1. Obstetric Anesthesia Overview for Family Medicine Maternal and Child Health Éva Szabó, M.D. June 3, 2015

2. Learning Objectives Upon completion of the learning activity, participants should be able to: 1. Discuss the potential effects of labor analgesia on obstetric outcome 2. Compare the advantages and disadvantages of the most common neuraxial labor analgesia techniques 3. Identify those parturients who are at increased risk for anesthetic complications 4. Formulate a labor management plan for morbidly obese parturients to include early initiation of labor analgesia Explain the risks and benefits of neuraxial morphine administration for postcesarean analgesia 2

3. Topics Covered Today 1. Epidural analgesia and obstetric outcomes: progress of labor and method of delivery 2. Labor analgesia in the obese (especially the morbidly obese) parturient 3. Neuraxial opioid for postcesarean analgesia 3

4. Pain Pathways of Labor During first stage, pain results from uterine contractions and distention of lower uterine segment and cervix Visceral afferent nerve fibers travel with sympathetic nerves Visceral pain impulses entering the spinal cord at T 10 –L 1 must be blocked Late first stage and second stage: stretching of vagina, pelvic floor, and perineum Pain impulses travel via pudendal nerve Somatic impulses entering the spinal cord at S 2-4 must also be blocked 4

5. Neuraxial Labor Analgesia Most effective method of intrapartum pain relief Only form of analgesia to provide complete analgesia for both stages Additional benefits: reduced maternal catecholamine analgesia blunts hyperventilation-hypoventilation cycle catheter allows rapid conversion of analgesia to surgical anesthesia: safer than general anesthesia for emergency cesarean section Concerns about epidural’s effect on the progress of labor 5

6. Indications of Neuraxial Analgesia – Patient Selection Maternal request is sufficient indication For patients at risk of operative delivery (maternal or fetal) Early (prophylactic) insertion should be considered in high-risk patients for either obstetric or anesthetic indications to reduce the need for GA Preeclampsia Twins Difficult airway Obesity 6

7. Contraindications to Neuraxial Analgesia Absolute Patient refusal or inability to cooperate Infection at the site of needle insertion Coagulopathy Severe hypovolemia Sepsis Relative Systemic infection Neurologic disease Back pathology or surgery 7

8. Effects on Labor Concern about side-effects on the progress of labor Increased Cesarean rate?? Increased rate of instrumental delivery?? Prolongation of labor?? Difficult to study Observational studies – not considered in systematic reviews No studies where patients were randomly assigned to receive epidural analgesia vs. no analgesia Randomized controlled trials: epidural vs. systemic opioid 8

9. Cesarean Section Rate Early (1989) retrospective study of 711 consecutive nulliparous women with a spontaneous onset of labor showed 10% C-section rate for dystocia in the epidural group vs. 4% in the non-epidural group Another retrospective study by same author in 1991: even greater difference Retrospective studies suffer from selection bias Patients choose their analgesia Women with more pain/dysfunctional labor request epidural Greater labor pain in early labor may be a marker for increased risk for obstetric complication and operative delivery 9

10. Cesarean Section Rate: Prospective Randomized Trials First prospective, randomized trial of 93 women in 1993 [1] C/S: 12 of the 48 in the epidural group and1 in 45 in the meperidine group Increased risk of C-section was limited to dilation<5cm Primary investigators made decisions regarding mode of delivery More randomized controlled trials Meta-analysis of 18 prospective randomized trials, 2004 [2] 6701 patients No difference in the cesarean delivery rate Increased incidence (13% vs. 7%) of instrumental vaginal delivery Prolongation of first and second stage Limitations of randomized trials Cannot allocate patients to no analgesia: epidural compared to systemic Blinding is impossible Crossover is common 10

11. Operative Vaginal Delivery Early retrospective studies reported association between epidural analgesia and instrumental vaginal delivery Retrospective studies suffer from selection bias Studies in teaching institutions Series of randomized controlled trials 1987-90, Chestnut Dilute local anesthetic did not increase the incidence of instrumental vaginal delivery Dilute local anesthetic did not provide satisfactory second stage analgesia Maintenance of a dense block until delivery provided good analgesia but lead to more instrumental vaginal deliveries Effective neuraxial analgesia also resulted in prolongation of the second stage Dilute local anesthetic with opioid provided acceptable analgesia with less intense motor block and did not significantly increase the incidence of instrumental vaginal delivery 11

