Effects of dilutional hyponatremia on brain organic osmolytes and water content in patients with cirrhosis

Hyponatremia in cirrhosis: pathogenesis, clinical significance, and management

Hyponatremia is a frequent complication of advanced cirrhosis related to an impairment in the renal capacity to eliminate solute-free water that causes a retention of water that is disproportionate to the retention of sodium, thus causing a reduction in serum sodium concentration and hypo-osmolality. The main pathogenic factor responsible for hyponatremia is a nonosmotic hypersecretion of arginine vasopressin (or antidiuretic hormone) from the neurohypophysis related to circulatory dysfunction. Hyponatremia in cirrhosis is associated with increased morbidity and mortality. There is evidence suggesting that hyponatremia may affect brain function and predispose to hepatic encephalopathy. Hyponatremia also represents a risk factor for liver transplantation as it is associated with increased frequency of complications and impaired short-term survival after transplantation. The current standard of care based on fluid restriction is unsatisfactory. Currently, a new family of drugs, known as vaptans, which act by antagonizing specifically the effects of arginine vasopressin on the V2 receptors located in the kidney tubules, is being evaluated for their role in the management of hyponatremia. The short-term treatment with vaptans is associated with a marked increase in renal solute-free water excretion and improvement of hyponatremia. Long-term administration of vaptans seems to be effective in maintaining the improvement of serum sodium concentration, but the available information is still limited. Treatment with vaptans represents a novel approach to improving serum sodium concentration in cirrhosis.

Evaluation of mannitol effect in patients with acute hepatic failure and acute-on-chronic liver failure using conventional MRI, diffusion tensor imaging and in-vivo proton MR spectroscopy

AIM: To evaluate the effect of an intravenous bolus of mannitol in altering brain metabolites, brain water content, brain parenchyma volume, cerebrospinal fluid (CSF) volume and clinical signs in controls and in patients with acute liver failure (ALF) and acute-on-chronic liver failure (ACLF), by comparing changes in conventional magnetic resonance imaging (MRI), in vivo proton magnetic resonance spectroscopy (PMRS) and diffusion tensor imaging (DTI) before and after its infusion.

METHODS: Five patients each with ALF and ACLF in grade 3 or 4 hepatic encephalopathy and with clinical signs of raised intracranial pressure were studied along with five healthy volunteers. After baseline MRI, an intravenous bolus of 20% mannitol solution was given over 10 min in controls as well as in patients with ALF and ACLF. Repeat MRI for the same position was acquired 30 min after completing the mannitol injection.

RESULTS: No statistically significant difference was observed between controls and patients with ALF and ACLF in metabolite ratios, DTI metrics and brain volume or CSF volume following 45 min of mannitol infusion. There was no change in clinical status at the end of post-mannitol imaging.

CONCLUSION: The osmotic effect of mannitol did not result in significant reduction of brain water content, alteration in metabolite ratios or any change in the clinical status of these patients during or within 45 min of mannitol infusion.

[Dilutional hyponatremia, hepatorenal syndrome and liver transplantation]

Cirrhosis is a chronic, progressive disease characterized by complications associated with portal hypertension and liver failure. Renal function disorders are a common complication in patients with cirrhosis and are associated with high morbidity and mortality and poor prognosis. Renal function alterations in these patients include sodium and water retention and renal vasoconstriction. Sodium retention causes the formation of ascites and edema, solute-free water leads to dilutional hyponatremia, and renal vasoconstriction gives rise to the development of hepatorenal syndrome (HRS). Due to their poor prognosis, the presence of ascites, dilutional hyponatremia and HRS are indications for liver transplantation (LT). Recent studies have allowed new prognostic factors in these patients to be identified, novel treatments for dilutional hyponatremia and HRS to be applied, and the association of these complications with disease course and outcome before and after LT to be described. The present review discusses new concepts of the physiopathology, evaluation and treatment of cirrhotic patients with dilutional hyponatremia and HRS and the relationship of these entities with LT.

Longitudinal study of amnesic patients at high risk for Alzheimer's disease: clinical, neuropsychological and magnetic resonance spectroscopy features

BACKGROUND/AIMS

To prospectively follow up a group of amnesic patients at risk for Alzheimer's disease (AD), to characterize a group of patients whose features were intermediate between amnesic mild cognitive impairment (aMCI) and probable AD, prodromal AD (Prd-AD), and to investigate if these patients were at higher risk for AD conversion.

METHODS

A total of 109 subjects were assessed by neuropsychological evaluation and by 1H magnetic resonance spectroscopy (1H-MRS): 27 controls, and 16 aMCI, 34 probable AD and 32 Prd-AD patients.

