effects of preoperative sub-tenon block on intra- and post-operative complications in retinal detachment surgery

purpose: to evaluate the efficacy of sub-tenon block (preemptive analgesia) following general anesthesia and before the beginning of scleral buckling and cryopexy in retinal detachment (rd) surgery on decreasing intra- and post-operative complications. methods: sixty eight patients scheduled for rd surgical repair with asa (american society of anesthesiologists) class і or ii were enrolled in this clinical trial. the patients were randomly divided into two groups. both groups underwent general anesthesia (ga), but one group received sub-tenon block as preemptive analgesia following induction of general anesthesia (treatment group). intra- and post-operative (up to 24 hours) incidence of  oculocardiac reflex (ocr), mean blood pressure (bp), heart rate (hr), post-operative ischemic heart disease (ihd) changes, nausea and vomiting (ponv), delirium, total analgesic consumption, severity of ocular pain, frequency of analgesic requirement, and duration of hospitalization were compared between the two groups. results: there was no statistically significant difference between the two groups regarding age, sex, and preoperative blood pressure (bp) and heart rate. mean bp of patients in the treatment group and the control group was 126.6/74.8 and 126.4/74.4 mmhg, preoperatively (p>0.2) and 126.4/76.4 and 134.6/74.4 mmhg, postoperatively (p=0.01). pain complaint of any degree was more frequent in the control group such that 38% in the recovery room and 25% 6 hours after surgery complained of severe pain compared to none in the treatment group. (p= 0.001) incidence of delirium in the recovery room was 3.7% in the treatment group vs 24.1% in the control group. (p= 0.001) mean duration of hospitalization after surgery was 26.6±1.5 hr in the treatment group and 34.0±1.5 hr in the control group. (p<0.01) conclusion: sub-tenon block following induction of ga for rd surgery reduces intra- and post-operative complications effectively, therefore it is recommended for routine ophthalmologic procedures.