Spinal anesthesia is widely used for a variety of surgical procedures because of its simplicity, rapid onset, and favorable safety profile. Advantages also include nil airway manipulation, avoidance of polypharmacy, minimizing blood loss and minimal interference with cognition in the perioperative period. 

Despite these advantages, post-spinal hypotension remains one of its most frequent and clinically significant complications. This drop in blood pressure occurs as a result of sympathetic blockade, leading to vasodilation and a relative reduction in circulating blood volume. In vulnerable groups—such as elderly patients, individuals with chronic illnesses, or those with limited physiological reserve—this hemodynamic instability can result in organ hypoperfusion, postoperative morbidity, prolonged hospitalization, and increased mortality. 

Traditional methods for assessing intravascular volume, including invasive monitoring or ultrasound assessment of the inferior vena cava, may be difficult to apply in all surgical settings due to limitations such as technical difficulty, patient body habitus, and the need for specialized equipment. 

The internal jugular vein (IJV), located superficially in the neck, easily visualised offers a more accessible window for ultrasonographic evaluation. Its collapsibility during respiration has been shown to correlate with intravascular volume status. Hence assessing the IJV collapsibility index may serve as a practical and rapid method to estimate a patient’s volume status before spinal anesthesia. 

Hence the aim of this study is to determine whether the internal jugular vein collapsibility index (IJVCI), measured through ultrasonography in supine and 30 degree head-up position, can reliably predict the occurrence of post-spinal hypotension in geriatric patients undergoing surgery under spinal anesthesia. By evaluating the relationship between pre-anesthetic IJV measurements and subsequent blood pressure changes, the study seeks to assess whether this noninvasive method can serve as an effective tool for identifying patients at increased risk of hemodynamic instability.