title: Hemodynamic and electrocardiographic effects of magnesium sulfate in healthy dogs.
abstract: We investigated the effects of graded dosages of magnesium given i.v. to anesthetized dogs on blood pressure, cardiac output, and electrophysiology. Magnesium was infused at 0.12 mEq/kg/minute until ventricular fibrillation occurred naturally or was provoked by programmed electrical stimulation or until arrest of the sinuatrial node in 8 dogs. Plasma total magnesium concentrations doubled in 1 minute of that infusion rate, and a hemodynamically safe plasma concentration of 12.2 mEq/L was achieved after 16 minutes of infusion. Heart rate, inotropy, lusitropy, and cardiac output increased up to a cumulative infusion dosage of magnesium of 1.0-2.0 mEq/kg, which produced plasma magnesium concentrations of 8.5-12.2 mEq/L (n = 5). Above the cumulative infusion dosage, inotropy decreased and lusitropy increased until death occurred between cumulative infusion dosages of 5.9 mEq/kg and 10.9 mEq/kg. Arterial pressure and vascular resistance decreased, and PQ interval and QRS complex increased, in a dose-dependent fashion. The relationship between ionized and total magnesium was y = 0.624x - 0.542 (r2 = .986), where y is ionized and x is total magnesium in mEq/L in 3 dogs. In conclusion, a cumulative infusion dosage of 0.1-0.2 mEq/kg of magnesium may be given without changing hemodynamic parameters, but with higher cumulative infusion doses heart rate accelerates. Hemodynamic parameters except those related to blood pressure continued to increase to a cumulative infusion dosage of 2.0 mEq/kg. At higher cumulative infusion dosages dogs became hypotensive and the PQ interval was prolonged. However, dangerous arrhythmias were not provoked until a total dosage of 3.9 mEq/kg.
authors.affiliation: Department of Veterinary Biosciences, The Ohio State University, Columbus 43210-1092, USA.
authors.forename: T
authors.initials: T
authors.lastname: Nakayama
authors.forename: H
authors.initials: H
authors.lastname: Nakayama
authors.forename: M
authors.initials: M
authors.lastname: Miyamoto
authors.forename: R L
authors.initials: RL
authors.lastname: Hamlin
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004285:Dogs / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography / Q000187:drug effects / Q000662:veterinary; D006439:Hemodynamics / Q000187:drug effects*; D007262:Infusions, Intravenous / Q000662:veterinary; D008274:Magnesium / Q000097:blood; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000494:pharmacology*; D012016:Reference Values
chemical_list: D000889:Anti-Arrhythmia Agents; D008278:Magnesium Sulfate; D008274:Magnesium