7 obstetric analgesia10

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7 obstetric analgesia10

  1. 1. Obstetric analgesia and anesthesia The Third Affiliated Hospital of Sun Yat-sen University GUJIAN
  2. 2. theses must be concerned about during performing anesthesia for a parturient : <ul><li>safety of the mother </li></ul><ul><li>The effects on the uterine contraction </li></ul><ul><li>the effects of maternal-fetal barrier on drugs </li></ul><ul><li>The side effects on the fetus </li></ul><ul><li>…… </li></ul>
  3. 3. Main points <ul><li>1.Charateristics of obstetric analgesia and anesthesia </li></ul><ul><li>2.The techniques in obstetric analgesia and anesthesia </li></ul><ul><li>3. Analgesia and anesthesia for abnormal obstetrics </li></ul>
  4. 4. Charateristics of obstetric analgesia and anesthesia
  5. 5. definition <ul><li>Analgesia: </li></ul><ul><li>The loss or modulation of pain perception . (local, systemic) </li></ul><ul><li>Anesthesia: </li></ul><ul><li>the total loss of sensory perception (light tough, pain, temperature, and her capacity for vasomotor control) , and may include loss of consciousness. </li></ul>
  6. 6. Physical and chemical characteristics of anesthetics <ul><li>Rout of adminstration: </li></ul><ul><li>Oral </li></ul><ul><li>Parenteral routes: </li></ul><ul><li>subcutaneous, intramuscular, and intravenous </li></ul><ul><li>Intravenous: </li></ul><ul><li>avoid poor absorption </li></ul><ul><li>early onset of action </li></ul><ul><li>stable effects </li></ul><ul><li>smaller effective doses </li></ul>
  7. 7. Physical and chemical characteristics of anesthetics <ul><li>Local anesthetics components: </li></ul><ul><li>aromatic ring : lipid soluble </li></ul><ul><li>amine radical : exists partly as </li></ul><ul><li>base (un-ionized form) </li></ul><ul><li>resposible for penetration and diffusion </li></ul><ul><li>cation: (ionized form) </li></ul><ul><li>resposible for analgesia </li></ul>
  8. 8. Passing through the lipid membrane <ul><li>Henderson-Hasselbalch equation </li></ul><ul><li>Ph=pK a +log </li></ul><ul><li>pK a ↓ , ph↑ : base form ↑ </li></ul><ul><li>penetration ↑ </li></ul><ul><li>pK a ↑ , ph↓ : base form ↓ </li></ul><ul><li>penetration ↓ </li></ul>
  9. 9. <ul><li>Drugs pK a pene- efficacy </li></ul><ul><li>tration </li></ul><ul><li>Procaine 9.0 </li></ul><ul><li>Bupivacaine 8.1 </li></ul><ul><li>Ropivacaine 8.0 </li></ul><ul><li>Lidocaine 7.9 </li></ul><ul><li>Etidocaine 7.7 </li></ul>
  10. 10. Passing through the maternal-fetal barrier <ul><li>Drugs with molecular weighs ﹤600 cross the placenta easily </li></ul><ul><li>By simple diffusion according to the principles of Fick’s law: </li></ul><ul><li>Q/T=K[ ] </li></ul><ul><li>Q/T: rate of diffusion </li></ul><ul><li>A: the surface area available for drug transfer </li></ul><ul><li>C M : maternal drug concentration </li></ul><ul><li>C F : fetal drug concentration </li></ul><ul><li>D: membrane thickness </li></ul><ul><li>K : the diffusion constant of the drug </li></ul><ul><li>At term, transfer of drugs across the placenta↑ </li></ul>
  11. 11. <ul><li>The pH of the blood on the fetal side of the placenta is 0.1~0.2U lower than that of the maternal side. </li></ul><ul><li>ph↓, pK a ↑ : base form (un-ionized) ↓ </li></ul><ul><li>cation form (ionized) ↑ </li></ul><ul><li>ph↓ </li></ul><ul><li>Maternal placenta fetal </li></ul>un-ionized Total drugs (ionized+unionized)
  12. 12. <ul><li>the pKa values of local anesthetic=maternal blood PH, these agent tend to accumulate on fetal side </li></ul><ul><li>Acidic drug (thiopental): opposite direction </li></ul><ul><li>ph↓, pK a ↑ : base form (un-ionized) ↓ </li></ul><ul><li>cation form (ionized) ↑ </li></ul><ul><li>ph↓ </li></ul><ul><li>Maternal placenta fetal </li></ul>un-ionized Total drugs
  13. 13. The rate of transfer of drug is governed by <ul><li>Lipid solubility muscle relaxants are water soluble </li></ul><ul><li>Degree of drug ionization </li></ul><ul><li>Placental blood flow </li></ul><ul><li>Molecular weight most sedatives ﹤600 </li></ul><ul><li>Placental metabolism </li></ul><ul><li>Protein binding </li></ul>
