Bacterial meningitis in children: pathophysiology and treatment.

Recent studies of the pathophysiology of bacterial meningitis have suggested that the development of neuronal injury is related to the release of vasoactive substances or alteration of blood-brain barrier permeability. Cerebral edema, increased intracranial pressure (ICP), systemic hypotension, decreased cerebral perfusion pressure, vascular inflammation, thrombosis, and a variety of other vascular changes may result in global or regional reductions in cerebral blood flow (CBF), which contribute to this insult. Approximately one-third of infants and children with bacterial meningitis will have markedly reduced CBF, and even in those children with normal total flow, regional hypoperfusion is common. Reduced CBF is associated with cerebral edema and a poor prognosis. A poor prognosis also is associated with reduced cerebral perfusion pressure. This occurs early in the course of meningitis and is primarily due to increased ICP rather than systemic hypotension. Autoregulation is preserved, suggesting that local ischemic tissue injury is more related to factors such as regional edema formation, focal vascular pathology, or specific intrinsic flow/metabolic abnormalities than to a reduction in systemic blood pressure. In contrast with other acute CNS insults, CBF/PCO2 reactivity is well preserved in many patients with meningitis; this raises the possibility that hyperventilation may cause further ischemic injury in those patients with marginal CBF. Although it is still unclear that treatment of increased ICP will affect outcome, we propose a treatment paradigm based on the results of neuroimaging studies and ICP measurements.