Obstetric Analgesia and Anesthesia

1. Obstetric Analgesia and Anesthesia Clinical Management Guidelines For Obstetrician-Gynecologists—ACOG Practice Bulletin OBSTETRICS & GYNECOLOGY, Vol 100, NO.1, JULY 2002 By R2 彭育仁

2. Purpose • To help obstetrician-gynecologists understand the available methods of pain relief to facilitate communication with their colleagues in the field of anesthesia • To optimizing patient comfort while minimizing the potential for maternal and neonatal morbidity and mortality.

3. Labor Pain • Uterine contractions and cervical dilatation result in visceral pain (T10 to L1). As labor progresses, the descent of fetal head and subsequent pressure on the pelvic floor, vagina and perineum generate somatic pain transmitted by pudendal nerve (S2 to S4).

4. Parenteral Anesthesia and Analgesia • Drugs can be given in intermittent doses or via patient-controlled administration(PCA). • Clinical usage is limited and the primary mechanism of action is heavy sedation. • Significantly higher visual analog pain scores compared with regional anesthesia. • The number infants requiring naloxone therapy increases compared with Epi. • Increased risk of aspiration and respiratory arrest on patient.

5. Regional Analgesia • Partial to complete loss of pain sensation below the T8 to T10 level. A varying degree of motor blockade may be present, depending on the agents used. • Spinal, epidural and combined spinal epidural are the most flexible, effective and lest depressing to the CNS.

6. Regional Analgesia : Epidural(1) • Epidural analgesia offers the most effective form of pain relief. • Mostly, the primary indication for epidural analgesia is the patient’s desire for pain relief. • Medical indications for epidural analgesia include anticipated difficulty in intubation, a history of malignant hyperthermia, selected cardiac or respiratory disease and prevention or treatment of autonomic hyperreflexia in high spinal cord injury.

7. Regional Analgesia : Epidural(2) • Continuous epidural infusion of local anesthetics or narcotics. • Medication can be titrated. • Can be used for C/S or postpartum tubal ligation. • Combination of a low dose local anesthetic, such as bupivacaine, with an opioid are preferred because they decrease motor blockade and result in an increased rate of NSD.

8. Regional Analgesia : Spinal • Single-shot spinal analgesia provides excellent pain relief for procedures of limited duration, such as C/S, the second stage of labor, rapidly progressing labor and postpartum tubal ligation. • Long-acting local anesthetic often is used with or without an opioid. • Limited use for the management of labor due to its inability to extend the duration of action.

9. Regional Analgesia : Combined Spinal Epidural • Rapid onset, prolonged duration. • The spinal component may be an intrathecal narcotic plus a small dose of local anesthetic. • Emergency C/S for fetal bradycardia is increased compared with Epidural only.

10. Regional Analgesia : Side Effects (1) • Hypotension: prevented with prehydration or prophylactic ephedrine. Left uterine displacement to maximize uterine perfusion. • Transient fetal heart rate deceleration esp epidural is responsive to conservative tx. • Postdural puncture headache: conservative therapy includes analgesics, supine positioning and hydration. 36% require an autologous epidural blood patch.

11. Regional Analgesia : Side Effects (2) • Transient neurologic symptoms (painful sensations in the buttocks or legs): 3~7% spinal. • Pruritus: spinal or epidural opioid, treated by naloxone. • 10% inadequate anesthesia with epidural. • Systemic absorption of epidural narcotic. • Total spinal blockade, hematoma, abscess and neurotoxicity. • Fever: 24% nulliparous epidural, longer the duration.

12. General Anesthesia(1) • Induction with IV agents, rapid sequence intubation. • Maintenance with N2O supplemented with low concentrations of halogenated gas. • All inhaled anesthetic agents readily cross the placenta and have been associated with neonatal depression. • Ideally, induction-to-delivery time should be minimized by 8 min.

13. General anesthesia(2) • Halogenated agents are potent uterine relaxants in high concentration. • Useful in situations such as uterine inversion and fetal entrapment although IV NTG and terbutaline may have the same goal with fewer side effects. • Increase blood loss during C/S.

14. Maternal Mortality(1) • Anesthesia-related maternal mortality (1.7 per 1000000 live births) accounts for more than 5% of maternal deaths. • The increased safety of regional analgesia has increased the relative risk of GA (32/1000000 v.s. 1.9/1000000). • Failed intubation occurs in 1/250, approximately 10-fold higher than normal population.

15. Maternal Mortality(2) • Regional anesthesia is the preferred method of pain control and C/S compared with GA unless contraindications to regional exist. • General anesthesia is indicated in some cases of fetal heart rate abnormality and urgent C/S (eg, severe intrauterine growth restriction)

16. Contraindications to Regional Anesthesia • Refractory maternal hypotension. • Maternal coagulopathy. • Maternal use of once-daily dose of LMW heparin within 12 hours. • Untreated maternal bacteremia. • Skin infection over site of needle placement. • IICP due to mass lesion.

17. What factors should be considered in the choice of parenteral agent for labor pain?(1) • Significant transplacental passage of all parenteral drugs. 2- to 3-fold increased risk of Apgar scores lower than 7 at 5 min and 4-fold increased need for neonatal naloxone. • Fentanyl has relatively short half-life, less nausea, vomiting and sedation than demerol. • Normeperidine (active metabolite of demerol) has prolonged duration of neonatal sedation.

