[Individualized treatment of postoperative pain using a small externally portable programmable morphine pump]

After abdominal surgery, 16 patients (group I) received a bolus of 2 mg morphine hydrochloride followed by a continuous morphine infusion adapted to the patient's subjective pain, both via an epidural catheter. The initial basal rate of the infusion was 0.16 mg per hour. From the beginning of the operation, 6 patients (group II) received an epidural infusion of 2.3 +/- 0.6 mg morphine hydrochloride (mean +/- sem) until the end of the operation, and preceding the postoperative morphine infusion. The continuous injection of morphine was guaranteed by means of a small, externally portable, automatic infusion device. According to the morphine demand, additional preprogrammed doses could be released by the device. Under the treatment, continuous pain relief was observed throughout the postoperative period even with diminished morphine dose rates. Morphine demand in the immediate postoperative period was significantly reduced with the initial morphine bolus injection. Total morphine demand until 8 p.m. on the second postoperative day in group I was 9.5 +/- 0.7 mg and in group II, 12.1 +/- 1.5 mg morphine hydrochloride (mean +/- sem). Neither clinically nor by blood gas analysis symptoms of central respiratory depression could be detected. Only 2 out of 14 patients who received mepivacaine intraoperatively showed urinary retention. Under the individualized treatment with morphine, serum levels of free morphine immunoreactivity diminished continuously. There was no morphine accumulation in the blood and no tachyphylaxis. The described method for pain relief is superior to the intermittent morphine bolus injections.