This prospective, randomized, double-blinded study evaluated the effect of the timing of
ondansetron administration on its
antiemetic efficacy in children undergoing elective
strabismus surgery. One hundred and twenty children aged one to 15 years, ASA physical status 1 or 2, were randomly allocated to receive intravenous
ondansetron 100 micrograms/kg either at induction (Group 1) or at the end of the surgery (Group 2). All patients had general anaesthesia induced and maintained with
nitrous oxide and
halothane, muscle relaxation with
vecuronium, endotracheal intubation, reversal with
neostigmine and
glycopyrrolate, and
pethidine 0.5 mg/kg
analgesia. Episodes of
nausea and
vomiting were evaluated at 0 to 2, 2 to 6 and 6 to 24 hour intervals by a blinded observer. Demographic data, duration of anaesthesia, type of surgery, incidence of previous
postoperative nausea or
vomiting and
motion sickness and number of patients who developed oculocardiac reflex requiring
atropine treatment were similar in both groups. The incidence of
emesis in the first 24 hours following surgery was similar in both groups (35% Group 1, 33.3% Group 2, P = 1.00). Severity of
emesis (median number of
emetic episodes, rescue
antiemetic requirement and mean time to the onset of first episode of
emesis) and mean time to discharge from the post anaesthesia care unit were also similar in the two groups. We conclude that the timing of
ondansetron administration either before or after the surgical manipulation of extraocular muscles had similar
antiemetic efficacy following
strabismus surgery in children.