Obstetrical Anesthesia By - PowerPoint Presentation

1. Obstetrical AnesthesiaBy Dr : Miaad Adnan Dr. Bassim Mohammed Jabbar2022

2. Physiological Change In Pregnancy :From early in the 1st trimester of pregnancy, a woman’s physiology changes rapidly , under the influence of increasing progesterone and oestrogen production.1

3. Physiological Changes-CVSAlmost all the changes seen are due to high levels of progesterone and include:35%  Total Blood Volume heart rate 15 beats/min40%  CO30%  SV 15%  SVRSys BP decreased 10-15% (second trimester), dias BP decrease500ml/min  blood flow to uterus venous return from legsAORTOCAVAL COMPRESSION (mechanical)

4. Impact of CVS changesPatients with pre-existing cardiac disease may decompensate either during labor or immediately post delivery. This corresponds to the time of maximal COApprox 400 – 600ml blood loss occurs at deliverySupine hypotensive syndrome

5. Aortocaval Compression

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7. Physiological Changes – Resp. oxygen consumption ~ 20% (100% in labor) due to increased metabolic rate minute ventilation ~ 50% (due to increased RR 15% and tidal volume 30-50%) arterial pCO2 FRC 10-25% causing a decrease in oxygen reserves

8. Impact of Resp. changes Uptake of inhalational agents is fasterDecreased FRC and increased oxygen consumption increase the risk of hypoxia with apneaPre-oxygenation prior to GA less effective

9. Physiological Changes- AirwayVenous engorgement of airway mucosaEdema of airway mucosaWorsening of Mallampati score in labor

10. Impact of Airway ChangesTrauma to upper airway with suctioning, intubationIncreased incidence of difficult/failed intubation x10Require smaller ETT

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13. Physiological Changes-CNSDecrease in MAC by 25 – 40%Decreased dose of Local Anesthetic requirement for regional techniquesMore rapid onset of neural blockade

14. Impact of CNS ChangesDecreased inhalation anesthetic agent requirements Decreased dose of local anesthetic for same effectIncreased risk of local anesthetic toxicity

15. Physiological Changes - GITIncreased gastric fluid volumeIncreased gastric fluid acidityDecreased competency of lower esophageal sphincter

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17. Impact of GIT ChangesIncreased risk of aspirationAll parturients are a “full stomach”Aspiration prophylaxis recommended for C/S0.3M Sodium citrate 30 mls poRanitidine 50mg ivMetoclopramide 10mg iv

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21. Analgesia for labor and deliveryWhere is the pain coming from?Is pain bad in labor?Analgesic options

22. Pain of childbirthNociceptive pathways involvedT10 – L1 during laborplusS2-S4 for delivery

23. Is pain bad in labor?Psychological stress can cause: increased levels of catecholamines hyperventilationThese may result in decreased uterine blood flow leading to hypoxia and acidosis in the fetus

24. Factors affecting pain perception in laborMental preparationFamily supportMedical supportCultural expectationsParity Size and presentation of the fetusMaternal pelvic anatomyDuration of laborMedications

25. Analgesia for labor and deliveryNon-medicationInhalationalParenteralRegional

26. Analgesia- Non medication optionsBreathing exercisesAutohypnosisAcupunctureWhite Noise/ MusicMassage/ walkingTENSWater bath

27. Inhalation MedicationsNitronox: 50:50 mixture of oxygen and nitrous oxideLow dose Isoflurane in oxygenAdvantages: on demand delivery, relatively safeDisadvantages: variable efficacy, nausea, drowsiness, neonatal depression

28. Parenteral MedicationsNarcotics: meperidine, morphine fentanylAdvantages: relatively good analgesiaDisadvantages: nausea, vomiting, sedation, neonatal depression (max. 2 hours after meperidine dose), short duration of action

29. Regional techniquesEpidural, spinal, combined spinal-epiduralAdvantages: excellent pain control, minimal impact on progress of labor with low doses, less drug transfer to fetus, improved uterine blood flow, decrease in birth trauma e.g. use of forceps, minimal neonatal depressionDisadvantages: invasive technique, side effects (hypotension, headache, itching, nausea, urinary retention, limited mobility), nerve damage, infection

30. Anesthesia in the parturientGeneral considerations of the parturient undergoing surgeryObstetric surgery

31. General considerationsAltered physiology as mentionedRisks to the fetus:Effect of the disease process/therapiesPossible teratogenicity of anesthetic agentsIntraoperative effects on uteroplacental blood flowIncreased risk of preterm labor/ risk of abortion

32. Maternal considerationsAltered physiologyAltered response to anesthesiaDecrease in MACIncreased sensitivity to neuraxial agentsDecreased plasma cholinesteraseDecreased protein binding (more free drug)Limited drug information in parturients

33. Anesthetic management in the parturient should be directed to:Avoidance of hypoxemiaAvoidance of hypotensionAvoidance of acidosisMaintain PaCO2 in the normal range for the parturientMinimize effects of aortocaval compression

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35. Anesthesia for Caesarean SectionPreparationPreventing complicationsChoice of Anesthetic techniqueEffects on the fetus

36. PreparationPremeds: antacid (sodium citrate)IV access and fluid bolus within 30 minutes of operating (avoid glucose containing fluids)Left lateral tilt with wedge under right pelvisRoutine Monitors: ECG, NIBP, pulse oximeter, fetal monitoring Additional monitors for GAs: ETCO2, nerve stimulator, temp probe

