Mechanism of the excessive sedative response of cirrhotics to benzodiazepines: model experiments with triazolam

Management of the acute on chronic liver failure in the intensive care unit

Acute on chronic liver failure (ACLF) reflects the development of organ failure(s) in a patient with cirrhosis and is associated with high short-term mortality. Given that ACLF has many different 'phenotypes', medical management needs to take into account the relationship between precipitating insult, organ systems involved and underlying physiology of chronic liver disease/cirrhosis. The goals of intensive care management of patients suffering ACLF are to rapidly recognize and treat inciting events (e.g. infection, severe alcoholic hepatitis and bleeding) and to aggressively support failing organ systems to ensure that patients may successfully undergo liver transplantation or recovery. Management of these patients is complex since they are prone to develop new organ failures and infectious or bleeding complications. ICU therapy parallels that applied in the general ICU population in some complications but differs in others. Given that liver transplantation in ACLF is an emerging and evolving field, multidisciplinary teams with expertise in critical care and transplant medicine best accomplish management of the critically ill ACLF patient. The focus of this review is to identify the common complications of ACLF and to describe the proper management in critically ill patients awaiting liver transplantation in our centres, including organ support, prognostic assessment and how to assess when recovery is unlikely.

Congenital Portosystemic Shunts in Dogs and Cats: Treatment, Complications and Prognosis

Congenital portosystemic shunts (CPSS) are a common vascular anomaly of the liver in dogs and cats. Clinical signs of CPSS are non-specific and may wax and wane, while laboratory findings can raise the clinical suspicion for CPSS, but they are also not specific. Definitive diagnosis will be established by evaluation of liver function tests and diagnostic imaging. The aim of this article is to review the management, both medical and surgical, complications, and prognosis of CPSS in dogs and cats. Attenuation of the CPSS is the treatment of choice and may be performed by open surgical intervention using ameroid ring constrictors, thin film banding, and partial or complete suture ligation or by percutaneous transvenous coil embolization. There is no strong evidence to recommend one surgical technique over another. Medical treatment strategies include administration of non-absorbable disaccharides (i.e., lactulose), antibiotics, and dietary changes, and are indicated for pre-surgical stabilization or when surgical intervention is not feasible. After CPSS attenuation, short- and long-term post-surgical complications may be seen, such as post-operative seizures and recurrence of clinical signs, respectively. Prognosis after surgical attenuation of CPSS is generally favorable for dogs and fair for cats.

The Perioperative Anesthetic Management of the Pediatric Patient with Special Needs: An Overview of Literature

The perioperative management of pediatric patients with psycho-physical disorders with related relational and cognitive problems must be carefully planned, in order to make the entire hospitalization process as comfortable and as less traumatic as possible. This article reports an overview of the anesthetic management of non-cooperative patients between 6 and 14 years old. The pathologies most frequently responsible for psycho-physical disorders can be summarized into three groups: (1) collaboration difficulties (autism spectrum disorders, intellectual impairment, phobia); (2) motor dysfunction (cerebral palsy, epilepsy, other brain pathologies, neuromuscular disorders), and (3) craniofacial anomalies (Down syndrome, other genetic syndromes). Anesthesia can be performed safely and successfully due to careful management of all specific problems of these patients, such as a difficult preoperative evaluation (medical history, physical examination, blood sampling, evaluation of vital parameters and predictive indices of difficult airway) and the inapplicability of a "standard" perioperative path (timing and length of the hospitalization, anesthetic premedication, postoperative management). It is necessary to ensure a dedicated perioperative process that is safe, comfortable, tailored to specific needs, and as less traumatic as possible. At the same time, all necessary precautions must be taken to minimize possible complications.

Novel Drugs for the Management of Hepatic Encephalopathy: Still a Long Journey to Travel

Hepatic encephalopathy (HE) is one of the reversible complications of chronic liver disease, associated with a higher mortality rate. In current clinical practice, treatment with rifaximin and lactulose/lactitol is the first line of treatment in HE. With the advance in pathophysiology, a new class of ammonia lowering drugs has been revealed to overcome the hurdle and disease burden. The mechanism of the novel agents differs significantly and includes the alteration in intestinal microbiota, intestinal endothelial integrity, oxidative stress, inflammatory markers, and modulation of neurotoxins. Most of the trials have reported promising results in the treatment and prevention of HE with fecal microbiota transplantation, albumin, probiotics, flumazenil, polyethylene glycol, AST-120, glycerol phenylbutyrate, nitazoxanide, branched-chain amino acid, naloxone, and acetyl-l-carnitine. However, their clinical use is limited due to the presence of major drawbacks in their study design, sample size, safety profile, bias, and heterogenicity. This study will discuss the novel therapeutic targets for HE in liver cirrhosis patients with supporting clinical trial data.

Hepatic impairment as a risk factor of adverse drug reactions

There are a lot of clinical variants of hepatic impairment ranging from asymptomatic increase in transaminases to acute liver failure and fulminant hepatitis. Hepatic impairment is a polietiologic syndrome. According to the epidemiological study conducted in the United States (19982008), the main causes of hepatic impairment were paracetamol overdose (46%), idiopathic liver dysfunction (14%), other drugs (excluding paracetamol, 11%), viral hepatitis B (7%), other infectious and non-infectious diseases with liver damage (except for viral hepatitis) 7%, autoimmune hepatitis (5%), ischemic hepatitis (syn. hypoxic hepatitis, liver infarction) 4%, viral hepatitis A (3%) and Wilson's disease (2%). Hepatic impairment have a direct impact on the pharmacokinetics and pharmacodynamics of drugs decreasing clearance, elimination and excretion of drugs. Also Transjugular intrahepatic porto-systemic shunts, which are often used to treat portal hypertension in patients with liver cirrhosis, can significantly reduce the presystemic elimination of drugs, thereby increasing their absorption. Moreover, in patients with liver cirrhosis, concomitant renal dysfunction also requires an adjustment of the dose of drugs. Correction of pharmacotherapy in accordance to pharmacokinetic and pharmacodynamic changes of drugs ingested by patients with impaired liver function will improve the quality of medical care and reduce the risks of adverse drug reactions.

Novel Agents in the Management of Hepatic Encephalopathy: A Review

Hepatic encephalopathy is an often devastating complication of chronic liver disease, associated with high mortality and increased burden on patients and healthcare systems. Current agents (such as nonabsorbable disaccharides and oral antibiotics) are often only partially effective and associated with unpleasant side effects. With our improved understanding of the pathophysiology of hepatic encephalopathy, multiple treatment modalities have emerged with promising results when used alone or as an adjunct to standard medications. The mechanisms of these agents vary greatly, and include the manipulation of gut microbial composition, reduction of oxidative stress, inhibition of inflammatory mediators, protection of endothelial integrity, modulation of neurotransmitter release and function, and other novel methods to reduce blood ammonia and neurotoxins. Despite their promising results, the studies assessing these treatment modalities are often limited by study design, sample size, outcome assessment heterogeneity, and paucity of data regarding their safety profiles. In this article, we discuss these novel agents in depth and provide the best evidence supporting their use, along with a critical look at their limitations and future directions.

