Interscalene Brachial Plexus Blockade Using Ropivacaine 0.50% as Effective as 0.75% in Postoperative Shoulder Replacement Surgery: Presented at AACP

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Title: Interscalene Brachial Plexus Blockade Using Ropivacaine 0.50% as Effective as 0.75% in Postoperative Shoulder Replacement Surgery: Presented at AACP
URL: http://www.pslgroup.com/dg/22C9FA.htm
Doctor's Guide
September 17, 2008

By Maggie Schwarz

PHILADELPHIA -- September 17, 2008 -- There appears to be no difference between 0.50% and 0.75% formulation of ropivacaine for interscalene brachial plexus blockade prior to elective shoulder replacement surgery, according to research presented here at the American College of Clinical Pharmacology (ACCP) 37th Annual Meeting.

Eiman Anvari, Osteopathic Medical Student, Philadelphia College of Osteopathic Medicine, Philadelphia, Pennsylvania, and co-investigators evaluated the 2 concentrations of ropivacaine in 40 patients undergoing surgery at Methodist Hospital, Philadelphia.

Few studies to date have found evidence in support of one concentration over the other for postoperative analgesia, according to Anvari and colleagues. But severe adverse reactions within the central nervous and cardiovascular systems have been reported after administration of high plasma concentrations of ropivacaine.

To compare 0.50% and 0.75% concentrations of ropivacaine for interscalene brachial plexus blockade prior to elective total shoulder replacement surgery, the investigators analysed the amount of pain medications required by each patient as well as patients' pain scores in the immediate postoperative period in hospital.

Results showed that the higher ropivacaine dose significantly decreased time to onset of pain by an average of 8 minutes (P < .05), confirming the findings of previous studies. The results did not, however, show a dose-response relationship with ropivacaine.

One of the more compelling findings was that increasing the concentration of ropivacaine from 0.50% to 0.75% did not reduce the amount of patient-controlled morphine consumption, the researchers said. In fact, subjects in the 0.50% group consumed less morphine than those in the 0.75% group by an average of 4 mcg/kg/h. This difference was not statistically significant, however, and results indicated that both concentrations of ropivacaine provided similar analgesia as shown by patient-controlled analgesia morphine use.

Anvari concluded that, since injection of ropivacaine 0.50% reduces the risk of serious systemic toxicity compared with 0.75% and both concentrations confer similar clinical efficacy regarding pain relief, the lower concentration is the superior choice for interscalene blockade prior to elective shoulder replacement.

[Presentation title: Comparison of 0.50% and 0.75% Ropivacaine for Interscalene Brachial Plexus Blockade on Pain Reduction and Use of Analgesic Medication in Immediate Post-Operative Period in Patients Undergoing Elective Total Shoulder Replacement Surgery. Abstract 77]

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