ANALGESIA FOR LABOR AND VAGINAL DELIVERY PRESENTOR : DR. BHUMIKA KALRA MODERATOR : DR. ASHA TYAGI

1. ANALGESIA FOR LABOR AND VAGINAL DELIVERY PRESENTOR : DR. BHUMIKA KALRA MODERATOR : DR. ASHA TYAGI University College of Medical Sciences & GTB Hospital, Delhi www.anaesthesia.co.in email: anaesthesia.co.in@gmail.com

2. Philosophy Of Labor Analgesia As noted by the ASA & ACOG(1992) There is no other circumstance where it is considered acceptable for a person to experience severe pain, amenable to safe intervention, while under a physician’s care. Unacceptable high no. of females involuntarily experience severe pain during labor

3. McGill pain questionnaire

4. Adverse Sequelae of Labour Pain

5. Loss of Morale PAIN Suffering Sympathetic Stimulation Anxiety Cardiac Output O2 Consumption Blood Pressure Delayed gastric emptying Hyperventilation Hypocarbia  Catecholamine release Lactic Acid Impaired uterine contractions Free fatty acid  Uteroplacental blood flow Maternal metabolic acidosis Fetal pH  Fetal O2

6. Hyperventilation Maternal respiratory alkalosis Leftward shift of oxyhaemoglobin dissociation curve Hypocarbia Increased maternal affinity for oxygen Hypoventilation between contractions Reduced oxygen delivery to fetus Decrease in maternal PaO2

7. Pathways of Labour Pain

8. Stages of labor

9. First Stage of Labour • From: onset of regular uterine contractions to complete cervical dilatation • Visceral component of pain : - transmitted slowly, poorly localized, primarily in the lower abdomen - referred to lumbosacral area, gluteal region, thighs

10. First Stage of Labour • Uterine contractions: myometrialischaemia and release of bradykinin, histamine, serotonin. • Stretching of LUS and cervix: stimulates mechanoreceptors • Noxious impulses: sensory nerve fibres (Að and C), accompany sympathetic nerve endings, travel through paracervical ganglion and hypogastric plexus to enter lumbar sympathetic chain • They enter spinal cord at T10 , T11 , T12 and L1 spinal segments

11. Second stage of Labor • From end of first stage  delivery of baby • Visceral and somatic component of pain • Sharp, well localized and not referred • Pain of 1st stage does not end with start of 2nd stage but is superseded by pain of 2nd stage

12. Second stage of Labor • Distension of pelvic structures and perineum due to descent of presenting part • Distension, ischaemia and frank injury • Somatic afferent nerve fibres transmit impulses through pudendal nerve to the spinal cord at S2, S3, and S4 levels.

13. Analgesia for Labour and Vaginal Delivery

14. History of Labor Analgesia

15. James Young Simpson ( 1811 – 1870 ) • First to use ether in obstetric practice to anaesthetise a female with deformed pelvis for delivery on 19th Jan 1847 • Discovered the anaesthetic properties of chloroform in 1847 • Strongly believed chloroform to be more advantageous over ether • Harshly attacked on moral grounds for using pain relief in labor

16. John Snow ( 1813 – 1858) • Invented ether inhaler in 1847 • Later abandoned ether for chloroform • 1853 : acted as anaesthetist at the birth of Queen Victoria’s eighth child, Prince Leopold, at the request of Sir James Clark,using chloroform • 1857 : birth of her ninth child Princess Beatrice • First woman anesthetized for childbirth in the United States : Fanny Longfellow Queen Victoria Fanny Longfellow

17. Labor Analgesia 1. Desirable characteristics of labour analgesic techniques. 2. Methods of labour analgesia • Pharmacological methods • Non-pharmacological methods

18. DESIRABLE CHARACTERISTICS OF LABOR ANALGESIA • Safety to mother and fetus • Effective and controllable • Predictable in its effects • High technical success rate • Shouldn’t weaken uterine contractions • Shouldn’t alter progress of labor and delivery • Shouldn’t depress the fetus • Shouldn’t interfere with mobility

19. METHODS OF PAIN RELIEF IN LABOR

20. Pharmacologic methods1. Inhaled analgesics including entonox2. Systemic analgesics3. Regional analgesia

21. Inhaled Labour analgesia • Subanaesthetic concentrations of inhalational anaesthetic agents • Mother remains awake with protective laryngeal reflexes • Doesn’t alter progress of labor

22. Administered - intermittently ( during contractions) - continuouslyvia a mask or mouthpiece • Can be self administered, but, requires presence of a health care provider to ensure an adequate level of consciousness • Drawback – overdose causes unconsciousness – nausea, vomiting

23. ENTONOX • 50 : 50 Nitrous oxide / Oxygen premixed in cylinder • Administration: facemask or mouthpiece connected to Entonox supply through demand valve system. • Self administered by patient or attendant. • Provides analgesia within 20-30 sec of inhalation, max effect: 45 sec Safest agent with no reported organ toxicity, does not depress uterine activity or prolong labour or has any detrimental effect on neonatal outcome

24. Equipment for self administration of nitrous oxide and oxygen (Entonox) with a mouth piece (top) and a face mask (bottom)

