Factors associated with treatment for hypotension in extremely low gestational age newborns during the first postnatal week

Abstract

Objective: The goals were to identify the blood pressures of extremely low gestational age newborns that prompt intervention, to identify other infant characteristics associated with receipt of therapies intended to increase blood pressure, and to assess the interinstitutional variability in the use of these therapies.

Methods: The cohort included 1507 extremely low gestational age newborns born at 23 weeks to 27 weeks of gestation, at 14 institutions, between March 2002 and August 2004; 1387 survived the first postnatal week. Blood pressures were measured as clinically indicated. Interventions were grouped as any treatment (ie, vasopressor and/or fluid boluses of >10 mL/kg) and vasopressor treatment, and logistic regression analyses were performed.

Results: At each gestational age, the lowest mean arterial pressures in treated and untreated infants tended to increase with advancing postnatal age. Infants who received any therapy tended to have lower mean arterial pressures than infants who did not, but uniform thresholds for treatment were not apparent. The proportion of infants receiving any treatment decreased with increasing gestational age from 93% at 23 weeks to 73% at 27 weeks. Treatment nearly always began during the first 24 hours of life. Lower gestational age, lower birth weight, male gender, and higher Score for Neonatal Acute Physiology-II values were associated with any treatment and vasopressor treatment. Institutions varied greatly in their tendency to offer any treatment and vasopressor treatment. Neither the lowest mean arterial pressure on the day of treatment nor other characteristics of the infants accounted for center differences in treatment.

Conclusions: Blood pressure in extremely premature infants not treated for hypotension increased directly with both increasing gestational age and postnatal age. The decision to provide treatment was associated more strongly with the center where care was provided than with infant attributes.

FIGURE 1

Lowest MAP values on postnatal days 0 to 6 for infants who survived the first postnatal week, according to gestational age. Dark shaded boxes indicate data for infants who received any treatment for low blood pressure at any time during the first week of life; light shaded boxes indicate data for infants not treated for low blood pressure. Each box represents the 25th to 75th percentiles, the center line represents the median, and the whiskers mark the real data point that is closest to 1.5 times the interquartile range. The dots indicate outliers. A, Infants born at 23 and 24 weeks (n = 331); B, infants born at 25 weeks (n = 289); C, infants born at 26 weeks (n = 338); D, infants born at 27 weeks (n = 429).