Introduction: Obstetric patients are at increased risk of aspiration of gastric contents secondary to gastric stasis caused by pain, stress, and narcotics, as well as mechanical and hormonal factors. This risk decreases after delivery (1). However, the exact time that gastric emptying returns to the non-pregnant state is still not clear. There are no contraindications to tubal sterilization in the immediate postpartum period if a woman has had a major anesthetic for delivery and the anesthetic can be continued safely. Nonetheless, a major anesthetic (conduction, regional, or general inhalation) to accomplish a tubal sterilization should be continued only after careful evaluation by the anesthesia service. Because the parturient may have an increased risk of regurgitation and aspiration of acidic gastric contents, it is preferable to wait 8 hours after delivery before initiating a major block to allow for:

1) decreased risk of aspiration,
2) increased maternal cardiovascular stability and
3) more assurance of the neonatal condition.

A sensory level to T4 (as determined by pin-prick) is required for any intra-abdominal operation including tubal ligation (2). With a lower dermatomal level, for example, T10, skin incision may be tolerable but intra-abdominal manipulation and pulling on the Fallopian tubes can cause pain. In a patient with cardiovascular disease in whom a relatively high block to T4 is risky (Chapter 83), a lower level is acceptable and anesthesia is supplemented by intraperitoneal instillation of 80 ml of 0.5% lidocaine 5 minutes earlier (3).

The local anesthetic requirement for each spinal segment block after spinal anesthesia is less in cesarean section than in gynecologic operation, the ratio being 1:1.5. During the postpartum period, the doses of local anesthetic lie between that for cesarean section and gynecologic operation. For example, with spinal or epidural anesthesia the dose requirement per segment with cesarean section compared with Post-partum Tubal Ligation (PPTL) is 1:1.3 (4, 5).

The types of regional anesthesia techniques available for PPTL are spinal, epidural, combined spinal and epidural, continuous spinal, or local (Chapter 68).

Spinal Anesthesia: Spinal anesthesia is the simplest and safest technique. The cardiotoxicity and neurotoxicity of local anesthetic drugs arising from inadvertent intravascular or subarachnoid injection associated with epidural anesthesia are eliminated with spinal anesthesia. Moreover, with a spinal block, the onset of action is fast, the analgesia is superb, and the recovery is smooth. The incidence and severity of hypotension and the occurrence of nausea and vomiting under spinal anesthesia are much less with PPTL than with cesarean section (4). Intravenous infusion of lactated Ringer's solution, 15 ml/kg, is administered within 20 minutes of the spinal block. While monitors are being applied, i.v. sedation of the patient is performed. L2-3 may be preferable to L3-4 because of the more predictable level associated with the former interspace. The dose of local anesthetic should be based on patient's height (Table 67.1). The addition of 0.2 mg epinephrine intensifies the block and prolongs its duration of action (6). The addition of 0.2 mg morphine to hyperbaric bupivacaine also intensifies the spinal block and prolongs the postoperative analgesia (7). The combination of epinephrine and morphine to bupivacaine provides better analgesia than the addition of either one alone (8). For PPTL only morphine is added to the local anesthetic. Using a small gauge (Chapter 97), pencil-tip needle (Chapter 59) is advisable as this will reduce the incidence of post-dural puncture headache.

References:
1. Whitehead BEM, Smith M, O'Sullivan G: An evaluation of gastric emptying times in pregnancy and parturim. In Abstracts of Scientific Papers, Society of Obstetric Anesthesia and Perinatology, Annual Meeting, 1990.

2. Abouleish E: Subarachnoid block: In Abouleish E, editor: Pain Control in Obstetrics, Philadelphia, 1977, JB Lippincott.

3. Cruikshank DP, Laube DW, DeBaker LF. Intraperitoneal lidocaine for postpartum tubal ligation, Obstet Gynecol 1973; 42:127.

4. Abouleish E. Postpartum tubal ligation requires more bupivacaine for spinal anesthesia than does cesarean section. Anesth Analg 1986; 65:897.

5. Brooks GZ, Mandel ALZ: The early postpartum dermatomal spread of epidural 2-chloroprocaine. In Abstract of Scientific Papers, Society for Obstetric Anesthesia and Perionatology, Annual Meeting, San Antonio, Texas, 1984.

6. Abouleish E: Epinephrine improves the quality of spinal hyperbaric bupivacaine for cesarean section. Anesth Analg 1987; 66:395.

7. Abouleish E, Rawal N, Fallon K, Hemandez D: Combined intrathecal morphine and bupivacaine for cesarean section. Anesth Analg 1988; 67:370.

8. Abouleish E, Rawal N, Tobon-Randal B, et al: A clinical and laboratory study to compare the addition of 0.2 mg morphine, 0.2 epinephrine or their combination to hyperbaric bupivacaine for spinal anesthesia in cesarean section. Anesth Analg 1993; 77:457.