Use of S+Ketamine During Target-Controlled Intravenous Anaesthesia After Abdominal Hysterectomy

Overview

The investigators want to investigate the effect of low dose S+ ketamine compared to placebo on cumulative morphine consumption at 24 hours in 90 women undergoing open abdominal hysterectomy with remifentanil-propofol target controlled infusion (TCI) in KK Women's and Children's Hospital. The secondary aims are to investigate the use of low dose S+ ketamine on the incidence of nausea, vomiting, pruritus (opioid side effect), sedation score and psycho mimetic assessment compared to placebo group. The investigators propose to conduct a double blinded, randomized controlled study in women undergoing open abdominal hysterectomy with remifentanil-propofol TCI. (1) Treatment Group: intravenous ketamine 0.5 mg/kg at the beginning and 0.5 mg/kg 20 minutes before extubation. (2) Control Group: intravenous normal saline (as placebo) at the beginning and 20 minutes before extubation.

A number of 90 American Society of Anesthesiologists (ASA) I and II patients undergoing elective open abdominal hysterectomies will be randomly distributed in two groups of 45 patient's each and assigned to receive one of the of the following: 1. Treatment Group: intravenous S+ketamine 0.25 mg/kg (i.v. bolus) at the beginning and 0.25 mg/kg (i.v. bolus) 20 minutes before extubation along with remifentanil according to Minto model and propofol infusion according to Marsh model through target control infusion pump. 2. Control Group: intravenous normal saline (as placebo, with similar volume) at the beginning and 20 minutes before extubation along with remifentanil according to Minto model and propofol according to Schnider model through target control infusion pump. Randomization procedure is performed by the unblinded study team investigator. Patients will be randomized to either the treatment or control groups with a 1:1 allocation ratio. Sequence generation will be performed using a computerized random number generator, employing a permuted block randomization scheme. Allocation concealment will be maintained by having the random numbers pre-generated by an off-site statistician who will not be involved in subject recruitment. Implementation will be via serially numbered opaque sealed envelopes. Throughout the study period, blinded study members will perform drug administration and data collection, while unblinded study members will be in charge for the investigational drug storage, dispensing and preparation. Any premature unblinding (e.g. accidental unblinding, unblinding due a serious adverse event) of the investigational product will be promptly documented and explained. In the case of adverse effect or severe adverse effect requiring information on the study treatment to manage a patient, the treatment code of the patient will be unblinded.