Comparison of the non-invasive Nexfin® monitor with conventional methods for the measurement of arterial blood pressure in moderate risk orthopaedic surgery patients

Objective Continuous invasive arterial blood pressure (IBP) monitoring remains the gold standard for BP measurement, but traditional oscillometric non-invasive intermittent pressure (NIBP) measurement is used in most low-to-moderate risk procedures. This study compared non-invasive continuous arterial BP measurement using a Nexfin (R) monitor with NIBP and IBP monitors. Methods This was a single-centre, prospective, pilot study in patients scheduled for elective orthopaedic surgery. Systolic BP, diastolic BP and mean arterial blood pressure (MAP) were measured by Nexfin (R), IBP and NIBP at five intraoperative time-points. Pearson correlation coefficients, Bland-Altman plots and trending ability of Nexfin (R) measurements were used as criteria for success in the investigation of measurement reliability. Results A total of 20 patients were enrolled in the study. For MAP, there was a sufficient correlation between IBP/Nexfin (R) (Pearson=0.75), which was better than the correlation between IBP/NIBP (Pearson=0.70). Bland-Altman analysis of the data showed that compared with IBP, there was a higher percentage error for MAP(NIBP) (30%) compared with MAP(Nexfin)(R) (27%). Nexfin (R) and NIBP underestimated systolic BP; NIBP also underestimated diastolic BP and MAP. Trending ability for MAP(Nexfin)(R) and MAP(NIBP) were comparable to IBP. Conclusion Non-invasive BP measurement with Nexfin (R) was comparable with IBP and tended to be more precise than NIBP.