Learning Objectives: After reading this article, the physician should be able to:
1. Define current recommendations for treating cutaneous abscess and the current controversy regarding the need for antibiotics after incision and drainage.
2. Summarize technical aspects of performing a lumbar puncture and recognize cerebral spinal fluid laboratory findings suggestive of bacterial meningitis.
3. Describe the clinical presentation of spinal epidural abscess, the preferred imaging modality when it is suspected, and its definitive treatment.
Release Date: May 2009
From the 2009 LLSA Reading List
Are Antibiotics Necessary after Incision and Drainage of a Cutaneous Abscess?
Hankin A, et al
Ann Emerg Med
Cutaneous abscesses are a common presenting complaint in the ED. Patients with cutaneous abscesses are treated with incision and drainage (I&D) and unpredictably with or without antibiotics. Current guidelines from the Infectious Diseases Society of America and the Centers for Disease Control and Prevention state that abscesses can be effectively treated with I&D alone. This review addresses the question of whether the advent of methicillin-resistant Staphylococcus aureus (MRSA) should change current practice. Curiously, evidence for treatment recommendations is scant in the literature.
In 2006, Moran et al published a study of 422 adults seen in EDs in 11 U.S. cities, and concluded MRSA is the most common cause of purulent skin and soft tissue infections in the United States. (N Engl J Med 2006;355:666.) Patients treated with I&D alone had identical outcomes to those treated with I&D plus antibiotics, even when the antibiotics were appropriate to cover MRSA. The authors of this review concluded that the current literature does not support routine antibiotic therapy after I&D despite the high prevalence of MRSA.
From the 2008 LLSA Reading List
How Do I Perform a Lumbar Puncture and Analyze the Results to Diagnose Bacterial Meningitis?
Straus SE, et al
The authors of this article performed a systematic literature review to identify studies on interventions that improve the success of performing a lumbar puncture and minimize adverse side effects. Additionally, the authors examined the accuracy of cerebral spinal fluid analysis in adult patients with suspected bacterial meningitis. The review also included five studies (587 patients) that compared the use of atraumatic needles with standard needles.
Adverse events following LPs are common and include post-LP headache in up to 60 percent of patients and transient back pain in up to 40 percent. More serious events have been reported, including cerebral herniation, intracranial subdural hemorrhage, spinal epidural hemorrhage, and infection.
It has been previously shown that an LP can be done safely without neuroimaging if certain clinical criteria and examination findings are met. Preprocedure imaging should be performed in patients older than 60 with immunocompromise, known CNS disease, altered mental status, focal neurologic findings, papilledema, and seizure within a week of presentation. (N Engl J Med 2001;345 :1727.) Local infection at the puncture site is a contraindication to LP. Antibiotics should be given after blood cultures are drawn, but should never be delayed pending the results of a CT.
The authors were particularly interested in how interventions, such as operator experience, patient position, reinsertion of stylet prior to removal of needle, use of atraumatic needles, and bed rest or mobilization after the procedure affected the rate of post-LP headache, back pain, and overall success of the procedure. No studies have looked at the value of operator experience or patient position on LP success. Having the patient in a sitting position with the feet supported and chest resting on the knees appears to open the interspinous distance and ease the performance of the procedure; it precludes the measurement of opening pressure, however.
When traditional needles were used, the risk of headaches was reduced when a 26-gauge needle instead of a 22-gauge needle was used. The reinsertion of the stylet before needle removal resulted in fewer patients with headaches, presumably by preventing an arachnoid strand from prolapsing through the dural hole while withdrawing the needle. A nonsignificant decrease in post-LP headache occurrence was found with the use of atraumatic needles, but use of these required more attempts to complete the LP. The incidence of back pain did not change. Finally, early mobilization was associated with a insignificant decrease in post-LP headache.
In CSF analysis, a CSF white blood cell count of greater than 500/μl increases the likelihood of bacterial meningitis (LR=15) as does a CSF-toblood glucose ratio of 0.4 or less (LR =18). A CSF lactate level of 31.5 mg/dL or higher is also predictive of bacterial meningitis (LR=21).
