title: Efficacy of sub-Tenon's block using an equal volume of local anaesthetic administered either as a single or as divided doses. A randomised clinical trial.
abstract: BACKGROUND
  Sub-Tenon's anaesthetic is effective and reliable in producing both akinesia and anaesthesia for cataract surgery. Our clinical experience indicates that it is sometimes necessary when absolute akinesia is required during surgery to augment the block with 1-2 ml of local anaesthetic. Hypothesis was that after first injection some of the volume injected may spill out and before second injection the effect of hyaluronidase has taken place and second volume injectate will have desired effect.
  
  
  METHODS
  A prospective, randomised, control trial in which patients were randomly allocated to one of two groups. In group 1, single injection of 5 ml of local anaesthetic was injected. In group 2, 3 ml of the same anaesthetic solution was injected followed by application of gentle orbital pressure for 2 minutes. A further 2 ml of the same anaesthetic solution was injected through the same conjunctival incision. Measurement of movement in four quadrants of eye was done by the surgeon at 3 and 6 minutes. Intraocular pressure, chemosis, and subconjuctival haemorrhage were also measured.
  
  
  RESULTS
  Significant differences at 3 minutes between groups for overall movement, medial, superior, and lateral quadrants occurred. At 6 minutes no significant group differences emerged for the overall movement or for any of four quadrants.
  
  
  CONCLUSIONS
  Single injection of local anaesthesia for sub-Tenon's block with mixture of lignocaine with adrenaline, bupivacaine and hyaluronidase was found to be superior to provide akinesia of ocular muscles compared to divided dose given by two injections. No difference in groups in terms of haemorrhage, chemosis, patient's satisfaction and intraocular pressure was found.
  
  
  BACKGROUND
  Trial registration no-ISRCTN73431052.
authors.affiliation: Dept of Anaesthesia, Cork University Hospital and University College Cork, Ireland, Wilton, Cork, Co Cork, Ireland. eikhan@yahoo.co.uk.
authors.forename: Ehtesham I
authors.initials: EI
authors.lastname: Khan
authors.forename: Jawad
authors.initials: J
authors.lastname: Mustafa
authors.forename: John
authors.initials: J
authors.lastname: McAdoo
authors.forename: George
authors.initials: G
authors.lastname: Shorten