Comparison of Blood Pressure in Mature and Premature Neonates Using Direct and Indirect Methods of Measurement

The aim of this study was to evaluate the correspondence of blood pressure (BP) measured using the direct intra-arterial method and indirect oscillometric monitor method. Twenty-three newborns with radial arterial catheters inserted were enrolled in this study. The gestational age (GA) ranged from 25-40 weeks and birth weight (BW) ranged from 700-3,550 g. Direct BP was measured using radial arterial catheters. Indirect BP was concurrently measured from the contralateral forearm using an oscillometric monitor. The systolic BP (SBP), diastolic BP (DBP), and mean BP (MBP) obtained using these two methods were analyzed. Although there was a significant correlation between the pairs of readings for SBP, DBP, and MBP (r = 0.80, 0.70, 0.83, respectively, p < 0.001 for all); the 95% confidence intervals for individual measurements exceeded 20 mm Hg for SBP and DBP, and 15 mm Hg for MBP. SBP, DBP, and MBP obtained using the indirect method of measurement were significantly different from those obtained using the direct method (p < 0.001 for all). The pressure differences and percentage of error were greater in groups of direct MBP > 35 mm Hg, GA > 32 weeks, and BW > 1,500 g than in groups of direct MBP ≤ 35 mm Hg, GA ≤ 32 weeks, and BW ≤ 1,500 g. In conclusion, for MBP, the discrepancy found between these two methods of measurements was clinically acceptable. For SBP and DBP, there was a large variability between these two methods. It is not appropriate to interpret the indirect oscillometric BP readings according to these available normative direct BP values. Direct BP monitoring should be used in newborns in intensive care. Cautious interpretation of oscillometric BP values for newborns in intensive care is mandatory.