Liver Transplantation in Acute-on-chronic Liver Failure

Liver transplantation (LT) has revolutionized outcomes for cirrhotic patients. Current liver allocation policies dictate patients with highest short-term mortality receive the highest priority, thus, several patients become increasingly ill on the waitlist. Given cirrhosis is a progressive disease, it can be complicated by the occurrence of acute-on-chronic liver failure (ACLF), a syndrome defined by an acute deterioration of liver function associated with extrahepatic organ failures requiring intensive care support and a high short-term mortality. Successfully bridging to transplant includes accurate prognostication and prioritization of ACLF patients awaiting LT, optimizing intensive care support pre-LT, and tailoring immunosuppressive and anti-infective therapies post-LT. Furthermore, predicting futility (too sick to undergo LT) in ACLF is challenging. In this review, we summarize the role of LT in ACLF specifically highlighting (a) current prognostic scores in ACLF, (b) critical care management of the ACLF patient awaiting LT, (c) donor issues to consider in transplant in ACLF, and (d) exploring of recent post-LT outcomes in ACLF and potential opportunities to improve outcomes including current care gaps and unmet research needs.

Intensive care management of acute-on-chronic liver failure

The syndrome of acute-on-chronic liver failure combines deterioration of liver function in a patient with chronic liver disease, with the development of extrahepatic organ failure and high short-term mortality. Its successful management demands a rapid and coherent response to the development of dysfunction and failure of multiple organ systems in an intensive care unit setting. This response recognises the features that distinguish it from other critical illness and addresses the complex interplay between the precipitating insult, the many organ systems involved and the disordered physiology of underlying chronic liver disease. An evidence base is building to support the approaches currently adopted and outcomes for patients with this condition are improving, but mortality remains unacceptably high. Herein, we review practical considerations in critical care management, as well as discussing key knowledge gaps and areas of controversy that require further focussed research.

Acute-on-chronic liver failure: Objective admission and support criteria in the intensive care unit

Cirrhosis is a leading cause of morbidity and mortality throughout the world. Significant complications include variceal bleeding, hepatic encephalopathy, hepatorenal syndrome, and infection. When these complications are severe, admission to the intensive care unit (ICU) is often required for organ support and management. Intensive care therapy can also serve as a bridge to liver transplantation. Along with decompensation of cirrhosis, the concept of acute-on-chronic liver failure (ACLF) has emerged. This involves an acute precipitating event, such as the development of infection in a patient with cirrhosis, which leads to acute deterioration of hepatic function and extrahepatic organ failure. Extrahepatic complications often include renal, cardiovascular, and respiratory failures. Patients with significant extrahepatic and hepatic failures need ICU admission for organ support. Again, in patients who are deemed suitable liver transplant candidates, intensive care management may allow bridging to liver transplantation. However, patients with a Chronic Liver Failure Consortium ACLF score greater than 70 at 48 to 72 hours post-ICU admission do not seem to benefit from ongoing intensive support and a palliative approach may be more appropriate.

Update on the Therapeutic Management of Hepatic Encephalopathy

PURPOSE OF REVIEW

Hepatic encephalopathy (HE) is a common and devastating complication to chronic liver disease. In this paper, we summarize the latest research and evidence of both conventional and up-coming treatments.

RECENT FINDINGS

Meta-analyses report beneficial effects of lactulose, branched-chain amino acids, rifaximin, and to some degree L-ornithine L-aspartate on the manifestations of HE in patients with cirrhosis, and generally the numbers needed to treat are low. Recent studies on newer HE treatments including ornithine phenylacetate, spherical carbon, and fecal microbiota transplant also report potentially beneficial effects on HE manifestations. The conventional treatments benefit patients with HE. Newer treatments are under study and more research is needed for their validation.

Intensive Care Management of Patients with Cirrhosis

PURPOSE OF REVIEW

Cirrhosis is a major worldwide health problem which results in a high level of morbidity and mortality. Patients with cirrhosis who require intensive care support have high mortality rates of near 50%. The goal of this review is to address the management of common complications of cirrhosis in the ICU.

RECENT FINDINGS

Recent epidemiological studies have shown an increase in hospitalizations due to advanced liver disease with an associated increase in intensive care utilization. Given an increasing burden on the healthcare system, it is imperative that we strive to improve our management cirrhotic patients in the intensive care unit. Large studies evaluating the management of patients in the intensive care setting are lacking. To date, most recommendations are based on extrapolation of data from studies in cirrhosis outside of the ICU or by applying general critical care principles which may or may not be appropriate for the critically ill cirrhotic patient. Future research is required to answer important management questions.

A Controlled Study of Sorbent Suspension Dialysis in Chronic Liver Disease and Hepatic Encephalopathy

To investigate the role of extracorporeal detoxification in cirrhotic patients with advanced hepatic encephalopathy not responding to medical treatment, 20 patients were randomized to receive six hours of additional sorbent dialysis or ongoing standardized medical treatment. Following treatment, the clinical stage of encephalopathy remained unchanged in both groups. Abnormal sensory evoked potentials improved following sorbent dialysis (N70 latency, 128 ms before versus 110 ms after treatment, P<0,05; cervico-cranial transmission, 7.7 ms versus 6.8 ms, P<0.01) indicating improvement in important aspects of cerebral function. In contrast, brain function remained unchanged following medical treatment (N70 latency, 114 ms versus 113 ms; cervico-cranial transmission, 7.7 ms versus 7.2 ms, P=NS, respectively). Serum benzodiazepine levels decreased significantly after sorbent dialysis but not after medical treatment. Biocompatibility of sorbent dialysis was limited and clinical complications occurred in a proportion of patients. In conclusion, a six-hour treatment with sorbent suspension dialysis did not ameliorate the clinical stage of HE but improved neurophysiologic function in cirrhotic patients who had not responded to conventional medical treatment.

Critical care management of the patient with cirrhosis awaiting liver transplant in the intensive care unit

Patients with cirrhosis who are awaiting liver transplantation (LT) are at high risk for developing critical illnesses. Current liver allocation policies that dictate a "sickest first" approach coupled with a mismatch between need and availability of organs result in longer wait times, and thus, patients are becoming increasingly ill while awaiting organ transplantation. Even patients with well-compensated cirrhosis may suffer acute deterioration; the syndrome of acute-on-chronic liver failure (ACLF) results in multisystem organ dysfunction and a marked increase in associated short-term morbidity and mortality. For patients on transplant waiting lists, the development of multisystem organ failure may eliminate candidacy for transplant by virtue of being "too sick" to safely undergo transplantation surgery. The goals of intensive care management of patients suffering ACLF are to rapidly recognize and treat inciting events (eg, infection and bleeding) and to aggressively support failing organ systems to ensure that patients may successfully undergo LT. Management of the critically ill ACLF patient awaiting transplantation is best accomplished by multidisciplinary teams with expertise in critical care and transplant medicine. Such teams are well suited to address the needs of this unique patient population and to identify patients who may be too ill to proceed to transplantation surgery. The focus of this review is to identify the common complications of ACLF and to describe our approach management in critically ill patients awaiting LT in our centers. Liver Transplantation 23 1465-1476 2017 AASLD.

Flumazenil versus placebo or no intervention for people with cirrhosis and hepatic encephalopathy

BACKGROUND

Hepatic encephalopathy is a common complication of cirrhosis which results in poor brain functioning. The spectrum of changes associated with hepatic encephalopathy ranges from the clinically 'indiscernible' or minimal hepatic encephalopathy to the clinically 'obvious' or overt hepatic encephalopathy. Flumazenil is a synthetic benzodiazepine antagonist with high affinity for the central benzodiazepine recognition site. Flumazenil may benefit people with hepatic encephalopathy through an indirect negative allosteric modulatory effect on gamma-aminobutyric acid receptor function. The previous version of this review, which included 13 randomised clinical trials, found no effect of flumazenil on all-cause mortality, based on an analysis of 10 randomised clinical trials, but found a beneficial effect on hepatic encephalopathy, based on an analysis of eight randomised clinical trials.