12. Timing of Labor Epidural ACOG guideline 2002: delay until 4-5 cm (to reduce the risk of C-section) 2005 NEJM article by Wong (728 women) [3] Early CSE (2cm!) vs. IV/IM opioid followed by epidural later (4 cm) No significant difference between the groups in the rate of Cesarean delivery and instrumental vaginal delivery Shorter first stage in the early group Meta-analyses Early epidural not associated with increased risk of C-section or instrumental vaginal delivery Early systemic opioid associated with non-reassuring fetal status Early systemic opioid associated with lower umbilical artery pH 12

13. Key Points Administered with modern protocols, neuraxial labor analgesia does not increase the risk of cesarean delivery when compared with systemic opioid Early initiation does not increase the cesarean rate Severe pain in early labor may signal a higher risk for operative delivery Early initiation does not prolong the first stage Effective analgesia does prolong the second stage Dense block increases the rate of instrumental vaginal delivery 13

14. Epidural Technique 14

15. Types of Neuraxial Analgesia Epidural Caudal Spinal Single shot continuous Combined spinal-epidural Dural puncture epidural analgesia (DPEA) 15

16. Continuous Lumbar Epidural Analgesia Most common technique Analgesia is initiated with bolus injection after test dose Analgesia can be maintained until after delivery Intermittent bolus, infusion, PCEA, programmable pumps Allows conversion to epidural anesthesia Local anesthetic spreads both cephalad and caudad T 10 -L 1 has to be blocked during 1 st stage S 2 -S 4 added for 2 nd stage 16

17. Caudal Epidural Analgesia Approach through sacro-coccygeal ligament Older technique Technically more difficult Requires large volumes of LA solution Risk of fetal injury Double catheter technique Remains an option for patients with L-spine pathology, surgery etc. 17

18. Spinal Analgesia Single shot if delivery is imminent (or if no epidural service available) Continuous spinal No FDA approved microcatheter Epidural catheter requires large-gauge introducer needle (epidural needle, 18 or 17 gauge) High incidence of headache Option after “wet tap” (preferred option at UNM) Intentional spinal catheter controversial Greatest advantage: easily converted to spinal anesthesia if necessary 18

19. Combined Spinal-Epidural 19

20. Combined Spinal-Epidural The needle-through-needle technique 1. Epidural space is identified with the LOR technique 2. Spinal needle through epidural needle; dural puncture 3. Intrathecal dose administered; spinal needle removed 20

21. Combined Spinal-Epidural 21

22. Combined Spinal-Epidural Increasing popularity Fast onset Complete analgesia in early labor with IT opioid ± LA “Walking epidural” – no motor block Higher success rate of epidural Optimal midline placement Increased incidence of fetal bradycardia Cannot initially confirm correct catheter placement 22

23. Dural Puncture Epidural Needle-through-needle Without injecting anything into the intrathecal space Additional confirmation of epidural space Allows for testing the epidural catheter Hypothesis: transfer of medication across the dural puncture hole 23

24. Obesity: Definition Excessive body fat with adverse health implications Metabolic disease Ideal body weight: lowest mortality rate for given height and gender Broca index: height(cm)-100, height(cm)-105 (women) BMI: weight/height 2 (kg/m 2 ) 18-25 normal 25-30 overweight >30 obesity (class I, II) >40 morbid obesity (class III) >50 (55) super obesity 24

25. The Obesity Epidemic 2011-12 National Health and Nutrition Examination Survey: 35% of adults were obese (BMI>30) 8% of reproductive-aged women are morbidly obese Certain ethnic groups have higher incidence The prevalence of childhood obesity is 2.5 times higher in offspring of obese women Majority of LGA babies are born to obese mothers Insulin resistance shunts nutrient excess to the fetus Metabolic disease is programmed in utero Increases risk for chronic diseases: OSA, HTN, CAD, DM, gall bladder disease, DJD, DVT 25

