If Meningitis Is Suspected, When Is a Lumbar Puncture Indicated?
Lumbar puncture in cases of suspected meningitis should be performed before CT scan.
Advances in environmental sanitation, immunizations, antimicrobial therapy, and medical research have greatly reduced the impact of infectious diseases (IDs) on our communities. Nonetheless, infections and the cost of treating them remain a burden to the health care system.
In primary care practice, we may spend more time making referrals for suspected ID than actually treating infected patients. Here, as a brush up, is the fifth in our series of 10 practical ID pearls.
5. When meningitis is suspected, is a lumbar puncture (LP) always indicated? What are important considerations when obtaining an LP?
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Answer: Every patient with suspected meningitis should undergo lumbar puncture (LP) as soon as possible unless the procedure is relatively contraindicated.
To LP or not to LP is not the question. Rather, we need to ask, “When should an LP be performed if the diagnosis of meningitis is entertained?”
If the LP cannot be performed in a timely manner, obtain blood culture and give the first IV dose of antibiotics. Prior administration of antimicrobials tends to have minimal effects on the chemistry (high protein level and possible depressed glucose) and cytology (leukocytosis) findings of the cerebrospinal fluid (CSF) analysis,1 but can reduce the yield of Gram stain and culture.2 However, a pathogen can still be cultured from the CSF in most patients up to several hours after the administration of antibiotics.
Although there are no absolute contraindications to performing an LP, caution should be used in patients with evidence of raised intracranial pressure (eg, mass effect on CNS imaging or clinical signs of impending herniation), thrombocytopenia or another bleeding diathesis, or spinal epidural abscess. Also, best practice evidence does not support obtaining CT scans of the brain before the LP unless the patient has or recently has had CNS-related disease or events such as cerebrovascular accidents or seizures, severe changes in mental status, focal neurological deficits, immune-suppression status (HIV infection, cancer), or signs or symptoms that maybe indicate increased intracranial pressure (eg, papilledema).
Hasbun and colleagues1 found that patients who underwent a CT of the brain before LP had a 2-hour delay in diagnosis and a 1-hour delay in initiation of therapy. A delay of 1 hour or more before initiation of antibiotics for suspected meningitis has been associated with higher mortality and additional negative outcomes.3
References
1. Hasbun R, Abrahams J, Jekel J, Quagliarello V. Computed tomography of the head before lumbar puncture in adults with suspected meningitis. N Engl J Med. 2001;345:1727-1733.
2. Kanegaye JT, Soliemanzadeh P, Bradley JS. Lumbar puncture in pediatric bacterial meningitis: defining the time interval for recovery of cerebrospinal fluid pathogens after parenteral antibiotic pretreatment. Pediatrics. 2001;108:1169-1174.
3. Kumar A, Roberts D, Wood K, et al. Duration of hypotension before initiation of effective antimicrobial therapy is the critical determinant of survival in human septic shock. Crit Care Med. 2006;34:1589-1596.
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