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

Abstract

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 μg kg-1, or oral clonidine 4 μg 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 ≥ 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 μg kg-1 and clonidine 4 μg kg-1 groups. The MAC(EI)s and MACs decreased dose-dependently. The MAC(EI)/MAC ratio (1.4) was not affected by clonidine.