The analgesic effect of continuous subacromial bupivacaine infusion after arthroscopic shoulder surgery: a randomized controlled trial.

BACKGROUND: The benefits of subacromial local anesthetic infusion are controversial. The aim of this study was to evaluate the efficacy of subacromial bupivacaine infusion after arthroscopic acromionplasty and rotator cuff procedures. METHODS: Ninety patients with subacromial impingement disease scheduled for elective shoulder arthroscopy were enrolled in this randomized, prospective and placebo-controlled study. The patients received subacromially either 5.0 mg/ml bupivacaine or 9.0 mg/ml saline at the rate of 2 ml/h post-operatively for 48 h. The primary outcome measure was the use of rescue oxycodone. The consumption of opioids, ibuprofen, paracetamol and codeine, and the intensity of pain were recorded. RESULTS: Patients receiving bupivacaine infusion used significantly less oxycodone compared with patients receiving saline [15 vs. 20 mg (median) oxycodone intravenously on the day of surgery, 0 vs. 10 mg (median) perorally on the first post-operative day]. There was no significant difference in the use of ibuprofen, paracetamol and codeine, except that paracetamol was used more in patients receiving saline during the day of surgery (P = 0.009). The pain scores of patients receiving bupivacaine were lower at 18 h (P = 0.008). Average pain scores for the worst pain experienced did not differ between the groups. There were three (4%) premature discontinuations because of technical problems. CONCLUSIONS: Considering the low need of opioids, expenses and technical problems in these patients, subacromial 5.0 mg/ml bupivacaine infusion 2 ml/h confers only moderate and probably clinically insignificant efficacy compared with placebo. This efficacy might be overweighed by the disadvantages.

Plasma levels of bupivacaine and its metabolites after subacromial infusions in concentrations 2.5 or 5.0 mg/ml.

BACKGROUND: We studied plasma bupivacaine concentrations in patients with a continuous subacromial bupivacaine infusion after an ambulatory arthroscopic shoulder surgery to evaluate whether it is feasible to discharge patients with an on-going infusion early on the operation day. METHODS: Sixteen ASA I-III patients undergoing elective arthroscopic shoulder surgery were randomized in 1:1 ratio to receive a continuous infusion of either 2.5 or 5.0 mg/ml bupivacaine subacromially for 48 h post-operatively. Before the commencement of the infusion, 20 ml of 5.0 mg/ml bupivacaine was injected subacromially in both groups. Plasma bupivacaine concentrations were defined as the primary endpoint and concentrations of its metabolites, side effects and pain scores as the secondary endpoints. RESULTS: The mean total plasma bupivacaine concentration increased up to 48 h, the highest mean being 0.87 (SD 0.30) µg/ml during the 5.0 mg/ml treatment and 0.24 (0.10) µg/ml during the 2.5 mg/ml bupivacaine treatment. After 48 h, there was a significant difference between the groups in the plasma levels. The highest mean 4-hydroxy-bupivacaine and desbutylbupivacaine concentrations were 0.11 and 0.22 µg/ml, respectively. In the pain scores, no significant difference was found. No clear signs of toxicity were observed. CONCLUSIONS: The concentrations of total bupivacaine and its metabolites remained below toxic levels. Excluding patients with renal or liver diseases, both 2.5 and 5.0 mg/ml bupivacaine as subacromial infusion 2 ml/h for 48 h following shoulder arthroscopy seem to be well tolerated, enabling patient discharge with an on-going infusion on the operation day. Because of similar side effects and pain scores in both groups, 2.5 mg/ml may be preferable.