Review Note

General Principles of Regional Anaesthesia (RA):

• Spinal Anaesthesia Contraindications:
  • Tethered Spinal Cord: Spinal anaesthesia is contraindicated if a tethered spinal cord has not been ruled out by appropriate imaging.
  • Abnormal Anatomy: Conditions like kyphoscoliosis, calcification of ligaments, osteoporosis, obesity, and anxiety may complicate RA due to positioning and needle insertion challenges.
  • Spinal Stenosis: May limit the spread and effectiveness of spinal anaesthesia.
  • Previous Surgery: Scar tissue or adhesions from previous surgery within the vertebral canal may interfere with the spread of anaesthesia.
  • Respiratory Insufficiency: Patients at risk of respiratory insufficiency due to neurological conditions should undergo RA incrementally to avoid a high block (e.g., CSE, incremental epidural technique).

Absolute Contraindications of Spinal Anaesthesia:

• Patient Refusal
• Sepsis at the Injection Site
• Hypovolaemia
• Coagulopathy
• Indeterminate Neurologic Disease
• Increased Intracranial Pressure (ICP)

Relative Contraindications:

• Infection (other than at the site of injection)
• Unknown Duration of Surgery
• Space-Occupying Lesions

Space-Occupying Lesions:

• Space-occupying lesions present a challenge due to the potential for increased ICP:
  • During labour, ICP increases to 40 cmH2O with uterine contractions and up to 70 cmH2O during the second stage.
  • Regional Anaesthesia Contraindicated: Spinal anaesthesia and inadvertent dural puncture may lead to cerebellar herniation.
  • Management: Best managed with elective LSCS under general anaesthesia.

Benign Intracranial Hypertension:

• Symptoms: Headache, visual disturbances, nausea. Symptoms often worsen during pregnancy and improve after delivery.
• Risks: Symptomatic patients are at risk if allowed to labour, due to increased CSF and epidural pressures during uterine contractions.
• Management: Asymptomatic patients can receive regional anaesthesia, but if symptoms are present, elective instrumental delivery should be considered to avoid increasing ICP.

Spinal Cord Injury:

• Women with spinal cord injuries are increasingly becoming pregnant.
  • Contractions: Not perceived in complete lesions above T5; perceived in lesions from T5 to T10.
  • Autonomic Dysreflexia: A risk if the injury is above T5.
    • Management: Epidural analgesia pre-emptively inserted can help protect against autonomic dysreflexia, and it should remain in situ for 48 hours postpartum.
    • Medication: Nifedipine, hydralazine, or labetalol may be needed.

Vaginal Delivery and Spinal Cord Injury:

• Onset of labour can trigger autonomic dysreflexia, which may continue up to 48 hours postpartum.
• Epidural analgesia helps prevent dysreflexia and should be maintained during this period.

LSCS (Lower Segment Caesarean Section):

• Spinal anaesthesia can be used.
• Avoid Suxamethonium: It should be avoided up to 9 months after the original injury.

Spina Bifida:

• Definition: A congenital abnormality due to failed closure of the neural tube.
  • Symptoms: Dimpling of the skin or a hair patch at the base of the spine may be present in up to 70% of patients with cord abnormalities.
  • MRI: Mandatory to rule out a tethered spinal cord.
  • Challenges: Associated with difficult intubation.
  • Regional Anaesthesia: Can be used at levels not affected by the abnormality. However, the spread of local anaesthesia (LA) can be poor, especially with chronic back issues (e.g., herniation, scoliosis).
  • Increased Risk: Risk of dural puncture due to abnormal ligaments, and altered dural permeability can lead to excessive cranial spread of epidural LA.

Neurofibromatosis (NF):

• Type 1: Peripheral nervous system affected by tumour growth, and CNS involvement in <10% of cases.
• Type 2: CNS tumours, with 90% of affected patients developing acoustic neuromas.
  • Regional Anaesthesia Contraindicated: Due to the potential for spinal cord lesions, unless excluded by imaging.
  • Warning: Increased likelihood of patchy epidural block.

Further References:

• CEACCP 2011
• BJA 2009
• NYsora Spinal Anesthesia