[Subarachnoid hemorrhage: cerebral damage, fluid balance, intracranial pressure and pressure-volume relation]

Monitoring neurologic patients in intensive care

The brain is sensitive to changes in substrate delivery. In neurologically critically ill patients (e.g., those with head injury, subarachnoid hemorrhage, or stroke), interruption of this supply causes ischemic brain damage and thus impairs the outcome. To prevent, detect, and treat these ischemic events as soon as possible, the cerebral blood flow is continuously monitored, its coupling or not with the consumption of oxygen and so forth, and the detected derangements of normal physiology. Intracranial pressure and cerebral perfusion pressure are two parameters that often reflect ischemic events, and thus it is mandatory to continuously measure them. To better assess cerebral hemodynamics, jugular bulb oxymetry and brain pressure tissue oxygen monitoring are two neuromonitoring techniques that allow for a better understanding of the balance between oxygen supply and consumption, and therefore are useful in directing therapy. Transcranial Doppler ultrasonography is a noninvasive technique with the same purpose but with less clinical relevance. The new neuromonitoring technique, microdialysis, is useful for understanding the mechanisms involved in brain ischemia. However, it is clear that the physician who interprets the measurements given by devices and the clinical data (e.g., temperature, glycemia) is still the cornerstone in the management of neurologically critically ill patients.

The possible role of CSF hydrodynamic parameters following in management of SAH patients

It is suggested that reduced intracranial compliance may be present even when measured ICP is normal and may precede clinical deterioration. Our findings reflect a decompensation of hydrodynamic parameters more pronounced 4-7 postictal days, when compliance is reduced not only in patients with poor clinical condition, but also in patients with Hunt-Hess grade I-III. Increased CSF outflow resistance in the first few days is not surprising; it is thought to be due to the blockage of flow of CSF through the basal subarachnoid cisterns and clogging of the arachnoid villi with erythrocytes and fibrin. Enlargement of ventricles seen on CT scan at the same time suggests the development of acute hydrocephalus. During the first days after SAH, our data reflects evidence of ventricular enlargement in patients presenting with both poor and better clinical condition. We conclude that the monitoring of ICP and dynamic measuring of CSF hydrodynamic parameters is important for longer than the generally accepted few days for selected cases after SAH.