26. Respiratory Function in Obesity Increasing weight  increased O 2 consumption, CO 2 production Increased minute ventilation Decreased chest wall compliance (weight) Decreased FRC Increased work of breathing (rapid, shallow – more efficient breathing pattern) Obstructive sleep apnea (OSA) Desaturation during sleep, snoring, daytime fatigue, chronic hypoxemia, pulmonary HTN, RV failure 26

27. Respiratory Function in Pregnancy Respiratory changes start early in pregnancy Progesteron is a respiratory stimulant Increased O 2 consumption, CO 2 production Increased minute ventilation Increased respiratory rate and tidal volume Decreased airway resistance Increased work of breathing Hyperventilation results in mild respiratory alkalosis Arterial CO 2 decreases from 40 to 30 mmHg Arterial O 2 increases (less increase in obese women) At 20 weeks, mechanical effects of the uterus Decreased FRC 27

28. Cardiovascular System Obesity Increases the Demands on the CV System Excess tissue needs additional oxygen Increased blood volume, increased cardiac output Increased incidence of mild to moderate HTN Arrhythmias: fatty infiltration of myocardium and conduction system Left ventricular dilation, hypertrophy, dysfunction Patients may be asymptomatic despite CV disease due to minimal physical activity, limited mobility 28

29. Cardiovascular Changes in the Obese Pregnant woman Physiologic effects of pregnancy and obesity are additive Blood volume and CO increases during pregnancy Obesity independently increases blood volume and CO Additional elevation of CO during labor, and postpartum; obese parturients are at risk in the peripartum period BP is maintained during normal pregnancy Obesity increases risk of HTN, preeclampsia Risk of cardiomyopathy Supine hypotension syndrome more pronounced; may be impossible to position properly on OR table 29

30. Cardiovascular Changes in Pregnancy and Obesity [6] 30 PregnancyObesityCombined Blood volume  Cardiac output   Blood pressure  HR  Supine hypotension 

31. Anesthetic Implications of Morbid Obesity Providing anesthesia presents unique challenges Comorbidities increase anesthetic risk (ASA 3, severe systemic disease Difficult access, line placement Difficulty moving and positioning the patient Difficulty monitoring (BP cuff may not fit) Technical difficulties when placing neuraxial block Potentially difficult airway management Neck circumference best predictor of difficult intubation 31

32. Anesthetic Implications of Obesity in Pregnancy Obesity increases maternal morbidity and mortality Comorbidities: HTN, preeclampsia, DM Long, difficult labor, induction, failed induction Obesity increases perioperative risk Cesarean delivery Surgical and anesthesia-related complications, postoperative complications Care of the morbidly obese parturient is challenging for everybody involved and requires planning and good communication Obesity = high-risk pregnancy 32

33. ACOG recommendation [4] : “Because these patients are at increased risk of emergent cesarean delivery and anesthetic complications, anesthesiology consultation early in labor should be considered” 33

34. Why do we worry? Anesthesia-related complications are the seventh leading cause of maternal mortality Maternal obesity increases the risk of maternal death Incidence of failed intubation 1:2200 in general surgical population, 1:300 in obstetric patients, even higher in obese patients Most morbidly obese parturients will require some sort of anesthetic intervention General anesthesia carries higher risk in these patients Anesthesia consult allows for planning and decreases the risk 34

35. Obesity, obstetric complications and cesarean delivery rate – A population-based screening study, Weiss et al., Am J Obstet Gynecol 2004; 190:1091 Question: is obesity associated with obstetric complications? Prospective multicenter review of 16,102 patients 13,752 control (BMI<30) 1,473 obese (BMI 30-35) 877 morbidly obese (BMI >35) Result: obesity had a statistically significant association with GHTN, preeclampsia, GDM, macrosomia (OR 2.4 – 4) Cesarean rate 33.8% for obese, 47.4% morbidly obese (control 20.7%) (nulliparous) 35

