Level of agreement between cardiac output measurements using Nexfin® and thermodilution in morbidly obese patients undergoing laparoscopic surgery.

Morbidly obese patients are at increased risk of intra-operative haemodynamic instability, which may necessitate intensive monitoring. Non-invasive monitoring is increasingly used to measure cardiac output; however, it is unknown whether the weight-based algorithm utilised in these devices is applicable to patients with morbid obesity. We compared the level of agreement and trending ability of non-invasive cardiac output measurements (Nexfin® ) with the gold-standard thermodilution technique in 30 morbidly obese patients undergoing laparoscopic surgery. Bland-Altman analysis revealed a mean (SD) bias of 0.60 (1.62) l.min-1 (limits of agreement -2.67 to 3.86 l.min-1 ) and the precision error was 46%. Polar plot analysis resulted in an angular bias of 2.61°, radial limits of agreement of -60.08° to 49.82° and angular concordance rate was 77%. Both agreement and trending were outside the Critchley criteria for the comparison of cardiac output devices with a gold-standard. Nexfin has an unacceptable level of agreement compared with thermodilution for cardiac output measurement in morbidly obese patients.

Maintenance of anesthesia in morbidly obese patients using propofol with continuous BIS-monitoring: a comparison of propofol-remifentanil and propofol-epidural anesthesia.

PURPOSE: Aim of this study was to evaluate maintenance of anesthesia using propofol with continuous Bispectral Index (BIS)-monitoring in morbidly obese patients receiving propofol-remifentanil and propofol-epidural anesthesia. METHODS: In the first group in ten morbidly obese patients receiving remifentanil analgesia, a propofol infusion was started at 10 mg/kg/hr and modified by aiming at BIS values between 40-60 together with predefined hemodynamic parameters. In the second group, the propofol dose resulting from the first group was prospectively evaluated in a matched cohort of six morbidly obese patients receiving propofol-epidural analgesia aiming for the same BIS and hemodynamic parameters. In both groups, propofol concentration and infusion rates, BIS and hemodynamic values were collected. RESULTS: In the propofol-remifentanil group (Body Mass Index (BMI) 39-60 kg/m2), the mean propofol infusion rate that corresponded to the predefined BIS and hemodynamic parameters was 4.8 mg/kg/hr (SD 1.5). On this basis, a maintenance dose of 5 mg/kg/hr was started in the propofol-epidural group (BMI 38-58 kg/m2). In this second group, the mean propofol infusion rate that corresponded to predefined BIS and hemodynamic parameters was 5.0 mg/kg/hr (SD 0.6). Between the two groups, there was no difference in the propofol concentration-BIS relation. CONCLUSION: Using both BIS and hemodynamic parameters as an endpoint, a maintenance dose of propofol of 4-6 mg/kg/hr is proposed for maintenance of anesthesia in morbidly obese patients undergoing bariatric surgery either in combination with remifentanil or epidural analgesia. There was no difference in propofol concentration-BIS relation in morbidly obese patients receiving propofol-remifentanil or propofol-epidural anesthesia.