Clinical Research Directory

Inclusion Criteria: * Age \> 60 years. * American Society of Anesthesiologists (ASA) physical state I-II. * Body mass index (BMI) ≤35 kg/m². Patients above this value will be excluded because obesity may cause technical difficulty and poor image quality in femoral vein ultrasound assessment. * Elective lower-limb orthopedic surgery under spinal anesthesia. Exclusion Criteria: * Patients refusing to participate. * History of psychiatric illness or seizures. * Absolute contraindications to spinal anesthesia: infection at the puncture site, severe coagulopathy/anticoagulation \[defined as platelet count \<75,000/µL, International Normalized Ratio (INR) \>1.5, Activated Partial Thromboplastin Time (aPTT) \>1.5 times control, or the use of anticoagulants such as warfarin, heparin, low molecular weight heparin, or direct oral anticoagulants within the recommended safety interval for neuraxial anesthesia\], severe hypovolemia, increased intracranial pressure, or known allergy to local anesthetics. * Severe cardiac disease, including left ventricular ejection fraction \<30%, Severe valvular heart disease (e.g., critical aortic stenosis), clinically significant arrhythmias (atrial fibrillation with uncontrolled ventricular rate \>120 bpm, frequent ventricular ectopy or sustained ventricular tachyarrhythmia) and congestive heart failure such as New York Heart Association (NYHA) class III-IV. * Severe uncontrolled hypertension, defined as persistent mean arterial pressure (MAP) ≥120 mmHg or systolic blood pressure (SBP) ≥180 mmHg and/or diastolic blood pressure (DBP) ≥110 mmHg despite medical therapy. * Severe respiratory diseases (Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage III-IV chronic obstructive pulmonary disease, or forced vital capacity (FVC) \<50% predicted). * Baseline bradycardia (\<50) or mean arterial blood pressure less than 60mmHg. * Emergency surgeries.