Simple detecting of elevated ICP through liquor flow after lumbar puncture

Abstract

Elevated intracranial pressure (ICP) is defined as a cerebrospinal fluid (CSF) opening pressure (OP) greater than 25 cmH2O. When a diagnostic lumbar puncture is performed it is useful to estimate also intracranial pressure. To do this it is required a presence of pressure gauges, which are currently the gold standard, not available in most resource-constrained contexts. We decided to evaluate whether it is possible to estimate it simply by counting the drops of cerebrospinal liquor, which are collected after lumbar puncture, according to Poiseuille's law. Was examined a sample of 52 patients, aged between 18 and 85 years, belonging to the emergency room of "Santa Maria delle Grazie" Hospital in Pozzuoli (Naples) who needed a diagnostic lumbar puncture (LP). The ICP was initially measured using a standard narrow-gauge manometer by attaching it to the spinal needle. After removing the pressure gauge, the number of drops of cerebrospinal fluid flowing from the spinal needle in 30 seconds was counted. A statistical analysis was made with linear regression and ROC analysis. OP as measured by standard manometry was raised on 17 occasions with CSF drop rate median of 47 drops/30 seconds and range 30-74 drops/30 seconds. OP was normal on 35 occasions with CSF drop rate median of 23 drops/30 seconds with range of 14-34 drops/30 seconds. A linear regression analysis was performed which resulted in a Pearson correlation of 0.936 an adjusted R square of 0.874 (see Fig. 1). Analysis through ANOVA documented an F of 355.301 with p < 0.01 and Dubin Watson of 1.642. The analysis through ROC showed an AUC of 0.980, with a sensitivity of 100% and a specificity of 91% if chosen as a limit, 29 drops in 30 seconds (Youden Index of 0.9140). Therefore, we have concluded, that although there are several precautions, like patient's position, it is technically feasible to indirectly estimate cerebrospinal fluid pressure with good accuracy by counting the drops of cerebrospinal fluid flowing from a 22 G spinal needle.

Keywords: ICP monitoring; Intracranial pressure; Liquor drops; Lumbar puncture; Open pressure.