OBJECTIVES

To evaluate the beneficial and harmful effects of flumazenil versus placebo or no intervention for people with cirrhosis and hepatic encephalopathy.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, Embase, Science Citation Index Expanded, and LILACS; meeting and conference proceedings; and bibliographies in May 2017.

SELECTION CRITERIA

We included randomised clinical trials regardless of publication status, blinding, or language in the analyses of benefits and harms, and observational studies in the assessment of harms.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently. We undertook meta-analyses and presented results using risk ratios (RR) with 95% confidence intervals (CI) and I2 values as a marker of heterogeneity. We assessed bias control using the Cochrane Hepato-Biliary Group domains; determined the quality of the evidence using GRADE; evaluated the risk of small-study effects in regression analyses; and conducted trial sequential, subgroup, and sensitivity analyses.

MAIN RESULTS

We identified 14 eligible randomised clinical trials with 867 participants, the majority of whom had an acute episode of overt hepatic encephalopathy. In addition, we identified one ongoing randomised clinical trial. We were unable to gather outcome data from two randomised clinical trials with 25 participants. Thus, our analyses include 842 participants from 12 randomised clinical trials comparing flumazenil versus placebo. We classified one randomised clinical trial at low risk of bias in the overall assessment and the remaining randomised clinical trials at high risk of bias. The duration of follow-up ranged from a few minutes to two weeks, but it was less than one day in the majority of the trials.In total, 32/433 (7.4%) participants allocated to flumazenil versus 38/409 (9.3%) participants allocated to placebo died (RR 0.75, 95% CI 0.48 to 1.16; 11 randomised clinical trials; low quality evidence). The Trial Sequential Analysis and the one randomised clinical trial assessed as low risk of bias (RR 0.76, 95% CI 0.37 to 1.53) found no beneficial or harmful effects of flumazenil on all-cause mortality. The methods used to evaluate hepatic encephalopathy included several different clinical scales, electrophysiological variables, and psychometric tests. Flumazenil was associated with a beneficial effect on hepatic encephalopathy when including all randomised clinical trials (RR 0.75, 95% CI 0.71 to 0.80; 824 participants; nine randomised clinical trials; low quality evidence), or just the trial at low risk of bias (RR 0.78, 95% CI 0.72 to 0.84; 527 participants). The Trial Sequential Analysis supported a beneficial effect of flumazenil on hepatic encephalopathy. The randomised clinical trials included little information about causes of death and little information on non-fatal serious adverse events.

AUTHORS' CONCLUSIONS

We found low quality evidence suggesting a short-term beneficial effect of flumazenil on hepatic encephalopathy in people with cirrhosis, but no evidence of an effect on all-cause mortality. Additional evidence from large, high quality randomised clinical trials is needed to evaluate the potential benefits and harms of flumazenil in people with cirrhosis and hepatic encephalopathy.

Flumazenil versus placebo or no intervention for people with cirrhosis and hepatic encephalopathy

BACKGROUND

Hepatic encephalopathy is a common complication of cirrhosis which results in poor brain functioning. The spectrum of changes associated with hepatic encephalopathy ranges from the clinically 'indiscernible' or minimal hepatic encephalopathy to the clinically 'obvious' or overt hepatic encephalopathy. Flumazenil is a synthetic benzodiazepine antagonist with high affinity for the central benzodiazepine recognition site. Flumazenil may benefit people with hepatic encephalopathy through an indirect negative allosteric modulatory effect on gamma-aminobutyric acid receptor function. The previous version of this review, which included 13 randomised clinical trials, found no effect of flumazenil on all-cause mortality, based on an analysis of 10 randomised clinical trials, but found a beneficial effect on hepatic encephalopathy, based on an analysis of eight randomised clinical trials.

OBJECTIVES

To evaluate the beneficial and harmful effects of flumazenil versus placebo or no intervention for people with cirrhosis and hepatic encephalopathy.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, CENTRAL, MEDLINE, Embase, Science Citation Index Expanded, and LILACS; meeting and conference proceedings; and bibliographies in May 2017.

SELECTION CRITERIA

We included randomised clinical trials regardless of publication status, blinding, or language in the analyses of benefits and harms, and observational studies in the assessment of harms.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data independently. We undertook meta-analyses and presented results using risk ratios (RR) with 95% confidence intervals (CI) and I2 values as a marker of heterogeneity. We assessed bias control using the Cochrane Hepato-Biliary Group domains; determined the quality of the evidence using GRADE; evaluated the risk of small-study effects in regression analyses; and conducted trial sequential, subgroup, and sensitivity analyses.

MAIN RESULTS

We identified 14 eligible randomised clinical trials with 867 participants, the majority of whom had an acute episode of overt hepatic encephalopathy. In addition, we identified one ongoing randomised clinical trial. We were unable to gather outcome data from 2 randomised clinical trials with 25 participants. Thus, our analyses include 842 participants from 12 randomised clinical trials comparing flumazenil versus placebo. We classified one randomised clinical trial at low risk of bias in the overall assessment and the remaining randomised clinical trials at high risk of bias. The duration of follow-up ranged from a few minutes to two weeks, but it was less than one day in the majority of the trials.In total, 32/433 (7.4%) participants allocated to flumazenil versus 38/409 (9.3%) participants allocated to placebo died (RR 0.75, 95% CI 0.48 to 1.16; 11 randomised clinical trials; low quality evidence). The Trial Sequential Analysis and the one randomised clinical trial assessed as low risk of bias (RR 0.76, 95% CI 0.37 to 1.53) found no beneficial or harmful effects of flumazenil on all-cause mortality. The methods used to evaluate hepatic encephalopathy included several different clinical scales, electrophysiological variables, and psychometric tests. Flumazenil was associated with a beneficial effect on hepatic encephalopathy when including all randomised clinical trials (RR 0.75, 95% CI 0.71 to 0.80; 824 participants; 9 randomised clinical trials; low quality evidence), or just the trial at low risk of bias (RR 0.78, 95% CI 0.72 to 0.84; 527 participants). The Trial Sequential Analysis supported a beneficial effect of flumazenil on hepatic encephalopathy. The randomised clinical trials included little information about causes of death and little information on non-fatal serious adverse events.

AUTHORS' CONCLUSIONS

We found low quality evidence suggesting a short-term beneficial effect of flumazenil on hepatic encephalopathy in people with cirrhosis, but no evidence of an effect on all-cause mortality. Additional evidence from large, high quality randomised clinical trials is needed to evaluate the potential benefits and harms of flumazenil in people with cirrhosis and hepatic encephalopathy.

The effect of triazolam premedication on anxiety, sedation, and amnesia in general anesthesia

BACKGROUND

Benzodiazepines have been used preoperatively as part of an anesthesia regimen to attenuate the anxiety of patients. In this study, we aimed to examine the effect of oral triazolam, a short-acting benzodiazepine, on anxiety, sedation, and amnesia.

METHODS

Ninety patients, aged 20-55 years, were randomly assigned to receive no premedication, or to receive triazolam 0.25 mg or 0.375 mg 1 h before anesthesia. Anxiety score, sedation score, blood pressure, heart rate and psychomotor performance were measured on the evening before surgery and on the day of surgery. Additional tests of psychomotor performance were performed in the postanesthesia care unit and on the next day of surgery. The occurrence of amnesia, bispectral index (BIS), recovery profiles and patient satisfaction with overall anesthesia care were also evaluated.