37. Preventing complicationsAspiration prophylaxisDetailed airway assessmentFluid resuscitation/left lateral tilt to prevent hypotensionSafe practice for placement of neuraxial blocks

38. Anesthetic techniquesLocal infiltration by surgeonRegional anesthesia: spinal, epidural, combined spinal-epiduralGeneral anesthesia

39. Local InfiltrationRarely performedPatient usually in extremisSurgery must be done via midline incision, gentle retraction, no exteriorization of the uterusUsually done to supplement a regional technique if local anesthetic toxicity not a concern

40. Regional: Spinal AnesthesiaSimple to performRapid onsetSingle shot techniqueProfound neural blockTechnique of choice for uncomplicated elective caesarean sections and in many emergency caesarean sections

41. Regional: Epidural AnesthesiaMore technically challengingSlower onsetUsed when already placed for labor analgesiaUseful in parturient where a slow, controlled onset of block is neededAllows prolongation of block should surgery be complicated

42. Regional: Combined spinal-epiduralUsed when require the speed and density of a spinal anesthetic with the flexibility of prolonging the block by supplemental increments of local anesthesia via the epidural catheterComplications: as mentioned for spinals and epidurals

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44. General AnesthesiaUsed when Patient refuses regional techniqueRegional technique is contraindicatedEmergency C/S when there is inadequate/absent regional analgesia and to delay will cause undue risk to the fetus / mother

45. Suggested Technique for Cesarean Section :1. The patient is placed supine with a wedge under the right hip for left uterine displacement.2. Denitrogenation is accomplished with 100% oxygen for 3–5 min while monitors are applied.3. The patient is prepared and draped for surgery.4. When the surgeons are ready, a rapid-sequence induction with cricoid pressure is performed using Propofol, 2 mg/kg, or Ketamine, 1–2 mg/kg, and Succinylcholine, 1.5 mg/ kg. (Ketamine is used instead of Propofol in hypovolemic patients.)q5. Low MAC. The low dose of volatile agent helps ensure amnesia but is generally not enough to cause excessive uterine relaxation or prevent uterine contraction following oxytocin. A muscle relaxant of intermediate duration (atracurium, cisatracurium, or rocuronium) is used for relaxation, but may exhibit prolonged in patients who are receiving magnesium sulfate7

46. Suggested Technique for Cesarean Section :6. After the neonate and placenta are delivered, 20–80 units of oxytocin are added to the first liter of intravenous fluid, and another 20 units to the next. Additional intravenous agents, such as Propofol, opioid, or benzodiazepine, can be given to ensure amnesia. 7. If the uterus does not contract readily, an opioid should be given, and the halogenated agent should be discontinued. Methylergonovine (Methergine), 0.2 mg intramuscularly or in 100-mL normal saline as slow intravenous infusion, may also be given but can increase arterial blood pressure. 8. An attempt to aspirate gastric contents may be made via an oral gastric tube to decrease the likelihood of pulmonary aspiration on emergence. 9. At the end of surgery, muscle relaxants are completely reversed, the gastric tube (if placed) is removed, and the patient is extubated while awake to reduce the risk of aspiration.11

47. General AnesthesiaComplications:Failed intubationFailed ventilation causing death or neurological injuryAwarenessAspiration pneumonia

48. Anesthesia: Effects on the fetusAvoid hypotension, hypoxia, acidosis, hyperventilationLimit time between uterine incision and delivery to less than 3 minutesInfants exposed to GA have lower Apgar at one minute but no difference at 5 minsNo significant alteration in neurobehavioral scores with regional techniques

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51. Placenta praevia

52. Placenta praevia and accreta: Anaesthetic management : Patients with placenta praevia are at risk of hemorrhage because: • Placenta may have to be divided to facilitate delivery. • Lower uterine segment does not contract as effectively as the body of the uterus so the placental bed may continue to bleed following delivery.37

53. Placenta praevia and accreta: Technique :Experienced obstetricians and anaesthetists are essential.Interventional radiology should be consideredWhen Caesarean section is to be performed 2–8U of blood should be crossmatched, depending on the anticipated risk of haemorrhage.Two 14G cannulae should be inserted and equipment for massive haemorrhage must be present.Fluid resuscitate with crystalloid and/or colloid38

54. Placenta praevia and accrete : Technique :For bleeding patients a general anaesthetic is the preferred choice. oxytocin 30–50IU in 500ml crystalloid over 1–2hrIf massive bleeding does occur, hysterectomy may be the only method of controlling bleeding • bimanual compression of the uterus, ligation of internal iliac arteries, temporary compression of the aorta • Even if no signify cant bleeding occurred intraoperatively, continue to observe closely in the postnatal period as hemorrhage may still occur.Start appropriate monitoring of mother and fetus. Urine output andinvasive monitoring of central venous and arterial pressures treat the cause of hemorrhage. If surgery is required: • Do not perform a regional technique if the patient is hypovolemic.Warming devices and rapid transfusion devices should be available.Correct coagulopathy with Platelets, Fresh Frozen Plasma (FFP),and Cryoprecipitate as indicated .Continue care on HDU or ICU39

55. Retained placenta :42IV access with a 16G or larger cannula.Assess the total amount and rate of blood loss and CVS stability.If rapid blood loss is continuing, then urgent cross-matchFor GA, use an RSI technique with a cuffed ETTIf uterine relaxation is required, the MAC of inhalation anaesthesia concentration can be increased At the end of the procedure, give analgesics

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