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Delaying bacterial meningitis therapy can be fatal; start antibiotics before diagnostic tests.

CHICAGO -- Delay in administering antibiotics is an extremely powerful predictor of mortality in adults with acute bacterial meningitis, Dr. Normand Proulx reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

The red flag appears to be a 6-hour or greater duration between presentation to the ER and initiation of antibiotic therapy. In Dr. Proulx's review of 123 adults who were diagnosed with acute bacterial meningitis at the Ottawa Hospital, 13% of whom died, a 6-hour time lapse prior to administration of antibiotics was independently associated with an 8.3-fold increased risk of mortality.

The effect of a time delay was incremental. Delays of 8-10 hours were associated with higher mortality than delays of 6 hours, added Dr. Proulx of the University of Ottawa.

In his review, delays of 6 hours or longer generally came about in one of two ways. One involved transfer of patients by ambulance from a community hospital to the tertiary care hospital without first giving antibiotics. This is a common but problematic practice. Only 53% of patients in the Ottawa study with subsequently confirmed bacterial meningitis received antibiotics prior to transfer, and in published studies elsewhere the rate is consistently below 50%, he said at the meeting, sponsored by the American Society for Microbiology.

The other major contributor to delay in initiating antibiotics was reliance upon an inappropriate diagnostic/treatment sequence. In 22% of cases, physicians ordered a CT scan of the head first, then a lumbar puncture to confirm the diagnosis of bacterial meningitis, and only then gave antibiotics. This sequence was associated with a 5.6-fold increased likelihood of a 6-hour or greater delay.

The preferable approach is to begin with the antibiotics and then follow-up with the confirmatory studies when acute bacterial meningitis is suspected, as in patients with the classic triad of neck stiffness, altered mental status, and fever. In the 32% of study patients who were managed in this way, the mean time from arrival at the ER to antibiotic administration was 2.5 hours, Dr. Proulx continued.

Many physicians feel that they need to order a CT scan prior to a lumbar puncture in order to identify patients at risk of brainstem herniation due to the invasive test. In reality, the CT scan typically adds little information.

"I think there is a culture, a belief out there, that you must do a CT scan before lumbar puncture. But there's been a very good study which clearly shows that in the absence of a series of very practical clinical findings that can be assessed in the ER, you are almost assured to have a normal CT scan of the head, so you can go straight to lumbar puncture," he said.

He was referring to a prospective Yale University study involving 301 adults with suspected meningitis. Among those who were under age 60 years, immunocompetent, had no history of CNS disease, no history of seizures in the prior week, and were free of specific neurologic abnormalities, the CT scans were normal and there was no evidence of brain herniation following subsequent lumbar puncture.

Patients reliably had a normal CT scan if they did not have an abnormal level of consciousness; were able to answer two consecutive questions correctly or follow two consecutive commands; and didn't have facial palsy, gaze palsy, arm or leg drift, abnormal language, or abnormal visual fields (N. Engl. J. Med. 345[24]:1727-33, 2001).

In Dr. Proulx's study, other independent predictors of mortality in adults with acute bacterial meningitis--in addition to delayed use of antibiotics--were age greater than 60 years (4.4-fold increased risk), severely impaired mental status (12.6-fold increased risk), and afebrile presentation (39.4-fold increased risk).

He urged infectious disease specialists to push for implementation of ER pathways assuring early use of antibiotics in adults with suspected bacterial meningitis.
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Author:Jancin, Bruce
Publication:Internal Medicine News
Date:Nov 15, 2003
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