Comparison of oscillometric, non-invasive and invasive arterial pressure monitoring in patients undergoing laparoscopic bariatric surgery - a secondary analysis of a prospective observational study

Abstract

Background: Oscillometric, non-invasive blood pressure measurement (NIBP) is the first choice of blood pressure monitoring in the majority of low and moderate risk surgeries. In patients with morbid obesity, however, it is subject to several limitations. The aim was to compare arterial pressure monitoring by NIBP and a non-invasive finger-cuff technology (Nexfin®) with the gold-standard invasive arterial pressure (IAP).

Methods: In this secondary analysis of a prospective observational, single centre cohort study, systolic (SAP), diastolic (DAP) and mean arterial pressure (MAP) were measured at 16 defined perioperative time points including posture changes, fluid bolus administration and pneumoperitoneum (PP) in patients undergoing laparoscopic bariatric surgery. Absolute arterial pressures by NIBP, Nexfin® and IAP were compared using correlation and Bland Altman analyses. Interchangeability was defined by a mean difference ≤ 5 mmHg (SD ≤8 mmHg). Percentage error (PE) was calculated as an additional statistical estimate. For hemodynamic trending, concordance rates were analysed according to the Critchley criterion.

Results: Sixty patients (mean body mass index of 49.2 kg/m²) were enrolled and data from 56 finally analysed. Pooled blood pressure values of all time points showed a significant positive correlation for both NIPB and Nexfin® versus IAP. Pooled PE for NIBP versus IAP was 37% (SAP), 35% (DAP) and 30% (MAP), for Nexfin versus IAP 23% (SAP), 26% (DAP) and 22% (MAP). Correlation of MAP was best and PE lowest before induction of anesthesia for NIBP versus IAP (r = 0.72; PE 24%) and after intraoperative fluid bolus administration for Nexfin® versus IAP (r = 0.88; PE: 17.2%). Concordance of MAP trending was 90% (SAP 85%, DAP 89%) for NIBP and 91% (SAP 90%, DAP 86%) for Nexfin®. MAP trending was best during intraoperative ATP positioning for NIBP (97%) and at induction of anesthesia for Nexfin® (97%).

Conclusion: As compared with IAP, interchangeability of absolute pressure values could neither be shown for NIBP nor Nexfin®, however, NIBP showed poorer overall correlation and precision. Overall trending ability was generally high with Nexfin® surpassing NIBP. Nexfin® may likely render individualized decision-making in the management of different hemodynamic stresses during laparoscopic bariatric surgery, particularly where NIBP cannot be reliably established.

Trial registration: The non-interventional, observational study was registered retrospectively at ( NCT03184285 ) on June 12, 2017.

Keywords: Bariatric surgery; Blood pressure; Clear sight; Finger-cuff; Nexfin; Non-invasive monitoring; Obesity; Vascular unloading technique.

Fig. 1

Study participant flow diagram

Fig. 2

Pooled correlation and Bland-Altman analyses for all MAP data pairs measured by NIBP and Nexfin® versus IAP. Panels A and B: NIBP (A) or Nexfin® (B) (y-axis) derived values are plotted against IAP values (x-axis), with correlation coefficient (r) and P value displayed in the diagrams. Panels C and D: Bland-Altman plots, where differences of IAP and NIBP (C) or Nexfin® (D) (y-axis) are plotted against their common mean (x-axis). The bold dotted lines display the limits of agreement, where 95% (bias ±1.96 standard deviation of the difference) of all measurements are located. The middle line shows the mean difference (bias). Percentage error and bias are displayed in the diagrams. MAP: Mean arterial pressure, PE: Percentage error, IAP: Invasive arterial pressure, NIBP: Non-invasive oscillometric blood pressure, r: Correlation coefficient

Fig. 3

Bland Altman analyses for hypotension and hypertension. Bland-Altman Plots of all values, where MAP recorded by IAP was ≤50 mmHg (A and C) or > 70 mmHg (B and D). Differences of IAP and Nexfin®/NIBP (y-axis) are plotted against their common mean (x-axis). Bold dotted lines display the limits of agreement, where 95% (bias±1.96 standard deviation of the difference) of all measurements are located. The middle line shows the mean difference (bias). Percentage error and bias are displayed in the diagrams. MAP: Mean arterial Pressure, PE: Percentage error, IAP: Invasive arterial pressure

Fig. 4

Trending analysis for Nexfin® or NIBP measured MAP. Four square plots of the concordance for MAP values recorded by NIBP (Panel A) or Nexfin® (Panel B) vs. IAP. The y-axis shows changes (as percentages) of IAP, the x-axis shows changes (as percentages) of Nexfin® or NIBP derived arterial pressure measurements for the total data sample. The left lower and right upper quadrants include all arterial pressure values with the same (negative or positive) change. Changes with less than 5% were excluded from portrayal and statistical analysis. One data pair lies outside the depicted range in Panel A. MAP: Mean arterial pressure, NIBP: Non-invasive oscillometric blood pressure, IAP: Invasive arterial pressure