected during the first 72 h of life in 188 subjects 24-28 weeks of gestation. For each definition, outcomes of severe IVH (grade 3 or 4), death, or the composite outcome of either were evaluated using bivariate testing. Logistic regression determined independent predictors of composite outcome of death and/or grade 3 or 4 IVH. Results: Hypotension by either definition was significant for death and the composite outcome (p < 0.0001). Only the MAP <30 mm Hg definition was associated with severe IVH (p = 0.02). On logistic regression, significant predictors of the composite outcome were GA (OR 0.59, 95% CI 0.39-0.89) and vasopressor therapy (OR 5.5, 95% CI 2-17). Conclusions: Neither definition of hypotension independently predicts adverse outcome in multivariate logistic regression. Vasopressor therapy, however, is an independent predictor of IVH and death in premature infants.