RESULTS

Changes in the anxiety and sedation scores on the day of surgery were not significantly different among groups, whereas the increases in systolic blood pressure and heart rate were significantly less in both triazolam groups. The triazolam groups both showed a higher incidence of high satisfaction scores (≥ 2). The two triazolam groups also showed similar outcomes, except for a dose-dependent increase in the number of patients with amnesia and BIS values < 90. Delayed recovery from general anesthesia and psychomotor impairment were not observed in the triazolam groups.

CONCLUSIONS

Triazolam 0.25 mg or 0.375 mg reduced the hemodynamic changes associated with anxiety, produced potent amnesia, and improved patient satisfaction. We suggest that triazolam can be used effectively as anesthetic premedication in adults.

Benzodiazepine-associated hepatic encephalopathy significantly increased healthcare utilization and medical costs of Chinese cirrhotic patients: 7-year experience

BACKGROUND AND OBJECTIVES

In cirrhosis, hypersensitivity to benzodiazepines (BZD) and precipitating hepatic encephalopathy (HE) have been reported. The aim of this study was to evaluate the safety, economic impact and modifiable factors that are associated with the excess risk of BZD-associated HE in cirrhotic patients.

METHODS

Between July 2005 and March 2012, 1,612 Chinese cirrhotic patients with and without using long-t 1/2-BZD or short-t 1/2-BZD were enrolled and followed up for 6 months.

RESULTS

Among BZD users, the per-person HE-related healthcare utilization and medical costs were found to have progressively increased from 2005 to 2012. Cirrhotic BZD users had a higher percentage of smoking, alcohol drinking, simultaneous consumption of non-BZD drugs, and had a higher incidence of non-cirrhotic chronic illness than non-BZD users. Multivariate analysis indicated that hypoalbuminemia (<3 g/dL), long-acting (t 1/2 > 12-h), high-dosage (>1.5 defined daily dose equivalents) and long-duration (>2-months) BZD use, carrier of variant genotypes (AG + GG) of GABRA 1 (rs2290732) and having the wild genotype (TT) of GABRG 2 (rs211037) were significant predictors of the development of BZD-associated HE in cirrhotic patients. Additionally, synergistic effects of the above significant predictors on BZD-associated HE risk could be identified.

CONCLUSIONS

Our study confirms the clinical and economic impact of BZD-associated HE in cirrhotic BZD-users. Accordingly, extra caution is needed when treating cirrhotic BZD users with the above risk factors in order to avoid the BZD-associated HE in cirrhotic patients.

Theories of the pathogenesis of hepatic encephalopathy

The earliest hypothesis of the pathogenesis of HE implicated ammonia, although effects of appreciable concentrations of this neurotoxin did not resemble HE. Altered eurotransmission in the brain was suggested by similarities between increased GABA-mediated inhibitory neurotransmission and HE, specifically decreased consciousness and impaired motor function. Evidence of increased GABAergic tone in models of HE has accumulated; potential mechanisms include increased synaptic availability of GABA and accumulation of natural benzodiazepine receptor ligands with agonist properties. Pathophysiological concentrations of ammonia associated with HE, have the potential of enhancing GABAergic tone by mechanisms that involve its interactions with the GABAa receptor complex.

Propofol sedation for upper gastrointestinal endoscopy in patients with liver cirrhosis as an alternative to midazolam to avoid acute deterioration of minimal encephalopathy: a randomized, controlled study

OBJECTIVE

Midazolam sedation for upper gastrointestinal (GI) endoscopy exacerbates minimal hepatic encephalopathy (HE) in patients with liver cirrhosis, therefore an alternative drug regimen for these patients is warranted. The aim of this randomized, controlled study was to assess whether the use of the short-acting propofol as a sedative for GI endoscopy could prevent the exacerbation of minimal HE in patients with liver cirrhosis.

MATERIAL AND METHODS

The study comprised patients with liver cirrhosis without clinical HE who had undergone upper GI endoscopy for therapeutic purposes (intended variceal band ligation). Sixty patients were randomly assigned into two groups to receive propofol (n=40) or midazolam (n=20) for upper GI endoscopy. The study groups were matched for age, gender and Child-Pugh score. All patients completed number connecting tests (NCTs), as well as a porto-systemic encephalopathy (PSE) syndrome test before and at 2 h after completion of the endoscopic procedure. Time needed to fulfill the tests was documented. Baseline results of the psychomotor test batteries were compared with the post-interventional evaluations. Data were also compared with the results of a healthy control group (n=20) that did not undergo endoscopic sedation. Recovery time and quality (score system) were evaluated.

RESULTS

The differences in the NCT times before and after sedation (median delta NCT, midazolam group, 11 s (95% CI, -1.2 to 16.1 s) versus the propofol group, -9.5 s (95% CI, -15.7 to -4.6 s), p=0.002) and in the PSE scores (median delta PSE, midazolam group, -1 (95% CI, -1.5 to 0.2) versus the propofol group, 1 (95% CI, 0.5 to 1.5), p=0.0009) differed significantly between the two groups. In addition, the recovery time and quality in patients receiving propofol were significantly improved compared with in the midazolam group (7.8+/-2.9 min versus 18.4+/-6.7 min, 6.1+/-1.1 versus 8.2+/-1.3, both p<0.001).

CONCLUSIONS

The study demonstrates that propofol sedation for upper GI endoscopy does not cause acute deterioration of minimal hepatic encephalopathy and is associated with improved recovery in patients with liver cirrhosis. Propofol should be recommended for these patients as an alternative to midazolam.

Natural endogenous ligands for benzodiazepine receptors in hepatic encephalopathy

Benzodiazepines of natural origin (NBZDs) have been found in human blood and brains as well as in medicinal plants and foods. In plasma and brain tissue there are i.e. diazepam and nordiazepam equal to commercial drugs but there are also other benzodiazepine-like compounds termed "endozepines", which act as agonists at the benzodiazepine receptors of central type (CBR). A synthetic pathway for the production of NBZDs has not yet been found, but it has been suggested that micro-organisms may synthesize molecules with benzodiazepine-like structures. Hence NBZDs could be of both endogenous and exogenous source and be considered as natural anxyolitic and sedative. Interestingly there are also natural compounds, such as the polypeptide Diazepam Binding Inhibitor (DBI) acting as an "inversive agonist" implicated in fair and panic disorders. It has been suggested that NBZDs may play a role in the pathogenesis of hepatic encephalopathy (HE). Multidirectional studies evaluated NBZDs levels (1) in the blood of normal subjects, of cirrhotic with or without HE and in commercial benzodiazepine consumers; (2) in the blood of cirrhotic treated or not with a non-absorbable antibiotic; (3) in several constituents of our diet. In conclusion, NBZDs increase sometime in cirrhotics with or without HE but they reach concentrations not higher than those found in commercial benzodiazepines consumers. Hence NBZDs must be considered as occasional precipitating factor of HE and benzodiazepine antagonists only symptomatic drugs. The finding that NBZDs may be in part synthesized by intestinal bacterial flora and in part constituent of our diet underlines the importance to feed cirrhotic patients with selected food.

