Relative contribution of preload and afterload to the reduction in cardiac output caused by nitric oxide synthase inhibition with L-N(G)-methylarginine hydrochloride 546C88.

Journal Article (Journal Article)

OBJECTIVE: The nitric oxide synthase inhibitor L-N(G)-methylarginine hydrochloride (L-NMMA HC1 546C88) causes reductions in cardiac output (CO), a potential limitation to clinical application. This drop in CO exceeds that from phenylephrine at matched systemic arterial pressure. We tested the hypothesis that the greater fall in CO attributable to L-NMMA primarily reflects a difference in venoconstriction between agents, such that phenylephrine produces larger increases in preload (an independent determinant of CO). DESIGN: Random infusion of phenylephrine or L-NMMA. SETTING: An animal research laboratory. SUBJECTS: Eight healthy, conscious, male dogs. INTERVENTIONS: L-N(G)-methylarginine hydrochloride (20 mg/kg for 1 hr) and phenylephrine (0.5 to 3 microg/kg/min) were administered into eight dogs chronically instrumented to measure left ventricular pressure and dimension. Data were measured at a constant heart rate (140 beats/min) to render CO proportional to stroke dimension. MEASUREMENTS AND MAIN RESULTS: At a matched increase in afterload (effective arterial elastance), L-NMMA increased preload (end-diastolic dimension) to a lesser degree (3.8%+/-1.5%, p < .05) than phenylephrine (9.6%+/-1.6%, p < .05 vs. L-NMMA). Neither L-NMMA nor phenylephrine affected the slope of the end-systolic pressure dimension relationship, although L-NMMA shifted the relationship rightward (1.7+/-0.7 mm, p < .05), consistent with a mild negative inotropic effect. L-NMMA decreased the stroke dimension to a greater extent than phenylephrine (-24.1%+/-6.8% and -10.6%+/-3.4%, respectively, p < .05). CONCLUSIONS: Differential CO responses to phenylephrine and L-NMMA were primarily attributable to changes in preload. Variable venular vs. arteriolar constrictor effects must be considered when evaluating the integrated cardiovascular response to a vasoactive agent.

Full Text

Duke Authors

Cited Authors

  • Harrison, RW; Thakkar, RN; Senzaki, H; Ekelund, UE; Cho, E; Kass, DA; Hare, JM

Published Date

  • May 2000

Published In

Volume / Issue

  • 28 / 5

Start / End Page

  • 1263 - 1268

PubMed ID

  • 10834663

International Standard Serial Number (ISSN)

  • 0090-3493

Digital Object Identifier (DOI)

  • 10.1097/00003246-200005000-00001


  • eng

Conference Location

  • United States