The optimal dose of atropine via the endotracheal route

Fifty ASA class I or II patients, undergoing general or gynecological surgery under general anesthesia with endotracheal intubation, were randomly divided into five groups. Group I received 10 ug/kg atropine intravenously, group II to V received 10 ug/kg, 20 ug/kg, 30 ug/kg, 40 ug/kg, respectively via endotracheal route through an epidural catheter. All were given five manual deep breaths after the injection of atropine. The maximum increase in heart rate (MIHR) and the time to maximum heart rate (TMHR) were evaluated. There was no marked MIHR in group II. Group III had a MIHR similar to that of group I (17.5/min vs 20/min, p greater than 0.05), but had a longer TMHR than group I (120 sec vs 82.5 sec, p less than 0.005). Groups IV and V had greater MIHR than group I (28.7 and 29.5 vs 20/min, p less than 0.005), and a TMHR similar to that of group I (85 and 90.2 vs 82.5 sec, p greater than 0.05). For emergency procedures, if atropine must be given without an intravenous catheter, 30 ug/kg or more given endotracheally can achieve an effect comparable to that of 10 ug/kg given intravenously.