From the 2008 LLSA Reading List
Spinal Epidural Abscess
N Engl J Med
Despite advances in medical knowledge, imaging techniques, and surgical interventions, spinal epidural abscess is still a challenging problem that often eludes diagnosis and receives suboptimal treatment. The incidence has doubled in the past two decades due to an aging population and increases in spinal instrumentation, vascular access procedures, and intravenous drug abuse. Most patients have predisposing conditions such as diabetes, alcoholism, HIV infection, spinal abnormality or prior intervention, and a local or systemic potential source of infection, IV drug abuse, nerve acupuncture, tattooing, epidural analgesic, or nerve block. Contiguous spread occurs in a third of cases, hematogenous in about half. Staphylococcus aureus is the most common pathogen, with the proportion of MRSA isolates increasing. Less common pathogens include Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa (IV drug abuse patients).
There are four stages of progressive signs and symptoms of spinal epidural abscess: back pain at the affected spinal level; nerve root pain radiating from the involved spinal area; motor weakness, sensory deficit, bladder and/or bowel dysfunction; and paralysis. The classic triad of back pain (75%), fever (50%), and neurologic deficits (33%) is present in only a minority of patients. Abscesses are more common in posterior rather than anterior areas and in thoracolumbar rather than cervical spine levels.
The diagnosis should be based on clinical findings, laboratory data, and imaging studies, and should be confirmed only at surgery. Leukocytosis occurs in roughly 66 percent of patients, bacteremia in 60 percent, and erythrocyte sedimentation rate and Creactive protein elevations are almost always present. CSF cultures are positive only 25 percent of the time, but in almost all cases of positive CSF cultures, blood cultures are also positive. LP is contraindicated because of the potential risk of meningitis or subdural infection if the LP needle passes through the abscess. MRI with IV gadolinium is more than 90 percent sensitive and is the imaging modality of choice for diagnosing spinal epidural abscess. No other studies should replace MRI.
Most trials support the consensus that the treatment of choice consists of emergent surgical drainage (decompressive laminectomy) plus systemic antibiotics. Empiric antibiotic therapy should provide coverage for S. aureus including MRSA (vancomycin) and gram-negative bacilli with a third- or fourth-generation cephalosporin (ceftazidime, cefepime). Nafcillin or cefazolin is preferred for confirmed cases of methicillin-sensitive S. aureus infection. The most important predictor of neurologic outcome is the neurologic status immediately before surgery, and the most feared complication is irreversible paralysis, which occurs in four percent to 22 percent of patients. About half of all cases of spinal epidural abscess are initially misdiagnosed, and unfortunately, diagnostic delay leads to a worsened outcome.
Luis M. Lovato, MD, an Associate Clinical Professor at the David Geffen School of Medicine at UCLA, the Director of Critical Care in the Department of Emergency Medicine at Olive View-UCLA Medical Center, and the Medical Editor of www.emcme.com, serves as the medical editor of this column.
About the LLSA
As part of its continuous certification program, the American Board of Emergency Medicine has developed the Lifelong Learning and Self-Assessment (LLSA) program to promote continuous education of diplomates. Each year, beginning in 2004, 16 to 20 articles are chosen based on the Emergency Medicine Model. A list of these articles can be found on the ABEM web site, www.abem.org.
ABEM is not authorized to confer CME credit for the successful completion of the LLSA test, but it has no objection to physicians participating in such activities. EMN's CME activity, Living with the LLSA, is not affiliated with ABEM's LLSA program, and reading this article and completing the quiz does not count toward ABEM certification. Rather, participants may earn 1 CME credit from the Lippincott Continuing Medical Education Institute, Inc., for each completed EMN quiz.
CME Participation Instructions
To earn CME credit, you must read the article in Emergency Medicine News, and complete the quiz, answering at least 80 percent of the questions correctly. Mail the completed quiz with your check for $10 payable to the Lippincott Continuing Medical Education Institute, Inc., 770 Township Line Road, Suite 300, Yardley, PA 19067. Only the first entry will be considered for credit, and must be received by Lippincott Continuing Medical Education Institute, Inc., by May 31, 2010. Acknowledgement will be sent to you within six to eight weeks of participation.
Lippincott Continuing Medical Education Institute, Inc., is accredited by the Accreditation Council for Continuing Medical Education to provide medical education to physicians. Lippincott Continuing Medical Education Institute, Inc., designates this educational activity for a maximum of 1 AMA PRA Category 1 Credit.™ Physicians should only claim credit commensurate with the extent of their participation in the activities.