METHODS: A prospective observation study conducted in MV patients admitted in a mixed ICU between 1st May 2012 to 31st July 2013.All adult patients considered eligible for fluid resuscitation as decided by the attending physician were included. Exclusion criteria: Pregnant patients, head injury , intra-abdominal hypertension , amputees, those with incomplete records were excluded. PROTOCOL: Linear transducer with pulse wave doppler was used on common carotid artery for recording carotid artery FTc. A 4F thermistor-tipped arterial catheter (Pulsiocath thermodilution catheter; Pulsion Medical Systems, Germany) was inserted in the femoral artery, which was connected to the PiCCO (Pulsion Medical Systems, Germany) and the bedside monitor (IntelliVue MP50/70: Philips Medical System, Germany). Hemodynamic indices were determined using a triplicate injection of 15 mL ice-cold normal saline within 5 minutes through an additional 7 F central venous catheter introduced in the right internal jugular vein. The bolus thermodilution measurements were made by the same observer to avoid interobserver variation . All recordings taken at baseline in semi-recumbent positions. Patients were put supine and after 5 minutes, PLR was done. The maximum SV during the PLR was recorded. Carotid FTc was measured at 1, 2 and 3 minutes. Maximum carotid FTc value was considered. Fluid responsiveness was defined as >15% in SV after volume expansion (VE).