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.


1


Introduction


Elevated intracranial pressure (ICP) is a potentially fatal complication of a brain injury. Elevated ICP can complicate several pathologies, including head trauma, central nervous system (CNS) tumors, hydrocephalus, hepatic encephalopathy, cerebral vein thrombosis, and even cerebral ischemia [ ]. It is defined as a cerebrospinal fluid (CSF) opening pressure (OP) greater than 25 cmH2O. Effective management of patients with elevated ICP requires early recognition and therapy directed both at reducing ICP and treating its underlying cause [ ].


Therefore, when a diagnostic lumbar puncture is performed in the suspicion of an infectious, vascular, or inflammatory process of the nervous system it is useful to estimate, in addition to the biochemical parameters of CSF, also ICP routinely. To do this is required a presence of pressure gauges, which are currently the gold standard [ ]. However, they are not available in most resource-constrained contexts. There are other methods for estimating ICP indirectly including transcranial Doppler, like measuring the optic nerve sheath diameter 3 mm behind the eye or evaluate PI index on cerebral flow [ , ]. However, this method may be influenced by the examiner’s experience [ ]. We decided to evaluate whether it is possible to estimate ICP simply by counting the drops of cerebrospinal liquor, which are collected after lumbar puncture, according to Poiseuille’s law, Δρ =  (ηL/πr 4 )Qv. In this formula, L represents the length of the pipe, r its radius, η the viscosity coefficient of the fluid and Qv the flow rate of the pipe. Poiseuille’s law can be interpreted as a law of proportionality between the cause, Dp, which causes the flow and the effect, Q, which follows according to a constant of proportionality based on geometric characteristics of duct, fluid’’s viscosity, and hydraulic resistance, named R. Therefore, velocity of the flow of a liquid through a tube is directly proportional to the pressure difference between each end. It may be possible to indirectly determine ICP by measuring the flow of cerebrospinal fluid through a spinal needle instead of using a pressure gauge. We then carried out a prospective collection of data, relating the number of cerebrospinal CSF drops taken from patients with the intracranial pressure measured through a pressure gauge.


2


Methods


A sample of patients belonging to the emergency room of “Santa Maria delle Grazie” Hospital in Pozzuoli (Naples) who needed a diagnostic lumbar puncture (LP) was examined. The latter was performed from the same operator with sterile technique through a 22 G spinal needle (which are typically color-coded black) of 90-mm length. Patients aged between 18 and 85 years were consecutive enrolled between March and July 2023. The ICP was initially measured using a standard narrow-gauge manometer by attaching it to the spinal needle and allowing CSF to rise to a constant height with the patient lying in a lateral position. After removing the pressure gauge, the number of drops of cerebrospinal fluid flowing from the spinal needle in 30 seconds  was counted.


2.1


Statistical analysis


A linear regression was made between the number of drops in 30 seconds  and the intracranial pressure measured with a pressure gauge. Subsequently, a Receiver Operating Characteristic (ROC) analysis was performed to evaluate the accuracy of this method to predict an increase of intracranial pressure. Finally, the positive and negative predictive value were calculated. All statistical analyses were performed using SPSS 2022, version 29.0.


3


Results


From March and July 2023, 52 patients were recruited, including 27 males and 25 women. The median age was 53 years. The most frequent conclusive diagnosis was delirium (17 patients), followed by cerebral hemorrhage (11 patients), cerebral ischemia (8 patients), cerebral neoplasia (3 patients); Chronic Inflammatory Demyelinating Polyneuropathy (3 patients); Botulism (2 patients); Herpetic Meningitis (2 patients), Cryptococcal Encephalitis in HIV (2 patients), Idiopathic Intracranial Hypertension (2 patients), Hemiplegic Migraine (2 patients). 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 (see Table 1 ). The analysis through ROC showed an AUC of 0.980 (see Fig. 2 ), 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, see Table 2 ). This value allows to obtain a positive predictive value of 81% and a negative predictive value of 94%.


Tags:
Mar 29, 2024 | Posted by in EMERGENCY MEDICINE | Comments Off on Simple detecting of elevated ICP through liquor flow after lumbar puncture

Full access? Get Clinical Tree
Get Clinical Tree app for offline access