Application of Bedside Ultrasonography to Assess Axillary Veins and Predict Volume Responsiveness in Mechanically Ventilated Patients

Aim: This research aimed to explore the correlation between the axillary vein (AXV) and the inferior vena cava (IVC) for volume assessment following non-thoracic abdominal surgery in patients under mechanical ventilation.The primary objective was to determine whether the AXV could serve as a reliable indicator for evaluating volume responsiveness.Study Design: This retrospective cohort study included 106 critically ill patients admitted to the intensive care unit (ICU) of Peking University People's Hospital after non-thoracic abdominal surgery between November 2023 and June 2024.All patients were on invasive mechanical ventilation (volume-controlled; tidal volume 8 mL/kg, positive end-expiratory pressure 5 cmH 2 O) and had not yet recovered spontaneous respiration postoperatively.The relevant indices were monitored at postoperative admission to the ICU.The diameters of AXV and IVC were measured using ultrasonography, and the dilatation index (DI) was calculated.At admission, ultrasonography was performed on the left ventricle and the left ventricular outflow tract to determine the velocity time index (VTI).These indices were remeasured after a rapid infusion of 100 mL of sodium lactate Ringer's solution.The patients were categorized into volume-responsive and non-volumeresponsive groups according to VTI measurements before and after the volume-loading test, and the correlation between the relevant parameters and hypovolemia was analyzed. Results:The sensitivity and specificity of a critical AXV-DI value of 22.2% were 88.1% and 77.36%, respectively.Conclusions: Axillary vein dilatation index is a valid indicator for volume assessment in postoperative patients in surgical ICUs.