Effect of ionophore monensin on anaesthetized dogs in hemorrhagic hypotension

Progressive decompensation and irreversible cellular injury from the severe hemorrhagic shock can be reversed therapeutically with aggressive and timely resuscitation by administering volume expanding fluids. The possibility of the use of rapidly acting pressor agents which can effectively maintain the blood pressure and peripheral perfusion (without volume resuscitation) and prevent the progression of shock and providing in regular time interval for volume replacement has not been looked into. In the present investigation, two pressor agents, dopamine and a long acting carboxylic ionophore monensin, were examined for their potential role in hemorrhagic hypotension produced experimentally in dogs.

Two groups of animals were studied: (a) In the first group (n=10) 20% of the total blood volume i.e. moderate hemorrhage was induced. (b) In the second group (n=10) 35% of the total blood volume i.e. severe hemorrhage was induced. After 30 min of induction of hemorrhage both the groups were given intravenous infusion of dopamine (20 microgm/kg/min) for 10 min. Then after 30 min of stopping dopamine infusion, both the groups were given intravenously a single bolus dose (50 microgm/kg) of monensin.

In both moderate and severe hemorrhage monensin injection produced significant increases in systolic arterial blood pressure, mean arterial blood pressure, cardiac output and stroke volume. The effects persisted for 1 h of administration. In severe hemorrhage dopamine infusion produced significant decrease in mean arterial blood pressure, diastolic blood pressure and pH. Dopamine produced a significant rise in heart rate also while monensin did not have such an effect.

Monensin produced a rapid and sustained recovery of the arterial blood pressure without requiring adequate preload. Dopamine failed to produce such an effect because it requires adequate circulating blood volume for its pressor action. Thus monensin has the potential to prevent progression of shock and improving the prognosis in management of hemorrhagic hypotension.