Outcome Values of Adding Sodium Bicarbonate, Dexamethasone and Fentanyl to Local Anesthetic in Peribulbar Block during Vitreoretinal Surgeries. A Randomized Prospective Study

Abstract

Background and aims: we aimed to detect the outcome values of adding fentanyl, dexamethasone and sodium bicarbonate to mixture of local anesthetic in peribulbar block for vitreoretinal surgery. Methods: 120 adult ASA I & II patients, admitted for vitreoretinal surgery under peribulbar block were included in this comparative study. This study included 4 groups: Group I: (30) patients using a mixture of 1 ml normal saline, 4 ml lidocaine 2% plus 4 ml from bupivacaine 0.5% 20 ml vial containing hyaluronidase 1500 IU. Group II: (30) patients using a mixture of 1 ml of sodium bicarbonate (from 1 ml sodium bicarbonate 8.4% diluted in 10 ml normal saline), 4 ml lidocaine 2% plus 4 ml from bupivacaine 0.5% 20 ml vial containing hyaluronidase 1500 IU. Group III: (30) patients using a mixture of 1 ml fentanyl 20 μg (from a mixture of fentanyl 100 μg diluted in 5 ml normal saline), 4 ml lidocaine 2% plus 4 ml from bupivacaine 0.5% 20 ml vial containing hyaluronidase 1500 IU. Group IV: (30) patients using a mixture of 1 ml of 4 mg dexamethasone (1 ampoule = 8 mg/2 ml), 4 ml lidocaine 2% plus 4 ml from bupivacaine 0.5% 20 ml vial containing hyaluronidase 1500 IU. We measured the onset and duration of anesthesia, IOP, eyelid and global akinesia, postoperative pain by numerical pain rating scale, first analgesic requirement and postoperative side effects. Results: No significant differences were detected among the four groups as respect to age, sex and the intraocular pressure (IOP) before the anesthesia block. While the intraocular pressure (IOP) after the anesthesia block there was a significant difference, as IOP was markedly decreased postoperatively in group II compared with other groups. As regard to the onset & duration of anesthesia there was significant difference among all groups, there was rapid onset and prolonged duration of anesthesia in group III compared with other groups (1.77 ± 0.63 & 5.03 ± 0.89) respectively. As regard the onset of lid akinesia there was significant difference among the four groups with better outcome in group III, as in group III represented the most rapid onset of lid akinesia. As respecting to the onset of global akinesia there was significant difference among the four groups. There was better outcome in group III as it represented more rapid onset of global akinesia compared with other groups. There were significant differences among the four groups as regard postoperative pain all over 6 hours, better results were in group III (0.27 ± 0.69) compared with group I (2.23 ± 1.17), group II (2.00 ± 1.70), group IV (0.67 ± 0.71). As regarding to the first time for analgesic requirement there were significant differences among groups, there was no request for analgesia with better outcome in group III with increasing need to the analgesic medication in group I compared to group II and group IV. As regard side effects postoperatively there were few side effects in all groups with few numbers of cases in groups III only one patient. Although these differences in number of patients are not significant among the four groups. Conclusion: Addition of sodium bicarbonate to local anesthetic mixture was the best way in lowering the IOP other than other groups and addition of fentanyl to local anesthesia provided more rapid onset and duration of anesthesia, more rapid onset and duration for lid and global akinesia, less pain, less analgesic requirement and minimal side effects than the other groups.