Elsevier

Digestive and Liver Disease

Volume 47, Issue 9, September 2015, Pages 769-774
Digestive and Liver Disease

Liver, Pancreas and Biliary Tract
Bispectral index monitoring for diagnosis and assessment of severity of hepatic encephalopathy in cirrhotic patients

https://doi.org/10.1016/j.dld.2015.04.014Get rights and content

Abstract

Background

Recent evidence suggests that bispectral index may aid in the diagnosis of hepatic encephalopathy. We evaluated its utility to diagnose, grade and monitor clinical course of hepatic encephalopathy in patients with cirrhosis.

Methods

200 patients (70.5% males, mean age 39.5 ± 9.1 years) with cirrhosis and 20 healthy controls were enrolled prospectively. Cirrhotic patients were divided into groups based on encephalopathy grades I–IV assessed by West Haven criteria; minimal encephalopathy was assessed by psychometric tests. Bispectral index was measured at baseline and after one week of lactulose therapy in patients with overt encephalopathy, and after 3 months in patients with minimal encephalopathy.

Results

Bispectral index scores were significantly different in patients with different grades of encephalopathy; 79.5 ± 4.2, 67.5 ± 4.3, 56.4 ± 3.5, 44.8 ± 3.9 and 85.0 ± 4.3 respectively for grade I, II, III, IV overt and minimal hepatic encephalopathy, but similar (92.6 ± 3.7 vs 93.75 ± 2.8) in cirrhotics without encephalopathy and healthy controls. Bispectral scores’ cut off values for minimal and overt encephalopathy grade I, II, III, IV were 90.5 and 77.5, 70.5, 60.5, 50.5, respectively. Changes in bispectral index after treatment corresponded to cut-off scores for grades of overt and minimal hepatic encephalopathy.

Conclusions

Bispectral index was found to be useful in diagnosis, grading and monitoring of treatment response in cirrhotic patients with hepatic encephalopathy.

Introduction

Hepatic encephalopathy (HE) includes a spectrum of neuropsychiatric abnormalities seen in patients with liver dysfunction diagnosed after exclusion of other known causes [1].

HE is a challenging complication of advanced liver disease, occurring in approximately 30–45% of patients with cirrhosis [2], [3] and 10–50% of patients with transjugular intrahepatic portosystemic shunt [4], [5].

HE is broadly divided into overt and minimal HE (MHE). MHE represents the mildest form of HE in which there are no clinically overt symptoms, but patients have abnormal neuropsychologic and/or neurophysiologic findings indicative of cerebral dysfunction [6]. The prevalence of MHE in cirrhosis varies from 30 to 80% in various studies [7], [8].

The International Working Party acknowledged the difficulties associated with the diagnosis of HE [1]. It was suggested that this condition is best diagnosed by combining clinical grading of the mental state using West Haven criteria [9], psychometric tests [10], and where possible a quantitative neurophysiological measure such as electroencephalography (EEG).

However, psychometric tests are only suitable above a certain age and educational background [10], while EEG is time consuming and not always readily available. Also, most clinical systems are mired in subjectivity until the end stage of coma is reached and are not reproducible among examiners [11], with a lack of objectivity in clinical diagnosis of HE. West Haven criteria are used for staging overt HE while neuropsychiatric and neurophysiological tests (psychometric hepatic encephalopathy score) are used for diagnosis of MHE. However objective methods for evaluation of the entire spectrum of no, minimal and overt HE are lacking [12]. Also, as yet there is no gold standard for grading or monitoring the progression of HE.

The Bispectral index (BIS) is a recent technology used to measure the effects of anaesthetics and sedatives on the brain and consciousness. It uses a complex mathematical algorithm based upon descriptive EEG parameters from the frontal cortex to suggest various levels of sedation. BIS is the weighted sum of three sub parameters: “Beta Ratio”, a frequency domain feature; relative synchrony of fast and slow wave, “SynchFastSlow”, a bispectral domain feature; and “Burst suppression ratio”, a time domain feature. The BIS analysis uses a proprietary algorithm that allows different descriptors to dominate sequentially as the EEG changes its character [13]. A sensor placed on the patient's forehead sends raw EEG waveforms to the monitor, where they are analyzed and the BIS index is calculated which ranges from 0 (isoelectric EEG) to 100 (completely awake) [13], [14].

A recent study by Dahaba et al. [15] has shown the utility of BIS in overt HE and concluded that it is a useful measure for grading and monitoring the degree of involvement of the central nervous system in patients with chronic liver disease.

We aimed to evaluate the role of BIS to diagnose minimal and overt HE, to grade HE levels, and monitor the response of overt HE and minimal HE to treatment.

Section snippets

Patients and methods

The study was conducted in the Department of Gastroenterology at G. B. Pant Hospital, New Delhi, India from February 2014 to September 2014. It was a prospective case control, observer blinded study evaluating the role of BIS in patients with overt and minimal HE (Clinical Trial Registration number, CTRI/2014/03/004493).

Consecutive cirrhotic patients attending the outpatient department or admitted to the Gastroenterology ward of GB Pant Hospital were eligible for the study. Written informed

Results

Overall 324 patients with cirrhosis were screened, of whom 140 had no overt HE while 184 patients had overt HE. Of all patients with overt HE, 64 patients were excluded due to following reasons (34.7%): lactulose therapy (n = 38), history of stroke (n = 3), history of sedatives (n = 4), agitation during the procedure (n = 11), sleeping during the procedure (n = 8). Of the remaining 120 patients with overt HE (65.2%), 30 patients were enrolled in each of the four groups based on grades of HE (grade I to

Discussion

Our study has shown completely different BIS score between cirrhotics without HE, with MHE and with overt HE. Ours is the first study to diagnose MHE based on BIS score. Earlier Dahaba et al. [15] conducted study for overt HE and their cut off values were 95 for controls vs HE grade I; 87.8 for grade I vs grade II; 70.2 for grade II vs grade III; and 54.4 for grade III vs grade IV. The reason for differences in BIS cut off values for higher grade of HE may be due to non inclusion of MHE

Conflict of interest

None declared.

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