Hyponatremia is the most common electrolyte disorder in patients admitted to the neuro-intensive care unit (NICU). The incidence of hyponatremia is 38-50% in NICUs and can significantly affect patient outcomes. The etiology and treatment strategies for correcting hyponatremia are often related to the patient’s volume status. The intensivists often judge the patient’s volume status by clinical assessment and the information from the inferior vena cava (IVC) diameter measurement. However, with this, it may be difficult to differentiate between hypovolemia and euvolemia. Use of dynamic measures such as stroke volume variation (SVV) or pulse pressure variation by pulse contour analysis method are also employed to understand the volume status, however, the cardio-pulmonary interactions pose a significant limitation to the interpretation of underlying volume status . These methods are often misleading and thus addressing the underlying volume status even more challenging. The assessment of fluid responsiveness by a fluid challenge (FC) or the passive leg raise (PLR)-induced stroke volume (SV) change, can also be monitored with non-invasive cardiac output (CO) monitor (NICOM). The operating principle of NICOM is the bioreactance to the applied current to the thorax, which is devoid of heart-lung interaction and can thus be well utilised in spontaneously breathing patients. This modality has been observed as a reliable indicator of volume status, including in patients with sepsis, and found to be safe in guiding fluid administration and may improve outcomes . However, the application of the assessment of fluid responsiveness using the NICOM has not been studied in patients with hyponatremia. This study aims to assess the volume status using PLR response in patients admitted to NICU and who develops new-onset sodium abnormalities. The findings of this study shall help to better understand the underlying mechanisms and guide appropriate management strategies.