Permissive hypotension in the extremely low birthweight infant with signs of good perfusion

Introduction: Many practitioners routinely treat infants whose mean arterial blood pressure in mm Hg is less than their gestational age in weeks (GA). Objective: To assess the effectiveness of utilising a combined approach of clinical signs, metabolic acidosis and absolute blood pressure (BP) values when deciding to treat hypotension in the extremely low birthweight (ELBW) infant. Methods: Retrospective cohort study of all live born ELBW infants admitted to our neonatal intensive care unit over a 4-year period. Patients were grouped as either normotensive (BP never less than GA), hypotensive and not treated (BP<GA but signs of good perfusion; we termed this permissive hypotension) and hypotensive treated (BP<GA with signs of poor perfusion). Results: 118 patients were admitted during this period. Blood pressure data were available on 108 patients. 53% of patients were hypotensive (mean BP in mm Hg less than GA in weeks). Treated patients had lower birth weight and GA, and significantly lower blood pressure at 6, 12, 18 and 24 h. Normotensive patients and patients designated as having permissive hypotension had similar outcomes. Mean blood pressure in the permissive group increased from 26 mm Hg at 6 h to 31 mm Hg at 24 h. In a logistic regression model, treated hypotension is independently associated with mortality, odds ratio 8.0 (95% CI 2.3 to 28, p<0.001). Conclusions: Blood pressure spontaneously improves in ELBW infants during the first 24 h. Infants hypotensive on GA criteria but with clinical evidence of good perfusion had as good an outcome as normotensive patients. Treated low blood pressure was associated with adverse outcome.