27. Poynting effect • Dissolution of gaseous O₂ when bubbled through liquid N₂O with vaporisation of the liquid to form homogenous gaseous O₂/N₂O mixture. Pseudo critical temperature : -6 degrees

29. Storage of cylinder above 6 degree Celsius for 24 – 48 hrs in horizontal position for proper mixing of constituents. • Agitate cylinder by inverting them thrice for immediate remixing • Not to be used in vertical position

30. Volatile Halogenated Agents • Obsolete - Methoxyflurane (withdrawn in 1984 ) - Trilene (banned in 1993 ) • The usual range of concentrations of volatile inhalational agents administered with oxygen : - Desflurane 0.2% - Enflurane 0.25-1.25% - Isoflurane 0.2-0.25% - Sevoflurane 0.8% ( Sevox )

31. - No changes in uterine contractions, tone, or responsiveness to oxytocin; neonatal acid-base status, oxygenation, and clinical condition - Major risk : unconsciosness and loss of protective reflexes - Other drawbacks : drowsiness, unpleasant smell and high cost

32. Systemic Analgesics • Most common method used for labor analgesia • Advantages: • No specialised equipment • Easy to administer • Common agents: • Opioids – Sedatives and Tranquilisers used as adjuncts to opioids – Ketamine • Prolonged depressant effect on the neonate - cause of concern

33. Opioids • Most effective systemic analgesics • Typically don’t provide complete analgesia • Dose dependent efficacy and side effects • Maternal side effects

34. Cross placenta freely thus causing respiratory depression in neonate and neurobehavioural changes • Route : intermittently , intravenously/ intramuscularly/subcutaneously • Advantages of intravenous route: - less varaiability in peak plasma drug concentration - faster onset of analgesia - ability to titrate dose to effect

35. Opioids for Systemic Labour Analgesia

37. Patient Controlled Opioid Analgesia • Advantages : • Superior pain relief with lower doses of drug • Less placental transfer of drug • Lesser risk of maternal respiratory depression • Less need for anti - emetic agents • Higher patient satisfaction

38. Opioids used for intravenous PCA during labor

39. Opioid Antagonists • For reversing neonatal effects of maternal opioid administration - naloxone : 0.1 mg/kg intravenously - best to administer naloxone to new born - no benefit of maternal administration during labor or just before delivery • For reversing maternal respiratory depression - reverses analgesic action

40. Sedatives And Tranquilisers • To allay anxiety • To promote sleep in early labor • To aid in treatment of hypertension(??) • As an anti emetic • Along with systemic opioids • They are used infrequently now

41. Sedatives And Tranquilisers

42. Ketamine • Subanaesthetic doses 0.25 mg/kg • Bolus dose : 10-15 mg every 2-5 mins to a total of 1 mg/kg or 100 mg in 30 mins • Infusion : 0.25 µg/kg/hr • Dose > 2 mg/kg  psychomimetic effects and increased uterine tone, low apgar scores and abnormal neonatal muscle tone • Indication – imminent vaginal delivery – patchy epidural analgesia

43. Regional Analgesia • Provides pain relief while allowing parturient to be awake and be able to participate in labor and delivery • Doesn’t produce drug induced depression in fetus/mother. • Techniques:

45. Epidural Analgesia • Mainstay for many years • Only therapy providing complete analgesia for both stages by allowing cephalad and caudad spread of LA T10-L1 S2-S4 Most commonly: Mid-lumbar midline placement

46. Patient evaluation and preparationfor neuraxial analgesia • Informed consent • Medical and obstetric history • Evaluate airway • Targetted clinical examination • Back examination • Obstetric plan and fetal well being noted • Informed consent • Emergency equipment and rescitative drugs • Intravenous line secured(18G) and correction of hypovolemia

47. Drugs -sedative hypnotic agents -succinylcholine -ephedrine, epinephrine, phenylephrine -atropine -calcium chloride -calcium bicarbonate -naloxone Equipment -oxygen source -suction source -self inflating bag and mask -face mask -oral airway -laryngoscope and assorted blades -endotracheal tubes -pulse oximeter -qualitative carbon dioxide detector

48. Intravenous hydration - Lactated Ringer’s solution (without dextrose) - Co-loading preferable to pre-loading to prevent hypotension Maternal positioning Lateral position : Advantages - orthostatic hypotension less likely - continuous FHR monitoring Disadvantage - concealed aortocaval compression Sitting position : Preferred in obese NEVER SUPINE. AVOID AORTOCAVAL COMPRESSION AT ALL TIMES

49. Monitoring during maintainence of analgesia • Measure blood pressure every 1-1.5 mins after administration of doses of local anestheticfor 15-20 mins or until she’s haemodyanamically stable; subsequently every 15-30 mins • Continuous pulse oximetry • FHR monitoring • Position : lateral ; turn side to side every hour • Sensory level of analgesia and intensity of motor block

50. Administration Techniques • Intermittent bolus - additional therapeutic bolus doses of local anaesthetic when analgesia begins to wane - disadvantage : pain relief constantly interrupted by periods of regression of analgesia • Continuous infusion - maintainence of stable level of analgesia, less frequent need for bolus doses, maternal haemodyanamic stability - decreased workload for anaesthesiologist - disadvantage : administration of larger dose of local anaesthetic