Purpose: Blood pressure (BP) monitoring is an essential procedure in intensive care. There is controversy about the reliability of non-invasive BP measurements in very preterm infants. This prospective trial compared non-invasive BP monitoring with BP monitoring via an umbilical arterial catheter (UAC) in this population.
Methods: Preterm infants born at less than 32 weeks gestation requiring a UAC for clinical management were eligible. Enrolled infants had up to three BP measurements on the right arm (RA) and right leg (RL) when in a resting state. UAC-BP measurements were noted immediately after the non-invasive BP was displayed on the monitor. Measurements were analysed in subgroups according to birth weight: no greater than 750 g, 751-1,000 g, above 1,000 g. Statistical analysis reports median, range, and Bland-Altman analysis.
Results: Sixty infants were included. Median (range) gestational age was 26.4 weeks (23.6, 31.2); birth weight 924 g (581, 1,518). A total of 1,865 measurements were performed (RA: 935, RL: 930). Mean difference (95% limits of agreement) for infants no greater than 750 g: RA 2.53 mmHg (-11.18, 16.24), RL -0.804 mmHg (-12.65, 11.04); for infants 751-1,000 g: RA 3.535 mmHg (-9.6, 16.7), RL -1.239 mmHg (-13.14, 10.66); for infants above 1,000 g: RA -1.65 mmHg (-13.47, 10.17), RL -4.101 mmHg (-14.17, 5.96).
Conclusions: Although the average differences between invasive and non-invasive BP measurements are acceptable, the range of under- and overestimation of non-invasive BP measurements is large and not consistent, making reliance on non-invasive modalities to guide circulatory management problematic. If arterial BP monitoring is not available, our results suggest measuring non-invasive BP on the leg in preterm infants with a birth weight no greater than 1,000 g.