title: Dose-response characteristics of spinal bupivacaine in volunteers. Clinical implications for ambulatory anesthesia.
abstract: BACKGROUND
  Small doses of bupivacaine may be a reasonable choice for spinal anesthesia for patients having ambulatory surgery. However, few dose-response data are available to guide the selection of reasonable doses of bupivacaine for different ambulatory procedures.
  
  
  METHODS
  Eight volunteers per group were randomized to receive 3.75, 7.5, or 11.25 mg of 0.75% bupivacaine with 8.25% dextrose in a double-blind manner. Sensory block was assessed with pinprick, transcutaneous electrical stimulation equivalent to surgical incision at the ankle, knee, pubis, and umbilicus, and with duration of tolerance to pneumatic thigh tourniquet. Motor block at the quadriceps and gastrocnemius muscles was assessed with isometric force dynamometry. Times until recovery from spinal anesthesia were recorded. Dose-response relationships were determined by linear regressions. Mean (95% confidence intervals) for durations of sensory and motor block per milligram of bupivacaine administered were calculated from linear regressions.
  
  
  RESULTS
  Significant dose-response relationships (P < 0.006) were determined for sensory block, motor block, and time until recovery (R from 0.6 to 0.9). Within the range of doses studied, each additional milligram of bupivacaine was associated with an increase in duration of tolerance to transcutaneous electrical stimulation of 10 (7 to 13) min, an increase in tolerance to tourniquet of 7 (2 to 11) min, an increase in duration of motor block of 8 (5 to 12) min, and an increase in time until recovery of 21 (17 to 25) min.
  
  
  CONCLUSIONS
  These dose-response data may guide the selection of reasonable doses of bupivacaine for various outpatient procedures, although individual responses vary.
authors.affiliation: Department of Anesthesiology, Virginia Mason Medical Center, Seattle, Washington 98111, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Liu
authors.forename: P D
authors.initials: PD
authors.lastname: Ware
authors.forename: H W
authors.initials: HW
authors.lastname: Allen
authors.forename: J M
authors.initials: JM
authors.lastname: Neal
authors.forename: J E
authors.initials: JE
authors.lastname: Pollock
mesh_terms: D000328:Adult; D000556:Ambulatory Surgical Procedures; D000775:Anesthesia, Spinal / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002045:Bupivacaine / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007278:Injections, Spinal; D008297:Male; D017288:Pain Threshold / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine