Emergency Neurologic Life Support: Meningitis and Encephalitis

DOI: https://doi.org/10.1007/s12028-017-0455-y

Abstract-Summary Bacterial meningitis and viral encephalitis, particularly herpes simplex encephalitis, are severe neurological infections that, if not treated promptly and effectively, lead to poor neurological outcome or death.

Because of the value of early recognition and treatment, meningitis and encepha-

litis was chosen as an Emergency Neurological Life Support protocol.

This protocol provides a practical approach to recognition and urgent treatment

of bacterial meningitis and encephalitis.

Extended: Bacterial meningitis and bacterial or viral encephalitis are medical, neurologic, and, occasionally, neurosurgical emergencies which carry substantial morbidity and mortality despite modern medical management.

Introduction The two conditions that are most important to recognize in the first hour are bacte- rial meningitis and herpes encephalitis, as these diseases produce significant mor- bidity and mortality and have specific treatments that can improve patient outcome if administered quickly.

In one study, 48% of patients with bacterial meningitis presented within 24 h of

the onset of symptoms [389].

Patients who have a hyper-acute (hours) to acute (hours to days) onset of head- ache and altered mental status should be considered as potentially having meningi- tis or encephalitis.

In a large series of 696 adult patients with bacterial meningitis, the classic triad of fever, neck stiffness, and change in mental status was present in only 44% of patients, but 95% of patients had at least two symptoms when a fourth symptom— headache—was added to the classic triad [389].

Prehospital Considerations In the prehospital setting, EMS personnel should approach the patient based upon the chief complaint, assess the basic ABCs of resuscitation (i.e., Airway, Breathing,

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Circulation), and begin management as appropriate for the severity of the patient’s presentation and the training level of the EMS providers.

This may include obtaining basic vital signs, formal assessment of mental status uti- lizing the Glasgow Coma Score (GCS), measurement of serum glucose levels, placement of intravenous (IV) access, initiation of IV fluid resuscitation, and airway management.

If IV access cannot be rapidly obtained in an unstable patient, placement of an

intra-osseous (IO) cannula should be considered.

Initial Assessment Patients with bacterial meningitis are at risk for lung or bloodstream infections with the same pathogen, further reinforcing the need to closely monitor vital signs and hemodynamics.

In guidelines focusing on initial resuscitation, the Surviving Sepsis Campaign recommends beginning resuscitation immediately in patients with hypotension (systolic blood pressure < 90 mmHg; MAP < 65 mmHg) or a serum lactate of ≥4 with an initial fluid challenge of 30 ml/kg of crystalloid in the first 3 h. These recom- mendations changed from the strict algorithmic resuscitation model of the prior iterations to a more flexible model stressing rapid diagnosis and rapid administra- tion of fluids and antibiotics, followed by careful monitoring and reassessment of hemodynamic status with further fluid boluses as needed [390, 391].

CBC and CT In compliance with the Infectious Disease Society of America (IDSA) Practice Guidelines for the Management of Bacterial Meningitis [392], cranial computed tomography (CT) should be done prior to LP if the patient is at least 60 years of age, has a history of CNS disease (e.g., mass lesion, stroke, and focal infection), presents in an immunocompromised state (e.g., HIV infection or AIDS, immunosuppressive therapy, or transplantation), has had a history of seizure within 1 week before pre- sentation, or possesses certain specific abnormal neurologic findings (e.g., an abnor- mal level of consciousness, an inability to answer two consecutive questions correctly or to follow two consecutive commands, gaze palsy, abnormal visual fields, facial palsy, arm drift, leg drift, abnormal language).

Suspicion of Infection In the Initial Management and CBC and CT sections above, head CT prior to LP should be performed in the patient with suspected CNS infection when any of the following are present: papilledema or loss of venous pulsations on funduscopic examination; focal neurological signs; immunocompromised patients; known mass lesions; or seizures within 1 week of the presentation.

In patients who do not present with these signs, have normal mental status, and

have no focal neurologic deficits, a head CT is not always required prior to LP.

In most patients who have a clinical presentation consistent with acute bacterial meningitis or encephalitis, there will be enough diagnostic uncertainty that CT is advisable prior to LP.

In a study of the need for head CT prior to LP among 301 patients with suspected

bacterial meningitis, 78% of patients had a head CT performed prior to LP [393].

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Start Antibiotics The applicability of these findings to patients with bacterial meningitis is limited by the small percentage of patients in each study who had primary CNS infections.

For suspected CNS infections that evolve over hours, bacterial meningitis, viral

meningitis, and, less commonly, viral encephalitis may be considered.

Common initial antibiotic dosing for adults with normal renal function suspected of having bacterial meningitis are as follows: Ceftriaxone 2 g IV q 12 h, Vancomycin 15–20 mg/kg IV every 8–12 h (not to exceed 2 g per dose or daily total of 60 mg/ kg; adjust to achieve trough concentration of 15–20 mcg/ml), and Ampicillin 2 g IV q 4 h. Vancomycin and trimethoprim–sulfamethoxazole can be used in patients with a severe penicillin allergy (aztreonam may be used for Gram-negative coverage).

For suspected CNS infections that evolve over days in an immunosuppressed

patient, fungal meningitis should be considered.

