Low-dose ketamine infusion for analgesia during postoperative ventilator treatment

In a randomized, double-blind study with placebo, ketamine was used as an analgesic during ventilator treatment in the period of recovery after major abdominal surgery. Forty patients were orally intubated and ventilated by means of a volume-controlled ventilator. Twenty of them received an i.v. bolus of 30 mg of ketamine followed by an 8-h infusion of 1 mg per minute. End-tidal CO2-concentration was continuously monitored and ventilation was adjusted to metabolic demands prior to assessment of pain. If pain relief was not adequate, the infusion rate was doubled, and if this was still not sufficient, 5 mg injections of ketobemidone were given i.v. If the orotracheal tube was not tolerated, the internal branch of the superior laryngeal nerve was blocked. A total of 30 injections of ketobemidone were administered to 13 control patients, but only five were given to four ketamine patients. Ten control and three ketamine patients required an internal laryngeal nerve block. Dreams and hallucinations were recalled in three patients in the control group and five in the ketamine group. Only one control and two ketamine patients experienced these as unpleasant. In this investigation, ketamine infusion in a low dose appeared to offer satisfactory analgesia and to permit tolerance of the orotracheal tube.