Effect of Muscle Relaxants on Short-term Results of Exotropia Surgery: A Focus on Resection Procedures

PURPOSE: We investigated the effect of muscle relaxants (atracurium) on the outcomes of intermittent exotropia surgery under general anesthesia, with a focus on resection procedures. METHODS: Thirty four patients who underwent recession and resection (R&R) were divided into two groups: atracurium usage (group A, n=18) and no atracurium usage (group B, n=16). Patients were divided into two subgroups according to the amount of resection of the medial rectus (MR): less than 5 mm (group 1, n=13) or 5 mm and greater (group 2, n=21). Deviation angles were compared between groups and subgroups. Surgical outcome was defined as successful if distant deviation angles were equal to or less than 10 prism diopters. RESULTS: The overall postoperative deviation angles did not show statistically significant differences between groups A and B. However, in patients with larger MR resections (≥ 5 mm), the 1 week postoperative distant deviation was significantly larger in group A (1.8±2.6 PD) than in group B (-1.6±4.6 PD, p=0.048 by t-test). The overall undercorrection rate at 3 months postoperatively for group A was 16.7%, which was higher than that of group B (6.3%), and the difference was even larger in subgroups with larger MR resections (≥ 5 mm): 18.2% in group A and 0% in group B. CONCLUSIONS: Patients who underwent R&R procedures under general anesthesia with a muscle relaxant tended to be less corrected than those without muscle relaxant, especially in the early postoperative period and with a larger MR resection equal to or greater than 5 mm. However, there was no significant difference in the later postoperative period.