RESULTS

Episodic memory and frontal test scores resulted lower in Prd-AD compared to aMCI patients. Prd-AD patients obtained significantly higher scores than AD ones in language, perception, praxis and frontal functions. Although Prd-AD and AD patients had distinct 1H-MRS features from aMCI ones, there were no 1H-MRS differences between Prd-AD and AD patients. The AD annual conversion rate after 1 year of follow-up for Prd-AD (57.1%) was higher than in aMCI patients (20%; p<0.01). A logistic regression, in which all amnesic patients were treated as a single group, showed that the Visual Memory Test was a significant neuropsychological predictor for AD conversion.

CONCLUSIONS

Prd-AD patients are a clinically distinguishable group, with distinct neuropsychological and 1H-MRS features and a higher conversion rate to probable AD than aMCI patients.

Inadvertent hyponatremia leading to acute cerebral edema and early evidence of herniation

INTRODUCTION

For years, the maintenance of normal or supranormal serum sodium (Na) concentrations has been believed to be beneficial in brain injuries. Recently published guidelines for cerebral trauma recommend the use of hypertonic saline to achieve hypernatremia for the management of increased intracranial pressure and these standards are generally practiced across most diseases in neurocritical care including stroke, hemorrhage and tumors. Severe hyponatremia has long been known to be detrimental, but objective evidence for the harm of mild hyponatremia as a secondary injury has been scarce.

DESCRIPTION OF CASE

In this case report, we describe a child with aneurysmal subarachnoid hemorrhage who had a sudden, inadvertent decrease in serum Na (128 meq/l) that was associated with a deterioration of her neurological examination and evidence of early transtentorial herniation on emergent brain CT scan. These findings were quickly reversed after the serum Na was corrected.

DISCUSSION

This report emphasizes that close monitoring of serum Na and osmolarity in acute head injured children is important, and provides evidence that alterations of these parameters is a substantial risk for cerebral edema in children with evolving brain injuries and briefly reviews the literature regarding the risks of hyponatremia in children.

Renal function and cognitive impairment in patients with liver cirrhosis

OBJECTIVE

Cognitive impairment is a common problem in patients with liver cirrhosis. Its pathogenesis is multifactorial and ammonia is considered to play a central role. Renal function has been shown to be important for ammonia metabolism in cirrhosis. Although renal dysfunction is common in cirrhotic patients, its effect on cognitive function is largely unexplored.

MATERIAL AND METHODS

A total of 128 consecutive cirrhotic patients were prospectively evaluated for the presence of cognitive dysfunction according to the West-Haven criteria and by means of two psychometric tests. Serum creatinine, sodium and potassium as well as plasma ammonia concentrations were assessed. Glomerular filtration rate was also measured by (51)Cr- EDTA clearance in a subgroup of patients.

RESULTS

Forty-one patients (32%) were found to have cognitive dysfunction (clinical evaluation and/or psychometric tests). Sixteen patients (13%) found with serum creatinine levels above reference values had cognitive dysfunction more frequently than patients with creatinine within the normal range (69% versus 31%; p = 0.001), but did not differ in aetiology or severity of cirrhosis (p >0.1). Patients with loop diuretics versus without did not differ in creatinine values (p >0.1). Multivariate analysis showed that cognitive dysfunction was related to hospital admission at inclusion in the study, international normalized ratio and serum creatinine (p <0.05 for all), but not to potassium or sodium levels. Plasma ammonia concentration was related to serum creatinine (r = 0.26, p = 0.004) and the glomerular filtration rate (r = -0.44, p = 0.023).

CONCLUSIONS

Renal dysfunction seems to be related to cognitive impairment in patients with liver cirrhosis and might be implicated in the pathogenesis of hepatic encephalopathy.

Management of ascites and hepatic hydrothorax

The natural course of patients with cirrhosis is frequently complicated by the accumulation of fluid in the peritoneal or pleural cavities and interstitial tissue. Functional renal abnormalities that occur as a consequence of decreased effective arterial blood volume are responsible for fluid accumulation in the form of ascites and hepatic hydrothorax. Ascites is the most common complication of cirrhosis and poses an increased risk for infections, renal failure and mortality. Patients have a poor prognosis and it is estimated that nearly half will die in approximately 2 years without liver transplantation. Hepatic hydrothorax is defined as a pleural effusion greater than 500 mL (mostly right-sided) in patients with cirrhosis without cardiopulmonary disease; the estimated prevalence is approximately 5-10%. Liver transplantation is the most definitive cure for both conditions in those patients that are suitable candidates. However, the mainstay of therapy for minimizing fluid accumulation in both conditions includes sodium restriction and administration of diuretics. This article reviews the most current concepts of pathogenesis, clinical findings, diagnosis, and treatment of these complications of cirrhosis.

