10 Intracranial Pressure Monitoring

Intracranial pressure (ICP) measurement is an extremely important part of the neurosurgical armamentarium. Not only is raised ICP the commonest cause of death in neurosurgical patients, it is extremely common in patients suffering from head injury. In this latter group, 40% of patients who are admitted in an unconscious state have raised ICP, and in 50% of those who die, raised ICP is the main cause (Miller et al., 1977). Numerous investigations have shown that sustained intracranial hypertension is associated with a poor prognosis (Becker et al., 1977; Johnston and Jennett, 1973; Langfitt, 1969; Narayan et al., 1982; Marshall, Smith and Shapiro, 1979a; Miller et al., 1981). The effective treatment of high ICP has been shown to decrease mortality (Marshall, Smith and Shapiro, 1979a, b). Even so, ICP must be measured before a diagnosis of raised ICP can be made. Obviously, an understanding of the principles of ICP measurement is an important prerequisite to considering the disturbances of brain function that follow head injury. The quest for developing the ideal method of recording ICP has been a difficult exercise. The first requirement for any method is that it is accurate; and it should also be safe and simple (North and Reilly, 1990). The search is still incomplete, since all current methods are invasive. The necessity to breach the skull to record ICP has resulted in a significant number of neurosurgeons being reluctant to embrace this technique. It took at least 15 years before ICP monitoring became fully accepted into clinical neurosurgical practice in more than a few centers. Even now, opinions vary as to the value of the technique, from those who claim that it makes no difference to the outcome of any neurosurgical disease to those who assert that it is an indispensable part of neurosurgical practice, without which many patients would surely die. The truth lies somewhere between these two extremes and it depends on the facilities and personnel available in any given neurosurgical unit (Miller, 1987).