Abstract:
Clonidine is an α2 adrenoceptor agonist used as both premedication and intraoperatively as an adjunct to anaesthesia. There is interest in the use of clonidine to reduce emergence delirium (ED) in children. This is a phenomenon whereby children exhibit agitation, hallucinations, misperceptions and fluctuating behaviour in the postoperative period. However there is concern that clonidine increases postoperative sedation and that this may result in a delayed discharge time, increasing hospital costs. Night terrors is a phenomenon whereby children suddenly awake during sleep and will exhibit symptoms similar to ED. The purpose of the studies for this thesis was to determine the effect of clonidine on ED, to characterise the dose-effect relationship for clonidine and anaesthesia recovery and to investigate correlation between night terrors and ED. An observational audit was carried out over a period of 4 months. Healthy children aged ≤15 years who were undergoing anaesthesia for adenoidectomy, (adeno) tonsillectomy and myringotomy procedures were reviewed. Multiple surgeons and anaesthetists were involved in the procedures and the choice of anaesthetic was left to the discretion of the anaesthetist. Sedation was determined at 30 minute intervals using the University of Michigan Sedation Scale (UMSS). ED was determined in the post anaesthesia care unit (PACU) using the Paediatric Anaesthesia Emergence Delirium (PAED) scale approximately 5 and 10 minutes after the child awoke from anaesthesia. Parents were asked if their child ever woke in a distressed state where they were difficult to console in order to determine a history of night terrors. A total of 406 children were assessed. Of these children, 369 were included in the ED data analysis. It was determined that there was no difference in average PAED scores or the incidence of ED between clonidine dosing groups. There were 177 children included in the mixed effect modelling analysis investigating the relationship between clonidine dose and anaesthesia recovery duration. The half-time to arousal after anaesthesia (Twakeup) for children not given clonidine was 10.8 minutes. Clonidine prolonged this emergence half-time in a dose dependent manner. Emergence half-time is increased to 15 minutes with clonidine 0.5 μg/kg, 20 minutes with clonidine 1.5 μg/kg, 25 minutes with clonidine 2 μg/kg and a predicted 100 minutes with clonidine 5 μg/kg. A total of 330 children had data available for determining the relationship between night terrors and ED. Regardless of which PAED threshold was used to define ED and whether or not those children treated with clonidine were included, the calculated positive predictive values (PPVs) and negative predictive values (NPVs) ranged from 16.11 – 26.85% and 76.80 – 84.98% respectively. These results suggest that a history of night terrors was not predictive of ED. However an absence of night terrors was predictive of an absence of ED. While these investigations found no effect of clonidine on ED, a dose of 2 μg/kg has previously been found useful in preventing ED. This dose caused greater sedation in the post anaesthesia care unit but did not impact on hospital discharge times. A history of night terrors was not predictive of ED.