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Comment to “Intraoperative apnea in children after buffered 5% povidone‐iodine site sterilization for strabismus surgery”

Sir–In the article by Emhardt et al., the authors reported intraoperative apnea in children after buffered 5% povidone-iodine site sterilization for strabismus surgery. As a referral center for different types of eye surgeries with plenty of patients with similar surgical and anesthetic procedures, we had not experienced the same. So, we decided to perform a study with similar methodology to compare the results. The study protocol was approved by the ethics committee of Tehran University of Medical Sciences. Forty-one patients aged 1-18 year who were scheduled for strabismus surgery under general anesthesia were recruited. Written informed consent was obtained from all patients or when applicable from their parents/guardians. After placing the standard monitoring, all patients received midazolam 0.5 mg/ kg PO (max: 12 mg). Anesthesia was induced with sevoflurane 8% in O2 100%. An IV line was secured and laryngeal mask airway was inserted. Patients were placed on Mapleson B circuit. Anesthesia was maintained by sevoflurane 5% in O2 100% while patients were spontaneously breathing. All patients received dexamethasone 0.5 mg/kg IV (max: 4 mg) with no other medication. The Surgical site was prepared by saline and povidone-iodine 10% (Tolid Daru company, Tehran, Iran). Respiratory rate was recorded before and after the site preparation. Apnea was defined as no respiratory effort for 20 seconds confirmed by the absence of capnograph trace. Despite their results, we did not observe apnea in any patient; however, the respiratory rate and, the heart rate decreased which was not associated with patients’ age and gender and could be explained by occulocardiac and diving reflexes. However, we cannot rule out the relationship between apnea and povidone-iodine as we used a more concentrated solution (10% povidone-iodine vs 5%). Low concentration solutions exhibit several differences, including pH, from those of high concentration, which might account for the difference between our results. It is also possible that the etiology of the apnea events in Emhart et al.’s patients might be caused by something other than the povidone-iodine itself, including other differences in the solution (we used a solution from a different company) as well as other aspects of patients’ preparation; for example, removing debris from eye lashes by cotton tipped swab, which was done in Emhardt et al.’s study. In conclusion, we recommend conducting more studies to evaluate the effect of ocular application of povidone-iodine on respiration.