BACKGROUND: Patient controlled analgesia (PCA) is now a widely accepted method of postoperative pain control. It usually begins at postanesthetic care unit, but it takes time to achieve satisfactory level. We have studied the differences in the onset of analgesic effects between starting PCA preoperatively and starting PCA postoperatively.

METHODS: Forty patients for subtotal gastrectomy were randomized to two groups. In group I, we started PCA at postanesthetic care unit, in group II, PCA was begun immediately after the induction of anesthesia. We visited each patient and measured 10 cm-visual analgue scale (VAS) score at 3, 6, 9, 12 and 15 hours after the end of operation. We also measured the time taken from the end of operation to extubation.

RESULTS: There were no differences in VAS score between two groups on 3 hour. But at 6, 9, and 12 hour, VAS score was significantly lower in group II (P < 0.05). On 15 hour there was no difference between two groups again. There was no significant difference in extubation time between two groups. Preemptive analgesia was not observed in group II.

CONCLUSIONS: We concluded that starting PCA immediately after induction of anesthesia can achieve effective analgesia more rapidly than starting PCA at postanesthetic care unit. VAS score was lower than 3 after 12 hours after the end of operation in group II and we speculated that starting PCA 15 hours prior to operation would maximize the analgesic effect of PCA because there was approximately three hours time difference between the two groups.