The effects of acute and chronic hydrocortisone treatment on neuromuscular blockade in the anesthetized cat.

It is fairly widespread clinical practice to administer large doses of corticosteroids to patients in cases of shock; doses of hydrocortisone as high as 50 mg X kg-1 given intravenously have been proposed and used. Hydrocortisone, when administered in this way during surgery, has been implicated in interactions with neuromuscular blocking agents. In order to determine the type and mechanism of this interaction, the authors undertook further investigation. The effects of hydrocortisone were studied in two ways. Firstly, a constant 50% depression of the indirectly elicited twitch tension of the tibialis-anterior muscle was established in cats, using a constant intravenous infusion of either pancuronium (1.0 +/- 0.2 micrograms X kg-1 X min-1) or succinylcholine (3.6 +/- 0.8 micrograms X kg-1 X min-1). The effects of intravenous hydrocortisone then were studied on this block. Secondly, cats chronically were treated with 2 mg X kg-1 of intramuscular hydrocortisone three times a week for 1 month, and then dose-response curves were constructed for pancuronium or succinylcholine. Acute administration of intravenous hydrocortisone (1-15 mg X kg-1) alone had no affect on the twitch tension of either the tibialis-anterior or soleus muscles, however, the corticosteroid (7 and 15 mg X kg-1) did significantly (P less than 0.05) enhance the 50% depression of the indirectly elicited twitch tension of the tibialis-anterior muscle produced by the constant intravenous infusion of pancuronium. The soleus muscle was affected similarly (n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)