, Volume 30, Issue 10, pp 1882-1885
Date: 09 Jul 2004

Intracranial pressure

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Introduction

Intracranial pressure (ICP) is a reflection of the relationship between alterations in craniospinal volume and the ability of the craniospinal axis to accommodate added volume. It cannot be estimated without directly measuring it.

Systemic physiological variables and intracranial pressure

The physiological variables that regulate cerebral blood flow (CBF) are the factors that influence acute changes in ICP. Arterial carbon dioxide gas tension (PaCO2) has a near linear relationship with CBF within the physiological range, producing a 2–6% increase of CBF for each millimetre of mercury of PaCO2 rise. An inverse relationship links low arterial oxygen content and CBF.

A direct relationship exists between CBF and cerebral metabolic rate for oxygen and glucose. CBF is kept constant throughout the normal physiological range of arterial pressure in health. These responses are often impaired after acute injury and, importantly, the lower limit for pressure autoregulation may be increas