Pharmacokinetics and dosage adjustment in patients with hepatic dysfunction

The liver plays a central role in the pharmacokinetics of the majority of drugs. Liver dysfunction may not only reduce the blood/plasma clearance of drugs eliminated by hepatic metabolism or biliary excretion, it can also affect plasma protein binding, which in turn could influence the processes of distribution and elimination. Portal-systemic shunting, which is common in advanced liver cirrhosis, may substantially decrease the presystemic elimination (i.e., first-pass effect) of high extraction drugs following their oral administration, thus leading to a significant increase in the extent of absorption. Chronic liver diseases are associated with variable and non-uniform reductions in drug-metabolizing activities. For example, the activity of the various CYP450 enzymes seems to be differentially affected in patients with cirrhosis. Glucuronidation is often considered to be affected to a lesser extent than CYP450-mediated reactions in mild to moderate cirrhosis but can also be substantially impaired in patients with advanced cirrhosis. Patients with advanced cirrhosis often have impaired renal function and dose adjustment may, therefore, also be necessary for drugs eliminated by renal exctretion. In addition, patients with liver cirrhosis are more sensitive to the central adverse effects of opioid analgesics and the renal adverse effects of NSAIDs. In contrast, a decreased therapeutic effect has been noted in cirrhotic patients with beta-adrenoceptor antagonists and certain diuretics. Unfortunately, there is no simple endogenous marker to predict hepatic function with respect to the elimination capacity of specific drugs. Several quantitative liver tests that measure the elimination of marker substrates such as galactose, sorbitol, antipyrine, caffeine, erythromycin, and midazolam, have been developed and evaluated, but no single test has gained widespread clinical use to adjust dosage regimens for drugs in patients with hepatic dysfunction. The semi-quantitative Child-Pugh score is frequently used to assess the severity of liver function impairment, but only offers the clinician rough guidance for dosage adjustment because it lacks the sensitivity to quantitate the specific ability of the liver to metabolize individual drugs. The recommendations of the Food and Drug Administration (FDA) and the European Medicines Evaluation Agency (EMEA) to study the effect of liver disease on the pharmacokinetics of drugs under development is clearly aimed at generating, if possible, specific dosage recommendations for patients with hepatic dysfunction. However, the limitations of the Child-Pugh score are acknowledged, and further research is needed to develop more sensitive liver function tests to guide drug dosage adjustment in patients with hepatic dysfunction.

Pharmacokinetics and dosage adjustment in patients with hepatic dysfunction

The liver plays a central role in the pharmacokinetics of the majority of drugs. Liver dysfunction may not only reduce the blood/plasma clearance of drugs eliminated by hepatic metabolism or biliary excretion, it can also affect plasma protein binding, which in turn could influence the processes of distribution and elimination. Portal-systemic shunting, which is common in advanced liver cirrhosis, may substantially decrease the presystemic elimination (i.e., first-pass effect) of high extraction drugs following their oral administration, thus leading to a significant increase in the extent of absorption. Chronic liver diseases are associated with variable and non-uniform reductions in drug-metabolizing activities. For example, the activity of the various CYP450 enzymes seems to be differentially affected in patients with cirrhosis. Glucuronidation is often considered to be affected to a lesser extent than CYP450-mediated reactions in mild to moderate cirrhosis but can also be substantially impaired in patients with advanced cirrhosis. Patients with advanced cirrhosis often have impaired renal function and dose adjustment may, therefore, also be necessary for drugs eliminated by renal exctretion. In addition, patients with liver cirrhosis are more sensitive to the central adverse effects of opioid analgesics and the renal adverse effects of NSAIDs. In contrast, a decreased therapeutic effect has been noted in cirrhotic patients with beta-adrenoceptor antagonists and certain diuretics. Unfortunately, there is no simple endogenous marker to predict hepatic function with respect to the elimination capacity of specific drugs. Several quantitative liver tests that measure the elimination of marker substrates such as galactose, sorbitol, antipyrine, caffeine, erythromycin, and midazolam, have been developed and evaluated, but no single test has gained widespread clinical use to adjust dosage regimens for drugs in patients with hepatic dysfunction. The semi-quantitative Child-Pugh score is frequently used to assess the severity of liver function impairment, but only offers the clinician rough guidance for dosage adjustment because it lacks the sensitivity to quantitate the specific ability of the liver to metabolize individual drugs. The recommendations of the Food and Drug Administration (FDA) and the European Medicines Evaluation Agency (EMEA) to study the effect of liver disease on the pharmacokinetics of drugs under development is clearly aimed at generating, if possible, specific dosage recommendations for patients with hepatic dysfunction. However, the limitations of the Child-Pugh score are acknowledged, and further research is needed to develop more sensitive liver function tests to guide drug dosage adjustment in patients with hepatic dysfunction.

Management of hepatic encephalopathy: role of rifaximin

Hepatic encephalopathy (HE) is a neuropsychiatric syndrome, which develops in patients with acute or chronic liver failure. It is widely accepted to be due to impairment of hepatic clearance of toxic products from the gut such as ammonia. Accumulation of ammonia induces a glutamate neurotoxicity leading to an increased tone of the gamma-aminobutyric acid A (GABA-A) receptor system in the brain which results in HE. Factors either increasing the ammonia levels (protein load, constipation, sepsis, or gastrointestinal bleeding) or potentiating the functional activity of the GABAergic system [natural benzodiazepine-like compounds (NBZDs) or exogenous benzodiazepines] may act as precipitating factors of HE. NBZDs are present in trace amounts in the blood of normal subjects and have been found to be increased in the blood of patients with liver cirrhosis, with or without HE. These compounds may derive either from the diet since they have been found in plants, vegetables and animals or from gut bacteria. The observation that intestinal bacterial flora is involved in the production of both primary agent of HE (ammonia) and precipitating factors (NBZDs) suggests that the use of nonabsorbable antibiotics such as rifaximin may be useful in preventing episodes of HE in patients with liver cirrhosis.

Impairment of psychomotor responses after conscious sedation in cirrhotic patients undergoing therapeutic upper GI endoscopy

OBJECTIVES

The aim of this study was to determine whether the number connection test (NCT) times of a group of cirrhotic patients without clinically overt hepatic encephalopathy and a group of healthy patients without liver disease who were undergoing endoscopy were prolonged after sedation with short acting i.v. benzodiazepines.

METHODS

All patients were administered the NCT in a standard fashion for 30 min before sedation for an upper GI endoscopy and then 2 h after sedation postprocedure. Two NCTs were carried out before and 2 h after sedation, and the mean of the tests pre- and postsedation calculated. Based on the upper limit of the 95% CI of the presedation NCT of patients without liver disease as the cut-off level for hepatic encephalopathy, the proportion of cirrhotic patients with subclinical encephalopathy before and after sedation were also determined.

RESULTS

A total of 61 consecutive cirrhotic patients who underwent therapeutic upper GI endoscopy completed the study. The mean presedation NCT time was 43.5 s (95% CI = 39.0-48.1 s) and the mean postsedation NCT time 60.0 s (95% CI = 50.7-69.3 s). The difference between the mean pre- and postsedation NCT times was 16.4 s (95% CI = 9.8-23.1 s; p < 0.001). A total of 38 consecutive patients without clinical or biochemical evidence of liver disease who presented for upper GI endoscopy completed the NCT as described for the group of cirrhotic patients. The mean (+/- SD) baseline NCT time was 34.7+/-7.9 s (95% CI = 32.1-37.2 s), whereas the mean postsedation NCT time was 33.7+/-8.5 s (95% CI = 30.9-36.5 s). This difference was not statistically significant (p = 0.177). Using the upper limit of the 95% CI of the mean (37.4 s) of the presedation time in the patients without liver disease as the cut-off between normal and encephalopathy, the number of cirrhotic patients with abnormal presedation NCT times was 33 patients (54.1%), and this number rose to 46 patients (75.4%) after sedation with midazolam. This increase in proportion of cirrhotic patients with prolonged NCT time was statistically significant (p < 0.001).

