• A collection of pus or inflammatory granular tissue in the epidural space with the potential for rapid, irreversible neurologic impairment and death. Requires prompt diagnosis and intervention.
• Epidural abscess associated with epidural catheter insertion is fortunately a rare occurrence. However, due to the lack of available information, clear guidelines for diagnosis, treatment, and prevention have not been established in anesthesiology. Extrapolation of infection reduction from other scenarios (surgical site infection) and case reports have been utilized to better understand and describe this complication.
• Potential routes of infection include iatrogenic inoculation or contamination, seeding from the bloodstream, or extension from a nearby infected structure.
• Among obstetrical patients, infection is the most common cause of neuraxial injury.

• Coexisting risk factors have been shown to be present in up to 80% of reported cases.
• Most common risk factors: IV drug use, infection elsewhere in the body, degenerative joint disease, trauma, alcoholism, placement of stimulators or catheters, and neurosurgical procedures
• Transient bacteremia and hematogenous spread of infection
• Diabetes mellitus
• Diagnostic and therapeutic spinal interventions (epidural steroid injections)
• Immunocompromised patients
• Malignancy
• Longer duration of epidural catheterization (possible increased risk after >4 days; however, studies with mean duration of catheter up to 6 days did not show increased risk)
• Age 30 years and older (peak incidence in 60s and 70s)
• Morbid obesity
• Males
• Penetrating injury to the spine or osteomyelitis
• Skin infection or abscess
• Caudal anesthesia
• Poor aseptic technique, performing neuraxial block without surgical mask and hat, or traumatic insertion

• Pus or inflammatory granular tissue collections can result in spinal cord dysfunction secondary to inflammation, as well as venous thrombosis, thrombophlebitis, edema, and ischemia secondary to compression of the spinal arteries.
• Most epidural abscesses lie posteriorly because the dura mater is adherent to the vertebral column anteriorly. Abscesses can extend easily over several vertebral segments because there are no anatomic barriers in the posterior epidural space.
• Potential mechanisms for inoculation include exogenous and endogenous sources: Iatrogenic contamination, the bloodstream, or infection from a nearby source.
• Epidural placement by anaesthetists is an opportunity for introduction of skin flora or other contaminants. Staphylococcus aureus is the most common infective organism. Additional bacteria, particularly Staphylococcus epidermidis, reside in large numbers in the deeper recesses of hair follicles and are often difficult to eradicate by antiseptic skin preparations.
  • Inappropriate sterile technique or a break in sterility
  • Prolonged catheterization
  • Traumatic catheter insertion may be associated with breaks in sterile technique and subsequent need for manipulation.
  • Blood in the epidural space provides a nidus for infection.
  • Immunocompromised patients (diabetics, chronic steroid therapy, malignancy)
  • Infection elsewhere: Inflammation at the epidural entry point occurs at a higher frequency when there is an infected wound elsewhere. However, it is not a contraindication to epidural insertion.
  • Lack of sterile dressing on an indwelling epidural catheter entry point
• Labor epidurals: Increased risk in obstetric patients has been associated with catheters being placed outside of the OR (delivery suite), the use of a surgical mask by the anaesthetist, and lack of prophylactic antibiotics.
• Bloodstream: Gross or silent bacteremia. In 30–40% of cases, there is no identifiable source and silent bacteremia is believed to be the culprit.
• Direct extension: Vertebral osteomyelitis or psoas muscle abscess
• Injectate: Racemic bupivacaine is bacteriostatic.
• Common bacteria
  • Gram-positive cocci: S. aureus comprises 50–66% of all cases; of those, 15–40% are caused by MRSA (particularly in patients with implantable spinal or vascular devices); S. epidermis
  • Gram-negative bacilli: Escherichia coli, Haemophilus influenzae
  • Atypical organisms and fungi: Pseudomonas and Mycobacterium tuberculosis are most commonly isolated from IV drug users and patients with tuberculous spondylitis.
• Severe and untreated cases can result in coma and cerebral edema.

• Aseptic technique: Wear mask, wash hands in alcohol or full surgical scrub after removing hand jewelry. Prep widely with chlorhexidine in alcohol twice, drape the patient's back, and use powder-free sterile gloves without touching any unsterile area.
• Chlorhexidine is superior to povidone-iodine before epidural catheterization and lowers the incidence of positive bacteriologic cultures.
• Use a bacterial filter during continuous epidural infusion.
• Limit disconnection and reconnection of neuraxial delivery systems.
• Accidentally disconnected catheters should be removed.
• Limit the duration of epidural catheterization.
• Daily evaluation of indwelling catheters for signs and symptoms of infection (fever, WBC elevation, erythema or tenderness over epidural insertion site).
• Monitor neurologic function.
• Evidence for prevention of epidural abscess is sparse. Extrapolation from other fields, indirect evidence, logic, and commonsense are utilized; case reports may be the only "evidence."

• Herniation of intervertebral disc
• Vertebral osteomyelitis or discitis
• Meningitis
• Metastatic tumor
• Spinal cord injury
• Low back pain
• Transient neurologic symptoms
• Epidural hemorrhage
• Perinephric abscess
• Postdural puncture headache

• Epidural abscess comprised 4.5% (4/89) of neuraxial anesthesia claims in obstetrical anesthesia (All Claims, n = 368).
• Epidural abscess comprised 4% (4/93) of all neuraxial block claims associated with steroid injection (All Claims, n = 93).
  • Claims resulting in payment: 43%
  • Payment range: $2,000–$1,812,500

• Epidural Hematoma
• Transient Neurologic Symptoms

324.9 Intracranial and intraspinal abscess of unspecified site

G06.2 Extradural and subdural abscess, unspecified

Sharon L. Lin , MD

Jane C. Ahn , MD