Subcutaneous ketamine analgesia: postoperative analgesia using subcutaneous infusions of ketamine and morphine.

A series consisting of 32 women undergoing total abdominal hysterectomy received a standard narcotic-free anaesthetic. For the first 24 h postoperatively, eight were given the standard regimen of intramuscular morphine sulphate whilst the other three groups received continuous subcutaneous infusions of either morphine sulphate, ketamine hydrochloride or the two drugs combined. The amount of time they were pain free, the incidence of sleep and nausea, together with cardiovascular and respiratory changes were recorded. All three subcutaneous regimens produced significantly more pain-free readings than intramuscular morphine, but ketamine resulted in higher respiratory rates and less sleepiness. No patient reported psychomimetic side effects, but ketamine on its own produced feelings of malaise in three patients on the second postoperative day. Subcutaneous infusions provide better postoperative analgesia than intermittent intramuscular morphine. Ketamine on its own cannot be advocated, but combined with morphine it allows a single infusion rate to be used for all patients, decreasing the need for nursing and medical involvement.