Pre-anaesthesia ultrasonography of the subclavian/infraclavicular axillary vein for predicting hypotension after inducing general anaesthesia A prospective observational study

BACKGROUND Bedside sonography of the inferior vena cava has been demonstrated to be a reliable tool for assessing intravascular volume status. Subclavian vein (SCV) assessment was proposed as a reasonable adjunct for measuring the inferior vena cava. OBJECTIVE We examined whether the preoperative diameter and collapsibility index of the SCV or the infraclavicular axillary vein could predict the incidence of hypotension after induction of general anaesthesia in patients undergoing laparoscopic cholecystectomy. DESIGN Prospective, observational study. SETTING Tertiary university hospital. PATIENTS Adults scheduled for laparoscopic cholecystectomy. INTERVENTION Sonographic evaluation of the SCV or the axillary vein (SCV-AV) before induction of anaesthesia. MAIN OUTCOME MEASURES The main outcome was the association between the SCV-AV measurements (diameter an collapsibility index) and intra-operative hypotension (IOH) after induction of anaesthesia. RESULTS Patients who developed IOH had a higher collapsibility index of the SCV-AV during spontaneous breathing (P = 0.009) and deep inspiration (P = 0.002). After adjusting for confounding variables, the collapsibility index of the SCV-AV during spontaneous breathing was not a significant predictor of a decrease in mean arterial blood pressure (MAP) after inducing anaesthesia (P = 0.127), whereas the collapsibility index of the SCV-AV during deep inspiration was a significant predictor (P < 0.001). CONCLUSION The collapsibility index of the SCV-AV during deep inspiration was a significant predictor of IOH occurrence and the percentage decrease in MAP after inducing anaesthesia. Further studies in patients with higher collapsibility index are needed to confirm our findings, before the collapsibility index of the SCV-AV can be recommended unequivocally for clinical use.