Management of hepatic encephalopathy in patients with cirrhosis

The term hepatic encephalopathy encompasses a spectrum of neuropsychiatric abnormalities seen in patients with liver dysfunction. Distinct syndromes are identified in acute liver failure and cirrhosis. Rapid deterioration in consciousness level and increased intracranial pressure that may result in brain herniation and death are a feature of acute liver failure whereas manifestations of hepatic encephalopathy in cirrhosis include psychomotor dysfunction, impaired memory, increased reaction time, sensory abnormalities, poor concentration and in severe forms, coma. In patients with acute-on-chronic liver failure the pathophysiology remains undefined. Ammonia has been considered central to its pathogenesis. In the brain, the astrocyte is the main site for ammonia detoxification, during the conversion of glutamate to glutamine. An increased ammonia level raises the amount of glutamine within astrocytes, causing an osmotic imbalance resulting in cell swelling and ultimately brain oedema. Recent studies suggest that inflammation and it modulators may play a synergistic role with ammonia in the pathogenesis of hepatic encephalopathy. Therapy of hepatic encephalopathy is directed primarily at reducing ammonia generation and increasing its detoxification. The currently accepted regimens to treat hepatic encephalopathy such as lactulose and protein restricted diets need further clinical trials and therefore placebo controlled clinical trials in hepatic encephalopathy are justified. In liver failure, ammonia metabolism involves multiple organs and therefore ammonia reduction will require simultaneous targeting of these organs. The present review describes the pathophysiological basis of hepatic encephalopathy and evaluates the available therapies.

Hyponatremia in cirrhosis: Results of a patient population survey

Low serum sodium concentration is an independent predictor of mortality in patients with cirrhosis, but its prevalence and clinical significance is unclear. To evaluate prospectively the prevalence of low serum sodium concentration and the association between serum sodium levels and severity of ascites and complications of cirrhosis, prospective data were collected on 997 consecutive patients from 28 centers in Europe, North and South America, and Asia for a period of 28 days. The prevalence of low serum sodium concentration as defined by a serum sodium concentration < or =135 mmol/L, < or =130 mmol/L, < or =125 mmol/L, and < or =120 mmol/L was 49.4%, 21.6%, 5.7%, and 1.2%, respectively. The prevalence of low serum sodium levels (<135 mmol/L) was high in both inpatients and outpatients (57% and 40%, respectively). The existence of serum sodium <135 mmol/L was associated with severe ascites, as indicated by high prevalence of refractory ascites, large fluid accumulation rate, frequent use of large-volume paracentesis, and impaired renal function, compared with normal serum sodium levels. Moreover, low serum sodium levels were also associated with greater frequency of hepatic encephalopathy, spontaneous bacterial peritonitis, and hepatorenal syndrome, but not gastrointestinal bleeding. Patients with serum sodium <130 mmol/L had the greatest frequency of these complications, but the frequency was also increased in patients with mild reduction in serum sodium levels (131-135 mmol/L). In conclusion, low serum sodium levels in cirrhosis are associated with severe ascites and high frequency of hepatic encephalopathy, spontaneous bacterial peritonitis, and hepatorenal syndrome.

Natural history of patients hospitalized for management of cirrhotic ascites

BACKGROUND & AIMS

Since the International Ascites Club published the diagnostic criteria of refractory ascites (RA) and hepatorenal syndrome (HRS), there have been few studies assessing the natural history of ascites. The aims of this study were to define the natural history of cirrhotic ascites and to identify prognostic factors for dilutional hyponatremia (DH), RA, HRS, and survival.

METHODS

Two hundred sixty-three consecutive cirrhotic patients were followed for 40.9 +/- 2.6 months after their first significant ascites.

RESULTS

During follow-up 74 (28.1%) patients developed DH, 30 (11.4%) RA (diuretic-resistant in 2 cases and diuretic-intractable because of the development of diuretic-induced complications in 28 cases), and 20 (7.6%) HRS (type 1, 7; type 2, 13). The 5-year probability of DH, RA, and HRS development was 37.1%, 11.4%, and 11.4%, respectively. The probability of survival at 1 and 5 years was 85% and 56.5%, respectively. The independent predictors for survival were baseline age, baseline Child-Pugh score, and DH development. The 1-year probability of survival after developing DH, RA, and type 2 HRS was 25.6%, 31.6%, and 38.5%, respectively. In contrast, the mean survival was only 7 +/- 2 days in those patients developing type 1 HRS.

