Influence of premedication on the sympathetic and endocrine responses and cardiac arrhythmias during halothane anaesthesia in children undergoing adenoidectomy.

The occurrence of cardiac arrhythmia was investigated in 80 children during halothane anaesthesia for adenoidectomy. Two different premedications were studied. Forty children (group A) were premedicated with diazepam 5 mg rectally and atropine 0.3-0.4 mg sublingually and 40 (group B) received a rectal solution including diazepam 0.5 mg kg-1, morphine 0.15 mg kg-1 and hyoscine 0.01 mg kg-1. In 17 of these children (nine in group A and eight in group B) plasma concentrations of catecholamines, ACTH and corticosteroids were measured. In group A the mean plasma concentration of catecholamines increased more than 300% during surgery, while it was virtually unchanged in group B (P less than 0.01). Plasma concentrations of ACTH, cortisol and 17-alpha-hydroxyprogesterone were also greater in group A than in group B. The occurrence of ventricular arrhythmias in group A was significantly more frequent (20.0%) than in group B (2.5%) (P less than 0.05). It was concluded that in these two comparable groups of patients ventricular arrhythmia during halothane anaesthesia was almost eliminated by the use of more effective premedication, as a result of decreases in the sympathetic and endocrine responses to surgery.