18. What factors should be considered in the choice of parenteral agent for labor pain?(2) • All drugs have decreased heart rate variability on fetus. • Maternal respiratory and neurobehavioral depression may occur by using opioid and naloxone is indicated intravenously.

19. What is the role of PCEA during labor? • Goal of PCEA: satisfactory pain control for labor with the lowest dose of analgesic to minimize motor blockade and reduce the potential side effects of epidural analgesia. • Similar pain control to standard epidural analgesia. • Intermittent bolus PCEA results in less motor blockade and lower total dosages than continuous infusion. • Acceptable alternative but no additional benefits over standard epidural techniques.

20. Is chronic back pain associated with epidural use? • Retrospective studies found an association. • Motor block of the lower back and legs leads to prolonged periods of poor posture and decreased perception of muscle strain. • Prospective cohort studies found no significant association between epidural and chronic back pain.

21. Dose epidural increase the rate of operative delivery? • Controversial. • Epidural plays in prolonging labor by 40-90 miniutes and in the approximate twofold increased need for oxytocin augmentation. • Combined relative risk of 1.9 of forceps delivery in women who received epidural.

22. What is the effect of the timing of epidural analgesia on the course of labor and the risk of C/S? • It appears that very early placement of epidural analgesia may increase the risk of C/S and that the risk decreases with delayed epidural placement. • ACOG recommend that, when feasible, epidural analgesia in nulliparous should be delayed until cervical dilatation reaches 4-5 cm and other form of analgesia be used until that time. • Women in labor should not be required to reach 4-5 cm of cervical dilatation before receiving epidural analgesia.

23. How can the risks of epidural or spinal hematoma be minimized?(1) • Risk factors: bleeding tendency, thrombocytopenia, and under medications that affect coagulation. • Obtaining platelet count for certain groups including those with severe preeclampsia, ITP, known placental abruption or other risk factors for DIC.

24. How can the risks of epidural or spinal hematoma be minimized?(2) • No complications for platelet > 50k. • Patients on unfractionated heparin with normal aPTT or low-dose aspirin are not at increased risk. • LMW heparin has longer half life and is not reflected in the aPTT. In patients receiving once-daily, low dose LMW heparin, regional anesthesia should not be offered until 12 hours after the last injection of LMW heparin. LMW heparin should be withheld for at least 2 hours after removal of epidural catheter.

25. How dose preeclampsia influence the choice of analgesia or anesthesia? • Regional is preferred for preeclampsia and eclampsia—both for labor and delivery while GA carries more risk. • Regional in preeclampsia is associated with 15-25% reduction in mean BP and ephedrine for hypotension may occur. • Prehydration and intra-op fluid bolus for hypotension results in an average additional fluid challenge of 600-800ml in preeclampsia.

26. How can the risk of maternal aspiration be minimized? • A fasting period of 6-8 hours for solids is preferable before elective C/S. • Agents to decrease gastric acidity should be used when the decision is made to perform C/S.

27. What are the potential negative effects of drugs on breastfeeding? • Intrapartum opioid use may decrease neonatal rooting reflexes and delay initiation of breatfeeding but no evidence showed these delays affect the ultimate success of breastfeeding. • Postdelivery analgesia may contribute. PCA with morphine results in less neurobehavioral depression than demerol for neonate. Epidural opioid decreases maternal opioid requirement. • Continuous epidural bupivacaine infusion results in significantly increased milk production and greater infant weight gain compared with diclofenac alone.

28. What are the optimal agents for post-op analgesia?(1) • For patients under C/S with regional anesthesia, the most cost-effective regimen of pain management for the first 24 hours is morphine hydrochloride placed in the intrathecal space at the time of the initial intrathecal anesthesia or after delivery when using epidural anesthesia. • 12-24 hours effective pain control. • Delayed respiratory depression with intrathecal morphine have led to the standard dose to 0.1-0.25mg.

29. What are the optimal agents for post-op analgesia?(2) • PCEA minimize the dosage of opioid and maternal sedation compared with IV opioid. • Addition of local anesthesia in PCEA results in increased motor weakness, which may inhibit patient mobilization. • All intrathecal and epidural opioid is accompanied with a dose-dependent 35-56% incidence of maternal pruritus which can be treated by prophylactic naloxone and IV ondansetron.

30. What are the optimal agents for post-op analgesia?(3) • For patients under GA, IV PCA is a reasonable choice because it is associated with increased patient satisfaction and decreased sedation levels compared with IM opioid. • Morphine and fentanyl are all acceptable drugs for IV PCA while demerol should be avoided. • NSAIDs are useful in minimizing the cumulative maternal opioid consumption by 30-39%.

31. Risk factors that may prompt anesthetic consultation(1) • Suspected difficult intubation (marked obesity,severe edema or anatomical abnormalities of face, abnormal dentition, small mandible, difficulty opening the mouth, short stature, short neck, arthritis of neck, goiter….and so on). • Serious maternal medical problems such as cardiac, pulmonary or neurologic disease.

32. Risk factors that may prompt anesthetic consultation(2) • Bleeding disorders. • Sever preeclampsia. • Previous history of anesthetic complications. • Obstetric complications likely to leda to operative delivery, eg, placenta previa or high-order multiple gestation.

33. Thank You For Your Attention