Evaluation of pharmacokinetic models of intravenous dexmedetomidine in sedated patients under spinal anesthesia

Little information is available on the predictive ability of previously published pharmacokinetic models of dexmedetomidine in patients under spinal anesthesia. We evaluated nine published pharmacokinetic models that were constructed in different study settings. Sixteen patients received dexmedetomidine infusions after spinal anesthesia according to the manufacturer's recommended regimen (6 A mu g/kg/h over 10 min followed by 0.2-0.7 A mu g/kg/h) or target-controlled infusion (initial target of 1.5 ng/ml using the Dyck model). Dexmedetomidine concentrations were measured and median performance error (MDPE), median absolute performance error (MDAPE), and wobble were calculated. A total of 84 blood samples were analyzed. The pharmacokinetic model reported by Hannivoort et al. had the greatest ability to predict dexmedetomidine concentrations (MDPE 5.6%, MDAPE 18.1%, and wobble 6.2%). Hannivoort et al.'s pharmacokinetic model, constructed with a dataset obtained from healthy volunteers, can predict dexmedetomidine concentrations best during continuous infusion under spinal anesthesia.