title: Two-quadrant high-volume sub-Tenon's anaesthesia for vitrectomy: a randomised controlled trial.
abstract: BACKGROUND
  Total volume using a standard single inferonasal injection for sub-Tenon's anaesthesia is limited by an increase in intraocular pressure (IOP) and commonly requires the operating surgeon to top-up the block intraoperatively. This study compares the efficacy and safety of a two-quadrant technique that allows the use of a higher volume of local anaesthetic.
  
  
  METHODS
  54 patients undergoing vitrectomy were randomised into two groups. The control group (n=27) received a standard 5 ml single inferonasal sub-Tenon injection of a 50:50 mixture of 2% lidocaine and 0.5% bupivacaine with 150 IU hyaluronidase. The study group (n=27) received a 5 ml inferonasal and 5 ml superotemporal injection of the same mixture (10 ml total). The primary outcome measure was the number of intraoperative top-ups required. Secondary outcome measures were intraoperative and postoperative pain scores, IOP, block onset time, ocular akinesia, eyelid akinesia and chemosis.
  
  
  RESULTS
  24 patients required a top-up in the control group. No patients required a top-up in the study group (p<0.001). IOP measurements were similar in both groups. Block onset was shorter, eyelid akinesia was improved and pain scores were also reduced in the study group intraoperatively and at 0-2 h, 4-6 h, 10-14 h and 20-24 h postoperatively.
  
  
  CONCLUSIONS
  Two-quadrant sub-Tenon's anaesthesia using 10 ml of a 50:50 mixture of 2% lidocaine and 0.5% bupivacaine with 150 IU hyaluronidase seems to be more effective than a single-quadrant technique at reducing intraoperative and postoperative pain during vitrectomy.
authors.affiliation: Department of Anaesthesia, Guy's and St Thomas' Hospital NHS Foundation Trust, Westminster Bridge Rd, London SE1 7EH, UK. drvipgill@aol.com
authors.forename: Vip S
authors.initials: VS
authors.lastname: Gill
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Presland
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Lord
authors.forename: Catey
authors.initials: C
authors.lastname: Bunce
authors.forename: Wen
authors.initials: W
authors.lastname: Xing
authors.forename: David G
authors.initials: DG
authors.lastname: Charteris
mesh_terms: D000368:Aged; D000772:Anesthesia, Local / Q000379:methods*; D019162:Anesthetics, Combined / Q000008:administration & dosage* / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D002045:Bupivacaine / Q000008:administration & dosage; D005260:Female; D006801:Humans; D006821:Hyaluronoglucosaminidase / Q000008:administration & dosage; D056965:Injections, Intraocular; D007429:Intraocular Pressure; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D019148:Neuromuscular Blockade; D010147:Pain Measurement; D010149:Postoperative Pain; D012163:Retinal Detachment / Q000601:surgery; D019233:Retreatment; D058475:Tenon Capsule / Q000187:drug effects*; D016896:Treatment Outcome; D014821:Vitrectomy
chemical_list: D019162:Anesthetics, Combined; D000779:Anesthetics, Local; D008012:Lidocaine; D006821:Hyaluronoglucosaminidase; D002045:Bupivacaine