Epidural Abscess After Neuraxial Anaesthesia

Epidural abscess is a collection of pus in the epidural space following neuraxial anaesthesia or catheter use. Delayed diagnosis leads to permanent paralysis.

Epidemiology. Incidence after epidural catheters is about 1 in 10,000 to 1 in 100,000 in general use, and higher after prolonged catheterisation (over 4 days), immunosuppression and diabetes. Most cases present 3 to 14 days after the procedure.

Risk factors. Diabetes, immunosuppression, bacteraemia, prolonged catheter use, non-sterile technique, obesity, trauma, steroid injection and distant infection (skin, urinary).

Organisms. Staphylococcus aureus (60% to 70%), including meticillin resistant strains, streptococci, Gram negative bacilli, Pseudomonas and Mycobacterium tuberculosis.

Pathophysiology.

Bacteria spread from skin along the catheter track or by blood. Pus and inflammation compress the cord, and thrombophlebitis of epidural veins causes ischaemia.

Classic triad of fever, back pain and neurological deficit (present in a minority at first). Stages: back pain with tenderness, then radicular pain, then weakness and sensory loss, and finally paralysis. Redness or discharge at the site, bladder dysfunction.

Red flags.

• New weakness or sensory loss.
• Bladder or bowel dysfunction.
• Fever with back pain after epidural.
• Sepsis.

Emergency MRI of the whole spine with gadolinium. Blood cultures before antibiotics, full blood count, C-reactive protein and erythrocyte sedimentation rate (raised in most). Culture pus at surgery or aspiration directed by CT. Send site swabs.

Differential diagnosis.

• Epidural haematoma.
• Vertebral osteomyelitis or discitis.
• Meningitis.
• Transverse myelitis.
• Disc herniation.
• Tumour.

Remove the catheter and send the tip for culture. Begin broad antibiotics at once once cultures are drawn. Surgical decompression within 24 hours for neurological deficit, with drainage of pus. Small collections without deficit can be managed with antibiotics alone and close neurological review.

• Vancomycin: 25 to 30 mg/kg IV loading dose, then 15 to 20 mg/kg every 8 to 12 hours; area under the curve 400 to 600; maximum 2 g in a single dose; monitor renal function and levels; extend interval in renal impairment.
• Ceftriaxone: 2 g IV every 12 hours (or ceftazidime 2 g every 8 hours or cefepime 2 g every 8 hours for Pseudomonas risk); maximum 4 g daily for ceftriaxone; monitor biliary effects and counts; reduce other agents for creatinine clearance under 50 mL/min.
• Narrow after culture: flucloxacillin 2 g IV every 4 to 6 hours for meticillin susceptible Staphylococcus aureus (maximum 12 g daily; monitor liver function; reduce interval in renal impairment).

Duration 6 to 8 weeks (4 to 6 weeks after surgical drainage), with oral step down only after specialist advice.

Monitoring. Neurological examination every 4 hours initially, weekly C-reactive protein and renal function, and repeat MRI if deterioration.

Referral and escalation. Neurosurgery and infectious diseases urgently. Critical care for sepsis.

Special groups. In injection drug use add cover for resistant organisms.