For example in the patient who has an acute neurological deterioration prior to CT scanning and surgical intervention. Hyperventilation should not take the PaCO 2 level to below 3.5- 4 kPa as there is minimal beneficial effect on ICP below this level. Occasionally hyperventilation may be necessary for longer periods in patients with persistently high ICPs who have not responded to other treatment modalities. Persistent hyperventilation should not be used in the first 24 hours and preferably not within the first 5 days following brain injury. Intravenous fluid therapy Patients with severe brain injury should be kept normovolaemic.
Dehydration has little effect on cerebral oedema.
Elevated blood sugar levels are associated with a worsening of neurologic injury after episodes of global cerebral ischaemia. Ischaemic brain metabolises glucose to lactic acid, lowering tissue pH and potentially exacerbating ischaemic injury. Hypertonic solutions and osmotic diuretics such as mannitol will have the opposite effect. This mechanism requires an intact blood brain barrier. If this is damaged, as may be the case following injury, low molecular weight, osmotically active particles may leak into the cerebral interstitium.