Comparison of combined suprascapular and axillary nerve block versus superior (upper) trunk block for phrenic nerve sparing analgesia in patients undergoing arthroscopic shoulder surgery A randomized controlled study

Patients undergoing shoulder arthroscopic surgeries experience intense pain in the postoperative period that interferes with recovery and rehabilitation. Peripheral nerve blocks (PNBs) are the preferred choice to provide adequate intraoperative and postoperative analgesia. Among PNBs, the interscalene approach of the brachial plexus block (ISB) is considered to be the standard and the most commonly used block for shoulder surgeries. It provides good perioperative analgesia but is inevitably known to cause hemidiaphragmatic paralysis due to ipsilateral phrenic nerve blockade which can lead to respiratory distress, especially in patients with cardio-pulmonary compromise. The superior trunk (ST) block has been described as a refinement of the conventional ISB technique where LA is injected around the ST which is formed by fusion of C5 and C6 nerve roots. ST block produces non-inferior analgesia of the shoulder compared to ISB as all the nerves innervating the shoulder arise distal to the ST. Also, the site of injection is further away from the phrenic nerve theoretically reducing the risk of hemidiaphragmatic paresis. The major nerve supply of the shoulder joint arises from the suprascapular nerve (SSN) and axillary nerve (AN). Combined blockade of these two nerves has been shown to provide equivalent analgesia to ISB in shoulder surgeries with complete elimination of the risk of hemidiaphragmatic paresis.

These two blocks i.e. ST block and combined SSN &AN block have not been compared for their phrenic nerve sparing analgesia. Therefore, we plan a study to compare these two block in terms of phrenic nerve sparing analgesia.

The enrolled patients will be randomly divided into two groups by using a computer-generated random number table and the allocation concealment will be done by a sealed opaque envelope method that will be opened just before starting premedication.

Group ‘ST’ (Superior Trunk Block)- All patients will receive ultrasound (US) guided ST block with 15 mL 0.5 percent ropivacaine.

Group ‘SSN & AN’ (combined SSN and AN block)- All patients will receive US-guided SSN and AN block with 20 mL 0.5 percent ropivacaine.

The outcome assessor/sonographer (assessing diaphragmatic excursion and NRS score) will be blinded to the group allocation.

On the day of surgery, in the preoperative area, a blinded observer will perform a US examination to determine baseline diaphragmatic excursion. The baseline pulmonary function, including forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and the FEV1/FVC ratio will be assessed and recorded using a portable spirometer.

30 minutes after placement of the block, a repeat assessment of diaphragmatic excursion and IC will be performed and recorded.