Subcutaneous infusion of ketamine and morphine for relief of postoperative pain: a double-blind comparative study

Low dose ketamine by subcutaneous infusion (0.1 mg.kg-1.h-1) was compared in a double-blind fashion with a similar infusion of morphine (0.03 mg.kg-1.h-1) for postoperative analgesia in 60 ASA-I adults after major abdominal surgery. Pain was assessed using visual analogue scales and sedation was graded on a four-point rank drowsiness score. Cardiovascular and respiratory parameters were also recorded. Pain relief was better with the ketamine infusion than with morphine infusion (P < 0.001). Both tidal and minute volume parameters improved better with ketamine (P < 0.001); patients were more awake and alert as evidenced by the drowsiness score (P < 0.001). Nine out of 30 patients who received morphine required catheterisation for urinary retention (P < 0.05). The study revealed higher analgesic efficacy of a low dose subcutaneous infusion of ketamine with lesser sedation and fewer side effects.