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OBSTETRIC ANALGESIA & ANAESTHESIA

MIKAH S

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INTRODUCTION

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  • Anaesthesia -1st in Genesis 2:21
  • October 1846 - public demonstration(William Morton)
  • January 1847- James Young Simpson used ether for pain relief in labour
  • Moral and religious objections!
    • Obstetricians-safety concerns
    • Clergy: labour pain as a divine punishment

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INTRODUCTION

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  • Several techniques used by anaesthesiologist to achieve effective pain relief.
  • GA, SA, Paracervical & Pudendal block, Local, Analgesia

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TREND

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  • GREAT STRIDES OVER TIME
  • Pain-free labour
  • SAFE - Reginal > GA
  • Anaesthetic death – <1 in 500,000 or 1.9 per million (regional), 20 – 32 per million (GA)

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Defining Anaesthesia

  • Anaesthesia- no sensation (Oliver Wendel Holmes)
  • Essentially a drug based speciality
  • Monotherapy with ether, now poly pharmacy of balanced anaesthesia

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  • Balanced anaesthesia comprises Hypnosis, analgesia and muscle relaxation

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ANALGESIA

  • Pain – unpleasant sensory or emotional experience due to actual or potential tissue damage or described in terms of such damage
  • Analgesia is the absence of pain

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OBSTETRIC ANAESTHESIA/ANALGESIA- SPECIAL CONSIDERATIONS

  • Two individuals involved – mother & fetus
  • Anatomical & physiological changes - anaesthesia hazardous
  • Fetus vulnerable as it changes from intrauterine to extra uterine life
  • Many life threatening conditions peculiar to pregnancy
  • Public interest
  • Medico-legal

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INDICATIONS IN OBSTETRICS

  • LABOUR
  • CAESAREAN SECTION
  • EUA
  • CERCLAGE
  • ERPC
  • RUPTURED UTERUS
  • SUTURES OF EPISIOTOMIES/INJURIES

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Properties of an ideal analgesic

  • Easy to administer
  • Effective
  • Rapid onset & short duration of action
  • Maternal comfort at 1st/2nd stages of labour
  • No toxicity
  • No interference with uterine contraction
  • No CNS or respiratory depression
  • No unpleasant side effect
  • High technical success rate
  • Minimal placental transfer

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THE PAIN OF LABOUR

  • Pain of labour varies among women
    • Severe in most women
    • Extremely severe for some
    • Very few have painless labour
  • Nullip > parous women
  • Other modifiers:
    • Fetal position
    • Dystocia

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MECHANISMS OF LABOUR PAIN

  • VISCERAL
    • Cervix, lower uterine segment, adnexae
    • Stretching and distends the cervix
    • Sensory fibres T10-L1
  • SOMATIC
    • Pelvic floor, vagina, perineum
    • Pudendal nerve S2-4
  • Pain is characterized
    • Abdominal contraction pain
    • Low-back contraction pain
    • Continuous low back pain

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Innervation of birth canal

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Effects of Labour Pain

  • Psychological
    • Suffering/Anxiety/Fear
  • Cardiovascular
    • ↑ Cardiac output/BP
    • ↑HR: O2 ↑ demand/ ↓O2 supply
  • Respiratory
    • Hyperventilation/hypocapnia

- Respiratory alkalosis

  • Uteroplacental
    • Decreases uteroplacental blood flow
  • Fetal
    • Fetal acidosis

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PAIN RELIEF IN LABOUR

NON-PHARMCOLOGICAL

Psychoprophylaxis :

  • Teach about physiology of labour & delivery
  • Relaxation exercises
  • Reduce anxiety & fear
  • Husband allowed in labour ward-

Hypnosis

Breathing & Relaxation exercise

Transcutanous electrical nerve stimulation

Acupuncture

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PAIN RELIEF IN LABOUR

PHARMACOLOGICAL METHODS

-Narcotics

-inhalational analgesics

-Regional analgesics

-Pudendal block

  • Paracervical block
  • Local infiltration

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NARCOTIC ANALGESICS

  • Opioids are most commonly employed
  • Pethidine, morphine, fentanyl, pentazocine
  • Intra-venous/intramuscular routes
  • Common side effects
    • Transplacental transfer
    • Depression of maternal/fetal ventilatory activities
    • Delay in maternal gastric emptying

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INHALATION AGENTS

  • Entonox, premixed nitrous oxide/oxygen in the same proportion
  • Worldwide usage
  • Maternal cooperation is important
  • Mask must be tight-fit
  • Good conc in brain prior to peak of contraction

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INHALATION METHOD…

  • Substantial analgesia in 50% of patients
  • Addition of vapour to improve analgesia
  • Entonox/0.125% isoflurane
  • Limitations:
    • Risk of maternal hypoxia
    • Variable quality of analgesia
    • Risk of environmental pollution

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EPIDURAL ANALGESIA

  • Most effective method in contemporary practice
  • Significant analgesia in most patients
  • Mitigates the physiological consequences of labour pain
  • Flexible

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COMBINED SPINAL EPIDURAL

  • Rapidity of spinal/flexibility of epidural
  • Commonly used in early or late labour
  • Fentanyl 25µg and/or bupivacaine 25mg
    • Early labour: spinal fentanyl only
    • Advanced labour: activate catheter
  • Typical walking epidural analgesia

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Anaesthesia for C-Section

  • C-section is an integral part of modern obstetrics
  • Anaesthesia for c-section could be tedious
  • M & M could be high
  • Data much improved
  • Due to development of subspecialty of Ob Anaesthesia

