Studies of peripheral nerve blocks for hand and shoulder surgery

Abstract

Performing regional anesthesia with a minimum effective volume (MEV) of local anesthetic may reduce the risk of systemic local anesthesia toxicity. The lateral sagittal infraclavicular block (LSIB) is a well-established anesthesia method for surgery distal to the shoulder. For LSIB using ropivacaine 7.5 mg/ml the MEV was previously not known and we estimated MEV95 to be 31 ml (95% CI, 18 – 45 ml). LSIB tends to result in supination of the hand/forearm, which may inhibit surgical access to the dorsum of the hand. Supination of the hand and forearm usually occurs by lateral rotation of the radius. When the upper limb is extended, supination may be obtained also by lateral rotation of the humerus. The main lateral rotator of the humerus is the infraspinatus muscle, innervated by the suprascapular nerve. In study II we hypothesised that this supination may be reduced by the addition of a suprascapular nerve block (SSNB) to the LSIB. The study showed that this combination provided a better hand/forearm position for dorsal hand surgery than LSIB alone. Interscalene brachial plexus block (ISB) has been the gold standard for pain management in patients undergoing shoulder surgery. It has a very high success rate, but with a high incidence of phrenic nerve block. Diaphragm-sparing alternatives have therefore been investigated. In study II we applied SSNB primarily because we wanted to prevent lateral rotation of the humerus, but chest radiographs documented that the combination of LSIB and SSNB did not cause paresis of the diaphragm. In study III we hypothesised that the combination of superficial cervical plexus block, SSNB and LSIB would provide a good alternative to the ISB with a lower risk of phrenic paresis. The triple block was shown to be feasible for arthroscopic shoulder surgery.