A comparison of simple identification tests to distinguish cerebrospinal fluid from local anaesthetic solution

Abstract

SummaryLocal anaesthetic solution is sometimes used to enlarge the epidural space in preparation for the insertion of an indwelling epidural catheter and during subsequent checking a small volume of fluid may be aspirated. Twelve anaesthetists were asked to distinguish 0.1 ml plain bupivacaine 0.25% from 0.1 ml simulated cerebrospinalfluid (CSF) solution. The distinction was based on differences in the physicochemical properties of the two test solutions, namely, temperature, presence of glucose, pH, and turbidity when mixed with thiopentone. Temperature difference resulted in correct identification of the two solutions in 75% of cases, the presence of glucose in 92%, pH in 83%, and turbidity in 25% of cases. No single test resulted in correct identification by all the anaesthetists. We suggest that more than one physicochemical test is required to identifv correctly the nature of the small volume of liquid which may be aspirated from an epidural catheter.

A comparison of epidural and cerebrospinal fluid glucose in parturients at term: an observational study

“…The volume of saline collected was not standardized, and this may be considered a study limitation since the volume injected may influence the volume leaking out. However, our observational study, unlike previous studies, 11,12 was designed to reflect clinical practice and therefore optimise external validity. The two dural punctures that occurred in the study were clinically obvious.…”

“…Studies by Walker and Brock-Utne 11 and Tessler et al 12 indicated that a sample size of 40 patients in each group would be suitable for an observational study. Data are presented using descriptive statistics and Kruskal-Wallis equality-of-populations rank test for testing differences between CSF and epidural fluid glucose for both glucometer and laboratory readings.…”

“…Previous studies have used qualitative and semi-quantitative methods, including pH and glucose measurements using urinary dipstick reagent strips. [10][11][12] Dural punctures generally occur during insertion of the epidural needle, 13 and therefore a bedside glucometer was used to measure glucose content at that time.…”

“…Several techniques to distinguish between CSF and saline have been proposed, including testing for the presence of protein or glucose, temperature, pH and changes in turbidity when mixed with thiopental. [10][11][12] No single test is reliable and all are qualitative tests that generally use CSF substitutes rather than real CSF. 11,12 No quantitative tests to distinguish between CSF and saline during epidural catheter insertion have been described.…”

“…[10][11][12] No single test is reliable and all are qualitative tests that generally use CSF substitutes rather than real CSF. 11,12 No quantitative tests to distinguish between CSF and saline during epidural catheter insertion have been described. Although bedside testing for glucose may be diagnostic for CSF, this has not been formally tested.…”