  14. 14. Fetal distribution <ul><li>The distribution of drugs in fetus is just the same as fetal circulation </li></ul>
  15. 15. Distribution of drugs between maternal and fetal compartments
  16. 16. The techniques in obstetric analgesia and anesthesia
  17. 17. The techniques in obstetric analgesia and anesthesia <ul><li>Systemic </li></ul><ul><li>Regional </li></ul>
  18. 18. Systemic analgesics and anesthetics <ul><li>Sedatives and hypnotics </li></ul><ul><li>Produce drowsiness </li></ul><ul><li>Reduce anxiety </li></ul><ul><li>eg. diazepam </li></ul><ul><li>Can be used in latent phase of the first stage of labor </li></ul><ul><li>It should be avoided during labor (long chemical half-time), and in preterm neonate (kernicterus) </li></ul>
  19. 19. Systemic analgesics and anesthetics <ul><li>Tranquilizers </li></ul><ul><li>Used to relieve anxiety </li></ul><ul><li>Hydroxyzine, diazepan </li></ul>
  20. 20. Systemic analgesics and anesthetics <ul><li>Narcotic analgesics </li></ul><ul><li>Meperiding </li></ul><ul><li>Morphine: not used in active laboring patients (excessive respiratory depression in the neonate) </li></ul><ul><li>Fentanyl: also used in the epidural analgesia </li></ul>
  21. 21. Systemic analgesics and anesthetics <ul><li>Thiobarbiturates </li></ul><ul><li>Thiopental </li></ul><ul><li>Thiamylal </li></ul><ul><li>The mother will lose consciousness and airway protective reflex </li></ul><ul><li>Only used in association with general endotracheal anesthesia </li></ul>
  22. 22. Systemic analgesics and anesthetics <ul><li>Ketamine </li></ul><ul><li>Useful in maternal hypotension and hemorrhage </li></ul><ul><li>(Stimulates the cardiovascular system to maintain HR, BP, cardiac output) </li></ul><ul><li>≥ 2mg/kg: respiratory suppress effect on neonate </li></ul>
  23. 23. Systemic analgesics and anesthetics <ul><li>Inhalation anesthetics </li></ul><ul><li>Nitrous oxide: </li></ul><ul><li>use subanesthetic concentration to treat contraction pain </li></ul><ul><li>Halothane: </li></ul><ul><li>Isoflurane: </li></ul><ul><li>Sevoflurane: </li></ul><ul><li>Must prepare endotracheal intubation </li></ul><ul><li>Halothane and isoflurane: uterine relaxation </li></ul>
  24. 24. Local anesthetic agents efficacy Duration of action Bupivacaine Spinal anestheisia Lidocaine: Epidural anesthesia Procaine Protein combina-tion Lipid solubility
  25. 25. <ul><li>Drugs pK a penetration </li></ul><ul><li>Procaine 9.0 </li></ul><ul><li>Bupivacaine 8.1 </li></ul><ul><li>Ropivacaine 8.0 </li></ul><ul><li>Lidocaine 7.9 </li></ul><ul><li>Etidocaine 7.7 </li></ul>
  26. 26. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2 . Systemic </li></ul>
  27. 27. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2. Systemic </li></ul>
  28. 28. Local infiltration analgesia <ul><li>Local tissue infiltration of dilute solutions of anesthetic drugs yields unsatisfactory results </li></ul><ul><li>The total dosage must keep below the accepted toxic dose </li></ul><ul><li>0.25~2% lidocaine (﹤400mg) </li></ul><ul><li>Infiltration in or near an area of inflammation is contraindicated </li></ul><ul><li>Pudendal block : often used in second stage pain relief ( lateral episiotomy) </li></ul><ul><li>Occasionally used in emergency cesarean section (eg. umbilical cord prolapse) </li></ul>
  29. 29. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2. Systemic </li></ul>
  30. 30. Lumbar epidural block <ul><li>Become more popular </li></ul><ul><li>Satisfactory results of analgesia, muscle relaxation </li></ul><ul><li>The catheter can be used for surgery and postoperative analgesia </li></ul><ul><li>The fetal outcome is not adversely affected </li></ul><ul><li>Well suited to obstetric anesthesia: vaginal delivery, or cesarean surgery </li></ul>
  31. 31. puncture sites:L2~3, L3~4
  32. 32. Puncture with the epidural needle and place the catheter
  33. 33. Lumbar epidural block <ul><li>Procedure : </li></ul><ul><li>Inject 3ml of a 1.5% lidocaine as a test dose . If spinal anesthesia dose not result after 5~10min, inject an additional 5 ml </li></ul>
  34. 34. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2 . Systemic </li></ul>