Hepatic encephalopathy in liver cirrhosis: pathogenesis, diagnosis and management

The pathogenesis of hepatic encephalopathy (HE) is unknown. Many theories have been proposed. Most established therapies are based on such theories but since no theory has have ever been proved, therapies have to be considered empiric. The spectrum of HE ranges from minimal cerebral functional deficits, which can only be found by sensitive psychometric tests, to coma with signs of decerebration. HE has arbitrarily been divided into stages. A number of precipitating factors are known and the first line of therapy should always be the elimination of these factors. The differential diagnosis includes all states of impaired consciousness and deficits in cerebral function in patients with chronic liver disease, and clinical and biochemical tests to differentiate are indicated. The therapeutic options for HE include: protein restriction only for a limited time in comatous patients; nonabsorbable antibiotics (aminoglycosides), which because of adverse effects are also limited to higher grades of HE: intestinal cleansing which is applicable in all degrees of HE; lactulose, branched chain aminoacids and ornithin aspartate which have been proven to be effective and can be applied long term in patients with lower grades of HE.

Pathogenesis of hepatic encephalopathy

Hepatic encephalopathy is considered to be a reversible metabolic encephalopathy, which occurs as a complication of hepatocellular failure and is associated with increased portal-systemic shunting of gut-derived nitrogenous compounds. Its manifestations are most consistent with a global depression of CNS function, which could arise as a consequence of a net increase in inhibitory neurotransmission, due to an imbalance between the functional status of inhibitory (e.g., GABA) and excitatory (e.g., glutamate) neurotransmitter systems. In liver failure, factors that contribute to increased GABAergic tone include increased synaptic levels of GABA and increased brain levels of natural central benzodiazepine (BZ) receptor agonists. Ammonia, present in modestly elevated levels, may also augment GABAergic tone by direct interaction with the GABAA receptor, synergistic interactions with natural central BZ receptor agonists, and stimulation of astrocytic synthesis and release of neurosteroid agonists of the GABAA receptor. Thus, there is a rationale for therapies of HE that lower ammonia levels and incrementally reduce increased GABAergic tone towards the physiologic norm.

Hepatic encephalopathy: molecular mechanisms underlying the clinical syndrome

Hepatic encephalopathy (HE) and portal-systemic encephalopathy (PSE) are the terms used interchangeably to describe a complex neuropsychiatric syndrome associated with acute or chronic hepatocellular failure, increased portal systemic shunting of blood, or both. Hepatic encephalopathy complicating acute liver failure is referred to as fulminant hepatic failure (FHF). The clinical manifestations of HE or PSE range from minimal changes in personality and motor activity, to overt deterioration of intellectual function, decreased consciousness and coma, and appear to reflect primarily a variable imbalance between excitatory and inhibitory neurotransmission. Pathogenic mechanisms that may be responsible for HE have been extensively investigated using animal models of HE, or cultures of CNS cells treated with neuroactive substances that have been implicated in HE. Of the many compounds that accumulate in the circulation as a consequence of impaired liver function, ammonia is considered to play an important role in the onset of HE. Acute ammonia neurotoxicity, which may be a cause of seizures in FHF, is excitotoxic in nature, being associated with increased synaptic release of glutamate (Glu), the major excitatory neurotransmitter of the brain, and subsequent overactivation of the ionotropic Glu receptors, mainly the N-methyl-D-aspartate (NMDA) receptors. Hepatic encephalopathy complicating chronic liver failure appears to be associated with a shift in the balance between inhibitory and excitatory neurotransmission towards a net increase of inhibitory neurotransmission, as a consequence of at least two factors. The first is down-regulation of Glu receptors resulting in decreased glutamatergic tone. The down-regulation follows excessive extrasynaptic accumulation of Glu resulting from its impaired re-uptake into nerve endings and astrocytes. Liver failure inactivates the Glu transporter GLT-1 in astrocytes. The second factor is an increase in inhibitory neurotransmission by gamma-aminobutyric acid (GABA) due to (a) increased brain levels of natural benzodiazepines; (b) increased availability of GABA at GABA-A receptors, due to enhanced synaptic release of the amino acid; (c) direct interaction of modestly increased levels of ammonia with the GABA-A-benzodiazepine receptor complex; and (d) ammonia-induced up-regulation of astrocytic peripheral benzodiazepine receptors (PBZR). Brain ammonia is metabolised in astrocytes to glutamine (Gln), an osmolyte, and increased Gln accumulation in these cells may contribute to cytotoxic brain edema, which often complicates FHF. Glutamine efflux from the brain is an event that facilitates plasma-to-brain transport of aromatic amino acids. Tryptophan and tyrosine are direct precursors of the aminergic inhibitory neurotransmitters, serotonin and dopamine, respectively. Changes in serotonin and dopamine and their receptors may contribute to some of the motor manifestations of HE. Finally, oxindole, a recently discovered tryptophan metabolite with strong sedative and hypotensive properties, has been shown to accumulate in cirrhotic patients and animal models of HE.

Effects of liver disease on pharmacokinetics. An update

Liver disease can modify the kinetics of drugs biotransformed by the liver. This review updates recent developments in this field, with particular emphasis on cytochrome P450 (CYP). CYP is a rapidly expanding area in clinical pharmacology. The information currently available on specific isoforms involved in drug metabolism has increased tremendously over the latest years, but knowledge remains incomplete. Studies on the effects of liver disease on specific isoenzymes of CYP have shown that some isoforms are more susceptible than others to liver disease. A detailed knowledge of the particular isoenzyme involved in the metabolism of a drug and the impact of liver disease on that enzyme can provide a rational basis for dosage adjustment in patients with hepatic impairment. The capacity of the liver to metabolise drugs depends on hepatic blood flow and liver enzyme activity, both of which can be affected by liver disease. In addition, liver failure can influence the binding of a drug to plasma proteins. These changes can occur alone or in combination; when they coexist their effect on drug kinetics is synergistic, not simply additive. The kinetics of drugs with a low hepatic extraction are sensitive to hepatic failure rather than to liver blood flow changes, but drugs having a significant first-pass effect are sensitive to alterations in hepatic blood flow. The drugs examined in this review are: cardiovascular agents (angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists, calcium antagonists, ketanserin, antiarrhythmics and hypolipidaemics), diuretics (torasemide), psychoactive and anticonvulsant agents (benzodiazepines, flumazenil, antidepressants and tiagabine), antiemetics (metoclopramide and serotonin antagonists), antiulcers (acid pump inhibitors), anti-infectives and antiretroviral agents (grepafloxacin, ornidazole, pefloxacin, stavudine and zidovudine), immunosuppressants (cyclosporin and tacrolimus), naltrexone, tolcapone and toremifene. According to the available data, the kinetics of many drugs are altered by liver disease to an extent that requires dosage adjustment; the problem is to quantify the required changes. Obviously, this requires the evaluation of the degree of hepatic impairment. At present there is no satisfactory test that gives a quantitative measure of liver function and its impairment. A critical evaluation of these methods is provided. Guidelines providing a rational basis for dosage adjustment are illustrated. Finally, it is important to consider that liver disease not only affects pharmacokinetics but also pharmacodynamics. This review also examines drugs with altered pharmacodynamics.

Does ammonia contribute to increased GABA-ergic neurotransmission in liver failure?

