Abstract
This paper studies an appropriate pharmacokinetic (PK) model for hypnosis control based on effect-site anesthetic concentration. For maintaining hypnosis, methods to keep plasma or effect-site concentration of propofol, an anesthetic drug, calculated using PK models at a target level are often used. In order to realize a desirable hypnosis control by such methods an accurate estimation of propofol concentration corresponding to the threshold of unconsciousness is critical. Since time variation of the calculated propofol concentration depends on the PK model, the performance of maintaining hypnosis also depends on it. In this paper, we compare the existing PK models of propofol focusing on sensitivity and specificity for detecting consciousness during anesthesia by a criterion based on cal ulated propofol concentration and measured aepEX, a hypnosis index. The results show that Barr model provides the highest sensitivity and specificity, and that Marsh, modified Marsh, and Schnider models, which are often used in target controlled infusion systems give fairly high sensitivity and specificity.
Highlights
During surgery, patients’ hypnosis must be kept at an appropriate level to avoid side effects of anesthetic drugs such as postoperative nausea and vomiting
During target controlled infusion (TCI), anesthesiologists determine a target level of anesthetic drug concentration based on their experience and adjust the level according to the patient condition
The sensitivities and specificities of the sixteen PK models obtained by the above procedure are shown in Table 3, and, those of Marsh, Schnider, and modified Marsh models with the original ke0 are shown in the same table
Summary
Patients’ hypnosis must be kept at an appropriate level to avoid side effects of anesthetic drugs such as postoperative nausea and vomiting. A hypnosis control method that maintains effect-site concentration of an anesthetic drug above a minimum estimate ( minimum effect-site concentration) to keep appropriate hypnosis has been proposed [8]. In [8], some existing PK models with the specific rate constant of effect-site compartment were compared from the viewpoint of the accuracy of distinction between unconscious and conscious states based on a small number of clinical data. We study which is the best model to calculate propofol concentration for effect-site concentration-based hypnosis control. Based on further clinical data, we evaluate the effectiveness of most existing PK models with the best rate constant, which provides the same peak time of propofol concentration as that of measured aepEX, by comparing sensitivity and specificity for detection of consciousness according to a criterion based on effect-site propofol concentration and aepEX. Automat Control Physiol State Func 2: 104. doi:10.4172/2090-5092.1000104
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