Oculocardiac reflex and postoperative vomiting in paediatric strabismus surgery. A randomised controlled trial comparing four anaesthetic techniques

Background : Oculocardiac reflex (OCR) and postoperative vomiting are major complications of paediatric strabismus surgery.
Methods : Children (3–16 yr) undergoing elective strabismus surgery as inpatients were randomly allocated to four anaesthetic techniques: (A) thiopentone induction and isoflurane maintenance; (B) as (A) plus ondansetron 5 mg · m^-2 iv; (C) propofol induction and maintenance; (D) as (C) plus lignocaine 2 mg · kg^-1 iv. All children received prophylactic atropine 0.02 mg · kg^-1 and alfentanil. Nitrous oxide was omitted.
Results : Data on 157 children were analysed. The cumulative incidence of vomiting within 6 and 24 h after surgery with thio-pentone-isoflurane was 26% and 46%, respectively. Adding ondansetron decreased the incidence to 8% and 33%, respectively. This improvement was significant within 6 h only; the number-needed-to-treat was 5.5 (95% CI 2.9–46). Propofol was not different from thiopentone-isoflurane. The addition of lignocaine to propofol was of no benefit. The risk of an OCR was significantly increased with propofol (incidence 40%) compared with isoflurane (14%); the number-needed-to-harm was 3.9 (95% CI 2.6–8).
Conclusions : Thiopental-isoflurane-air/O₂-alfentanil resulted in a moderate risk of vomiting. Adding ondansetron significantly decreased this risk, but 6 children have to be treated for one to benefit in the early postoperative period. Propofol and propofol-lignocaine showed no benefit on vomiting but significantly increased the risk of an OCR despite high-dose prophylactic atropine.