title: Onset of spinal block is more rapid with isobaric than hyperbaric bupivacaine.
abstract: OBJECTIVE
  To compare isobaric with hyperbaric 9.75 mg bupivacaine injected intrathecally, and to evaluate the effects of subsequent injection of lidocaine 2% into the epidural space.
  
  
  METHODS
  Patients in group 1 (n = 30) received isobaric 9.75 mg bupivacaine and in group 2 (n = 30) hyperbaric 9.75 mg bupivacaine injected into the subarachnoid space in a combined spinal-epidural technique. They were undergoing urological, gynecological, orthopedic, gastro-intestinal or vascular surgery. Using a double blind technique, the followings parameters were measured: cutaneous analgesia to pinprick, motor blockade, time for two segment regression, time for complete regression of the motor block, quality of anesthesia. In 12 patients the effect of epidural injections of 3 ml lidocaine 2% was observed.
  
  
  RESULTS
  Motor and sensory block developed more rapidly (five minutes) in the isobaric group (P<0.05). Maximum upper level (T7+/-2), two-segment regression (52 min in both groups), motor recovery (160 vs. 157 min), and quality of anesthesia did not differ between the two groups. Thirty nine epidural injections of 3 ml lidocaine 2% were given in 12 patients 10 min after spinal injection, 28 were in the hyperbaric group (P<0.05). Twenty six of the epidural injections produced an increase in sensory block of 0 or 1 dermatome, and 13, of 2 or more.
  
  
  CONCLUSIONS
  The block developed more rapidly in the isobaric group, but both isobaric and hyperbaric 9.75 mg bupivacaine produced adequate upper levels of analgesia for surgery. The effect of epidural injections of 3 ml lidocaine 2% was usually minimal.
authors.affiliation: Department of Anesthesia, University of Sherbrooke, Fleurimont, Québec, Canada. rmartin@courrier.usherb.ca
authors.forename: R
authors.initials: R
authors.lastname: Martin
authors.forename: C
authors.initials: C
authors.lastname: Frigon
authors.forename: A
authors.initials: A
authors.lastname: Chrétien
authors.forename: J P
authors.initials: JP
authors.lastname: Tétrault
mesh_terms: D000328:Adult; D000368:Aged; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002045:Bupivacaine / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013997:Time Factors
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine