Objectives: To determine the relationship between minimal stimulating current and success rate of interscalene brachial plexus block (IBPB), to assess the quality of anaesthesia and postoperative analgesia, and to evaluate the benefits and drawbacks of this technique in shoulder surgery.
Study design: Prospective study of a continuous series of clinical cases.
Patients: Series of 167 patients undergoing shoulder surgery under IBPB, obtained with Winnie's technique, in 1995.
Methods: The plexus was located with a nerve stimulator and an insulated needle, 25 mm long and with a short 30 degrees bevel (Stimuplex, Braun). Data were collected with questionnaires, filled in by the anaesthetists, the surgeon and patients.
Results: Shoulder surgery was performed either under IBPB alone in 51.5% of cases (group A), or under IBPB associated with sedation (midazolam: 1-3 mg) in 31.7% (group B), or under IBPB associated with general anaesthesia either on the patient's request (11.4% = group C) or due to IBPB failure (5.4% = group D). The success rate was 94.6% and the efficiency of postoperative analgesia obtained in 100% of cases (no pain at admission in the recovery room). For the nerve location a minimal stimulating current of 0.08 to 1 mA (mean minimal stimulating current 0.42 +/- 0.17 mA) had been required, with a significant difference (P = 0.0001) between group A (0.38 +/- 0.14 mA) and the others (0.43 +/- 0.15 mA in group B, 0.50 +/- 0.21 mA in group C, 0.59 +/- 0.23 mA in group D).
Conclusions: The correlation between minimal stimulating current and success rate has clearly shown the benefit of the nerve stimulation. IBPB, which provides a successful and efficient anaesthesia with minimal risk and satisfactory postoperative analgesia, has become the standard technique for shoulder surgery.