[Evaluation of the factors affecting the efficacy and safety of postoperative epidural analgesia using morphine]

Subjective and objective methods were used to assess pain in 390 surgical patients. The quality and duration of postoperative epidural analgesia (EA) with morphine was studied with regard to the analgesic concentration and volume of the solution, segment of its administration into the epidural space and its storage period. It has been shown that the degree of an antinociceptive effect does not depend on the segment of opiate administration into the epidural space, whereas the duration of analgesia increases when EA is performed into spinal segments innervating the source of pain. The effect of the first morphine dose was more durable with the increase in the analgesic concentration and decrease in the volume of the solution. Parallel enhancement of respiratory depression effect was observed. The incidence of side effects became greater towards the end of the storage period. Possible mechanisms of changes observed in EA pharmacodynamics are reviewed in terms of increased efficacy and safety of the procedure.