FENOLDOPAM IMPROVES RENAL HEMODYNAMICS IMPAIRED BY POSITIVE END-EXPIRATORY PRESSURE

Background: Mechanical ventilation with positive end-expiratory pressu re (PEEP) can impair renal hemodynamics. Fenoldopam, a dopamine recept or agonist, has been shown, in animal experiments, to improve renal pe rfusion. The purpose of the current study was to examine the effects o f this agent on altered renal hemodynamics secondary to positive press ure ventilation. Methods: Twelve patients requiring mechanical ventila tion of their lungs and PEEP for the treatment of hypoxemia after mult iple trauma or visceral surgery were studied. Hemodynamic variables, r enal vascular resistance, urine flow, creatinine, inulin and PAH clear ance, and excretion of sodium and potassium (NaE and KE) were measured before and after introduction of a level of PEEP high enough to decre ase urine flow rate by 25% or more, and after administration of intrav enous fenoldopam. Results: No hemodynamic effect resulted from 0.1 mug . kg-1 . min-1, but 0.2 mug . kg-1 . min-1 fenoldopam decreased both diastolic and mean arterial blood pressure from 66 +/- 37 (mean +/- SE M) to 57 +/- 21 mmHg, and from 83 +/- 3 to 74 +/- 4 mmHg, respectively . Renal vascular resistance was reduced from 54 +/- 12 to 19 +/- 5 dyn es . s . cm-1 at 0.2 mug . kg-1 . min-1. Fenoldopam produced a dose-re lated increase in renal blood flow and PAH clearance. With 0.2 mug . k g-1 . min-1 fenoldopam, urine flow increased from 81 +/- 25 to 116 +/- 29 ml/h, NaE from 28 +/- 7 to 85 +/- 70 muM/min, and KE from 65 +/- 1 2 to 109 +/- 16 muM/min. Conclusions: The results of the current study indicate that intravenous fenoldopam at a dose of 0.2 mug . kg-1 . mi n-1 improves renal hemodynamics and increases Na and K excretion in pa tients requiring mechanical ventilation of their lungs and PEEP. These effects are probably caused by an increased kidney perfusion secondar y to renal artery vasodilation.