<qa>  What is the measurement of the IVC?2. Ultrasonographic assessment of Inferior Vena Cava Measurement of the inferior vena cava diameter, and respiratory variation by ultrasound -assessment Ultrasonographic assessment of the IVC will be done using a transthoracic, subcostal approach. The transducer will be positioned just below the xiphisternum 1-2cms to the right of the midline, with the marker dot pointing towards the sternal notch. After obtaining a 2-D image of the IVC entering the right atrium and verifying that the IVC visualization is not lost during movements of respiration, an M-mode line will be placed through the IVC 1 cm caudal from its junction with the hepatic vein, and an M-mode tracing obtained. This placement ensures that the intrathoracic IVC is not measured during any part of the respiratory cycle. The M-mode tracing will be recorded through 3- 4 respiratory cycles, the image frozen and using calipers, the maximum and minimum diameters of the IVC tracing measured. IVC variation will be quantified by measuring the difference between the maximum and minimum diameters on the M-mode tracing. 