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Blood pressure ranges in premature infants. I. The first hours of life
T Hegyi1, M T Carbone, M Anwar
1Department of Pediatrics, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, St. Peter's Medical Center, New Brunswick 08903-0591.
Insights
This study on preterm infant blood pressure found that low Apgar scores are linked to lower pressures, while maternal hypertension is associated with higher pressures in newborns. Healthy premature infants
Area of Science:
- Neonatal Physiology
- Pediatric Cardiology
Background:
- Blood pressure regulation in preterm infants is critical for neonatal outcomes.
- Understanding factors influencing early neonatal blood pressure is essential for clinical management.
Purpose of the Study:
- To investigate the determinants of systolic and diastolic blood pressure in the initial hours of life for preterm infants.
- To assess the impact of mechanical ventilation, maternal hypertension, and low Apgar scores on neonatal blood pressure.
Main Methods:
- A cohort of 1105 preterm infants (501-2000 gm) was studied.
- Infants were categorized into healthy, mechanical ventilation, maternal hypertension, and low Apgar score groups.
- Systolic and diastolic blood pressures (minimum and maximum) were recorded within the first 3-6 hours of life.
Main Results:
- Healthy preterm infants had Smin 47 mmHg, Smax 59 mmHg, Dmin 24 mmHg, Dmax 35 mmHg.
- Infants on mechanical ventilation showed significantly lower minimum systolic and diastolic pressures (Smin 41 mmHg, Dmin 22 mmHg).
- Low Apgar scores were associated with significantly lower blood pressures (Smin 33 mmHg, Dmin 19 mmHg), with 20-50% below the 5th percentile for healthy infants. Maternal hypertension was linked to higher Smin (49 mmHg).
Conclusions:
- In healthy preterm infants, blood pressure limits are independent of birth weight and gestational age.
- Low Apgar scores are a significant risk factor for lower neonatal blood pressure.
- Maternal hypertension may lead to elevated blood pressure in preterm neonates.
Abstract:
We studied blood pressure in the first hours of life in a cohort of 1105 preterm infants weighing 501 to 2000 gm; these infants represented 83% of all births at these weights that resulted in admission to three intensive care nurseries during a 34-month period between 1984 and 1987. To assess the effects of specific risk factors, we identified 244 healthy infants, 164 infants who received mechanical ventilation but had no other conditions, 47 infants whose only risk factor was the presence of hypertension or preeclampsia in the mother, and 86 infants with depressed Apgar scores regardless of the presence of the other conditions. We documented each infant's minimum and maximum systolic (Smin, Smax) and diastolic (Dmin, Dmax) pressures during the first 3 to 6 hours of life. In the healthy group, Smin was 47 mmHg; Smax, 59 mmHg; Dmin, 24 mmHg; and Dmax, 35 mmHg. In the ventilation group, Smin was 41 mmHg; Smax, 57 mmHg; Dmin, 22 mmHg; and Dmax, 35 mmHg. The Smin and Dmin values were both significantly lower in infants who received mechanical ventilation than in healthy infants (p < 0.01). In the maternal hypertension group, Smin was 49 mmHg; Smax, 59 mmHg; Dmin, 25 mmHg; and Dmax, 34 mmHg. Only the Smin value was significantly higher than in healthy infants. In the group with low Apgar scores, Smin was 33 mmHg; Smax, 51 mmHg; Dmin, 19 Hg; and Dmax, 34 mmHg. Thus all these values were significantly lower than in all the other groups (p < 0.05). Of infants with low Apgar scores, 20% to 50% had values below the 5th percentile for healthy infants. Birth weight and gestational age correlated with blood pressure limits only in the infants with low Apgar scores. We conclude that in healthy premature infants the limits of systolic and diastolic blood pressure are independent of birth weight and gestational age. Infants with low Apgar scores tend to have lower pressures, and infants whose mothers have hypertension have higher pressures than infants in the healthy cohort.