Transcutaneous CO2 tension effects of clonidine in paediatric caudal analgesia

In adults, clonidine when added to bupivacaine, results in no detectable respiratory depressant effect except when carbon dioxide challenge is performed. However, to date no investigations have quantified this in children. Twenty-four children (nine months to seven years) were randomized in a double-blind study into two groups. After induction, a caudal block was performed with 1 ml.kg(-1) 0.25% bupivacaine. Clonidine 1 mu g.kg(-1) was added in the clonidine group, and 1 ml normal saline in the placebo group. Patients were monitored in the recovery room for three h from arrival to discharge with continuous pulse oximetry, respiratory rate, a trancutaneous CO2 tension (tcPCO(2)) every 15 min, and a four point sedation score every 30 min. Mean tcPco(2) and respiratory rate values were not different between the two groups. Apnoea and desaturation less than 97% were not observed. The sedation score decreased with time in both groups, and the score time interval was significantly higher in the clonidine group (P<0.05). All the patients left the recovery room with a sedation score of 1, excepting four in the clonidine group with a sedation score of 2. Clonidine 1 mu g.kg(-1) with 0.25% bupivacaine mixture in caudal analgesia in children did not induce an increase in tcPco(2) despite prolonged sedation.