title: Dilution of proparacaine in balanced salt solution reduces pain of anesthetic instillation in the eye.
abstract: OBJECTIVE
  Proparacaine (P), 0.5%, is often applied topically to the eye to diminish the pain of injection of anesthetic for eye surgery; however, application of 0.5% P itself can cause some degree of discomfort. This study evaluated the use of balanced salt solution to dilute P before instillation in the eye to prevent discomfort.
  
  
  METHODS
  In a double-blinded manner, 42 consenting adults about to undergo cataract surgery were given 0.5% P in one eye and 0.03% P in the other eye. One minute later the same solutions were instilled into each eye. Ten minutes later, 0.5% P was instilled into both eyes. After each instillation the patients were asked to describe the pain in each eye on a 0 to 10 scale.
  
  
  RESULTS
  Those receiving 0.5% as the first drop had a mean pain score of 1.28, which was greater than the score of 0.09 for the 0.03% P group (P < .01). No one reported pain after the second drop was applied 1 minute later. After receiving 0.5% P 10 minutes later, the group that had received 0.5% P reported a mean pain score of 0.09 while those who had received 0.03% P reported a score of 0.76, which was significantly greater than that reported by the 0.5% P group after the 10 minute instillation (P < .01) but significantly lower than the score reported after the first instillation of 0.5% P (P < .05).
  
  
  CONCLUSIONS
  Dilution of P in balanced salt solution to a concentration of 0.03% produces a solution that is significantly less painful than 0.5% P and reduces the discomfort of the instillation of 0.5% P.
authors.affiliation: Department of Anesthesiology, University of Kansas School of Medicine-Wichita 67214.
authors.forename: M D
authors.initials: MD
authors.lastname: Brady
authors.forename: R R
authors.initials: RR
authors.lastname: Hustead
authors.forename: R H
authors.initials: RH
authors.lastname: Robinson
authors.forename: K E
authors.initials: KE
authors.lastname: Becker
mesh_terms: D000287:Administration, Topical; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects*; D004311:Double-Blind Method; D005123:Eye; D005500:Follow-Up Studies; D006801:Humans; D013508:Ophthalmologic Surgical Procedures; D010146:Pain / Q000139:chemically induced / Q000517:prevention & control*; D011292:Premedication; D011430:Propoxycaine / Q000008:administration & dosage*; D012965:Sodium Chloride
chemical_list: D000779:Anesthetics, Local; D012965:Sodium Chloride; C005717:proxymetacaine; D011430:Propoxycaine