BACKGROUND: Early detection of arterial hypotension during cesarean delivery under spinal anesthesia is important. This study aims to compare the validity of Nexfin^TM as beat-to-beat noninvasive blood pressure monitoring with conventional intermittent oscillometric measurement of blood pressure during elective cesarean delivery.

METHODS: This open prospective observational bicentric study was performed between January 2013 and December 2015. We simultaneously recorded arterial blood pressure with both techniques in pregnant women undergoing elective cesarean delivery under spinal anesthesia. The primary outcome was a Bland-Altman analysis of systolic blood pressure measurement comparing Nexfin^TM and a conventional method. The secondary outcomes were the time to detect the first relevant hypotensive episode and the comparison of both devices using a four quadrant graph.

RESULTS: One hundred and seventy-four parturients completed the study, and 2640 pairs of systolic blood pressure measurements were analyzed. Bias was -10 mmHg with upper and lower limits of agreement of -61 and +41 mmHg. In 73.9% of the cases, the two techniques provided the same information (normotension or hypotension), but the conventional method missed 20.8% of measurements, with Nexfin^TM detecting 16.2% more hypotensive measurements. The median [25-75 percentiles] duration to detect the first hypotensive measurement was 331 [206-480] seconds for Nexfin^TM and 440 [300-500] seconds for intermittent oscillometry (p<0.001).

CONCLUSIONS: The agreement between Nexfin^TM and an intermittent method for the measurement of systolic blood pressure was not in an acceptable range during cesarean delivery, although Nexfin^TM may detect hypotension earlier than the standard method.

The following demographic characteristics of the pregnant women and their newborns were collected: age, weight, height, gestational weeks, indication for cesarean delivery, neonatal umbilical vein pH, and Apgar score at 1, 5 and 10 minutes. The tolerance of both devices was reported by the parturients based on a visual analogue scale (VAS; 0: extremely uncomfortable to 10: perfect). Any adverse event was collected, immediately analyzed, and declared to the health authorities if necessary.

Paired measurements were obtained using the Nexfin^TM (CNBP) and the BPosc every minute from the end of spinal injection. To obtain a single CNBP value in parallel to the BPosc value, the data for CNBP were filtered. An average value surrounding the “minute of interest” was calculated over an interval of 20 + 20 consecutive seconds that corresponded to the median duration of the oscillometric measurement.