Water Homeostasis in Propofol Based Total Intravenous Anesthesia

Previous study reported that propofol binded to glutamate receptors in the hypothalamus and inhibits AVP release mediated by endogenous γ-aminobutyric acid, as well as directly inhibits the regulated calcium currents leading to normal neuronal depolarization and AVP release. However, there is no clinical data demonstrating the mechanism of propofol can induce transient DI by inhibiting the release of AVP from the hypothalamus when applied to humans. Remifentanil, binding to the μ-receptor or partly κ-receptor, have been used in total intravenous anesthesia combined with propofol, also reported inhibiting AVP relaese in both the hypothalamus (κ receptor mediator mechanism) and posterior pituitary (μ receptor mediator mechanism). However, the effects of anesthetics on water homeostasis during surgery have been not well established. Therefore, we aim to investigate the changes of intraoperative water homeostasis, and related hormones and osmolality in patients with propofol based total intravenous anesthesia due to neuromonitoring for spine surgery.

"All patients will get the total intravenous anesthesia with propofol-remifentanil via an effective site-controlled infusion (TCI). For this, TCI continuous infusion pump will be used with Schnider pharmacokinetic model for propofol and Minto pharmacokinetic model for remifentanil. Propofol and remifentanil will be initiated with target effective site concentrations of 3 μg.ml-1 and 3 ng.ml-1, respectively, and controll these concentrations considering patient's consciousness loss and vital signs. And then 0.6 mg kg-1 rocuronium for muscle relaxation will be administered for intubation. Anesthesia will be maintained with BIS level 40-60 and vital signs will not be more than 20% of the baseline or less. In order to prevent the sudden movement of the patient during surgery, rocuronium will be infused continuously about 50% of TOF until the end of intraoperative neuromonitoring.