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Anaesthesia for C-section2�

  • Anaesthetic choices:
    • Indications for C-section
    • Urgency of the procedure

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    • Maternal health status
    • Desires of the mother

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TECHNIQUE FOR C-Section

  • General anaesthesia
  • Spinal anaesthesia
  • Epidural anaesthesia
  • Combined Spinal Epidural anaesthesia
  • Local infiltration

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GENERAL ANAESTHESIA: Indications

  • Foetal distress
  • Acute maternal hypovolaemia
  • Significant coagulopathy
  • Inadequate regional anaesthesia
  • Maternal refusal of inadequate analgesia

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GA for C-Section: problems

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-higher risk

-Fetal depression

-Hypertension & Tarchycardia

-Difficult / impossible intubation

-Risk of regurgitation/Aspiration

-Extubation problems

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GA for C-Section: problems

-Difficult airway management

-Hypoxaemia

-Supine hypotensive syndrome

-Haemorrhage

-Risk of postoperative DVT

- Awareness under GA

-Reduced Functional Residual Capacity

-Mendelson syndrome

-Musculo-skeletal injury

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Regional anaesthesia for c-section:

  • Shift from GA to RA
    • Safety is the drive!
  • REGIONAL ANAESTHESIA
    • SA is first choice!
    • Epidural
      • In patients with catheter
    • CSE

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SPINAL ANAESTHESIA

  • First choice world wide
  • Obviates problems associated with GA
  • It is simple, rapid onset & dense block
  • Maternal risk of systemic toxicity:low
  • Negligible transplacental transfer
  • Agents of use ± opioids
    • Bupivacaine
    • Lidocaine
    • Chlorprocaine
    • tetracaine

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SPINAL ANAESTHESIA -PROBLEMS�

-Hypotension

-Local anaesthetic systemic toxicity –CNS &CVS components. Dangerous!!!

-Allergy

-High or “Total” spinal

-Paralysis & nerve injury

-Spinal headache

-Effect on Labour & delivery

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EPIDURAL

  • Flexibility: incremental doses
  • Titration of LA
  • Slow onset allows for CV compensation for sympathetic block
  • Hardly a primary technique
  • More likely in patients with catheter in-situ

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EPIDURAL

  • Flexibility: incremental doses
  • Titration of LA
  • Slow onset allows for CV compensation for sympathetic block
  • Hardly a primary technique
  • More likely in patients with catheter in-situ

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EPIDURAL:Disadvantages

  • Slow onset of action
  • Risk of failure/inadequate anaesthesia
  • Risk of LA toxicity
  • Accidental dural puncture
  • PDPH

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LA INFILTRATION

  • INDICATED:
    • Skilled anaesthetist not available
    • Severe foetal distress
    • Severely compromised parturients
  • DISADVANTAGES:

-Patients discomfort

- Potential for systemic toxicity/Overdose

- Allergy

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    • Prolong time for onset of anaesthesia
    • Poor condition for the obstetrician

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MEDICAL DISORDERS IN PREGNANCY & ANAESTHESIA - PROBLEMS�

-Preeclampsia – oedema,volume depletion, vascular reactivity, drugs

-Asthma – Drugs (e.g narcotics) & intubation cause bronchospasms

-Cardiac disease – fluid overload, hypercoagulation, anti – coagulant effect

- SCDX

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-Bleeding disoders

-Neurological disorders

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Paracervical nerve block

  • Through lateral vaginal fornix at 3 & 9 O’clock
  • Inject L/A
  • Can be done at 5cm dilatation but preferably full cx dilatation
  • Effect is short lived
  • Continuous epidural preferred

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Perineal infiltration

  • Done in a fan wise manner from middle of fourchette
  • Aspirate to exclude blood
  • Used for episiotomy and perineal repair

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Pudendal block

  • Does not relief pain of labour
  • Perineal analgesia for forceps & breech deliveries
  • Simultaneous perineal & vulval infiltration needed
  • Transvaginal or transperitoneal route of adminstration
  • Infiltrate above ischial spine

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Common Analgesics in Obstetrics

  • Simple analgesics
  • NSAIDS
  • Weak Opioids
  • Strong Opioids

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Simple analgesics

  • Useful for mild pain e.g. PCM or ASA

-Acetaminophen

Efficacy similar to aspirin but not anti-inflammatory

>Mild on stomach and platelets

Use limited by hepatic dysfunction

Acetaminophen available in the parenteral form in Nigeria

Maximum dose 4 g per day in the adult. Children 90 mg/ kg per day

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NSAIDS�

- useful in Mild to moderate pain

-Useful for severe pain when combined with opioids , reduces opioid dose requirement.

- use is limited by complications; gastric erosion, bleeding, cardiac complications

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Safe use of NSAIDS

  • Oral preps –tab, cap, liquid and melts
  • Parenteral-Ketorolac, ketoprofen, diclofenac, diflunisal and dipyrone
  • Meticulous patient selection and education
  • Avoid in patients at risk of gi bleed, cvs, renal, hepatic & patients on anticoagulants
  • Careful follow up in prolonged use

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CONCLUSION

  • APPRECIATE SPECIAL MATERNAL RISK IN ANAESTHESIA
  • KNOW & INDIVIDUALISED EVERY PATIENT
  • KNOW YOUR DRUGS, EQUIPMENTS & PROCEDURES
  • BEWARE OF THE FETUS!

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THANK YOU

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