Erroneous measurement of intracranial pressure caused by simultaneous ventricular drainage: a hydrodynamic model study
Department of Quantitative Health Sciences; Meyers Primary Care Institute; Department of Surgery
Brain; Cerebral Ventricles; *Cerebrospinal Fluid Shunts; Humans; *Intracranial Pressure; *Models, Neurological
Biostatistics | Epidemiology | Health Services Research | Neurology
Intracranial pressure (ICP) is often measured from intraventricular catheters, a technique that allows therapeutic drainage of ventricular cerebrospinal fluid (CSF) as an aid in controlling ICP and circumventing obstruction. Drainage of CSF simultaneously with ongoing ICP measurement has been advocated as safe and efficient, and devices are commercially available to permit this practice; however, this concept has been seriously challenged, based on clinical observations. The inaccuracy induced by simultaneous CSF drainage and ICP monitoring is quantitated in this report in a mechanical brain model using a standard ventricular catheter. The following conclusions have been confirmed: 1) rapid CSF drainage induces a severe artifactual reduction in measured ICP, more extreme at higher pressures; 2) calibrated slower rates of CSF drainage produce a severe, although less immediate, reduction in measured ICP; 3) severe artifact appears even in the presence of continuous CSF outflow, so a system that measures ICP only in the presence of CSF flow does not prevent artifact; 4) with simultaneous CSF drainage, measured ICP is determined more by the outflow pressure setting than by actual brain pressure; 5) Since ICP elevation of 25 to 30 mm Hg blocks CSF production, even slow fluid drainage at high pressures should ultimately lead to ventricular collapse and severe artifact.
Neurosurgery. 1989 Mar;24(3):348-54. Link to article on publisher's site
Wilkinson, H. A.; Yarzebski, Jorge L.; Wilkinson, E. C.; and Anderson, Frederick A. Jr., "Erroneous measurement of intracranial pressure caused by simultaneous ventricular drainage: a hydrodynamic model study" (1989). Quantitative Health Sciences Publications and Presentations. 760.