title: Analgesic effectiveness of ropivacaine 0.2% vs 0.4% via an ultrasound-guided C5-6 root/superior trunk perineural ambulatory catheter.
abstract: BACKGROUND
  In this prospective, randomized, triple-blinded study, we tested the hypothesis that a 48 h continuous C5-6 root/superior trunk patient-controlled infusion of ropivacaine 0.4% would provide superior analgesia after shoulder surgery compared with the same infusion of ropivacaine 0.2%.
  
  
  METHODS
  Patients presenting for painful shoulder surgery were recruited. A perineural catheter was placed under ultrasound guidance immediately adjacent to the C5-6 roots/superior trunk. Ropivacaine 5 mg ml(-1) (30 ml) was administered via this catheter before surgery under general anaesthesia. At the end of surgery, patients were randomized to receive ropivacaine 2 mg ml(-1) (0.2%) (n=32) or 4 mg ml(-1) (0.4%) (n=33) via an elastomeric pump delivering 2 ml h(-1) with on-demand patient-controlled boluses of 5 ml as required. Acetaminophen and diclofenac were administered if any postoperative pain occurred, ropivacaine boluses for a numerical rating pain score (NRPS, 0-10) of >2, and rescue tramadol for an NRPS >3. All patients were phoned on postoperative days 1 and 2 and questioned for indices of treatment effectiveness and adverse effects.
  
  
  RESULTS
  NRPS, patient ropivacaine demands, and supplemental tramadol consumption were similar in each group [median 'average daily pain' days 1/2 (0.2%=1/3, 0.4%=2/3)]. Episodes of an insensate/densely blocked arm occurred only with ropivacaine 0.4% (5 vs 0 episodes, P=0.05). Satisfaction (numerical rating scale, 0-10) was higher for ropivacaine 0.2% [mean difference (95% confidence interval)=1.3 (0.3-2.4), P=0.01)].
  
  
  CONCLUSIONS
  After major shoulder surgery, ropivacaine 0.2% at 2 ml h(-1) with on-demand 5 ml boluses administered via an ultrasound-guided C5-6 root/superior trunk perineural catheter produces similar analgesia, but higher patient satisfaction compared with ropivacaine 0.4%.
  
  
  BACKGROUND
  ANZCTR: ACTRN12608000591358. URL: www.anzctr.org.au/registry/trial_review.aspx?ID=83028.
authors.affiliation: Department of Anaesthesia, Auckland City Hospital, Auckland, New Zealand. fredrickson@actrix.co.nz
authors.forename: M J
authors.initials: MJ
authors.lastname: Fredrickson
authors.forename: D J
authors.initials: DJ
authors.lastname: Price
mesh_terms: D000328:Adult; D000368:Aged; D000577:Amides / Q000008:administration & dosage* / Q000009:adverse effects; D016058:Analgesia, Patient-Controlled / Q000379:methods; D000768:Anesthesia, General / Q000379:methods; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D001917:Brachial Plexus; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D010147:Pain Measurement / Q000379:methods; D010149:Postoperative Pain / Q000517:prevention & control; D019990:Perioperative Care / Q000379:methods; D011446:Prospective Studies; D000077212:Ropivacaine; D012785:Shoulder Joint / Q000601:surgery*; D020069:Shoulder Pain / Q000517:prevention & control; D018084:Ultrasonography, Interventional
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine