title: Effective volumes of 1.5% mepivacaine with different sodium concentration for ultrasound guided popliteal block.
abstract: OBJECTIVE
  To determine if a solution of 1.5% mepivacaine diluted with 5% dextrose, which decreases the sodium concentration by 30%, results in reduced volume requirements for a complete sensory block, in the case of an ultrasound guided popliteal nerve block.
  
  
  METHODS
  A randomized controlled study.
  
  
  METHODS
  Operating room.
  
  
  METHODS
  We included seventy ASA 1-3 patients, undergoing unilateral "hallux valgus" repair under ultrasound guided popliteal nerve block.
  
  
  METHODS
  An ultrasound guided popliteal nerve block was performed on all patients, with 1.5% mepivacaine using the normal dilution (ND group, thirty-five patients) or the 5% dextrose dilution (D5 group, thirty-five patients). Starting with 25ml in each group, increasing or decreasing it by 1ml on subsequent patients, depending on the success or failure in the previous one (Dixon's "up-and-down" sequential allocation).
  
  
  METHODS
  Effective dose in 50, 90, and 95% of patients (ED50, ED90, and ED95) of 1.5% mepivacaine in both groups. Onset time and duration of the blocks, side effects, and neurological complications.
  
  
  RESULTS
  There were no statistically significant differences between ED50 in ND group (6.2ml; 95% confidence interval, 5.2-7.5), and D5 group (5.8ml; 95% CI, 5.1-7). Also no statistically significant differences in ED90 (7.7ml, 95% CI 6.9-8.1 in the D5 group; 7.8ml, 95% CI 7-8.1 in the ND) or in ED95 (7.9ml, 95% CI 7.1-8.2 in the D5 group; 8ml, 95% CI 7.2-8.2 in the ND) were found. Onset time for a complete sensory block in D5 group was 14min (95% CI, 12-17) and 15min in ND (95% CI, 13-18), p=0.66. Neither severe side effects, nor neurological complications were reported.
  
  
  CONCLUSIONS
  A dilution of 1.5% mepivacaine with 30% less sodium concentration does not decrease volume requirement for ultrasound guided sciatic nerve block at popliteal level.
authors.affiliation: Department of Anesthesia, "La Paz" University Hospital, Paseo de la Castellana 261, 28046 Madrid, Spain. Electronic address: mercelopezmartinez@yahoo.es.
authors.forename: Mercedes
authors.initials: M
authors.lastname: López
authors.affiliation: Department of Anesthesia, "La Paz" University Hospital, Paseo de la Castellana 261, 28046 Madrid, Spain. Electronic address: mcalvomacarro@gmail.com.
authors.forename: Miguel
authors.initials: M
authors.lastname: Calvo
authors.affiliation: Department of Anesthesia, "La Paz" University Hospital, Paseo de la Castellana 261, 28046 Madrid, Spain. Electronic address: azahara.sa@hotmail.com.
authors.forename: Azahara
authors.initials: A
authors.lastname: Sancho
authors.affiliation: Department of Anesthesia, "La Paz" University Hospital, Paseo de la Castellana 261, 28046 Madrid, Spain. Electronic address: nicolas0brogly@gmail.com.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Brogly
authors.affiliation: Department of Anesthesia, "La Paz" University Hospital, Paseo de la Castellana 261, 28046 Madrid, Spain. Electronic address: emiguasch@hotmail.com.
authors.forename: Emilia
authors.initials: E
authors.lastname: Guasch
authors.affiliation: Department of Anesthesia, "La Paz" University Hospital, Paseo de la Castellana 261, 28046 Madrid, Spain. Electronic address: fgilsanz.hulp@salud.madrid.org.
authors.forename: Fernando
authors.initials: F
authors.lastname: Gilsanz
mesh_terms: D000328:Adult; D000368:Aged; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005947:Glucose / Q000008:administration & dosage; D006215:Hallux Valgus / Q000601:surgery*; D006801:Humans; D008297:Male; D008619:Mepivacaine / Q000008:administration & dosage / Q000494:pharmacology*; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D012584:Sciatic Nerve / Q000187:drug effects*; D012964:Sodium / Q000008:administration & dosage / Q000494:pharmacology*; D018084:Ultrasonography, Interventional
chemical_list: D000779:Anesthetics, Local; D012964:Sodium; D008619:Mepivacaine; D005947:Glucose
keywords: Mepivacaine; Nerve block; Sciatic nerve; Ultrasound