0.25% levo-bupivacaine for interscalene block during shoulder surgery. A survey on 20 patients.

BACKGROUND: Interscalene brachial plexus block (ISB) is an alternative procedure to general anaesthesia for shoulder surgery, and consents the anaesthetist to easily control postoperative pain that, indeed, is known to be intense and often requires strong analgesic administration. The introduction of regional anaesthesia for this type of surgery, contributed to the relief of acute postoperative pain occurring in the recovery room since the analgesic effects of block persist for several hours after surgery depending upon the selected drug. The aim of this study was to determine the effects of 40 ml of 0.25% levo-bupivacaine, a local anaesthetic derived from the racemic mixture of bupivacaine, on the speed of onset, quality and duration of ISB.
METHODS: Twenty adult ASA I-II patients, undergoing shoulder surgery for various pathologies, were enrolled in this study. All patients were examined before surgery and were given a full explanation; written informed consent was asked for and obtained. ISB was placed with the classic Winnie approach and the plexus was localised by means of a 40 mm, 22G Teflon(R) coated needle connected to an electro neural stimulator distributing 0.5 mA at 2 Hz. Once twitching was observed, 16 ml of 0.25% levo-bupivacaine were injected on shoulder lift, 12 ml on forearm abduction and 12 ml on forearm adduction. Monitoring: the time elapsing from last injection to loss of sensibility of pin-prick on the shoulder area, degree of motor block expressed on a 4 points scale, surgery time, as well as total time of analgesia were recorded for statistical analysis. STATISTICS: data were analysed at the STATISTICS Department of the University of Messina (Italy) and results are expressed as means and standard deviations.
RESULTS: Eighteen patients were operated under ISB and light sedation while 2 patients were scheduled for interscalene block plus deep sedation, the position being very discomforting and surgery supposed to last more than 60 min (shoulder arthroscopy). Less than 9 min were required for the block to be complete with satisfactory muscle relaxation, optimal intraoperative anaesthetic condition and more than 13 hours of postoperative analgesia occurred.
CONCLUSIONS: Levobupivacaine is a newly developed local anaesthetic derived from a bupivacaine racemic mixture from which the right isomer has been eliminated. Levo-bupivacaine, compared to racemic mixture, is acknowledged to be less cardiotoxic, faster at equal dosage, and ensures a longer analgesic interval. Zero point twenty-five percent concentration was preferred in this study in order to inject large volumes (40 ml) with a minimal anaesthetic amount (100 mg), resulting in short time for obtaining loss of sensibility, optimal intraoperative conditions and long lasting block with adequate postoperative analgesia.