Cerebrospinal fluid in critical illness.

OBJECTIVE To detail the physiology, pathophysiology and recent advances in diagnostic analysis of cerebrospinal fluid (CSF) in critical illness, and briefly review the pharmacokinetics and pharmaco-dynamics of drugs in the CSF when administered by the intravenous and intrathecal route. DATA SOURCES A review of articles published in peer reviewed journals from 1966 to 1999 and identified through a MEDLINE search on the cerebrospinal fluid. SUMMARY OF REVIEW The examination of the CSF has become an integral part of the assessment of the critically ill neurological or neurosurgical patient. Its greatest value lies in the evaluation of meningitis. Recent publications describe the availability of new laboratory tests on the CSF in addition to the conventional cell count, protein sugar and microbiology studies. Whilst these additional tests have improved our understanding of the pathophysiology of the critically ill neurological/neurosurgical patient, they have a limited role in providing diagnostic or prognostic information. The literature pertaining to the use of these tests is reviewed together with a description of the alterations in CSF in critical illness. The pharmacokinetics and pharmacodynamics of drugs in the CSF, when administered by the intravenous and the intrathecal route, are also reviewed. CONCLUSIONS The diagnostic utility of CSF investigation in critical illness is currently limited to the diagnosis of an infectious process. Studies that have demonstrated some usefulness of CSF analysis in predicting outcome in critical illness have not been able to show their superiority to conventional clinical examination. With further advances in our understanding of neurological function and refinement in biochemical analysis there remains the possibility of useful cerebrospinal fluid diagnostic and prognostic markers in the future.