• Sérgio M Pereira, Bruno E Sinedino, CostaEduardo L VELVDivision of Pneumology (Laboratory of Medical Investigation 09) Faculty of Medicine, University of São Paulo, São Paulo, Brazil; Syrian-Lebanese Institute of Teaching and Research, Hospital Sírio-Libanês, São Paulo, Brazil., MoraisCaio C ACCADivision of Pneumology (Laboratory of Medical Investigation 09) Faculty of Medicine, University of São Paulo, São Paulo, Brazil; and Department of Physiotherapy, Federal University of Pernambuco, Recife, Brazil., Michael C Sklar, Cristhiano Adkson Sales Lima, NakamuraMaria A MMAMDivision of Pneumology (Laboratory of Medical Investigation 09) Faculty of Medicine, University of São Paulo, São Paulo, Brazil., Otavio T Ranzani, Ewan C Goligher, Mauro R Tucci, Yeh-Li Ho, Leandro U Taniguchi, Joaquim E Vieira, Laurent Brochard, and AmatoMarcelo B PMBPRespiratory Intensive Care Unit and Laboratory of Medical Investigation 09, INCOR, Heart Institute, Faculty of Medicine, University of São Paulo, São Paulo, Brazil..
• Division of Pneumology (Laboratory of Medical Investigation 09), Faculty of Medicine, University of São Paulo, São Paulo, Brazil; Department of Anesthesia and Pain Medicine, Unity Health Toronto; Interdepartmental Division of Critical Care; and Keenan Center for Biomedical Research, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Ontario, Canada.
• Anesthesiology. 2022 May 1; 136 (5): 763-778.

BackgroundStrong spontaneous inspiratory efforts can be difficult to control and prohibit protective mechanical ventilation. Instead of using deep sedation and neuromuscular blockade, the authors hypothesized that perineural administration of lidocaine around the phrenic nerve would reduce tidal volume (VT) and peak transpulmonary pressure in spontaneously breathing patients with acute respiratory distress syndrome.MethodsAn established animal model of acute respiratory distress syndrome with six female pigs was used in a proof-of-concept study. The authors then evaluated this technique in nine mechanically ventilated patients under pressure support exhibiting driving pressure greater than 15 cm H2O or VT greater than 10 ml/kg of predicted body weight. Esophageal and transpulmonary pressures, electrical activity of the diaphragm, and electrical impedance tomography were measured in pigs and patients. Ultrasound imaging and a nerve stimulator were used to identify the phrenic nerve, and perineural lidocaine was administered sequentially around the left and right phrenic nerves.ResultsResults are presented as median [interquartile range, 25th to 75th percentiles]. In pigs, VT decreased from 7.4 ml/kg [7.2 to 8.4] to 5.9 ml/kg [5.5 to 6.6] (P < 0.001), as did peak transpulmonary pressure (25.8 cm H2O [20.2 to 27.2] to 17.7 cm H2O [13.8 to 18.8]; P < 0.001) and driving pressure (28.7 cm H2O [20.4 to 30.8] to 19.4 cm H2O [15.2 to 22.9]; P < 0.001). Ventilation in the most dependent part decreased from 29.3% [26.4 to 29.5] to 20.1% [15.3 to 20.8] (P < 0.001). In patients, VT decreased (8.2 ml/ kg [7.9 to 11.1] to 6.0 ml/ kg [5.7 to 6.7]; P < 0.001), as did driving pressure (24.7 cm H2O [20.4 to 34.5] to 18.4 cm H2O [16.8 to 20.7]; P < 0.001). Esophageal pressure, peak transpulmonary pressure, and electrical activity of the diaphragm also decreased. Dependent ventilation only slightly decreased from 11.5% [8.5 to 12.6] to 7.9% [5.3 to 8.6] (P = 0.005). Respiratory rate did not vary. Variables recovered 1 to 12.7 h [6.7 to 13.7] after phrenic nerve block.ConclusionsPhrenic nerve block is feasible, lasts around 12 h, and reduces VT and driving pressure without changing respiratory rate in patients under assisted ventilation.Editor’s PerspectiveCopyright © 2022, the American Society of Anesthesiologists. All Rights Reserved.

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