Determinants of blood pressure in very low birth weight neonates: lack of effect of antenatal steroids.

OBJECTIVES

To define the range of normal blood pressures (BP) for very low birth weight (VLBW;</=1500 g) neonates and to study perinatal variables affecting BP measurements after birth, including the effects of antenatal steroids.

STUDY

DESIGN

Antenatal steroids were rarely administered at Parkland Memorial Hospital before May 1994, permitting us to establish a cohort of VLBW neonates exposed to antenatal steroids [n=70, 1166+/-253 (S.D.) g, and 28.7+/-2.1 weeks] who were matched with neonates delivered during the prior year (n=46, 1100+/-241 g, 28.9+/-1.8 weeks). Maternal and neonatal charts were abstracted for pertinent data, and neonatal BP measurements (determined directly when an arterial catheter was available or indirectly by the oscillometric method) were extracted every 3 h for the first 12 h and every 6 h until 72 h postnatal.

RESULTS

Antenatal steroids did not affect BP immediately after birth or for the subsequent 72 h postnatal. Therefore, data from all neonates </=1500 g were combined and the pattern of BP change over 72 h postnatal assessed. Systolic, diastolic and mean BP increased (P<0.001) 33%, 44% and 38%, respectively, during the first 72 h. Although neonates weighing </=1000 g and 1001-1500 g demonstrated gradual increases (P<0.001) in systolic, diastolic and mean BP by 72 h, values were consistently lower (P<0.01) in neonates </=1000 g. Of interest, only 11 neonates (9.5%) were treated for clinical hypotension.

CONCLUSIONS

In VLBW neonates antenatal steroids do not modify BP measurements either immediately after birth or the 30-40% rise occurring in the first 72 h postnatal. Further, BP is developmentally regulated and is gestationally and birth weight dependent. These data provide additional insight into assessing the need for treating hypotension.