Predictive and clinical performance of a TCI device for sevoflurane at a conventional workstation: Pharmacokinetic correlation of the model used

© 2014 Sociedad Colombiana de Anestesiología y Reanimación. Introduction: Good governance of resources and global warming has attracted interest on minimal flow (0.3-0.5l/min) inhalation anesthesia. Objectives: To evaluate the predictive and clinical performance of a TCI (Target-controlled infusion) device, and its pharmacokinetic correlation for sevoflurane. Methods: Prospective, longitudinal, and analytical study on 25 adult patients. Fresh gas flow used 0.5l/min. Target concentration of 1.2% (v/v). Continuous and variable infusion into the circuit of the anesthesia workstation. Controller developed with LABVIEW 6.1. Hemodynamic, respiratory and anesthetic depth data collected every 5 s using the anesthesia workstation software. Bias (Median of Predictive Error, MDPE%), inaccuracy (Absolute Mean of Predictive Error, MDAPE%), wobble, and divergence of the TCI device were determined in the first hour. STATA-12 pk collapse was used to analyze the area under the curve of the target and expired concentrations. The results are expressed as mean (95% CI) and median [IQR]¿. Results: Target concentration used 1.22 [1.14-1.37]%¿, reached in 04:07 [03:15-06:15]¿ min:s (expiratory branch). Anesthetic duration 1:10:50 (00:56:57-1:24: 43) h:min:s. Sevoflurane consumption 6.9 (5.7-8.0) ml. MDPE% -12.8 (-17.6 to -8.1) %; MDAPE% 15.9 (11.9-19.8) %; wobble 6.9 (5.0-8.7)% and divergence 0.89% (-5.96 to 7.7)%h-1. Interactions per hour on the TCI of 3 (2-4). Correlation of the area under the curve, Spearman's rho = 0.8577, p < 0.00001. ¿15% inaccuracy was associated with age >65 years and obesity. Conclusions: The TCI sevoflurane© showed good performance, and the target concentration was rapidly reached and remained stable, with few interactions with the device needed during the first hour. There were neither overdosing nor clinically significant alterations.