Theoretical advantages in maintaining an effective blood concentration of the analgesic medication using basal infusions with or without standard intermittent PCA dosing regimens is controversial. The purpose of this study was to compare the effectiveness and incidence of side effects among three modes which include PCA only(group 1), PCA+ basal infusion(group 2), and basal infusion only(group 3).

Sixty ASA physical status 1 or 2 female patients who scheduled elective cesarean section were randomly allocated into one of three modes. Loading/PCA/basal infusion dose and lockout interval was 0.05 mg/kg, 0.02 mg/kg, 0.015 mg/kg/hr, and Smin, respectively. In each group, visual analog scale(VAS), pain score, sedation score, degree of satisfaction, total amount of morphine used, history of attempt or injection and incidence of side effects were checked.

Group 2 did not show any improvement of VAS, and group 3 showed significantly higher VAS from 2 hours after initiation of morphine infusion compared to group 1(P<0.05). Degree of satisfaction was lower in group 3 compared to group 1 and 2(P<0.05). Total amount of morphine was increased in group 2(P<0.05) and reduced significantly in group 3 compared to group 1(P<0.01). There was no evidence of respiratory depression. Incidence of nausea and pruritus did not show any difference among groups.

Addition of basal infusion did not show any improvement of postoperative pain control compared to conventional PCA method.