Systemic hemodynamic, forearm vascular, renal, and humoral responses to sustained cardiopulmonary baroreceptor deactivation in well-compensated cirrhosis

The aim of this study was to assess baroreceptor function in well-compensated cirrhosis by determining the forearm vascular, renal, and humoral responses to sustained baroreceptor deactivation. The effect of sodium status on baroreceptor function was also assessed. Eight cirrhotic patients and 10 age- and sex-matched controls were studied twice after a 20 mmol and 200 mmol of sodium/d diet for 7 days. Systemic and renal hemodynamics, renal sodium handling, forearm blood flow, and neurohumoral factors were assessed before, during, and after the application of lower body negative pressure (LBNP) for 1 hour. Controls and cirrhotic patients had similar baseline mean arterial pressure, heart rate, forearm and renal hemodynamics. High-sodium intake resulted in suppression of sympathetic nervous activity in the controls (plasma norepinephrine, 1.06 +/- 0.11 nmol/L on low vs. 0.76 +/- 0.08 nmol/L on high sodium; P = 0.01) but not in the cirrhotic patients (1.35 +/- 0.22 nmol/L on low vs. 1.26 +/- 0.11 nmol/L on high sodium; P > 0.05). Both groups responded to LBNP with significant further increases in plasma norepinephrine, resulting in significant decreases in forearm blood flow on both sodium diets. Controls also responded with a significant worsening of renal hemodynamics on low-sodium diet only, but this was not observed in the cirrhotic patients on either diet. Therefore, in well-compensated cirrhotic patients: (1) sympathetic activation occurs despite an adequate, effective arterial filling, and this may contribute to sodium retention; and (2) baroreceptor function is normal. Apparent end organ unresponsiveness within the renal circulation may account for the lack of renal hemodynamic changes to reflex sympathetic stimulation.