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.