Lumbar Puncture (LP) After prepping and draping the patient in the usual, sterile fashion, and accessing the sub-arachnoid space with a spinal needle, the OP should be measured with a manometer prior to the collection of CSF.

CSF should be collected in a minimum of four tubes. Tubes 1 and 4 should be sent for red blood cell (RBC) and WBC counts; tube 2 for protein, glucose, and lactic acid; tube 3 for Gram’s stain, antigens, and culture (and India ink if fungal infection is suspected).

Larger volumes of CSF increase the sensitivity of a Gram’s stain and culture. Additional laboratory tests that may be performed at some centers include bacte- rial PCR (particularly for Mycobacterium), Herpes simplex PCR, enterovirus PCR, immunoglobulin M (IgM) for arboviruses, fungal antigens, and viral culture.

Clinicians should be aware of local laboratory policies regarding minimum

amounts of CSF required for Gram’s stain and culture.

Normal LP An LP is considered normal if there are no RBCs/high-powered field (HPF), fewer than five WBCs/HPF, the CSF glucose/serum glucose ratio is >0.67, the CSF pro- tein <50 mg/dL, and no organisms are seen on Gram’s stain.

If all of the above are true, meningitis is excluded, as is encephalitis in most cases.

Very High CSF White Cells The finding of a marked elevation in WBCs (neutrophils of 100–1000 per HPF or higher without a significant number of RBCs) is consistent with bacterial meningitis.

The CSF/serum glucose ratio will usually be significantly reduced (<0.67), and the CSF protein is usually markedly elevated and almost always >50 mg/ dL. Organisms are seen on Gram’s stain in approximately 70% of cases.

Mildly Elevated WBC and No RBCs A mild elevation in CSF WBCs without RBCs is consistent with a viral meningitis or viral (not herpes) encephalitis.

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WBCs often range from 10 to several 100 and the CSF possesses a normal CSF glucose/serum glucose ratio, and protein <50 mg/dL. Organisms are absent on the Gram’s stain.

Elevated WBCs and RBCs A patient with herpes encephalitis will typically have an elevated CSF RBC count (10–100/HPF or higher), WBCs in the hundreds/HPF (typically with a lymphocytic predominance), CSF glucose/serum glucose ratio >0.67, a protein level that may either be <50 mg/dL or elevated, and no organisms on Gram stain.

The presence of seizures and findings of uni- or bilateral hypodensities in the temporal lobes on brain MRI, and rarely on brain CT scans, are also compatible with this diagnosis.

Elevated RBCs or Xanthochromia If the CSF reveals an elevated RBC count (100–1000/HPF or higher), either a WBC count <5/HPF or fewer than 1 WBC/500 RBC, a CSF glucose/serum glucose ratio

0.67, and a protein <50 mg/dL; no organisms are seen on Gram’s stain; and xan- thochromia is detected, then the patient likely has suffered a subarachnoid hemor- rhage that was not detected on the CT scan.

Xanthochromia may be absent if the LP was done within the first few hours of

headache onset (when RBCs are typically not seen).

Bacterial Meningitis In patients with CSF demonstrating bacterial meningitis, clinicians should continue antibiotics, stop acyclovir, and continue dexamethasone.

To antibiotics and dexamethasone, supportive care and management of other

organ systems is important in patients with bacterial meningitis.

Some patients may have a concomitant bloodstream infection with the offend- ing pathogen and may require focused resuscitation for severe sepsis or sep- tic shock.

Viral Meningitis and Viral Encephalitis The treatment for herpes encephalitis has been discussed above.

The treatment of viral meningitis or non-herpetic viral encephalitis is primarily

supportive in nature.

Many of these patients will have a significantly depressed level of consciousness,

making close observation and airway management crucial.

Pediatric Considerations The empiric antibiotic regimen should be broadened in infants and children with immune deficiency, recent neurosurgery, penetrating head trauma, or other ana- tomic defects Adjunctive therapy with dexamethasone has been a topic of consider- able debate.

In a 2013 meta-analysis, the administration of dexamethasone did not affect overall mortality or long term neurological sequelae such as focal neurologic defi- cits, epilepsy, ataxia, and memory or concentration disturbance in children with bacterial meningitis.

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The American Academy of Pediatrics Committee on Infectious Diseases sug- gests that dexamethasone therapy may be beneficial in children with HiB menin- gitis if given before or at the same time as the first dose of antimicrobial therapy [394].

The committee also suggests that dexamethasone therapy be considered for infants and children with pneumococcal meningitis after weighing the potential risks and benefits.

As in the case of children with bacterial meningitis, the initial management includes restoration of normal oxygenation, ventilation, and perfusion, as well as detection and management of hypoglycemia, acidosis, and coagulopathy.

Communication Most patients with bacterial meningitis and viral encephalitis require the oversight and care that an ICU can provide.

Careful observation of the patient’s respiratory status and close monitoring of his

or her neurological exam with attention to decline is critical.

Acknowledgement A machine generated summary based on the work of Gaieski, David F.; O’Brien, Nicole F.; Hernandez, Ricardo. 2017 in Neurocritical Care.

Optimal management strategies for primary headache in the emergency department