Ultrasound Assessment of Internal Jugular Vein for Cannulation and Venous Pressure Prediction

Inclusion Criteria: * Adult patients aged 18 years or older. * Patients admitted to the Intensive Care Unit (ICU), Emergency Department, or Operating Theatres who require internal jugular vein (IJV) cannulation for clinical indications. * Patients in whom ultrasound-guided right internal jugular vein cannulation is planned. * Patients who are hemodynamically stable enough to undergo ultrasound examination before cannulation. * Patients able to undergo vascular ultrasound examination in the supine position (0-30° head elevation according to the study protocol). * Patients in whom complete ultrasound assessment of the internal jugular vein can be performed (including maximum diameter, minimum diameter, cross-sectional area, and collapsibility/distensibility index). * Patients with a clinically indicated assessment of central venous pressure (CVP) or jugular venous pressure (JVP) allowing comparison with ultrasound measurements. * Patients providing written informed consent, or consent obtained from a legally authorized representative when applicable. Exclusion Criteria: * Patients younger than 18 years of age. * Previous surgery, radiotherapy, or significant trauma involving the neck. * Known thrombosis, stenosis, or congenital anomalies of the internal jugular vein. * Local infection, cellulitis, burn, or hematoma at the intended cannulation site. * Large neck masses, thyroid enlargement, or cervical pathology causing distortion of neck anatomy. * Severe coagulopathy or uncontrolled bleeding disorders contraindicating internal jugular vein cannulation. * Patients with cervical spine instability or those in whom proper positioning for ultrasound examination is not possible. * Inadequate ultrasound visualization of the internal jugular vein. * Severe tricuspid valve disease or conditions causing marked alterations in central venous hemodynamics that interfere with accurate interpretation of IJV measurements. * Refusal of the patient or legally authorized representative to provide informed consent.