Haemodynamic Effects of Different Corticosteroids in Controlled Haemorrhagic Shock in the Dog

The haemodynamic effects of massive doses of hydrocortisone (80–320 mg.kg-1), methylprednisolone (4–32 mg.kg-l), betamethasone (1.6–12.8 mg.kg-1) and aldosterone (0.1–0.8 mg.kg-1) and the interaction with phenoxybenzamine and propranolol have been studied during controlled haemorrhagic shock in the anaesthetized dog. Hydrocortisone was the only steroid which showed any significant vasodilating ability when given alone. The alpha-receptor blocking agent phenoxybenzamine distinctly decreased the total peripheral resistance. The effect of the phenoxybenzamine was increased in combination with hydrocortisone or methylprednisolone, especially if the steroid was given as the first drug. The vasodilation found was efficiently abolished by the beta-receptor blocking agent propranolol. The ability of hydrocortisone or methylprednisolone to potentiate phenoxybenzamine was not shared by betamethasone or aldosterone. Thus, the haemodynamic effect of the steroid does not seem to be correlated to either a glucocorticoid nor a mineralocorticoid effect. It is suggested that the steroid effect studied is related to the ability of hydrocortisone or methylprednisolone to block the extra neuronal amine uptake which decreases the rate of elimination of the sympathetic transmitter from the vicinity of the adrenergic receptor of the vascular smooth muscles.