title: Sodium bicarbonate--an alternative to hyaluronidase in ocular anaesthesia for cataract surgery.
abstract: OBJECTIVE
  To evaluate and compare the safety, efficacy and cost-effectiveness of 7.5% sodium bicarbonate buffered lidocaine (pH 7.2) with hyaluronidase mixed lidocaine (pH 4.6) for local anaesthesia in cataract surgery.
  
  
  METHODS
  This prospective study comprised two parts. Part I: We evaluated the ocular and systematic anaesthetic safety and efficacy of 7.5% sodium bicarbonate buffered lidocaine on 112 consecutive patients undergoing cataract extraction with intraocular lens (IOL) implantation. At 12-week postoperative follow up final visual acuity and detailed fundus examination was done. Part II: It was conducted as a double blind, randomized comparative clinical trial involving 120 patients undergoing cataract surgery under retrobulbar anaesthesia. Patients were randomly assigned to one of the two groups: 60 eyes received 2 ml of 2% lidocaine with 1:200,000 epinephrine and 1 ml of 7.5% sodium bicarbonate, (0.299 mmol/ml); the remaining 60 eyes received 2 ml of 2% lidocaine with 1:200,000 epinephrine and 450 units of hyaluronidase (15 U/ml). In the event of incomplete akinesia, retrobulbar blocks were supplemented at 10 minutes. Onset and duration of anaesthesia and akinesia were assessed and compared in both groups.
  
  
  RESULTS
  The pH-adjusted lidocaine group did not show any demonstrable variation in blood pressure (BP) or other systemic reaction. No anaesthesia-related adverse ocular effects were observed either during or after surgery. Thirty-one eyes (51.6%) achieved complete anaesthesia and akinesia within 5 minutes compared to 13 eyes (21.6%) in the hyaluronidase group. However, the overall mean onset time of anaesthesia and akinesia, repeat block rate and the duration of the anaesthesia were comparable in both the groups--p: 0.14). Twelve weeks postoperatively 88.39% of patients showed a best corrected visual acuity of 6/18 or better (73.21%-6/12 or better).
  
  
  CONCLUSIONS
  In this study, sodium bicarbonate buffered 2% lidocaine was found to be a safe and effective local anaesthetic, with reduced time of onset, and improved quality of both anaesthesia and akinesia. Sodium bicarbonate (7.5%) may be used as an alternative to hyaluronidase in ocular anaesthesia. It is readily available and is cost effective.
authors.affiliation: Aravind Eye Hospital & Postgraduate Institute of Ophthalmology, 1, Anna Nagar, Madurai-625 020, India. aravind@aravind.org
authors.forename: M
authors.initials: M
authors.lastname: Srinivasan
authors.forename: M
authors.initials: M
authors.lastname: Vamshidhar
authors.forename: R
authors.initials: R
authors.lastname: Gopal
authors.lastname: Banushree
mesh_terms: D000328:Adult; D000368:Aged; D000772:Anesthesia, Local / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002387:Cataract Extraction; D004311:Double-Blind Method; D004338:Drug Combinations; D004837:Epinephrine / Q000008:administration & dosage; D005260:Female; D006801:Humans; D006821:Hyaluronoglucosaminidase / Q000008:administration & dosage*; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000187:drug effects; D009801:Oculomotor Muscles / Q000187:drug effects; D009883:Ophthalmic Solutions; D011446:Prospective Studies; D012449:Safety; D017693:Sodium Bicarbonate / Q000008:administration & dosage*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage; D014792:Visual Acuity / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D004338:Drug Combinations; D009883:Ophthalmic Solutions; D014662:Vasoconstrictor Agents; D017693:Sodium Bicarbonate; D008012:Lidocaine; D006821:Hyaluronoglucosaminidase; D004837:Epinephrine