Blood pressure ranges in premature infants: II. The first week of life.

OBJECTIVE

To examine the arterial blood pressure in the first week of life in a healthy premature population.

DESIGN

Population-based cohort study.

SETTING

Three intensive care nurseries in central New Jersey.

PATIENTS

Premature infants with birth weights less than 2000 g.

MAIN OUTCOME MEASURES

We documented daily maximum and minimum systolic and maximum and minimun diastolic blood pressures during the first 7 days of life. To examine the effects on the ranges of blood pressure, we identified four groups of infants: (1) healthy infants without any of the major risk factors (n = 193); (2) infants who were mechanically ventilated but free of any of the other conditions (n = 225); (3) infants with histories of maternal hypertension or preeclampsia (n = 38) and (4) infants with low Apgar scores (less than 3 at 1 minute and less than 6 at 5 minutes) regardless of the presence of other conditions (n = 86).

RESULTS

Blood pressure increased steadily in the first week of life in all four groups. There was no relationship between any of the four blood pressure variables, or trends in blood pressure over time, with birth weight, gender, or race. Regression equations (based on all infants with available data) for blood pressure ranges by day of life revealed that the maximum systolic blood pressure increased by 2.6 mm Hg/d, the minimum systolic blood pressure increased by 1.8 mm Hg/d,the maximum diastolic blood pressure increased by 2.0 mm HHg/d, and the minimum diastolic blood pressure increased by 1.3 Hg/d.

CONCLUSIONS

Infants with birth asphyxia and ventilated infants had significantly lower systolic and diastolic blood pressures than healthy infants.