Addition of Fentanyl or High-Dose Morphine to Bupivacaine Is Superior to Bupivacaine Alone during Single-Shot Spinal Anesthesia

Background: Single-shot spinal anesthesia (SSSA) with bupivacaine is a useful technique for pain control during the active phase of labor due to its simplicity and rapid onset. In this study, we evaluated the efficacy of the addition of fentanyl or high-dose morphine to bupivacaine during SSSA. Methods: Ninety healthy consecutive multiparous parturients in the active phase of progressing labor (cervical dilatation ≥7 cm; pain score >4) requesting analgesia were included in this study. The patients were randomly allocated into 3 SSSA groups as follows: group 1 (n = 30) receiving 2.5-mg hypobaric bupivacaine alone, group 2 (n = 30) receiving a combination of 2.5-mg hypobaric bupivacaine and 10-μg fentanyl, and group 3 (n = 30) receiving a combination of 2.5-mg hypobaric bupivacaine and 0.5-mg morphine. The duration of analgesia, VAS scores, side effects, and obstetric and neonatal outcomes were compared. Results: The main gestational age and cervical dilatation of the patients were 38.7 ± 1.5 months and 7.2 ± 2.2 cm (p = 0.14 and p = 0.65), respectively. The main VAS score significantly decreased in all groups at 3 h from baseline: from 8.25 to 1.75 in group 1, from 7.61 to 1.28 in group 2, and from 8.12 to 1.26 in group 3 (p < 0.001). The duration of the second phase of delivery was similar in all groups (45.5, 44, and 38 min, respectively; p = 0.67). The total analgesia duration was significantly higher in group 3 (172, 180, and 190 min for groups 1, 2, and 3, respectively; p = 0.01). The Apgar scores and fetal heart rates were similar in all groups (p = 0.95). Side effects were similar, except for pruritus in group 3 (p = 0.01). Conclusion: The addition of fentanyl or high-dose morphine to bupivacaine increases the efficacy and duration of SSSA in the active phase of progressing labor without increasing side effects.