Comparison of Interscalene Block ,Superior Trunk Block and Combined Infraclavicular and Suprascapular Block on Regional Lung Ventilation in Patients Undergoing Shoulder Surgery - Randomized controlled Trial

Regional anaesthesia has an established role in providing perioperative analgesia for shoulder surgeries. Interscalene block is considered as the gold standard analgesia ,but it holds a high risk of involving phrenic nerve (100%) and thereby hemi diaphragmatic palsy. It can increase morbidity in patients with pre existing respiratory diseases. Several alternatives to the Interscalene block have been proposed in order to avoid the effect on the diaphragm function ,which include Superior Trunk block, Combined Infraclavicular and Suprascapular Nerve block . The phrenic nerve lies in close proximity to the brachial plexus and diverge as it descends over the anterior scalene muscle and as it approaches the root of the neck ,the phrenic nerve usually lies between the subclavian artery and vein , before coursing medially in front of the Internal thoracic artery . Incidence of  phrenic nerve involvement in Superior Trunk block and Combined Infraclavicular and Suprascapular Nerve block ranges between 25 - 76.3% and 6 % respectively. Even though the involvement of phrenic nerve is studied, its influence on respiratory parameters such as regional lung ventilation  is not studied much in any other studies conducted before about these blocks. Electrical Impedence Tomograph is one of the recent lung imaging technique that can provide dynamic information on distribution of regional lung ventilation . EIT possess high temporal and functional resolution allowing the visualisation of dynamic physiological and pathological changes on a breath to breath basis. EIT detect changes in electrical impedence   (i.e changes in gas/fluid ratio ) and describes them in real time,  both visually through images and waveforms and numerically allowing the clinician to monitor the disease evolution .In this we are comparing the effect of Interscalene block, Superior Trunk block and Combined Infraclavicular Brachial and Suprascapular nerve block on regional lung ventilation by using Electrical Impedence Tomograph.