Precision and Bias of Target‐Controlled Prolonged Propofol Infusion for General Anesthesia and Sedation in Neurosurgical Patients

Abstract

The aim of this study was to determine the relationship, precision, and bias of a propofol target-controlled infusion (TCI) system during prolonged infusion in neurosurgical patients. We retrospectively included patients undergoing general anesthesia for elective neurosurgical removal of brain tumors and postoperative sedation in the intensive care unit over a period of 3 months. TCI of propofol (Diprifusor - Marsh model) and remifentanil were used for general anesthesia and sedation. We compared propofol blood concentration (C ) measured by liquid chromatography-mass spectroscopy with predicted concentrations (C ) by the TCI system at 40 minutes (T0), 2 hours (T1), and 4 hours (T2) and every 8 hours after starting the drug infusion and at the time of emergence from sedation. Ninety-four paired determinations of C and C from 15 adult ASA I patients (8 men and 7 women 54.9 ± 13 years old; BMI, 24 ± 3.2 kg/m ) were analyzed. Mean duration of drug administration was 31 ± 6 hours. The coefficient of determination (R ) of the linear regression model for the relationship of C and C was 0.43. At the time of emergence, C was 0.5 ± 0.18 μg/mL. The bias of the TCI system (median performance error) was -34.7%, and the precision (median absolute performance error) was 36%. Wobble and divergence were 0.3% and 12.3%, respectively. This study found bias of the system out of the range of tolerability and showed a high tendency toward overestimation. These findings may lead to undersedation when propofol TCI is used for prolonged infusion.

propofol-target-controlled-infusion-performance-of-the-schnider-model-in-the-clinical-setting-for-major-surgical-procedures

“…Theoretically, there could have been an increase in metabolism of propofol in the patients studied, which could not be predicted by the TCI system used. Reasons for that could be the administration of inotropes intraoperatively or the previous intake of enzyme inductors such as certain anti-epileptics [15]. However, both were not the case in our patients.…”

Comparison of predicted and real propofol and remifentanil concentrations in plasma and brain tissue during target‐controlled infusion: a prospective observational study

“…As shown in Figure 2, the literature shows inconclusive results regarding under-or over-prediction of plasma propofol concentrations with the Marsh model [19][20][21][22][23][24][25].These conflicting results can be partly attributed to the varied cohorts of patients investigated, to the associated differences in distribution/redistribution and/or elimination, and to how the plasma concentrations were measured. It has been demonstrated that coexisting conditions like obesity or sarcopenia have a great impact on the Marsh model performance [23,26,27].…”