CHANGES IN REGIONAL LUNG VENTILATION AFTER ULTRASOUND-GUIDED INTERSCALENE BRACHIAL PLEXUS BLOCK WITH 4 AND 15 ML OF 0.5% BUPIVACAINE
LHC Ferraro, A Takeda, F Mehlmann, PCCB de Sousa, AS Gonçalves, LFR Falcao
Discipline of Anaesthesiology, Pain and Critical Care Medicine, Federal University of São Paulo, Brazil.
Background and goal of study
Interscalene brachial plexus block (ISBPB) is widely used in regional anaesthesia for upper limb surgeries and is associated with phrenic nerve paralysis in as many as 100% of patients in some studies with reduction of ventilation. Previous studies have shown that smaller volumes of local anaesthetic reduce the incidence of this complication. The aim of this pilot study is to evaluate whether lower volumes of local anaesthetics in ISBPB causes shorter and less intense phrenic nerve paralysis than larger volumes.
Materials and methods
Pilot study with five ASA P2 patients submitted to shoulder surgery with combined general anaesthesia and ISBPB using different volumes of 0.5% bupivacaine (15 mL vs 4 mL). The brachial plexus block was ultrasound-guided (US). After US visualization of the nerve roots and the trunks of the brachial plexus between the anterior and middle scalene muscles, the injection was given between the C5 and C6 roots. Electrical impedance tomography was used to evaluate regional lung ventilation before, 30 minutes and 5 hours after the ISBPB in spontaneous ventilation.
Results and discussion
After the block onset, all patients showed reduced ipsilateral lung ventilation (ILV), in the cases of 4 mL of bupivacaine a reduction of 36 ± 33% was observed while the ISBPB with 15 mL the decrease were 45 ± 33% (figure 1). Moreover, 5 hours after block and recovery of general anaesthesia with conditions for discharge, there were still a 41 ± 22% reduction of ILV in the patients blocked with 15 mL of bupivacaine; meanwhile, there were only 2 ± 1% reduction of ILV with 4 mL (figure 2).
All patients showed decreased regional ventilation in the ipsilateral lung immediately after block onset. But in the patients blocked with 4 mL phrenic nerve paralysis was shorter and less intense than in the patients blocked with 15 mL.