Sub-Tenon's ropivacaine block for pain relief after primary strabismus surgery

Purpose: Pain is the main cause of patient distress/dissatisfaction after strabismus surgery. The aim of the study was to evaluate the effect of sub-Tenon's block with ropivacaine at the end of strabismus surgery on post-operative pain. Methods: A prospective trial was conducted in 79 patients (age 1.0-65 years) scheduled for outpatient primary strabismus surgery with fixed sutures under general anesthesia (GA) at a major tertiary hospital. Half the patients were randomly allocated to receive sub-Tenon's block with ropivacaine 0.2% at conclusion of the operation. Primary outcome measures were visual analog scale (VAS) scores at arrival to the post-anesthesia care unit (PACU), at discharge 3hr later, 12-16hr post-operatively, and 24hr post-operatively. Supplemental analgesia requirements and patient satisfaction were recorded as well. Data were presented as median (range). MannWhitney test, Pearson χ²-test or Fisher's exact test was used for statistical analysis; p≤0.05 was considered significant. Results: There were no between-group differences in median VAS scores at arrival to the PACU and at discharge, with a borderline difference at 24hr post-operatively (p=0.06). At 12-16hr post-operatively, the median score was 0.0 (range 05) in the study group and 4.0 (range 06) in the controls (p<0.001). The lower VAS score in the study group was associated with a lower rate of supplemental analgesia use (21.9% versus 57.9%, p0.001), fewer doses of supplemental analgesia (10 doses versus 35, p=0.03), and higher patient satisfaction (p<0.001). Conclusions: Sub-Tenon's block with ropivacaine 0.2% at the completion of outpatient primary strabismus surgery with fixed sutures under GA reduces pain 12-16hr post-operatively and analgesia requirements 423hr post-operatively.