Normative values for blood pressure in preterm infants: identification of elevated blood pressure at discharge in infants <1000 gms.1187

Onset of hypertension (HTN) is a serious event causing immediate and perhaps long term morbidity in the premature infant. While multiple factors have been associated with HTN, there is a paucity of data available to guide either intervention or maintenance of therapy in this population. To determine normative values for blood pressure in the preterm infant over time, we documented daily maximum and minimum blood pressures in a consecutive sample of all preterm infants admitted to our nurseries with birthweights <1500 gms from July 1995 to June 1996. Blood pressures were obtained by oscillometric technique and recorded at birth, at 1 week of age, and monthly until discharge. Information collected included birthweight, gestational age, maternal factors and common neonatal diagnoses and exposures. During the study period 11 of 76 infants expired; 65 were followed for a mean of 18 weeks. Mean birthweight was 1060± 290 gms and mean gestational age was 28.9±3.19 weeks. As in previous short term studies, blood pressures in our population gradually increased from birth through the first week of life. Over the next month BPs were stable and then inceased modestly as weight increased. Table

Table 1

Blood pressures were not correlated with gestational age, sex, antenatal dexamethasone therapy, or maternal substance abuse. Discharge high (H) and low(L) mean blood pressures at a mean gestational age of 38 weeks (N=65) were H 54±11; L 46±10 mmHg. When stratified for birthweights greater(HBW) or less (LBW) than 1000 grams, a significant difference p<0.003 was noted in the LBW infants' discharge blood pressures: LBW (N=28) BPH 59±12; L 49±11 vs. HBW (N=32) BPH 50±11; L 45±10. These observations provide usefull blood pressure values for the evaluation of HTN in the preterm infant and support the theory that preterm LBW infants may be our next hypertensive population.