Hyponatremia in hepatic encephalopathy: an accomplice or innocent bystander?

Hyponatremia, a common complication inpatients with advanced liver disease and impaired free water clearance, has been shown to be an important predictor of short-term mortality. Hepatic encephalopathy, also a late complication of end-stage liver disease, has been associated with low-grade cerebral edema as a result of swelling of astrocytes. Guevara et al. hypothesized that hyponatremia and the resultant depletion of organic osmolytes (e.g.,myo-inositol) from brain cells contribute to brain edema, playing an important role in the pathogenesis of hepatic encephalopathy. Using a multivariable analysis, they demonstrated that hyponatremia increased the risk of hepatic encephalopathy more than eightfold, after adjustment for serum bilirubin and creatinine concentrations and previous history of encephalopathy. Their magnetic resonance spectroscopy data correlated low brain concentrations of myoinositol with hepatic encephalopathy. As both hyponatremia and encephalopathy occur in patients with advanced liver disease, it has been difficult to implicate hyponatremia independently in the pathogenesis of hepatic encephalopathy. Guevara's data do suggest that hyponatremia is more likely an accomplice than an innocent bystander.