title: Hyaluronidase reduces local anaesthetic volumes for sub-Tenon's anaesthesia.
abstract: BACKGROUND
  Volumes of local anaesthetics for sub-Tenon's anaesthesia vary. Lower volumes produce less akinesia, whereas higher volumes increase chemosis and intra-ocular pressures. Hyaluronidase is often added to local anaesthetics to improve akinesia without increasing the volume of the injection, but this is controversial. This randomized, sequential allocation study examines the addition of hyaluronidase on the minimum local anaesthetic volume (MLAV) required for a sub-Tenon's block.
  
  
  METHODS
  Sixty-two patients having sub-Tenon's blocks for cataract surgery were randomized into two groups. The control group (n=31) received 2% w/v lidocaine and the study group (n=31) received 2% w/v lidocaine with hyaluronidase 15 IU ml(-1). Using parallel up-down sequential allocation from a 4 ml starting volume, the volumes in both groups were changed using a testing interval of 1 ml according to the quality of globe akinesia. The median effective local anaesthetic volume (MLAV) was calculated for both groups using probit regression.
  
  
  RESULTS
  The groups were similar for age, sex, and ocular axial length. The MLAV in the hyaluronidase group was 2.6 ml [95% confidence interval (CI), 2.1-3.l] and 6.4 ml (95% CI, 5.1-8.1) in the control group (P<0.002).
  
  
  CONCLUSIONS
  Hyaluronidase permits a significant 2.4-fold (95% CI, 1.8-3.4) reduction in MLAV for sub-Tenon's anaesthesia.
authors: Department of Anaesthesia, D Floor, Jubilee Building, The General Infirmary at Leeds, Great George Street, Leeds LS1 3EX, UK. schulies_snh@hotmail.com
authors: H E
authors: HE
authors: Schulenburg
authors: C
authors: C
authors: Sri-Chandana
authors: G
authors: G
authors: Lyons
authors: M O
authors: MO
authors: Columb
authors: H A
authors: HA
authors: McLure
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000556:Ambulatory Surgical Procedures; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002387:Cataract Extraction; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D006821:Hyaluronoglucosaminidase / Q000494:pharmacology*; D008012:Lidocaine / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D010147:Pain Measurement / Q000379:methods
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine; D006821:Hyaluronoglucosaminidase