The effect of varying sodium intake on blood volume, forearm blood flow and vascular responsiveness to sympathetic stimulation in pre-ascitic cirrhosis.

OBJECTIVES

To assess, in patients with well-compensated pre-ascitic cirrhosis, (1) the extent of vasodilatation, if any, in the forearm circulation and (2) the effect of sodium status on its response to reflex sympathetic stimulation.

DESIGN

Case-control study.

SETTING

Clinical investigation unit of the Toronto Hospital, a tertiary referral hospital.

PATIENTS

Eight male, alcoholic patients with pre-ascitic cirrhosis and 10 age- and sex-matched controls.

INTERVENTIONS

Patients and controls were given a diet containing 20 mmol of sodium per day for 7 days, then a diet containing 200 mmol of sodium per day for the subsequent 7 days. On the seventh day of each diet, systemic hemodynamics, forearm circulation and effective arterial blood volume were assessed. A cold pressor test was performed after both diets to assess the response of the forearm circulation to reflex sympathetic stimulation.

OUTCOME MEASURES

Heart rate, mean arterial pressure, forearm blood flow, forearm vascular resistance, central venous pressure, atrial natriuretic factor concentrations and neurohumoral pressor levels (plasma renin activity, aldosterone and plasma norepinephrine levels).

RESULTS

No forearm vasodilatation was evident in the patients with pre-ascitic cirrhosis; their forearm blood flow and forearm vascular resistance were similar to those of the controls. Sodium loading did not influence baseline forearm blood flow. Cold pressor stimulus resulted in a significant decrease in forearm blood flow and a significant increase in forearm vascular resistance, mean arterial pressure, heart rate and plasma norepinephrine levels in both groups after the low-sodium diet. High sodium intake resulted in significantly greater reduction in forearm blood flow (-19%, standard error of the mean [SEM] 3% v. -8%, SEM 3%; p < 0.05) and significantly greater increase in forearm vascular resistance (+46%, SEM 7% v. +25%, SEM 8%; p < 0.05) in the patients with cirrhosis than in the controls.

CONCLUSIONS

Well-compensated pre-ascitic cirrhotic patients do not have forearm vasodilatation. Sodium loading does not increase baseline forearm blood flow in these patients, but it does lead to a heightened response to reflex sympathetic stimulation. Sodium loading, with the associated sympathetic hyper-responsiveness, may therefore contribute to further sodium retention in these patients.