Pneumocephalus After Neuraxial Anaesthesia

Pneumocephalus after neuraxial anaesthesia is air within the cranial cavity introduced through the epidural or subarachnoid space, usually after loss of resistance to air during epidural placement with dural puncture.

Epidemiology. Rare. It follows accidental dural puncture when air (typically 2 to 10 mL or more) is used for loss of resistance. Case reports are the main evidence.

Pathophysiology.

Air injected into the epidural or intrathecal space rises when the patient sits or stands and travels along the spinal subarachnoid space to the cranium. Air bubbles irritate meninges and cause traction headache, and nitrous oxide expands the pocket.

Sudden severe headache during or soon after epidural injection, often immediately after air injection. Headache may be non-positional, with nausea, vomiting, confusion, neck stiffness, seizures, dizziness and focal deficits.

Red flags.

• Seizure.
• Altered consciousness.
• Focal deficit.
• Headache after nitrous oxide use.

CT head confirms intracranial air (black pockets, often frontal or in the ventricles). Exclude other causes: meningitis, haemorrhage and post-dural puncture headache.

Differential diagnosis.

• Post-dural puncture headache.
• Meningitis.
• Subarachnoid haemorrhage.
• Venous thrombosis.
• Pre-eclampsia.

Stop nitrous oxide use and avoid it in future. Give 100% oxygen by non-rebreathing mask (to speed absorption by nitrogen washout), lie the patient flat, and give analgesia and anti-emetics.

• Paracetamol: 1 g orally or IV every 6 hours; maximum 4 g daily; reduce to 2 to 3 g daily if under 50 kg, malnourished or hepatic impairment.
• Ondansetron: 4 mg IV every 8 hours; maximum 16 mg single dose and 24 mg daily in this use; monitor QTc; reduce in severe hepatic impairment.
• Levetiracetam: 500 mg IV or orally twice daily if seizures occur; maximum 3 g daily; monitor mood; reduce in creatinine clearance under 80 mL/min.

Air is usually absorbed within days. Surgical intervention is needed only in tension pneumocephalus.

Prevention. Use saline rather than air for loss of resistance, or limit air to 2 mL.

Monitoring. Neurological observation and repeat CT if worsening.

Referral and escalation. Neurosurgery for tension pneumocephalus or deterioration.