Ondansetron Reduces the Incidence and Severity of Poststrabismus Repair Vomiting in Children

Abstract

Comment: Postoperative nausea and vomiting (PONV) after strabismus surgery in children are distressingly frequent, with some investigators reporting an incidence of 85%, or higher, when no prophylactic antiemetic is provided.1 The etiology of PONV asso- dated with strabismus surgery remains unconfirmed but is believed to result from altered visual perception after muscle resection or from a central response arising from manipulation of eye muscles (the oculo-emetic reflex, which is similar to the oculocardiac reflex).2 Several drugs or techniques have been used, with variable success, to reduce the incidence of PONV associated with strabismus correction. These have included droperidol, metoclopramide, promethazine, lorazepam, scopolamine, dimenhydrinate, pro-pofol, lidocaine, dixyrazine, and even P6 acupressure. Studies involving these therapies are difficult to compare, however, because they varied in several aspects, including the definition of vomiting, exclusion criteria, premedication, use of narcotics, neuromuscular blocking drugs, reversal agents, gastric decompression, as well as timing of extubation, discharge criteria, and duration of follow-up. Indeed, although anesthesiologists are decreasing the incidence of vomiting in the postanesthesia care unit, it may be that we are merely postponing this complication. Although administration of prophylactic antiemetics for high-risk procedures may prevent vomiting in the hospital, the duration of these agents is insufficient to prevent vomiting at home Selection. of drug dosage and timing of administration are important. There is consensus that antiemetics should be given before manipulation of the extraocular muscles. Although several investigators were unable to demonstrate significant antiemetic efficacy in children who had strabismus surgery and received i.v. droperidol in doses of less than 75 (μg/kg,1,3 Brown and colleagues4 reported that 20 μg/kg droperidol was as effective as the 75 Hg/kg dose. Recently Stead et al.5 reported that the efficacy of prophylactic droperidol in reducing PONV after pediatric strabismus surgery is dose-dependent. Similarly, although Broadman and associates6 found i.v. metoclopramide (0.15 mg/kg) to be effective in this setting, Lin and colleagues7 reported that 0.25 mg/ kg of this agent was required to provide antiemetic efficacy comparable with 75μ.g/kg of droperidol. Now the efficacy of ondansetron, a selective 5-HT, receptor antagonist, in reducing PONV after strabismus surgery is being assessed, and initial reports are encouraging.8,9 Although expensive, ondansetron is attractive because its use is not associated with such side effects as extrapyramidal signs, sedation, dry mouth, and urinary retention. The most significant side effects of ondansetron appear to be rare hypersensitivity reactions and transient increases in liver enzymes in patients receiving concomitant antineoplastic drugs. Nonpharmacologic interventions to decrease PONV should also be used. These include careful attention to airway management to avoid gastric distention, gentle surgical traction on the eye muscles intraoperatively, minimizing oropharyngeal stimulation by avoiding excessively aggressive suctioning, and timely removal of an inserted oral airway. Vestibular and visual stimulation should be minimized by limiting patient movement and by avoiding exposure to other patients who are vomiting. Additional help ful measures include preventing pain, hypoxia, and hypotension. Liberal hydration with i.v. crystalloid is advocated. Indeed, we do not offer our pediatric strabismus patients oral fluids until they complain of hunger, in the belief that hunger signals the return of peristalsis. In deference to the concept that psychologic factors influence PONV, we do everything possible to foster a sense of security and allay anxiety in these children. Not only is PONV distressing, it is also expensive because it is consistently the most common reason for unanticipated overnight admission after intended outpatient surgery. Further study is required to determine whether ondansetron is more cost effective and more efficacious than alternative pharmacologic agents in reducing vomiting after pediatric strabismus surgery.