Effect of intravenous S-ketamine on the MAC of sevoflurane: a randomised, placebo-controlled, double-blinded clinical trial

Abstract Background Ketamine is routinely used in operating theatres, emergency departments, ICUs, and even outpatient units. Despite the widespread use of ketamine, only basic aspects of its interactions with inhalation anaestheticagents are known, and formal testing of interactions in humans is lacking. The minimum alveolar concentration(MAC) of inhalation anaestheticsis used to guide the depth of anaesthesia, and several drugs are known to influence the MAC. The aim of this study was to investigate whether intravenous application of ketamine influences the MAC of sevofluranein humans. Methods Adult patients undergoing elective surgerywere included in this randomised, double-blinded, placebo-controlled study. Patients were assigned to one of three groups, each of which received a bolus of placebo, 0.5 mg kg −1 S- ketamine, or 1 mg kg −1 S- ketaminefollowed by an infusion of the same amount per hour after inhalation induction with sevofluranewas performed. The response to skin incision (movement vs non-movement) was recorded. The MAC of sevofluranewas assessed using an up-and-down titration method. Results Sixty patients aged 30–65 yr were included. Each group consisted of 20 patients. The MAC of sevofluranewas higher in the placebo group (2.1 (sd 0.1) %) than in the low-dose ketamine group (0.9 (0.1)%, P P Conclusions The administration of S- ketaminesignificantly and dose-dependently reduced the MAC of sevofluranein humans. Clinical trial number EudraCT ref. no. 2012-001908-38.