Effect of epidural morphine on post-operative respiration

The respiratory effect of epidural morphine injection was assessed after minor gynecological surgery and was compared to that of intramuscular pentazocine injection. Patients received either morphine or pentazocine immediately after the emergence from anesthesia and the respiratory status of each subject was monitored for 6 hours there-after with the aid of respiratory inductive plethysmography (RIP). Although minute volume and PaCO2 were not significantly changed on intermittent measurements, cotinuous monitoring by RIP revealed several transient episodes of hypopnea in the epidural morphine group. In the intramuscular pentazocine group, the inadequate pain relief seemed to cause respiratory stimulation. In addition, transient hypopnea was also seen in the latter group. These results suggest that possible risks of transient ventilatory disturbance may exist following epidural mophine. Thus, continuous monitoring tech-nique such at RIP would be useful for assessment of respiratory status in patients who receive epidural morphine.