CEREBROVASCULAR PRESSURE TRANSMISSION ANALYSIS AS A GUIDE TO THE PATHOPHYSIOLOGY OF RAISED INTRACRANIAL-PRESSURE

1. Raised intracranial pressure (ICP) is a major factor associated wit h morbidity and mortality in patients with severe head injury. Identif ying the mechanisms responsible for raised ICP may be difficult and, a s a result, treatment prescribed may be non-specific and often ineffec tive, 2. Research aimed at obtaining more information from measurement of ICP was initially focused on measurements of compliance. This aas achieved by introducing fluid volume into the craniospinal compartment and measuring the response. Although shown to be clinically useful, a ssociated technical problems have precluded the routine use of these m easurements. 3. Cerebrovascular pressure transmission (CVPT) analysis has been suggested as an alternative method of deriving more informati on from the ICP wave-form; Pressure transmission across the cerebrovas cular bed is assessed by a systems analysis approach whereby blood pre ssure and ICP wave-form pairs are resolved by fast Fourier transform a nalysis into component harmonic frequencies, each,vith a specific ampl itude and phase. These are expressed as a ratio or 'transfer function' for each harmonic peak, 4. Laboratory models have identified specific CVPT patterns associated with various causes of raised ICP. These stu dies have been extended to clinical practice and have been used to def ine patterns of CVPT in head-injured patients, which may be used to id entify mechanisms responsible for raised ICP, thus assisting in direct ing treatment strategy. Clinical usefulness of this technique in patie nt management is currently under investigation.