Function of the Autonomic Nervous System in Patients With Hepatic Encephalopathy

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Abstract
To obtain further pathophysiological details concerning the development of cardiovascular disturbances in severe liver disease, the state of the autonomic nervous system, the function of the baroreceptor reflex pathway and the responsiveness of the cardiovascular system to noradrenaline, angiotensin II and isoprenaline were investigated in 11 patients with hepatic encephalopathy and in 10 healthy control subjects. Increased plasma levels of noradrenaline and adrenaline and an attenuated increase in heart rate in response to atropine were found in patients with hepatic encephalopathy. These changes and the hemodynamic disturbances tended to be more pronounced in patients with hepatic encephalopathy Grades III-IV as compared to hepatic encephalopathy Grades I-II. The increase in systolic blood pressure induced by infusion of noradrenaline (400 ng per kg per min) and angiotensin II (20 ng per kg per min) was higher in the patients than in healthy control subjects (hepatic encephalopathy Grades I-II: p < 0.001; hepatic encephalopathy Grades III-IV: p < 0.02). The changes in mean and diastolic blood pressure in response to angiotensin II were more pronounced in hepatic encephalopathy grades I-II than in hepatic encephalopathy Grades III-IV (p < 0.02). The decrease of heart rate in response to blood pressure increase in patients with hepatic encephalopathy was not different from control subjects except a smaller decrease during angiotensin II infusion in hepatic encephalopathy grades III-IV (p < 0.05). The responsiveness to isoprenaline was diminished (p < 0.001). The present results indicate that the increased activity of the sympathetic nervous system in hepatic encephalopathy is associated with decreased parasympathetic tone. In addition, patients with hepatic encephalopathy have normal function of the baroreceptor reflex and excellent responsiveness of vascular tissue to endogenous vasoconstrictors.