Sub-Tenon’s local anaesthesia: the eVect of hyaluronidase

Aims—A prospective, randomised, double blind study was used to investigate the eVect of hyaluronidase on the quality of block achieved with sub-Tenon’s local anaesthesia. Methods—150 patients scheduled for elective cataract surgery were randomly allocated to either sub-Tenon’s block with 3 ml lignocaine 2%/adrenaline 1:200 000 alone or with the addition of 30 IU/ml of hyaluronidase. The blocks were assessed for degree of akinesia and reduction of eyelid movement, and also post-injection and postoperative pain scores. Results—Akinesia and reduction of eyelid movement measured 10 minutes after injection were significantly better in the group with hyaluronidase added to the anaesthetic solution. Postoperative pain scores were not significantly diVerent between the two groups but the postinjection pain score was greater (marginally significant) in the group with hyaluronidase added. Conclusion—The addition of hyaluronidase significantly improves the quality of the motor blockade achieved with subTenon’s local anaesthesia, but has no eVect on the sensory blockade. (Br J Ophthalmol 2000;84:435–436) The single quadrant technique for sub-Tenon’s local anaesthesia was popularised by Stevens in 1992 as a safe and eVective method for ophthalmic anaesthesia, avoiding the risks of sharp needle techniques. Delivery of the local anaesthetic solution to the posterior sub-Tenon’s space is followed by diVusion of the solution through Tenon’s capsule and into the retrobulbar compartment where the anaesthetic exerts its eVect. 2 Hyaluronidase is an enzyme which catalyses the depolymerisation of hyaluronic acid to a tetrasaccharide and potentially increases diVusion of local anaesthetic through tissue planes. The use of hyaluronidase in retrobulbar anaesthesia has been shown to be of benefit 4 in terms of speed of onset and quality of block, but the results with peribulbar techniques are more conflicting. To ascertain whether hyaluronidase had any eVect on the quality of block with the sub-Tenon’s technique, we conducted a randomised double blind study. Patients and methods Ethics committee approval for the study was obtained and informed consent given by 150 patients scheduled to undergo elective cataract surgery under local anaesthetic. Exclusion criteria were patients with learning diYculties, profound deafness, dementia, high anxiety scores, and those with a known adverse reaction to lignocaine or hyaluronidase. Using random number tables, each of the patients was randomly allocated to one of two groups. The control group received 3 ml lignocaine 2%/adrenaline 1:200 000 (Xylocaine, Astra Pharmaceuticals Ltd) alone whereas the hyaluronidase group received 3 ml lignocaine 2%/adrenaline 1:200 000 with the addition of 30 IU/ml of hyaluronidase (Hyalase, CP Pharmaceuticals Ltd). The syringes were prepared at the start of the list by an independent assistant who took no further part in either administering or assessing the block. The ophthalmologist administering the block, the operative surgeon, and the nursing staV were unaware of the contents of the syringe. The blocks were performed by one of three ophthalmologists (SAR, JH, RDF) using the technique described by Stevens but using a Visitec 19 gauge sub-Tenon’s cannula (5176) and only injecting 0.5 ml of anaesthetic at the equator. A McIntyre intraocular pressure reducer was applied over the eye for 10 minutes. Pain experienced during administration of block was measured immediately after injection and pain experienced peroperatively was measured immediately after surgery. The pain assessments were made by a trained ophthalmic theatre nurse without the investigator being present, using a visual pain analogue 10 cm in length (0 being no pain and 10 excruciating pain). Questions, phrasing, and intonation were as standardised as possible to avoid any bias. Akinesia and eyelid movement was assessed by the ophthalmologist administering the block 10 minutes after administration. The degree of akinesia was measured using a four point scale: 0 = complete movement remaining 1 = moderate movement 2 = slight movement (<3 mm in any direction) 3 = no movement. Eyelid movement was assessed using a three point scale: 0 = normal movement 1 = reduced movement 2 = absent movement.