Intracranial pressure (ICP) is derived from cerebral blood and cerebrospinal fluid (CSF) circulatory dynamics and can be affected in the course of many diseases of the central nervous system. Monitoring of ICP requires an invasive transducer, although some attempts have been made to measure it non-invasively. Because of its dynamic nature, instant CSF pressure measurement using the height of a fluid column via lumbar puncture may be misleading. An averaging over 30 minutes should be the minimum, with a period of overnight monitoring in conscious patients providing the optimal standard. Computer-aided recording with online waveform analysis of ICP is very helpful.
Although there is no “Class I” evidence, ICP monitoring is useful, if not essential, in head injury, poor grade subarachnoid haemorrhage, stroke, intracerebral haematoma, meningitis, acute liver failure, hydrocephalus, benign intracranial hypertension, craniosynostosis etc. Information which can be derived from ICP and its waveforms includes cerebral perfusion pressure (CPP), regulation of cerebral blood flow and volume, CSF absorption capacity, brain compensatory reserve, and content of vasogenic events. Some of these parameters allow prediction of prognosis of survival following head injury and optimisation of “CPP-guided therapy”. In hydrocephalus CSF dynamic tests aid diagnosis and subsequent monitoring of shunt function.
- intracranial pressure
- waveform analysis
- ABP, arterial blood pressure
- AMP, pulse amplitude of ICP
- CBF, cerebral blood flow
- CPP, cerebral perfusion pressure
- CSF, cerebrospinal fluid
- ICP, intracranial pressure
- PRx, pressure-reactivity index
- RAP, index of compensatory reserve
- Slow, magnitude of slow waves of ICP
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↵* M Czosnyka is on leave from Warsaw University of Technology, Poland.
Grant support: Medical Research Council No G9439390 ID 65883.
Competing interests: none declared
This review is complementary to a review of raised ICP published in Hughes RAC, ed. Neurological Emergencies. London: BMJ Books, 2003.