CONCLUSIONS

(1) The survival of cirrhotic patients with first episode of ascites is relatively high, and it is mainly influenced by age and Child-Pugh score at the time of ascites decompensation, as well as by DH development. (2) The probability of RA and HRS development is relatively low, but they are associated with a poor prognosis.

Hyponatremia in cirrhosis: clinical features and management

The presence of dilutional hyponatremia has a poor prognosis for survival in patients with cirrhosis and ascites. Effective and safe treatments are needed to improve prognosis in patients with cirrhosis and dilutional hyponatremia. The initial approach to management includes fluid restriction, low sodium diet, and minimizing the use of diuretics. In addition, the use of hypertonic saline should be avoided in patients with cirrhosis and dilutional hyponatremia. Furthermore, patients should be placed on the top of the list for liver transplantation if they are appropriate candidates. Although V2 arginine vasopressin receptor antagonists that selectively enhance solute-free water excretion in patients with cirrhosis seem very promising, two points must be considered in relation to the available data. First, although the results of phase-2 studies are encouraging, the efficacy and safety of these compounds should be further evaluated. Second, the clinical utility of these agents in cirrhosis has only been assessed in short-term studies. The long-term effects of these drugs remain unknown. Future research with these compounds should not only focus on the effects on serum sodium, but also on treatment and prevention of recurrence of ascites. In addition, the possible beneficial effects of these drugs in the prevention of hepatic encephalopathy would be worth studying.

Brain volume regulation in response to hypo-osmolality and its correction

Hyponatremia exerts most of its clinical effects on the brain. An acute onset (usually in <24 hours) of hyponatremia causes severe, and sometimes fatal, cerebral edema. Given time, the brain adapts to hyponatremia, permitting survival despite extraordinarily low serum sodium concentrations. Adaptation to severe hyponatremia is critically dependent on the loss of organic osmolytes from brain cells. These intracellular, osmotically active solutes contribute substantially to the osmolality of cell water and do not adversely affect cell functions when their concentration changes. The adaptation that permits survival in patients with severe, chronic (>48 hours' duration) hyponatremia also makes the brain vulnerable to injury (osmotic demyelination) if the electrolyte disturbance is corrected too rapidly. The reuptake of organic osmolytes after correction of hyponatremia is slower than the loss of organic osmolytes during the adaptation to hyponatremia. Areas of the brain that remain most depleted of organic osmolytes are the most severely injured by rapid correction. The brain's reuptake of myoinositol, one of the most abundant osmolytes, occurs much more rapidly in a uremic environment, and patients with uremia are less susceptible to osmotic demyelination. In an experimental model of chronic hyponatremia, exogenous administration of myoinositol speeds the brain's reuptake of the osmolyte and reduces osmotic demyelination and mortality caused by rapid correction.

Portal hypertension

PURPOSE OF REVIEW

Report on significant advances in the pathophysiology, diagnosis, and management of the complications of portal hypertension that have occurred in the last year.

RECENT FINDINGS

The specific areas reviewed refer to experimental studies aimed at modifying the factors that lead to portal hypertension (increased intrahepatic vascular resistance and splanchnic vasodilatation) and recent advances in the diagnosis and management of the complications of portal hypertension. The specific complications reviewed in this paper are varices and variceal bleeding (primary prophylaxis, treatment of the acute episode, and secondary prophylaxis), ascites and some of its complications (hyponatremia, hepatic hydrothorax), hepatorenal syndrome, spontaneous bacterial peritonitis, and hepatic encephalopathy.

SUMMARY

Important studies, mostly prospective, regarding the management of the complications of portal hypertension are reviewed, including trials that demonstrate the value of the hepatic venous pressure gradient in predicting these complications, a trial of beta-blockers in patients with small varices, a randomized trial of transjugular intrahepatic portosystemic shunt using covered stents and another pilot study using this shunt in the treatment of hepatorenal syndrome, a trial of antibiotic prophylaxis in preventing early variceal rebleeding, and a trial of synbiotic therapy in hepatic encephalopathy. These trials will contribute to advancing the practice of hepatology and defining future research areas.

Hyponatremia in liver cirrhosis: pathophysiological principles of management

Hyponatremia is common in cirrhosis, where it impairs encephalopathy. It could be either due to excess water, or reduced Na, or a combination of both. The diagnosis can be established with clinical skills aided by simple data like weight, blood pressure and plasma electrolytes. The quantitative estimates of the water surfeit or solute deficit, easily performed with simple formulas and measurements, guide accurate and programmed treatment procedures, avoiding the occurrence of the ominous central pontine myelinolysis.