Supportive care

There has been increasing recognition that antibiotic administration is only one component of management of patients with meningitis. Neurological derangement often coexists with circulatory insufficiency, impaired respiration, metabolic derangement, and convulsions. Measures to detect and correct any coexisting physiological derangement are important in improving prognosis.

Management of raised intracranial pressure

Elevated ICP is almost universal in bacterial meningitis. Signs of raised ICP include altered level of consciousness, altered pupillary responses, hyper- or hypotension, reduction in resting pulse rate, and altered respiratory pattern. Papilledema is a late sign of raised ICP. Raised ICP should be suspected in any patient with a severely depressed level of consciousness and measures should be instituted in order to prevent brainstem compression and herniation.

Simple measures to reduce ICP include nursing the patient in a quiet environment in a head-up position at 20° to 30° from horizontal. Other interventions include the use of osmotic agents, fluid restriction, and control of cerebrovascular tone through manipulation of arterial CO 2 concentration.

Patients with bacterial meningitis may have been vomiting or have had reduced fluid intake in the days preceding admission. Further fluid restriction may impair circulating volume and further reduce cardiac output. In the past, emphasis on the possibility of inappropriate ADH secretion (SIADH) has led to the practice of fluid restriction in all patients with meningitis, even in the face of severe hypovolemia. Recent studies indicate that increased levels of ADH, which are seen in individuals with meningitis, represent an appropriate response to dehydration. With adequate rehydration the level returns to normal.

Correction of hypovolemia improves cardiac output and may have a beneficial effect on cerebral blood flow. In patients with incipient shock, the use of inotropic agents as well as colloid infusions may be important in optimizing cerebral perfusion.

Sedation and control of convulsions

A patient with a significantly reduced level of consciousness due to bacterial meningitis should not be sedated, even if extremely irritable or combative. Irritability or combativeness may indicate hypoxia due to disturbed respiratory drive. The addition of hypnotic or tranquilizing agents may precipitate respiratory failure or respiratory arrest and a further rise in ICP. Simple analgesics or antipyretic agents alone should be used in those patients who are not critically ill. Patients who require endotracheal intubation and mechanical ventilation should receive a combination of drugs to provide analgesia, amnesia, and sedation, occasionally with a muscle relaxant.

Barbiturates have been used to treat refractory raised ICP. However, large doses of barbiturates may impair cardiac output and should only be used in patients with cardiovascular stability who should be carefully monitored. Thiopental (thiopentone) is particularly useful for induction of anesthesia prior to endotracheal intubation in patients with raised ICP.

Seizures occur within 48 h of presentation in 20 to 30 per cent of patients with bacterial meningitis. Seizures are particularly dangerous in patients with raised ICP as they cause extreme metabolic demands and increased cerebral blood flow, and may precipitate a further rise in ICP. Convulsions may be difficult to detect in patients who are pharmacologically paralysed for mechanical ventilation. In such patients cerebral function monitoring should be used to detect seizure activity. The use of anticonvulsant treatment in non-ventilated patients may precipitate respiratory arrest; therefore careful observation of ventilation should be undertaken during the treatment of seizures. Short-acting anticonvulsants (e.g. diazepam or paraldehyde) can be used to control acute seizures, and barbiturates or phenytoin are generally used for longer-term control (B.eikowit.z ...§! §L 1996.)

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