Introduction to intracranial pressure monitoring Intracranial pressure monitoring remains a central tenet of neurocritical care monitoring and has the potential to improve outcome (1-3). While the importance of monitoring and controlling intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in traumatic brain injury is fairly well understood, its significance in acute cerebrovascular disease and the modulatory effect of therapies remain largely unexplored. This review helps to clarify basic principles and evidence for ICP monitoring and ICP-based treatment and applies these principles to the management of acute cerebrovascular disease. Principles of intracranial dynamics The intracranial contents (and average volumes in the adult male) contributing to the ICP are the brain (1300 mL), blood (110 mL) and cerebrospinal fluid (CSF) (65 mL) (4). In normal subjects, average ICP has been reported to be approximately 10 mmHg (5). According to the Monro-Kellie doctrine, because the intracranial contents are encased in a rigid skull and the components are relatively inelastic, change in the volume of one component must be compensated for by reduction in the volume of another component of the system or ICP will increase. Without this compensation, increased ICP may result in brain herniation by direct compression or ischemia/infarction by compromising cerebral blood flow (CBF). While arguably a simplification of the complex pathophysiology involved, the Monro-Kellie doctrine remains a helpful principle in understanding derangements in intracranial pressure.
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