Ultrasound-guided tourniquet pressure setting enhances hemodynamic stability and pulmonary function by attenuating...

OBJECTIVE: This study aimed to determine whether ultrasound-guided pneumatic tourniquet pressure setting reduces pulmonary ventilation dysfunction and enhances hemodynamic stability in patients undergoing lower-limb surgery. METHODS: This was a prospective, single-center, assessor-blinded, randomized controlled trial. Forty-four patients scheduled for lower-limb surgery requiring tourniquet application were assessed for eligibility. Two patients were excluded because of protocol deviations (one received combined sedative medication and one was converted to general anesthesia intraoperatively). The remaining 42 patients were randomly allocated to a control group and an ultrasound-guided group (n = 21 each). In the ultrasound-guided group, the optimal tourniquet pressure was defined as the pressure at which the popliteal arterial blood flow ceased under ultrasonographic imaging. The control group underwent the conventional pressure-setting method. The primary outcome was the arterial-to-alveolar oxygen partial pressure ratio (A/a ratio) at 6 h after tourniquet deflation (T4). Secondary outcomes included mean arterial pressure (MAP), heart rate (HR), plasma malondialdehyde (MDA) and superoxide dismutase (SOD) concentrations, arterial oxygen partial pressure (PaO₂), arterial carbon dioxide partial pressure (PaCO₂), respiratory index (RI), alveolar-arterial oxygen partial pressure difference (PA–aDO₂). All outcomes, including A/a ratio, were measured at designated time points: immediately before tourniquet inflation (T0), and at 1 h (T1), 0.5 h (T2), 2 h (T3), 6 h (T4), and 24 h (T5) after inflation. RESULTS: Compared with the control group, the ultrasound-guided group exhibited higher MAP and lower HR at T2. At T4, PaO₂ and A/a ratio increased, while PA–aDO₂ and RI decreased. From T3 to T5, MDA concentration was significantly lower and SOD concentration significantly higher in the ultrasound-guided group compared with the control group. CONCLUSION: Ultrasound-guided tourniquet pressure setting enhances hemodynamic stability and reduces pulmonary ventilation dysfunction in patients undergoing lower-limb surgery. These findings were accompanied by lower MDA levels and higher SOD activity, suggesting a potential association with reduced oxidative stress during ischemia–reperfusion. TRIAL REGISTRATION: The study was registered in the Chinese Clinical Trial Register website ( www.chictr.org.cn , ChiCTR1900026552,2019/10/13).