Reduction in standard MAC and MAC for intubation after clonidine premedication in children

We examined the relative effects of different doses of oral clonidine on the MAC for endotracheal intubation (MAC(EI)) and the MAC for skin incision (MAC) in children. We studied 90 children (15 in each group) (age range 2-8 yr, weight 10-27 kg, height 89-124 cm) who received one of three preanaesthetic medications: placebo (control), oral clonidine 2 mug kg(-1), or oral clonidine 4 mug kg(-1) 100 min before anaesthesia. Anaesthesia was induced and maintained with sevoflurane in oxygen and air without i.v. anesthetics and neuromuscular relaxants. The end-tidal sevoflurane concentration was kept constant for greater than or equal to 15 min before tracheal intubation or skin incision. MACs were determined using Dixon's 'up-and-down method'. Mean (SD) MAC(EI)s of sevoflurane were 2.9 (0.1)%, 2.5 (0.1) % and 1.9 (0.1) % (P<0.05), and MACs were 2.3 (0.1) %, 1.8 (0.1) % and 1.3 (0.1) % (P<0.05), respectively, in control, clonidine 2 mug kg(-1) and clonidine 4 mug kg(-1) groups. The MAC(EI)s and MACs decreased dose-dependently. The MAC(EI)/MAC ratio (1.4) was not affected by clonidine.