July 2005 - The Hong Kong College of Anaesthesiologists

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Bull HK Coll Anaesthesiol Volume 14, Number 2 July 2005Figure 2. Skin puncture site with pus discharge(circle). This photograph was taken at the timeof decompressive laminectomy.of voluntary reporting and more liberal use ofimaging diagnostic tool including MRI scan. 5,6There are numerous etiologies in thedevelopment of an epidural abscess.Hematogenous spread of the causative bacteriato the epidural space seems to be the commonestcause where patients are very often nursed in anovercrowded ward. The bacteria can then travelfrom the skin puncture site into the epiduralspace over the next few days following catheterinsertion. 7 The spread of bacteria during theprocess of epidural catheterization via acontaminated needle or catheter is also apossible mechanism. 8,9 As in our patient, it ishighly likely that her local skin infection notedupon removal the catheter was the origin of thebacterial spread. Despite the skin had beencleaned with 10% povidine solution beforeneedle insertion, colonization of bacteria to thecatheter and subsequent infection could stilloccur.Various species of bacteria have been isolated.The commonest pathogen found isStaphylococcus aureus. It is responsible for 60% ofabscesses following catheterization. 4 Otherpossible organisms include Staphylococcusepidermidis, Pseudomonas aeruginosa, Streptococcuspneumoniae and Enterococcus species. 4,10 MRSA isan uncommon offending organism and onlyfour cases have been reported in theliterature. 11,12 It is also a potential pathogen in97immunocompromised patients undergoingmajor surgery and the spectrum seems to bebroadening. 11The immunological status of the patient isconsidered an important factor in developing anepidural abscess. The possible risk factorsinclude malignancy, diabetes mellitus, steroidadministration, chronic alcoholism and chronicrenal insufficiency. 4,13 Our patient has largebowel tumor as well as diabetes mellitus formany years.Heuser first described the clinical presentationof an epidural abscess in 1948. 14 Four differentphases were described. Phase I is back painoccasionally associated with local tendernessand fever. Phase II occurs over 2 to 3 days and isfeatured by radicular pain and fever. Phase III isconsidered a late stage accompanied byneurological deficit and sphincter dysfunction.Progression from Phase III to IV may be veryrapid and signifies complete paralysis within thenext 24 hours.However, not all these classical symptomsmanifest in every patient. It is only found in 37%of them. Motor deficits are absent in up to 29%of patients. 6 Epidural abscess is first suspectedin only about 40% of cases. 15 Other presentingfeatures that may be helpful includeinflammation of the catheter site, headache, stiffneck, nausea and abdominal pain. 11 Theinflammatory markers are useful butnonspecific. 4 In our patient, changes in phases Iand II were subtle. It was not until the patientpresented with urinary retention andsubsequently lower limb weakness (phase III)that spinal cord compression was suspected.Symptoms of abscess formation can occur atvarious times, ranging from one day to fivemonths after catheter placement. 11 Kindler et alnoted that 52% of epidural abscess occurred ator sooner than five days. 4 In another report, theincidence of infection following the use oftunneled catheters varied from 5.4% to 9.7%. 16,17Furthermore, 58% of patients showed symptomsafter removal of the epidural catheter. 11 Thehighly variable presentation often makesdiagnosis difficult. A high index of suspicion istherefore vital in early detection of an epidural
Bull HK Coll Anaesthesiol Volume 14, Number 2 July 2005abscess. Communications between the acutepain service, ward clinicians and nurses arecritical.The definitive diagnosis relies on imagingstudies. MRI scan of the spine with or withoutgalolinium enhancement is now the goldstandard. 18,19 Both the extent and location of theabscess can be clearly defined. MRI scan issuperior to computerized tomographic (CT)myelography as the former allows directmultiplanar imaging and visualization of softtissue including the spinal cord and theparaspinal musculature. However, not allhospitals in Hong Kong has a 24‐hour MRIservice and very often, as in this case, the patienthas to be transferred to another hospital forimaging. This often creates further delay indiagnosis and treatment.Once the diagnosis of an epidural abscess ismade, an expedited management strategy mustbe initiated. The mainstay of treatment involvesemergency multilevel decompressivelaminectomy, evacuation of pus and parenteralantibiotics. Empirical broad spectrum antibioticswith bactericidal activity against Staphylococcusaureus and gram negative organisms must bechosen. They should be continued for no lessthan four weeks regardless of the requirement ofsurgery followed by oral therapy for at least twomore months. 6,20 The duration of antibiotictherapy is determined by the clinical response,biochemical markers and radiological resolutionof the lesion. Further treatment is required whenthere is concomitant osteomyelitis, persistentlyelevated inflammatory markers and bacteremia. 6In some cases, patients can be treatedconservatively without surgical decompression.21,22 The nonsurgical approach can beconsidered for patients with severe medicalcomorbidities, absence or minimal neurologicalsymptoms, extensive abscess precluding surgeryand paraplegia of more than 72 hours when thechance of neurological improvement aftersurgery is minimal. 7,23 If the conservativeapproach is chosen, serial MRI scans withregular and frequent neurological examinationsare essential. Further surgical intervention canthen be initiated if necessary. High dose98intravenous steroid therapy is relativelycontraindicated as it may exacerbate theongoing infection and sepsis. 24The neurological outcome is closely related tothe time between the development of symptomto surgical decompression. In a studyinvestigating long term outcome afterneurosurgery for epidural abscess followingcatheter insertion, only 31% of the patientsreferred to neurosurgery improved aftersurgery. 1 Only 20% with paraplegia made acomplete recovery without deficits at hospitaldischarge. Long term follow up revealed that55% of patients with paraplegia had experiencedsome improvement in motor function at somestage but 44% still suffered from bladder and, orbowel dysfunction. 1 Our patient had someimprovement in motor function after dischargebut still suffered from bladder dysfunction sixmonths after her initial surgery.Infection control measures aiming atminimizing the risks of infection followingepidural catheter insertion have beenrecommended. 25,26 The guidelines include:(1) strict aseptic technique;(2) closed delivery system;(3) use of a 0.22 μm bacterial filter within thesystem;(4) inspection of the epidural punctured siteevery eight hours;(5) change of filter, infusion line and infusate at96 hours or discontinue use and(6) preparation of the infusate under sterileconditions in the pharmacy. 26In our case, the infusate was prepared in 500ml bag by the anesthesiologist in a clean but notsterile condition and the catheter site wasinspected only once a day by our acute painservice team.Furthermore, more isolates from cultureswere obtained following skin disinfected with 10% povidine iodine than in those disinfected with0.5% chlorohexidine in 80% ethanol. 27 It has alsobeen recommended that the disinfectant shouldbe left in contact with skin for at least oneminute before skin puncture. Our hospital hasnow replaced all povidine solution by 0.5%chlorohexidine in 80% alcohol as disinfectant in
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July 2005 - The Hong Kong College of Anaesthesiologists

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