Cardiovascular function during induced hypotension by fenoldopam or sodium nitroprusside in anesthetized dogs

N. D. Kien, Peter G Moore, R. S. Jaffe

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Abstract

Fenoldopam, a selective dopamine1 receptor agonist, has been recommended for induced hypotension because it effectively lowers arterial blood pressure and improves renal perfusion. We examined cardiovascular functions during hypotension induced by fenoldopam or sodium nitroprusside. In eight halothane-anesthetized dogs, the left ventricle (LV) was instrumented with pressure and ultrasonic dimension transducers for the assessment of LV contractility using the analysis of the pressure-diameter relationship. Blood flow distribution was measured by radioactive microspheres. Doses of fenoldopam and nitroprusside were titrated to reduce mean arterial blood pressure to 60 mm Hg. After 40 min of hypotension, fenoldopam and nitroprusside caused similar increases in heart rate (17% ± 4% vs 19% ± 10%, respectively) and decreases in systemic vascular resistance (-24% ± 5% vs -27% ± 4%). Hypotension induced by fenoldopam was associated with higher LV end-diastolic pressure (4.4 ± 0.6 vs 2.5 ± 1.1 mm Hg) and end-systolic meridional wall stress (33.0 ± 4.3 vs 17.8 ± 2.1 g/cm2) when compared with nitroprusside. There were no significant changes in cardiac output and cardiac contractility as expressed by the slope (E(es)) of the LV end-systolic pressure-diameter relationship, velocity of shortening of the diameter, and percentage of wall thickening of the LV. In contrast to nitroprusside, which decreased renal blood flow from 197 ± 19 to 163 ± 15 mL/min, renal blood flow increased during fenoldopam-induced hypotension from 187 ± 20 to 239 ± 18 mL/min. The increase in renal perfusion was similar in upper, middle, and lower regions of the kidney; however, it was more in the medulla compared with the cortex (37% ± 17% vs 25% ± 7%). Both fenoldopam and nitroprusside decreased splenic blood flow, but neither altered flow to the brain, skin, or myocardium. Muscle and hepatic arterial blood flow were significantly less with fenoldopam than with nitroprusside. Fenoldopam was associated with significantly larger increases in plasma renin activity compared with nitroprusside. The results of this study show an increase in renal blood flow during fenoldopam infusion that may be of advantage particularly when renal hypoperfusion should be avoided.

Original languageEnglish (US)
Pages (from-to)72-78
Number of pages7
JournalAnesthesia and Analgesia
Volume74
Issue number1
StatePublished - 1992

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

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