36. Maternal superobesity and perinatal outcomes, Marshall et al., Am J Obstet Gynecol 2012;206:417.e1-6 Question: is there an increased risk of maternal and fetal complications in maternal superobesity when compared with maternal obesity and morbid obesity Retrospective cohort-study 64,272 women with BMI≥30 82.5% obese, 15.6% morbidly obese, 1.8% superobese Result: Increasing BMI was associated with increased risk of cesarean delivery (49% in the superobese) Dose-response relationship between worsening obesity and Cesarean delivery, macrosomia, neonatal hypoglycemia, preeclampsia 36

37. Anesthetic Management of Labor Obese parturients need good analgesia Effective pain relief improves respiratory function, decreases O 2 consumption Effective pain relief attenuates cardiovascular response to contraction pain (BP, HR, CO) Higher incidence of macrosomia, complicated labor, pain Higher incidence of induction, failed induction Cesarean rate increases with BMI Need a flexible plan for labor analgesia for vaginal delivery or labor analgesia ending in Cesarean delivery Continuous technique can be extended for cesarean delivery 37

38. Continuous Neuraxial Analgesia & Anesthesia Techniques Can be extended when cesarean delivery becomes necessary Lumbar epidural labor analgesia Combined spinal-epidural analgesia Continuous spinal analgesia All of the above can be very challenging in obese patients Obscured landmarks Distance to epidural space - long needle available All require proper positioning and take time Nothing can be done STAT in a morbidly obese parturient/patient [6] 38

39. Technical Difficulties 39

40. Continuous Lumbar Epidural Analgesia Placement can be difficult in the morbidly obese (multiple attempts) Obscured landmarks; identification of midline may be difficult Ultrasound imaging also difficult Distance to epidural space correlates with BMI High failure rate due to catheter migration during labor Block has to be PERFECT! If any doubt, epidural catheter has to be replaced [7] 40

41. Tuohy Needles: 9 cm and 15 cm 41

42. Cesarean Section in the Morbidly Obese Parturient with Good Labor Analgesia Moving the patient to the operating room (heavy bed+ IV pole with pumps) – need moving help Transfer to OR table Two pairs of extenders Careful attention to IV, epidural Left uterine displacement as soon as possible Long safety straps, monitors (consider A-line) Start dosing epidural Leave FHR monitor on as long as possible 42

43. Case 33-y-o G1 P0, EGA 39 weeks, 129kg, 163 cm (5’4”), BMI 48.5 admitted for induction of labor Type II diabetes, macrosomia Saturday evening induction started; anesthesia consult on Sunday Pt. requested epidural Monday morning; cervix 2 cm Epidural placement; loss of resistance at 9 cm 20 hours later: no change in the last 6 hours Chorioamnionitis 43

44. Case continued Patient consented for C-section (Tuesday morning) Anesthetic plan discussed : Excellent labor analgesia  plan epidural anesthesia Pt. taken to OR at 0858 Pt. moved herself (with some help) to OR table (7 minutes) IV, epidural catheter intact Left uterine displacement 44

45. Left Uterine Displacement 45

46. Left Uterine Displacement 46

47. Lidocaine 2% injected to establish surgical anesthesia. 0920 (22 minutes later): sensory level adequate to retract the pannus. 47

48. Case continued Incision at 0940 Uterine incision 0951 Delivery at 0953 (almost 1 hour after we started moving the patient from her room to the operating room) Apgars 9, 9, 4155g. Total operating time 1 hour 11 minutes, EBL 600 ml Discharged home on POD #4 48

49. General Anesthesia for Cesarean Delivery GA is riskier than regional in the obstetric patient (relative risk 1.7). Why? Intubation is more difficult in the obstetric patient GA is often chosen in emergencies GA is most commonly used in highest risk patients Combination of morbid obesity and pregnancy increases the risk of GA GA cannot be avoided if it is an emergency and: The patient does not have an epidural catheter If there is no time for spinal anesthesia If there is a contraindication to any neuraxial technique 49

50. Emergency Cesarean Section under General Anesthesia in the Morbidly Obese Parturient Added complexity of providing care Additional staff to help move the patient All components are more time consuming Risk of losing IV access Technical issues to safely manage the morbidly obese parturient Appropriate table, extenders, safety straps Ramp or wedge to position for intubation Safe positioning to avoid fall Safe positioning to avoid aortocaval compression All of the above are difficult to achieve in an emergency situation 50

