Objective: To evaluate the possible role of vagal impairment in the disturbances of urinary sodium and water excretion observed in cirrhosis.
Methods: Standard cardiovascular reflex tests were used to assess Autonomic function in 11 cirrhotic patients, and the response to an acute intravenous water load was determined. Changes in plasma noradrenaline, antidiuretic hormone, renin, and atrial natriuretic peptide also were evaluated.
Results: Patients with vagal dysfunction were shown to have significantly impaired urinary sodium and water excretion, compared with those whose cardiovascular tests were normal (5-h urinary sodium excretion, 32.3 +/- 9.0 vs. 69.4 +/- 12.7 mmol, p < 0.05; % water load excreted at 5 h, 67.8 +/- 10.5 vs. 109.2 +/- 3.67%, p < 0.008). This was associated with higher circulating noradrenaline, renin, and antidiuretic hormone levels after the water load in the vagal dysfunction group. Urinary sodium excretion correlated with the heart rate variation on deep breathing (r = 0.74, p < 0.013) and the heart rate response to atropine (r = 0.75, p < 0.020); the % water load excreted correlated with the number of abnormal cardiovascular tests in each patient (rS = 0.67, p < 0.02). Although patients with vagal abnormalities had worse liver function, urinary sodium and water excretion correlated better with parasympathetic tests than with standard parameters of hepatic function.
Conclusions: The presence of vagal impairment in cirrhosis appears to be associated with impaired urinary sodium and water excretion, as well as disturbances in circulating vasoactive hormones. These findings could be due to an afferent defect resulting in diminished inhibitory input from intrathoracic volume and arterial baroreceptors, although a confounding effect of worse hepatic function in patients with vagal impairment cannot be excluded.