Peribulbar anaesthesia: the role of local anaesthetic volumes and Thiomucase in motor block and intraocular pressure.

Peribulbar anaesthesia is a useful regional anaesthesia and akinesia technique for eye surgery. We studied changes in muscular akinesia and intraocular pressure under peribulbar anaesthesia caused by different volumes of 0.75% bupivacaine with or without the addition of Thiomucase (chondroitin sulphatase) in patients undergoing cataract surgery. A total of 120 patients were randomly allocated into four groups: group 1, bupivacaine 5 mL; group 2, bupivacaine 5 mL plus Thiomucase 10 U mL-1; group 3, bupivacaine 9 mL; group 4, bupivacaine 9 mL plus Thiomucase 10 U mL-1. We assessed: (1) akinesia according to mobility in the four quadrants of the eyeball and the palpebral opening using a scoring system between 0 (total akinesia) and 10 (full movement); and (2) intraocular pressure before, immediately after and 15 min after peribulbar anaesthesia. A significantly better motor blockade was observed in groups 2, 3 and 4 than in group 1 (P < 0.05). Thiomucase increased the quality of motor blockade in group 2, but not in group 4. Intraocular pressure increased by 5-10 mmHg in comparison with baseline values and, after 15 min application of Honan's balloon, decreased by 8-10 mmHg in comparison with baseline values, with no significant differences between groups. Thiomucase can improve the motor block if a lower volume of local anaesthetic is used. The administration of 5 or 9 mL volumes or the addition of Thiomucase decreases the the intraocular pressure in a similar way.