Effects of ephedrine on intubating conditions following priming with rocuronium

Onset of action of muscle relaxants is influenced by cardiac output and muscle blood flow. Ephedrine reduces the onset time of rocuronium. Onset is also shortened by priming. Accordingly, we hypothesized that priming combined with ephedrine is superior to either technique used separately.

Four groups of randomly allocated patients (n = 31), ASA I - II, were induced with propofol 2.5 mg kg(-1). In groups I and II, 0.04 mg kg(-1) of rocuronium was followed by a 3-min priming interval. Induction was followed by an intubation dose of 0.04 mg kg(-1). Then a 30-s intubation was attempted. In groups III and IV the same sequence was repeated except for sham priming and an intubation dose of 0.44 mg kg(-1). In groups I and II, ephedrine (210 microg kg(-1)) was injected before propofol. In groups II and V, an equivalent volume of normal saline was injected. Jaw relaxation, vocal cord position, and diaphragmatic response were used to assess intubating conditions.

All patients of group I were intubated 30 s after the intubating dose and within a 20-s interval compared with 74% of patients in groups II and III, and 84% of patients in group IV. Intubating conditions were graded good to excellent in all patients in group I compared with 42% of those in group II, 35% in group III and 52% in group IV (P < 0.01 vs. group I). During the priming interval, no adverse effects were observed or reported.

Ephedrine in combination with propofol significantly improved clinical intubating conditions at 30 s following priming with rocuronium compared with priming with ephedrine without priming.