The ammonia and GABAergic neurotransmission hypotheses of the pathogenesis of hepatic encephalopathy (HE) have appeared to be unrelated and perhaps mutually exclusive. Observations in animal models of fulminant hepatic failure, that are consistent with increased GABAergic inhibitory neurotransmission contributing to the manifestations of HE, include: (i) abnormal visual evoked potential waveforms that resemble those induced by GABA(A)/benzodiazepine (BZ) receptor complex agonists; (ii) GABA(A)/BZ receptor complex antagonist-induced ameliorations of encephalopathy; (iii) increased resistance to drugs which decrease GABAergic tone; and (iv) hypersensitivity of CNS neurons to depression by GABA(A)/BZ receptor complex agonists. Mechanisms of increased GABAergic tone in HE may include the following: (i) increased brain concentrations of natural BZs; and (ii) increased GABA concentrations in synaptic clefts, possibly due to increased blood-brain-barrier permeability to GABA and a decrease in GABA(B) receptor density. Both neuroelectrophysiological and behavioral data indicate that ammonia concentrations in the range 0.75-2 mM induce increased excitatory neurotransmission. In contrast, recently, ammonia concentrations in the range 0.15-0.75 mM, i.e. concentrations that commonly occur in plasma in precoma HE, have been shown: (i) to increase GABA-induced chloride current in cultured neurons; and (ii) to enhance synergistically the binding of GABA(A)/BZ receptor agonists. In addition, increased ammonia concentrations enhance synthesis of neurosteroids in astrocytes, and some neurosteroids potently augment GABAergic neurotransmission. Thus, the modestly elevated concentrations of ammonia, that commonly occur in liver failure, may contribute to the manifestations of HE by enhancing GABAergic inhibitory neurotransmission. This concept appears to unify the ammonia and GABAergic neurotransmission hypotheses.

Effect of hepatic insufficiency on pharmacokinetics and drug dosing

The liver plays a central role in the pharmacokinetics of many drugs. Liver dysfunction may not only reduce the plasma clearance of a number of drugs eliminated by biotransformation and/or biliary excretion, but it can also affect plasma protein binding which in turn could influence the processes of distribution and elimination. In addition, reduced liver blood flow in patients with chronic liver disease will decrease the systemic clearance of flow limited (high extraction) drugs and portal-systemic shunting may substantially reduce their presystemic elimination (first-pass effect) following oral administration. When selecting a drug and its dosage regimen for a patient with liver disease additional considerations such as altered pharmacodynamics and impaired renal excretion (hepatorenal syndrome) of drugs and metabolites should also be taken into account. Consequently, dosage reduction is necessary for many drugs administered to patients with chronic liver disease such as liver cirrhosis.

Cerebral changes in hepatic encephalopathy

Hepatic encephalopathy (HE) accompanied by an impairment of consciousness from orientation disorder (grade II) to coma (grade IV) is considered to be overt HE and is treated as an emergency. However, subclinical hepatic encephalopathy (SHE) can be detected by sensitive and quantitative neuropsychological examinations in cirrhotic patients without overt HE. The introduction of the SHE concept is clinically important for preventing the deterioration of SHE (grades 0 and I) to overt HE (grade II and more severe), prolonging the compensated state of cirrhosis without its deterioration to hepatic failure, and the continuation of patient treatment at home. We developed a new diagnostic method for SHE using a quantitative neuropsychological test, with the computerization of all operations. Evaluations of cerebral function and morphology are useful for the determination of the pathophysiology of HE, and assist the diagnosis of SHE. The latencies of the P3 wave in the visually evoked potential and the P300 wave in the event-related potential are prolonged in cirrhotic patients with SHE and are well expressed in three-dimensional coloured topograms (brain mapping). Automated polysomnographic analysis is useful for continuous-monitoring electroencephalograms (EEG) and for the detection of the sleep disturbance observed in cirrhotic patients with SHE. Brain atrophy in computed tomography (CT), magnetic resonance imaging (MRI) and high signals in the basal ganglia in the MR-T1-weighted images have frequently been observed in patients with SHE. The reduction of regional cerebral blood flow (rCBF) by 99mtechnetium-1, 1-ethylcysteinate dimer (99mTc-ECD)-single photon emission computed tomography (SPECT) and the choline/N-acetylaspartic acid ratio by proton-magnetic resonance spectroscopy (1H-MRS) were observed in the hippocampus in patients with SHE. These approaches (cerebral function tests and imaging diagnoses of the brain) can also be used to evaluate the effectiveness of treatments for HE; for example, branched-chain amino acid (BCAA) was shown by automated continuous polysomnographic analysis to be a psychotropic drug which acts directly on the central nervous system and the clinical significance of choline administration to HE patients is now being evaluated by 1H-MRS and neuropsychological tests.

Oral management of the patient with end-stage liver disease and the liver transplant patient

The patient with end-stage liver disease who is in need of a liver transplant should have a pretransplant dental evaluation. Such a patient faces lifelong immunosuppression with an increased risk of infection. This article discusses both the need for control of oral diseases before liver transplantation and guidelines for oral care in the immediately postoperative and long-term transplant patient. Specific indications for antibiotic prophylaxis and antibiotic regimens are presented; in addition, adverse reactions and side effects of immunosuppressant drugs are discussed. Pertinent drug interactions salient to the dental management of patients with end-stage liver disease are reviewed, and specific management recommendations for these patients are presented.

Portal systemic encephalopathy

The goal of this article is to update the status of Portal systemic encephalopathy (PSE) in the light of new data. First, PSE is the context of other types of hepatic encephalopathy. Subsequently, current views of the pathogenesis of the disorder are discussed, followed by an analysis of therapeutic options. Diagnosis will not be considered, as no major new developments have recently been documented in this area.

Cortico-spinal pathways and inhibitory mechanisms in hepatic encephalopathy

Transcranial magnetic stimulation of the cerebral cortex was used to study motor system function in 31 cirrhotics (29 post-necrotic and 2 cryptogenic) with and without hepatic encephalopathy (HE). The results were compared with those of 14 healthy subjects matched for age. A significant increase of central motor conduction time, a significant raising of the motor evoked potential (MEP) threshold at rest and a significant reduction of the MEP/muscle action potential (MAP) amplitude ratio were found only in patients with chronic stable (12 patients) and recurrent (9 patients) HE. Vice versa, a significant shortening of the central silent period was observed in all 31 cirrhotic patients. The peripheral silent period was normal in all instances. These results indicate that the damage to the cortico-spinal pathways is related to the progression of cirrhosis to HE, and that cirrhotic patients present a dysfunction of the inhibitory motor mechanisms before HE is clinically manifest.

Benzodiazepine Utilization Review for Inpatients at a Tertiary Medical Center in Taiwan

Objectives:

To examine benzodiazepine prescribing patterns by physicians for inpatients relative to indications and drug characteristics in a tertiary medical center.

Design:

Prescription pattern analysis was done by checking computer-based pharmacy records. Benzodiazepine utilization was evaluated through retrospective chart review.

Results:

A total of 2,195 inpatients were surveyed, of whom 945 were given benzodiazepines. Of these, 827 charts were available for review. The mean number of prescriptions written for benzodiazepines was 1.62 per patient. Of the benzodiazepines available, triazolam was most frequently prescribed. The use of benzodiazepines ranged from 38.7% in the internal medicine ward to 85.1% in the oncology ward. We found that 60% of prescriptions were appropriate, 24.9% were prescribed without documentation, and 15.1% were used inappropriately.

