Efficacy of Ketamine-fentanyl VS Fentanyl for Analgosedation in Postoperative Ventilated SICU Patients

Upon SICU admission, patient eligibility will be assessed, and informed consent will be obtained. A fentanyl bolus will be titrated by attending physicians to reach the target of patients' NRS pain scores at < 4 (self-report) or CPOT scores < 3 (unable to self-report pain) or patients' Richmond agitation and sedation scale (RASS) scores between -2 and 0.

After enrollment, patients will be randomly assigned in a 1:1 ratio by their sequential number of enrollment to receive either ketamine infusion (Group K) or placebo (Group C) together with fentanyl at 20 mcg/hr, initially. Randomization will be performed using a computer-generated randomization table derived from www.randomization.com. This process will be performed by an investigator (K.W.) who has no other role in patient enrollment or management. The other investigators, the patients, the patients' relatives, the attending physicians, and the nurses will all blinded to the study assignment. The study drug (ketamine or placebo) will be prepared by a pharmacist, who has no other role in the trial. The study drugs are packaged in identically shaped containers labeled with sequential numbers according to the randomization table order. For the study drug, 50 mg of ketamine is mixed with 50 ml of 0.9% NaCl (NSS), giving a final ketamine concentration of 1 mg/ml. For the placebo comparator, 50 ml of NSS will be prepared. The study drug will infuse via either peripheral line or central venous catheter (when available) at an individually adjusted rate according to the patient's body weight to achieve a dose of ketamine of 1.5 mcg/kg/min. The study drug will infuse for a period of 48 hours or until discontinue if narcotic medication without titration in both groups.

All eligible patients will receive narcotic and sedative medication according to the pain and sedation protocol. This included infusion of narcotic medication (fentanyl) and sedative medication to keep target NRS scores at < 4 and RASS scores between 0 and -2. Additional 20-mcg fentanyl IV bolus every 10 minutes will be administrated if needed. If more than 2 boluses are given per hr, the fentanyl rate will be increased by 10 mcg/hr to achieve pain and sedation goals. Blinded nurses will record pain scores, RASS, and medication doses every 4 hours.

Fentanyl IV infusion will be held if the RASS score is less than -2, indicating oversedation. If fentanyl is not administered for over one hour and the patient's RASS score remained below -2, the study drug will be discontinued.

A telephone follow-up will be conducted 12-60 months after ICU discharge using the Thai version of the Posttraumatic Symptom Scale (PTSS-10 questionnaire) to screen for the occurrence of PTSD as well as traumatic memories in the ICU. The interviews will be conducted by a research team unaware of the patients' group assignment.