^¶Does hyaluronidase permit volume reduction in sub‐Tenon's anaesthesia for cataract extractions?

Abstract

seem, therefore, that this technique would be detrimental to patients. However, when undertaken under controlled conditions for short periods of time (usually 2-3 h) and followed by careful resuscitation, it has produced, in our unit, excellent results in terms of minimal liver dysfunction, blood transfusion requirements and mortality. Volumes of local anaesthetic for sub-Tenon's anaesthesia vary between 2 ml and 11 ml. Lower volumes produce less akinesia, whilst higher volumes increase chemosis and intra-ocular pressures [1]. This randomised, blinded, sequential allocation study examined the effect of adding hyaluronidase on the minimum local anaesthetic volume (MLAV) required for a sub-Tenon's block, in patients having cataract extractions. MethodsFollowing Local Research Ethics Committee and Medicines and Healthcare products Regulatory Agency approval, 62 patients having sub-Tenon's blocks for cataract surgery were randomly assigned to two groups. The control group (n ¼ 31) received plain lidocaine 2% and the study group (n ¼ 31) received lidocaine 2% with 15 iu.mlhyaluronidase. Using parallel up-down sequential allocation, from a 4-ml starting point, the volumes in both groups changed by 1 ml according to the quality of globe akinesia, as judged by a blinded researcher using a standardised scoring system. The MLAV was calculated for both groups using Dixon and Massey formulae. Student's t-tests were used to compare the groups. ResultsThe groups were similar for age, sex and axial length. There was a difference in MLAV of 3.0 ml ( Fig. 1; control: 5.9 ml (95%CI 4.3-7.9 ml); hyaluronidase: 2.9 ml (95% CI 2.4-3.5 ml); p < 0.001). The hyaluronidase group showed less variability (p < 0.01).