title: Prevention of pain during injection of microemulsion propofol: application of lidocaine mixture and the optimal dose of lidocaine.
abstract: BACKGROUND
  Similar to lipid emulsion propofol, microemulsion propofol also causes a high incidence of pain during intravenous injection. Various methods have been used to minimize the incidence and severity of pain on injection of lipid emulsion propofol. In this study, we investigated the effect of a lidocaine mixture on pain induced by microemulsion propofol injection, and sought to determine the optimal dose of lidocaine that could reduce pain on injecting a propofol-lidocaine mixture.
  
  
  METHODS
  One hundred sixty (n = 160) patients of American Society of Anesthesiologists physical status class I or II were randomly allocated to four groups: Group A, control; Group B, 20 mg lidocaine; Group C, 30 mg lidocaine; Group D, 40 mg lidocaine. In each patient, pain on microemulsion propofol solution injection was graded as none, mild, moderate, or severe.
  
  
  RESULTS
  The incidence of pain in groups A, B, C, and D was 97.5%, 80%, 65%, and 50%, respectively. Increasing the lidocaine dose significantly reduced pain (P < 0.05). One patient in Group D (2.5%) had moderate to severe pain, which was significantly lower than groups B (42.5%) and C (32.5%) (P < 0.05).
  
  
  CONCLUSIONS
  The lidocaine and propofol mixture is effective in alleviating pain associated with microemulsion propofol injection. Within this dose range and in this patients population, increasing lidocaine dosage significantly reduced pain during injection of microemulsion propofol.
authors.affiliation: Department of Anesthesiology and Pain Medicine, Busan Paik Hospital, College of Medicine, Inje University, Busan, Korea.
authors.forename: Hyun-Sik
authors.initials: HS
authors.lastname: Kim
authors.forename: Kwang Rae
authors.initials: KR
authors.lastname: Cho
authors.forename: Jeong Han
authors.initials: JH
authors.lastname: Lee
authors.forename: Young Hwan
authors.initials: YH
authors.lastname: Kim
authors.forename: Se Hun
authors.initials: SH
authors.lastname: Lim
authors.forename: Kun Moo
authors.initials: KM
authors.lastname: Lee
authors.forename: Soon Ho
authors.initials: SH
authors.lastname: Cheong
authors.forename: Young Jae
authors.initials: YJ
authors.lastname: Kim
authors.forename: Chee-Mahn
authors.initials: CM
authors.lastname: Shin
authors.forename: Jin-Young
authors.initials: JY
authors.lastname: Lee