The use of vitamin B1 as a perineural adjuvant to middle interscalene block for postoperative analgesia after shoulder surgery.

BACKGROUND: Perineural administration of thiamine, via axonal flow, could strenghthen synthesis of ACh in the dorsal horn inhibitory interneurons, thus potentiating analgesia. The purpose of the present retrospective analysis is therefore to investigate whether adding perineurally 2 mg/Kg of thiamine to 0.75% levobupivacaine in patients undergoing middle interscalene block may prolong the duration of analgesia. METHOD: The hospital records of all ASA status 1-2 patients, undergoing a single-shot interscalene block for arthroscopic rotator cuff repair from January 2011 to May 2012 were retrospectively reviewed. All blocks were performed with 0.75% levobupivacaine or a solution of thiamine hydrochloride and 0.75% levobupivacaine. The local anesthetic solution, postoperative visual analogue score for pain at rest and rescue medication were registered. We calculated the time interval elapsing between block anesthetic mixture injection and the patient's first analgesic requirement, ie time to end of analgesia. Eventual postoperative side effects were also reported. RESULTS: 59 patients received 0.4 ml/Kg of 0.75% levobupivacaine (Group L) and 51 patients received a mixture of 2 mg/Kg of thiamine hydrocloride (maximum dose 200 mg) with 0.4 ml/Kg of 0.75% levobupivacaine (Group B1). Tea was 11.4 ± 3.0 hours in Group L versus 17.6 ± 3.0 hours in Group B1 (p < 0.001). The scores for pain in the two Groups at the time of the first analgesic rescue were comparable. CONCLUSION: The present retrospective analysis suggests that thiamine helps to prolong postoperative analgesia when added to the local anesthetic solution. Further prospective studies are necessary to confirm these preliminary results.Word count: 250.

Buprenorphine added to levobupivacaine enhances postoperative analgesia of middle interscalene brachial plexus block.

PURPOSE: The aim of this study was to assess whether addition of epineural buprenorphine prolonged postoperative analgesia of middle interscalene brachial plexus block (MIB) with levobupivacaine. METHODS: One hundred and fifty consenting adult patients, scheduled for shoulder arthroscopic surgery for a rotator cuff tear under MIB with 29.5 ml of 0.75 % levobupivacaine, were randomized to receive additionally either saline or intramuscular buprenorphine 0.15 mg or epineural buprenorphine 0.15 mg. Onset of sensory and motor blocks, duration of postoperative analgesia, and consumption of postoperative analgesics were compared among the groups. RESULTS: There were significant (P < 0.05) differences in the onset and the duration of the sensory block and in the duration of postoperative analgesia. Duration of both sensory block and postoperative analgesia was longer (P < 0.05) in patients who had received epineural buprenorphine (856.1 ± 215.2 and 1,049.7 ± 242.2 min) than in patients who had received intramuscular buprenorphine (693.6 ± 143.4 and 820.3 ± 335.3 min) or saline (488.3 ± 137.6 and 637.5 ± 72.1 min). Requirement of postoperative rescue analgesics was lower in the epineural buprenorphine group than in the other two groups. Few complications occurred from MIB (<1 %) and none from buprenorphine. CONCLUSIONS: Epineural buprenorphine prolonged postoperative analgesia of MIB more effectively than intramuscular buprenorphine, which suggests that buprenorphine acts at a peripheral nervous system site of action.