Effects of fenoterol and ipratropium on respiratory resistance of asthmatics after tracheal intubation

We have studied the effects of a beta-agonist, fenoterol, and a cholinergic antagonist, ipratropium, on post-intubation total respiratory system resis tance (Rrs) in asthmatics who developed increased Rrs after tracheal intuba tion. Sixteen stable asthmatics in whom Rrs increased after intubation were allocated randomly to receive either 10 puffs of fenoterol (group F) or 10 puffs of ipratropium (group 1B) via a metered dose inhaler 5 min after int ubation. Anaesthesia was induced and maintained with propofol i.v. Rrs was recorded before treatment and again 5, 15 and 30 min after treatment. Rrs d ecreased significantly from pretreatment values by mean 53 (SD 8)%, 53 (7)% and 58 (6)% at 5, I 5 and 30 min, respectively, in group F, but declined b y only 12 (6)%, 15 (4)% and 17 (5)% in group 1B, At all times after treatme nt, patients in the fenoterol group had significantly tower Rrs values than those in the ipratropium group. We conclude that increased Rrs after trach eal intubation in asthmatics can be reduced effectively by treatment with f enoterol. A secondary finding of our study was that even after induction of anaesthesia with propofol, patients with a history of asthma may develop h igh Rrs.