Aortic Blood Pressure in Normal Newborn Infants During the First 12 Hours of Life

Indwelling umbilical arterial catheters were used without difficulty to measure direct arterial blood pressure in newborn infants. Normal values were determined for mean aortic blood pressure during the first 12 hours of life in 45 infants who were expected, from history, to be subject to cardiopulmonary insufficiency at birth but who, after birth, were judged to be clinically well. Birth weights of these infants ranged from 1,050 to 4,220 gm, and gestational age ranged from 26 to 41 weeks. All infants were of appropriate weight for gestational age. Mean blood pressure correlated closely with birth weight and the relationship was best described by a parabolic regression y = 35.53 + 0.36 (x) + 1.01 (x2), where y = mean aortic blood pressure in millimeters mercury and x = birth weight in kilograms. The lower limit of normal mean aortic blood pressure was 30 mm Hg at 1,001 to 2,000 gm, 35 mm Hg at 3,000 gm, and 43 mm Hg at 4,000 gm. It is recommended that aortic blood pressure be measured routinely in all infants who are apt to develop cardiopulmonary insufficiency and have indwelling umbilical arterial catheters.