[Neurohumoral changes induced by hemofiltration in congestive heart failure: physiopathological inferences]

Hemofiltration is a method suitable for rapid substraction of plasma water that generally allows reduction of circulating levels of norepinephrine. Using that non-pharmacological approach we investigated the mechanisms involved in the metabolism of the hormone as well as the hemodynamic correlates of a prompt and great fall of the sympathetic neurotransmitter in patients with chronic refractory congestive heart failure (CHF). In 23 patients with CHF, hemofiltration of 2983 +/- 1228 ml of plasma water (in 5 +/- 2 hours of treatment) increased urinary output by 606 +/- 415 ml in the day of the procedure as well as sodium excretion by 53 +/- 38 mEq/24 h; simultaneously, a mean fall in plasma norepinephrine concentration by 515 +/- 444 pg/ml was observed. These effects were prompt and persisted or even rose in the next 24 and 48 hours, not being related to changes in plasma renin activity, right atrial, wedge pulmonary artery and renal perfusion pressures and to the amount and duration of hemofiltration. Our data did not clarify the mechanism involved in the increase of the diuresis and for its coupling with the fall in plasma norepinephrine. Nevertheless, we found a strong and statistically significant correlation (r = 0.7; p less than 0.01) between percent changes from baseline values of norepinephrine and diuresis. It is therefore suggested that the same, still unknown, mechanism which increased urinary output also potentiated norepinephrine removal by the kidney: or that water reabsorption from extravascular spaces (triggered by hemofiltration and continued by increased diuresis) resulted in regression of organ congestion leading to an improved clearance of norepinephrine by different organs.(ABSTRACT TRUNCATED AT 250 WORDS)