Is There Any Correlation Between Respiratory Variation Ratios of Internal Jugular Vein and Inferior Vena Cava?

The investigators measure the internal jugular vein (IJV) diameter in the short axis by using the linear probe (12-5 MHz) and M-mode of the ultrasound device in the junction of cricothyroid membrane level and midclavicular line. The inferior vena cava (IVC) is visualized in the subxiphoid long axis by using the convex probe (5-1 MHz). Diameter of the IVC is measured 2 cm caudally to the junction of the hepatic vein in M-mode. All measurements are done separately by 3 different doctors; one senior anesthesiology resident, one anesthesiology and critical care medicine fellow and one professor in anesthesiology and critical care. The first measurements of the IVC and the IJV are done in the supine position and the second ones are done after passive leg raise. Passive leg raise is done for 1 minute in the first group and for 3 minutes in the second group. Then distensibility (maximum diameter - minimum diameter / minimum diameter) and collapsibility (maximum diameter - minimum diameter / maximum diameter) indices are calculated. No fluid therapy or medication are given to the patients according to these measurements. Oxygen saturation, hearth rate and blood pressure levels are recorded before and after the measurements. The investigators also record age, gender, weight, height, body mass index, causes of admission, comorbidities, ventilator settings, vasoactive and diuretic medications, fluid intake and output volumes, Acute Physiology and Chronic Health Evaluation II (APACHE II) and Sepsis-Related Organ Failure Assessment (SOFA) scores in the day of admission, Acute Physiology Score (APS) and SOFA scores in the day of measurement and length of stay in the intensive care unit. Patients with infection or surgical sutures in the site of measurement areas, intraabdominal hypertension, severe aortic regurgitation or lower extremity amputation history are excluded from the study.