  35. 35. Caudal block <ul><li>An epidural block approached through the caudal space </li></ul><ul><li>Seldom used </li></ul><ul><li>Hard to perform (the landmarks of the sacral hiatus is obscured , and the fetus is injured by the needle ) </li></ul>
  36. 36. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2 . Systemic </li></ul>
  37. 37. Spinal anesthesia <ul><li>Is currently used to alleviate the pain of delivery and cesarean delivery </li></ul><ul><li>0.25~0.5% bupivacaine 2-5mg, with narcotic (fentanyl 25 μ g) are used </li></ul><ul><li>Good relaxation of pelvic floor , lower birth canal and abdominal muscle </li></ul><ul><li>Short onset time </li></ul><ul><li>duration time 50~70mins </li></ul><ul><li>The dosage is small </li></ul><ul><li>the complications (hypotension) are fewer </li></ul>
  38. 38. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2 . Systemic </li></ul>
  39. 39. C ombined S pinal- E pidural A nesthesia <ul><li>Immediate onset of analgesia by spinal anesthesia </li></ul><ul><li>After spinal anesthesia complete, an epidural catheter can be placed immediately prior the surgery </li></ul><ul><li>Drug can be re-injected according to the duration of the surgery </li></ul><ul><li>Most common used in cesarean section delivery </li></ul>
  40. 40. Puncture the spinal needle, fluid from the subarachnoid space Place the catheter Inject 1.5%lidocaine Inject 0.5%bupivacaine
  41. 41. side effects of epidural and spinal anesthesia The block of Sympathetic nerve fibers arterial resistance ↓ 1. Blood pressure ↓ venous pooling ↑ Venous return ↓ Compression of inferior vena cava by uterus
  42. 42. Treatment for hypotension <ul><li>1. Left lateral position </li></ul><ul><li>2. The mother receive oxygen by mask </li></ul><ul><li>3. Ringer’s lactate is given </li></ul><ul><li>4. Ephedrine 5~10mg iv to sustain a mild vasopressor effect </li></ul><ul><li>↑ BP: Effective </li></ul>
  43. 43. side effects of epidural and spinal anesthesia <ul><li>2. Nausea and vomiting </li></ul><ul><li>Due to rapid onset of hypotension and parasympathetic stimulation of the gastrointestinal tract (block of sympathetic nerve) </li></ul><ul><li>Atropine, Antiemetics, etc can be used </li></ul>
  44. 44. side effects of epidural and spinal anesthesia <ul><li>3. Postdural puncture headache </li></ul><ul><li>due to leakage of cerebrospinal fluid through the needle hole in the dura </li></ul><ul><li>Use a small-caliber needles (25F) </li></ul><ul><li>Recumbent position (bed sore) </li></ul><ul><li>Hydration </li></ul><ul><li>sedation </li></ul>
  45. 45. side effects of epidural and spinal anesthesia <ul><li>4.Cardiopulmonary arrest </li></ul><ul><li>Inadvertent intravascular injection of local anesthetic (toxic reaction) or intrathecal injection of anesthetic (total spinal) </li></ul><ul><li>Full cardiopulmonary resuscitation (CRR) is indicated </li></ul><ul><li>(establish a patent airway, intubate the trachea, O 2 supply,give vasoprssors, treat arrhythmias, provide external cardiac massage) </li></ul><ul><li>Then, immediate cesarean section delivery to savage fetus </li></ul>
  46. 46. <ul><li>The pregnant patient is more likely to have an intravascular drug injection because of the venous distention in the epidural space </li></ul><ul><li>Injection of the drug into a highly vascularized area will result in rapid systemic absorption </li></ul>
  47. 47. Prevention and treatment of local anesthetic overdose <ul><li>Toxic doses of local anesthetics used in obstetrics </li></ul><ul><li>Lidocaine: 5 mg/kg </li></ul><ul><li>Bupivacaine: 1.5 mg/kg </li></ul><ul><li>Ropivacaine: 3.0 mg/kg </li></ul><ul><li>Add epinephrine (1:200,000) to produce local vasoconstriction: prevent too-rapid absorption and prolong the anesthetic </li></ul>
  48. 48. Prevention and treatment of local anesthetic overdose <ul><li>If manifested by central nerve system toxicity (convulsion): </li></ul><ul><li>Recognize the prodromal sings: </li></ul><ul><li>ringing in the ears, diplopia, perioral numbness, slurred speech </li></ul><ul><li>Oxygen supply </li></ul><ul><li>protect the patient’s airway </li></ul><ul><li>Inject: thiopental 50mg, </li></ul><ul><li>midazolam 1~2mg </li></ul>
