The haemodynamic effects of intravenous prenalterol and ouabain in conscious dogs

Acta Medica Scandinavica. Supplementum
L EkB Johansson

Abstract

Experiments were performed on 5 resting conscious dogs supplied with an electromagnetic flow probe on the ascending aorta and a chronic aortic catheter for pressure recording. The animals were used repeatedly in four different types of experiment involving i.v. administration of 1. saline (controls), 2. prenalterol 45 nmol/kg (approximately 10 micrograms/kg) followed by an additional dose of 135 nmol/kg 20 min later, 3. ouabain 50 nmol/kg (approximately 30 micrograms/kg) and 4. a combination of protocols 2. and 3. Ouabain and the low dose of prenalterol exerted clear-cut positive inotropic effects as reflected in increased stroke volume and max dF/dt without significant changes in heart rate or arterial pressure. The PQ interval increased with ouabain but decreased with prenalterol. The higher dose of prenalterol caused a further rise in max dF/dt, a further shortening of the PQ time, increased heart rate and reduction in systemic vascular resistance. Higher doses of ouabain could not be given due to side-effects (vomiting). The combined treatment with ouabain and prenalterol showed their inotropic responses to be additive. Arrhythmias did not occur in any of the animals at the applied dose levels of the drugs. The experiments ...Continue Reading

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