FRCA Notes

Pain During Caesarean Section

Curriculum

  • Primary FRCA: "Provides neuraxial anaesthesia for operative delivery and other obstetric procedures... and manages the inadequate neuraxial block"
  • Final FRCA: "Demonstrates the ability to manage complications of regional block including failure to achieve an adequate block"

Resources


  • Neuraxial anaesthesia is used for over 90% of UK caesarean sections, yet 10 to 15% of those having elective surgery report some pain.
  • Pain during caesarean section has replaced accidental awareness under GA as the most common successful medicolegal claim against obstetric anaesthetists in the UK.

Incidence

  • Quoted rates vary widely (from <5% to 30%) depending on how 'inadequate' anaesthesia is defined
  • Older studies used surrogate markers such as need for analgesic supplementation or conversion to GA; these likely underestimate the true incidence
  • Studies questioning patients directly suggest:
    • Any intra-operative pain: around 12% in elective spinal anaesthesia
    • Severe pain (score ≥7/10): around 1%
  • Both anaesthetists and obstetricians tend to underestimate their patients' pain
  • Conversion of a labour epidural carries a higher risk of pain than de novo spinal anaesthesia:
    • Elective systematic review: inadequate anaesthesia in 10% with spinal/CSE vs 30% with epidural
    • UK audit of 5080 sections: failure to achieve a pain-free operation in 6% of spinals, 18% of CSEs and 24% of epidural top-ups

Consequences

  • Patients describe panic, fear, helplessness and loss of control
  • Associated with:
    • Post-traumatic stress disorder
    • Postpartum depression
    • Chronic pain
    • Fear of future pregnancy (tokophobia)
  • The most frequent cause of litigation against obstetric anaesthetists in the UK
    • Recurring themes in claims: consent, block assessment and management of pain
    • In 42% of claims surgery had started despite evidence of an inadequate block


Patient Surgical Anaesthetic
High BMI (epidural conversion) Category 1 urgency Epidural conversion rather than de novo spinal
Low BMI (spinal) Prolonged surgery >2 clinician top-ups in labour (OR 3.2)
Taller height and younger age (epidural conversion) Previous caesarean section High pain scores in the 2hrs before surgery
Substance use disorder Concomitant tubal ligation Non-obstetric anaesthetist (OR 4.6)
Preterm delivery (spinal) Inadequate dosing or omission of neuraxial opioid

  • Proposed mechanism for preterm delivery and low BMI: less aortocaval compression and intra-abdominal pressure, so larger CSF and epidural spaces and less spread of a given dose
  • Prolonged surgery (e.g. repeat sections with adhesions, high BMI) risks the block regressing before closure


Perioperative prevention and management of pain during caesarean section


Consent and counselling

  • Information provided should be what a reasonable person in the patient's position would want to know, not what the clinician deems necessary (GMC guidance)
  • Explain the range of expected sensations: pressure, pulling, movement, and how these differ from pain
  • Explicitly discuss:
    • The risk of intra-operative pain
    • The options available if it occurs, including conversion to GA
  • Explore the patient's values and preferences and agree a plan for managing pain should it arise
  • Document the discussion, including the risks covered
  • Time pressure in emergency sections limits this, but a brief explanation is still required

Planning the technique

  • Discuss the expected duration and complexity of surgery with the obstetrician
  • If prolonged surgery is anticipated, consider a CSE rather than a single-shot spinal so the block can be extended

Advantages of CSE Disadvantages of CSE
Block can be extended via the catheter if surgery is prolonged Takes longer to perform
Rapid, dense onset from the spinal component Epidural catheter is untested at the time of surgery
Allows postoperative epidural analgesia if required Risk of LA toxicity and high block with epidural top-ups

Assessing the labour epidural

  • The key is identifying catheters at high risk of failure before they are needed for surgery
  • Warning signs of a poorly functioning catheter:
    • Persistently high pain scores despite an indwelling catheter
    • Multiple clinician top-ups
    • Unilateral block or missed segments
  • Options for a dubious epidural:
    • Re-site the catheter during labour
    • Use an alternative neuraxial technique (spinal or CSE) for the section rather than attempting a top-up

Optimising the block

  • Spinal:
    • ED95 of hyperbaric bupivacaine (with intrathecal opioid) is around 11.5mg
    • A prophylactic phenylephrine infusion may raise this by around 20%, possibly by reducing epidural venous engorgement and restoring lumbar CSF volume
    • Intrathecal fentanyl reduces the need for intra-operative supplementation by around 80%