Conclusions:

Proper prescribing of benzodiazepines is essential in the management of the symptoms of mental illness. From both a diagnostic and treatment perspective, more education efforts are needed in the investigation, documentation, and treatment of mental illness symptoms.

GABAergic inhibition of the pituitary release of adrenocorticotropin and alpha-melanotropin is impaired in dogs with hepatic encephalopathy

gamma-Aminobutyric acid (GABA) is the principal depressant neurotransmitter system, but its possible role in the regulation of the hypothalamic-pituitary-adrenocortical (HPA) axis has not yet been investigated in the dog. Moreover, GABA is one of the factors underlying the syndrome of hepatic encephalopathy (HE), and in dogs with HE, the regulation of the HPA axis is deranged. We have therefore investigated the role of the GABA system in the regulation of the HPC system in 10 healthy dogs and 10 dogs with HE due to congenital portosystemic shunts. The effect of an intravenous injection of the GABA antagonist bicuculline on the release of adrenocorticotropin (ACTH), alpha-melanotropin (MSH), and cortisol was measured in plasma. In healthy dogs, a dose of 1.0 mg/kg caused a marked release of ACTH, MSH, and cortisol, but doses of 0.001 to 0.5 mg/kg produced an inconsistent or no response. The high release of MSH after bicuculline administration indicated that the effect of GABA was predominantly in the neurointermediate lobe of the pituitary. In order to investigate whether the effect of GABA was exerted in the pituitary or at a suprapituitary level, the effect of incubation with GABA on basal and corticotropin-releasing hormone-induced ACTH release was measured in primary cultures of anterior and neurointermediate lobe cells from healthy dogs, and no response was observed. We conclude that in healthy dogs, GABA inhibits the release of ACTH and MSH from the neurointermediate lobe of the pituitary at a suprapituitary level. In dogs with HE, 1.0 mg/kg of bicuculline caused virtually no stimulation of the secretion of ACTH, MSH, or cortisol, indicating deranged GABAergic neurotransmission in HE. This may be explained by an increased GABA tone that prevents the effect of the antagonist. Such a high GABA tone associated with HE has been documented in several other species. Dogs with HE had significantly increased basal levels of ACTH, MSH, and cortisol in plasma, and their cortisol:creatinine ratios in 24-hr urine samples (63 +/- 14.10(-6)) were higher than those of healthy dogs (9 +/- 2.10(-6)). An increased basal HPA activity in dogs with HE is not in agreement with augmented GABAergic inhibition, but this contradiction may be explained by the predominance of effects of dopaminergic disinhibition that has been reported in such dogs.

Chronic glucocorticoid excess and impaired osmoregulation of vasopressin release in dogs with hepatic encephalopathy

Chronic liver disease may be accompanied by disturbed sodium and water homeostasis. There is usually sodium retention and ascites. However, spontaneous natriuresis has also been reported in humans and experimental animals with liver cirrhosis. Chronic hypercortisolism, which may occur in dogs with advanced liver disease, is known to induce the inhibition of the osmostimulation of vasopressin (AVP) release. We have therefore investigated the osmoregulation of AVP release in 11 dogs with chronic hypercortisolism associated with advanced liver dysfunction and hepatic encepahlopathy and in 10 control dogs. Basal pituitary-adrenocortical activity was investigated by measuring the concentration in multiple plasma samples of adrenocorticotropin (ACTH), alpha-melanocyte-stimulating hormone (MSH), and cortisol and the cortisol:creatinine ratio in 24-hr urine. Urine specific gravity was also measured. The feedback regulation of the system was investigated by measuring these hormones in plasma after an intravenous (iv) injection of 0.01 mg/kg of dexamethasone. The osmoregulation of the release of AVP was investigated by the intravenous infusion of a 20% NaCl solution at a flow rate of 0.03 ml/kg for 2 hr and the measurement of AVP in plasma sampled at 20-min intervals. The AVP release was analyzed in terms of the threshold osmolality at which it commenced and the sensitivity, which reflects the magnitude of the response. All dogs had highly increased urinary cortisol:creatinine ratios, ranging from 21 to 210 x 10(-6) (normally < 10 x 10(-6)). The mean basal plasma concentrations of the three pituitary-adrenocortical hormones were significantly increased. ACTH values were 35 to 146 ng/l (normally, 14 to 68), MSH values were 26 to 118 ng/l (normally, 10 to 36), and cortisol values were 88 to 194 nmol/l (normally, 23 to 112). The feedback inhibition of the secretion of ACTH and cortisol in response to dexamethasone was unaffected. Urine specific gravity was significantly decreased. The regulation of AVP release was found to be abnormal in all dogs with hepatic encephalopathy. The osmotic threshold at which the release of AVP was induced was abnormally high in seven of the dogs with liver disease and in the normal range in one. It could not be determined in three dogs. The sensitivity of AVP release in response to increasing plasma hypertonicity was normal in two dogs and decreased in nine. In three dogs, there was no increase in AVP release. None of the dogs had normal values for both the sensitivity and the threshold.(ABSTRACT TRUNCATED AT 400 WORDS)

Assessment of liver metabolic function. Clinical implications

Inter- and intraindividual variability in pharmacokinetics of most drugs is largely determined by variable liver function as described by parameters of hepatic blood flow and metabolic capacity. These parameters may be altered as a result of disease affecting the liver, genetic differences in metabolising enzymes, and various types of drug interactions, including enzyme induction, enzyme inhibition or down-regulation. With the now known large number of drug metabolising enzymes, their differential substrate specificity, and their differential induction or inhibition, each test substance of liver function should be used as a probe for its specific metabolising enzyme. Thus, the concept of model test-substances providing general information about liver function has severe limitations. To test the metabolic activity of several enzymes, either several test substances may be given (cocktail approach) or several metabolites of a single test substance may be analysed (metabolic fingerprint approach). The enzyme-specific analysis of liver function results in a preference for analysis of the metabolites rather than analysis of the clearance of the parent test substance. There are specific methods to quantify the activity of cytochrome P450 enzymes such as CYP1A2, CYP2C9, CYP2C19MEPH, CYP2D6, CYP2E1, and CYP3A, and phase II enzymes, such as glutathione S-transferases, glucuronyl-transferases or N-acetyltransferases, in vivo. Interactions based on competitive or noncompetitive inhibition should be analysed specifically for the cytochrome P450 enzyme involved. At least 5 different types of cytochrome P450 enzyme induction may result in major variability of hepatic function; this may be quantified by biochemical parameters, clearance methods, or highly enzyme-specific methods such as Western blot analysis or molecular biological techniques such as mRNA quantification in blood and tissues. Therapeutic drug monitoring is already implicitly used for quantification of the enzyme activities relevant for a specific drug. Selective impairment of hepatic enzymes due to gene mutations may have an effect on the pharmacokinetics of certain drugs similar to that caused by cirrhosis. Assessment of this heritable source of variability in liver function is possible by in vivo or ex vivo enzymological methods. For genetically polymorphic enzymes and carrier proteins involved in drug disposition, molecular genetic methods using a patient's blood sample may be used for classification of the individual into: (i) the impaired or poor metaboliser (homozygous deficient); (ii) the extensive (homozygous active) metaboliser group; and (iii) the moderately extensive metaboliser (heterozygous) group. For hepatic blood flow determinations, galactose or sorbitol given at relatively low doses may be much better indicators than the indocyanine green.(ABSTRACT TRUNCATED AT 400 WORDS)