Postpartum Tubal Ligation Requires More Bupivacaine for Spinal Anesthesia than Does Cesarean Section

It is sometimes preferable to use regional analgesia rather than general anesthesia for postpartum tubal ligation (PPTL). Either epidural or spinal anesthesia is usually used. A paucity of papers exists regarding the use of spinal anesthesia for PPTL. Therefore, I decided to perform a prospective study to determine the dose requirement of local anesthetic used for spinal anesthesia in the postpartum period. It is known that for an intraabdominal operation, a sensory level to T-4 is optimal (1). To determine the dose requirement for T-4 dermatomal level in the postpartum period, an arbitrary dose is usually used and the resulting level of anesthesia then determined. The required dose of local anesthetic per blocked segment can then be calculated; thus the total dose to reach the T-4 level can be determined by multiplying the dose per segment by 19 (1 coccygeal + 5 sacrals + 5 lumbars + 8 thoracic segments). It is also known that a gynecologic patient requires a dose of local anesthetic for spinal anesthesia 50% greater than the dose needed to achieve the same dermatomal level in a patient having a cesarean section (CS) (2). Therefore, I arbitrarily chose an initial dose midway between that required for a CS and that for a hysterectomy because the postpartum period is a stage between full-term pregnancy and the nonpregnant state. Accordingly, the dose of bupivacaine chosen in this study was 25% higher than that customarily used for CS. To determine the actual relationship between the dose requirements of bupivacaine for CS and PPTL, a group of CS patients was used as the control group.