  • Epidural top-up:
    • Alkalinised lidocaine with adrenaline and fentanyl, or chloroprocaine, give the fastest onset
    • Chloroprocaine is associated with more intra-operative pain
    • 0.5% (levo)bupivacaine is associated with a greater need for supplementation than alternatives such as ropivacaine
    • Epidural fentanyl speeds onset but does not reduce the need for supplementation

Relevant anatomy

  • The uterus is innervated from T10 to L1 and S2 to S4
  • However, visceral afferents from intra-abdominal organs enter between T4 and L2, so a higher thoracic block is required
  • No patient with a block to touch above T5 experienced pain in a widely cited study; this has become the accepted standard, though it predates the routine use of neuraxial opioids

Testing the block

  • Adequacy should not be judged on a single modality
  • Test sensory level only once some motor weakness is evident

Modality Target and interpretation
Light touch Primary sensory modality; aim for block to light touch at T5 or higher bilaterally
Cold and pinprick Supplementary; levels are inconsistent with touch (cold usually highest, touch lowest)
Motor Inability to straight leg raise is essential; S1 block (no plantar flexion) is expected with a spinal but not an epidural, and normal ankle movement under epidural suggests inadequate sacral spread
Sympathetic Warm undersides of the toes bilaterally indicate sympathetic block, which develops at around a T10 sensory level
Surgical skin test Obstetrician tests the incision site and umbilicus as a final check; responsibility for assessing the block remains with the anaesthetist
  • Document modalities used, timing and block height; a dermatome map is the most reproducible method of recording sensory level

Pitfalls in block assessment

  • Anatomical: 1 in 7 anaesthetists misjudge the location of T5 by two dermatomes
  • Physiological: a zone of differential sensory block exists at the cranial edge
  • Interpersonal factors reducing reliability:
    • Patient distress, distraction or previous traumatic experience
    • Suggestive or closed questioning
    • Power dynamics and time pressure
    • Confirmation bias
  • Mitigate with rapport, neutral open questions and actively looking for signs of an inadequate block

Management of intra-operative pain

  • Acknowledge the pain promptly and believe the patient
  • Inform the surgical team and pause surgery if possible
  • Have a new discussion: pre-operative wishes should be considered, but the patient may now feel differently
  • Offer GA, and repeat the offer if pain persists
  • If an epidural catheter is in situ, reassess the block and top up with fast-acting LA
  • If pain occurs early, particularly before delivery, and the block cannot be extended, conversion to GA should be considered
  • If GA is declined, use fast-acting systemic analgesia (see below)
  • Minimise surgical stimulus, e.g. avoid uterine exteriorisation
  • Distinguish pain from anxiety; pain should not be treated with sedatives or anxiolytics
  • If pain remains unrelieved, convert to GA in a timely fashion
  • Document events, treatments and responses

Rescue option Dose and notes
Epidural top-up Alkalinised 2% lidocaine with adrenaline, or chloroprocaine; only if a functioning catheter is in situ
Fentanyl IV 25 to 50μg boluses
Alfentanil IV 250 to 500μg boluses; very rapid onset and short duration
Ketamine IV 10mg boluses
Entonox Familiar to many patients from labour
Others Remifentanil and dexmedetomidine are described; evidence for intraperitoneal LA is limited to case series


Psychological sequelae

  • Poorly managed pain increases the risk of post-traumatic stress symptoms: flashbacks, avoidance and hyperarousal
  • It is difficult to predict who will be affected, but lower Obstetric Quality of Recovery scores are associated with positive depression screening at 6 weeks
  • Absent or insensitive follow-up can worsen the psychological harm

Follow-up

  • Should be prompt and undertaken by the anaesthetist involved (with senior support for trainees)
  • Listen to and accept the patient's account of events
  • A senior anaesthetist should also visit during the postpartum period
  • Provide an explanation for the pain and address questions fully
  • Screen for signs of post-traumatic stress and refer for psychological support where needed
  • Send a written record to the GP
  • Advise the patient how to contact the anaesthetic department with ongoing concerns
  • Offer an appointment to discuss events and plan anaesthesia for any future pregnancy
  • The approach mirrors the structured follow-up recommended after awareness under GA

Staff welfare

  • These events can also affect the anaesthetist; there should be an opportunity to debrief with a colleague