Meningitis and encephalitis — empiric therapy and CSF interpretation

Working diagnosis. Strongly suspected meningococcal disease — fever, meningism, reduced GCS and a non-blanching purpuric rash (NICE red flag: haemorrhagic non-blanching rash with lesions larger than 2 mm). Absence of a rash would not have excluded the diagnosis.^[2]

Resuscitation (ABCDE). Resuscitation bay, monitoring, two large-bore cannulae. Treat shock, unprotected airway, respiratory compromise and uncontrolled seizures before any lumbar puncture. Droplet precautions.^[2]

Investigations that must not delay therapy. Draw blood culture, WCC, CRP or PCT, lactate, and whole-blood meningococcal/pneumococcal PCR. Perform LP before antibiotics only if it is safe and will not delay the first dose. Do not LP through extensive or rapidly spreading purpura. Bloods, antibiotics and stabilisation come before imaging.^[2]

Empiric therapy — within 1 hour of arrival.

• Ceftriaxone at the highest BNF/BNFC dose (UKHSA/BNFC adult pre-hospital dose for suspected IMD: 2 g IV/IM stat).^[2][10]
• Dexamethasone 10 mg IV with or before the first antibiotic if possible (de Gans: 10 mg every 6 hours for 4 days). Do not delay the antibiotic to wait for the steroid; if the steroid is delayed less than 12 hours, still give it. NICE does not routinely continue corticosteroids once the disease is meningococcal.^[5][2]
• At age 22 without immunocompromise, Listeria cover is not implied by NICE “risk factors” language; add aciclovir 10 mg/kg IV 8-hourly only if HSV encephalitis is strongly suspected (NICE: do not routinely give aciclovir).^[2]

Public health. Notify the health-protection team. Close-contact chemoprophylaxis (UKHSA): ciprofloxacin 500 mg orally once (12 years and over) first-line; rifampicin 600 mg twice daily for 2 days if ciprofloxacin cannot be used; IM ceftriaxone 250 mg (12+) if rifampicin cannot be offered. An index case already treated with ceftriaxone does not need carriage-eradicating prophylaxis.^[10]

Disposition. ICU/HDU if shock, falling GCS, seizures, or organ failure. If meningococcus is confirmed and the patient has recovered, NICE stops antibiotics after 5 days.^[2]