51. Summary: How to Avoid a Catastrophe Communication! Identify morbidly obese patients in prenatal clinic refer to a center where epidural analgesia is available Refer them to anesthesia preoperative evaluation Aggressive approach: recommend early epidural placement Technical issues: OR table, extenders, ramp/wedge ready Proper positioning for intubation if GA required Full preoxygenation takes minutes but is extremely important Nothing can be done STAT in a morbidly obese patient Anticipate problems to avoid a crash section 51

52. Other Medical Conditions Requiring Pre- delivery Anesthesia Evaluation Severe cardiac or pulmonary disease Coagulopathy or anticoagulation Prior anesthesia-related complication or family history Contraindication to regional anesthesia Back surgery/back pathology Spinal cord disease Facial deformity or limitation of neck mobility Neurologic/ neuromuscular disorders Placenta accreta/increta/percreta 52

53. “Duramorph” Preservative-free morphine for neuraxial administration: Subarachnoid (spinal, intrathecal): very small dose required Epidural: dose similar to single IV dose (small fraction crosses the dura) Opioid receptors in the spinal cord Intrathecal opioids do not cause motor block Mean duration of analgesia 20-23 hours Analgesic potency of morphine: IV 1 Epidural 10 Intrathecal 200 53

54. Benefits and Problems Better pain control facilitates: Early ambulation (less DVT) Early maternal-infant bonding Lower doses: 0.1-0.2 mg IT, 2-3 mg epidurally Lower plasma (breast milk) opioid levels Better maternal satisfaction Side effects Pruritus Nausea and vomiting Respiratory depression Herpes labialis (HSV-1) reactivation may be more likely 54

55. Pruritus Incidence 40-80% Most frequent cause of dissatisfaction Most severe at 3-6 hours after IT Morphine Treatment: Nalbuphine 2.5-5 mg IV q 4h Naloxone (0.4 mg/mL) 0.04-0.08 mg IV Diphenhydramine 25-50 mg IV q 4h Ondansetron Propofol 55

56. Nausea/Vomiting Incidence 10-60% Treatment: Nalbuphine 5-10 mg IV q 4 hours Ondansetron 4 mg IV q 6 hours Metoclopramide 10 mg IV Intractable nausea: Naloxone 0.04-0.08 mg IV bolus then 0.05-0.1 mg/h infusion 56

57. Respiratory Depression Definition? Failure to respond to PaO 2 50 Not synonymous with RR Peak 3.5 - 12 hours after injection Always preceded by sedation Exacerbated by sedatives, morbid obesity Risk is very low with currently used doses Treatment: naloxone, O 2 57

58. Breakthrough Pain Should not be treated with opioids in the first 24 hours without prior discussion with the anesthesia team “Anesthesia spinal morphine” order set allows for oxycodone if pain not controlled or small doses of IV morphine if pain not controlled with oxycodone Risk for of respiratory depression, hypoxemia Ketorolac and ibuprofen preferred; multimodal analgesia Morphine PCA rarely needed Small doses 0.5-1 mg No basal rate 58

59. References 1. Thorp et al. The effect of intrapartum epidural analgesia on nulliparous labor: a randomized, controlled, prospective trial. Am J Obstet Gynecol 1993;169:851-8 2. Leighton et al. Epidural analgesia and the progress of labor. In Evidence- Based Obstetric Anesthesia 2005. p 10-22 3. Wong et al. The risk of cesarean delivery with neuraxial analgesia given early vs. late in labor. NEJM 2005;352:655-665 4. ACOG Committee Opinion Obesity in Pregnancy 2013 5. Soens et al. Obstetric anesthesia for the obese and morbidly obese patient: an ounce of prevention is worth more than a pound of treatment. Acta Anaesthesiol Scand 2008; 52: 6-19 6. Lucas. The 30 minute decision to delivery time is unrealistic in morbidly obese women. Int J Obstet Anesth 2010; 19: 431-7 7. Roofthooft. Anesthesia for the morbidly obese parturient. Curr Opin Anaesthesiol 2009; 22:341-346 59