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Type: Journal article
Title: Acute cardiovascular effects of magnesium and their relationship to systemic and myocardial magnesium concentrations after short infusion in awake sheep
Author: Zheng, D.
Upton, R.
Ludbrook, G.
Martinez, A.
Citation: Journal of Pharmacology and Experimental Therapeutics, 2001; 297(3):1176-1183
Publisher: Amer Soc Pharmacology Experimental Therapeutics
Issue Date: 2001
ISSN: 0022-3565
Abstract: The temporal relationship between the systemic and myocardial concentrations of magnesium and some of its acute cardiovascular effects were examined after short i.v. infusion administration of magnesium (30 mmol over 2 min) in five awake chronically instrumented sheep. Magnesium decreased mean arterial blood pressure and systemic vascular resistance (SVR) by 23 and 41% from baseline, respectively. These hemodynamic changes were consistent with magnesium producing primary reductions in SVR with partial heart rate (HR)-mediated compensation of blood pressure. Cardiac output and HR increased by 38 and 38% from baseline, respectively. Magnesium had little effect on myocardial contractility, but substantially increased myocardial blood flow (MBF, 77% above baseline) primarily due to direct myocardial vasodilation. The peak arterial and coronary sinus serum magnesium concentrations were 6.94 ± 0.26 (mean ± S.E.M.) and 6.51 ± 0.20 mM, respectively, at 2 min. Both arterial and coronary sinus magnesium concentrations at the end of the study were still more than 3 mM, whereas all the cardiovascular effects were back to baseline. The myocardial kinetics of magnesium was consistent with rapid equilibration of magnesium (half-life 0.4 min) with a small distribution volume (71 ml) consistent with the extracellular space of the heart. In conclusion, magnesium was shown to have a rapid equilibration between the plasma/serum concentrations of magnesium and its extracellular concentration in the myocardium. However, the primary cardiovascular effect of magnesium (reductions in SVR) preceded its extracellular concentrations, and was a direct function of its arterial concentration. A "threshold" model for changes in SVR was preferred when linked to the arterial magnesium concentration.
Keywords: Myocardium; Cardiovascular System; Extracellular Space; Animals; Sheep; Magnesium; Blood Flow Velocity; Cardiac Output; Infusions, Intravenous; Wakefulness; Blood Pressure; Heart Rate; Vascular Resistance; Coronary Circulation; Myocardial Contraction; Models, Cardiovascular; Cardiovascular Physiological Phenomena
Description: Copyright © 2001 by The American Society for Pharmacology and Experimental Therapeutics
RMID: 0020010731
Appears in Collections:Anaesthesia and Intensive Care publications

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