title: Effects of a fixed low-dose ropivacaine with different volume and concentrations on interscalene brachial plexus block: a randomized controlled trial.
abstract: Ultrasound guidance has reduced the amount of local anesthetics to achieve a successful block. Previous studies of the relationship between the volume or concentration of local anesthetics and the effects of the block were based on relatively high doses of local anesthetics. We tested the hypothesis that providing low dose of ropivacaine at three combinations of volumes and concentrations for ultrasound-guided interscalene brachial plexus block would produce different effects in the aspect of onset time, pain control and the incidence of side effects.
  
  
  
  Ninety-nine patients undergoing elective arthroscopic shoulder surgery were randomized to receive an ultrasound guided combined with nerve stimulator mediated interscalene block with ropivacaine 0.75 % (6.7 ml, Group 0.75), 0.5 % (10 ml, Group 0.5) or 0.25 % (20 ml, Group 0.25). The primary end point was the onset time of the sensory blockade, assessed by using a pinprick in the C5-6 dermatome. The secondary end points included the onset time of the motor blockade, block success rate, postoperative pain rating score, rescue analgesics requirement, sleep quality, strength of the hand on the block side,and the incidence of hemi-diaphragmatic paresis which was evaluated by ultrasonography.
  
  
  
  There was a statistically significant difference of the sensory block median onset times among Group 0.75 (5 min), Group 0.5 (10 min) and Group 0.25 (20 min). One patient in Group 0.5 and 20 patients in Group 0.25 did not achieve a complete motor block within 30 min, which were also significantly different. No significant difference was observed in postoperative analgesia, decrease of handgrip strength and the incidence of hemi-diaphragmatic paresis among the 3 groups.
  
  
  
  This study demonstrates that ropivacaine 50 mg as 0.25, 0.5 or 0.75 % solution for interscalene brachial plexus block before arthroscopic shoulder surgery produces comparable blockade with few side effects, while 0.75 % seems to be more preferable as it is associated with faster onset time.
  
  
  
  ChiCTR-TRC-13004058 . Registered 4 December 2013.
authors.affiliation: Department of Anesthesiology, Peking University Third Hospital, No. 49, Hua Yuan North Street, Hai Dian District, Beijing, China.
authors.forename: Wenwen
authors.initials: W
authors.lastname: Zhai
authors.affiliation: Department of Anesthesiology, Peking University Third Hospital, No. 49, Hua Yuan North Street, Hai Dian District, Beijing, China.
authors.forename: Xuedong
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Anesthesiology, Peking University Third Hospital, No. 49, Hua Yuan North Street, Hai Dian District, Beijing, China.
authors.forename: Yulan
authors.initials: Y
authors.lastname: Rong
authors.affiliation: Department of Anesthesiology, Peking University Third Hospital, No. 49, Hua Yuan North Street, Hai Dian District, Beijing, China. liminanesth@aliyun.com.
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Anesthesiology, West Virginia University, 6245 Inkster Rd., Garden City, MI, 48135, USA. howang@med.wayne.edu.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage* / Q000009:adverse effects / Q000494:pharmacology; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology; D001182:Arthroscopy / Q000379:methods; D065527:Brachial Plexus Block / Q000379:methods*; D004305:Dose-Response Relationship, Drug; D017558:Elective Surgical Procedures / Q000379:methods; D005260:Female; D018737:Hand Strength; D006801:Humans; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement / Q000187:drug effects; D012133:Respiratory Paralysis / Q000139:chemically induced; D000077212:Ropivacaine; D012890:Sleep / Q000187:drug effects; D012996:Solutions / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D012996:Solutions; D000077212:Ropivacaine
keywords: Analgesia; Dose-response relationship; Interscalene brachial plexus block; Motor block; Sensory block; Shoulder arthroscopy