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-comp ensated cirrhosis by determining the forearm vascular, renal and humor al responses to sustained baroreceptor deactivation. The effect of sod ium status on baroreceptor function was also assessed. Eight cirrhotic patients and 10 age- and sex-matched controls were studied twice afte r a 20 mmol and 200 mmol of sodium/d diet for 7 days, Systemic and ren al hemodynamics, renal sodium handling, forearm blood flow and neurohu moral factors were assessed before, during, and after the application of lower body negative pressure (LBNP) for 1 hour. Controls and cirrho tic patients had similar baseline mean arterial pressure, heart rate, forearm and renal hemodynamics. High-sodium intake resulted in suppres sion of sympathetic nervous activity in the controls (plasma norepinep hrine, 1.06 +/- 0.11 nmol/L, on low vs. 0.76 +/- 0.08 nmol/L on high s odium; 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 gro ups responded to LBNP with significant further increases in plasma nor epinephrine, resulting in significant decreases in forearm blood flow on both sodium diets, Controls also responded with a significant worse ning of renal hemodynamics on low-sodium diet only, but this was not o bserved in the cirrhotic patients on either diet. Therefore, in well-c ompensated cirrhotic patients: (1) sympathetic activation occurs despi te an adequate, effective arterial filling, and this may contribute to sodium retention; and (2) baroreceptor function is normal. Apparent e nd organ unresponsiveness within the renal circulation may account for the lack of renal hemodynamic changes to reflex sympathetic stimulati on.