  49. 49. The techniques in obstetric analgesia and anesthesia <ul><li>Regional </li></ul><ul><li>Local infiltration analgesia </li></ul><ul><li>Lumbar epidural block </li></ul><ul><li>Caudal block </li></ul><ul><li>Spinal anesthesia </li></ul><ul><li>C ombined S pinal- E pidural A nesthesia </li></ul><ul><li>2 . Systemic </li></ul>
  50. 50. Systemic anesthesia <ul><li>Indicate for cesarean section delivery when regional techniques cannot be used: </li></ul><ul><li>Coagulopathy, infection (spinal), hypovolemia, or urgency , moderate to severe vulvular stenosis, progressive neurologic disease </li></ul><ul><li>… . </li></ul><ul><li>Mother :unconscious, no pain, unpleasant memories </li></ul><ul><li>Fetus: should not be injured with minimal depression and intact reflex irritability </li></ul>
  51. 51. Systemic anesthesia <ul><li>Procedure: </li></ul><ul><li>1. Be prepared with antacid </li></ul><ul><li>2. Give 100% oxygen with a close-fitting mask for 3’ </li></ul><ul><li>3. Patient’s abdomen is surgical scrubbed (disinfection) and draped for surgery (anesthetics act on the fetus ↓) </li></ul><ul><li>4. Thiopental, 2-5mg/kg iv </li></ul><ul><li>succinylcholing, 120~140mg iv </li></ul><ul><li>5. Endotracheal intubation </li></ul><ul><li>6.50% Nitrous oxide, 50% oxygen, (0.5%)halothane or isofluran </li></ul><ul><li>Induction to delivery time under 10 mins </li></ul><ul><li>fast!!! </li></ul>
  52. 52. <ul><li>Procedure </li></ul><ul><li>7. After delivery of the fetus ,the nitrous oxide concentration may be increase to 70%, intravenous narcotics and benzodiazepines injected for supplemental anesthesia </li></ul>
  53. 53. Special side effects of general anesthesia in obstetrics <ul><li>1.Aspiration of gastric contents into the lung </li></ul><ul><li>Before endotracheal intubation , apply cricoid pressure to prevent aspiration. </li></ul><ul><li>2.narcotics and barbiturates may cause neonatal depress after delivery. </li></ul><ul><li>The use of a narcotic antogonist (naloxone) may reverse the effects </li></ul>
  54. 54. Anesthesia apparatus Sevoflurane: isoflurane:
  55. 55. Analgesia for intrapartum obstetric <ul><li>Never promise a painless labor </li></ul><ul><li>The management of labor analgesia can be determined during the first 2 stages of labor </li></ul><ul><li>(start from the first stage phase Ⅱ:cervical dilatation ≥3cm) </li></ul><ul><li>Epidural block (common) </li></ul><ul><li>Spinal block </li></ul><ul><li>(last only 50~70mins) </li></ul>
  56. 56. Analgesia and anesthesia for abnormal obstetrics
  57. 57. The trapped head in breech delivery <ul><li>If an epidural block is in place, no further analgesia will be required (forceps?) </li></ul><ul><li>General anesthesia is acceptable </li></ul>
  58. 58. Fetal distress <ul><li>Fetus development of bradycardia and appearance of meconium </li></ul><ul><li>Uterine perfusion is correlated with BP. Hypotension will aggravate fetal distress </li></ul><ul><li>The probable choice are no analgesia, minimal systemic analgesia (small dose), or segmental epidural block </li></ul><ul><li>Neonatal resuscitation is needed </li></ul>
  59. 59. Preeclmpsia-Eclampsia <ul><li>Composed of hypertension, generalized edema, and proteinuria. </li></ul><ul><li>The primary pathologic characteristics is generalized arterial spasm </li></ul><ul><li>Regional and general anesthesia are used </li></ul><ul><li>Contraindications to regional anesthesia include coagulopathy, urgercy for fetal distress </li></ul>
  60. 60. Hemorrhage and shock <ul><li>Placenta previa and aruptio placenta are accompanied by serious maternal hemorrhage. </li></ul><ul><li>Treatment of shock must be formulated. </li></ul><ul><li>Ketamine can support BP for induction </li></ul><ul><li>Regional block is contraindicated in the presence of hypovolemia </li></ul>
  61. 61. questions <ul><li>Contraindications for epidural anesthesia in cesarean section? </li></ul><ul><li>The mechanism of hypotension in epidural anesthesia ? How to treat it </li></ul><ul><li>What kinds of anesthesia can be use in cesarean section </li></ul>
  62. 62. Thank you for your attention

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