The purpose of the study is to evaluate the predictive value of the inferior vena cava collapsibility index and caval aorta index for detecting hypotension after induction of general anesthesia.

Since cardiovascular depressant and vasodilatory effects of anesthetic agents, patients may be at risk of hypotension after induction of general anesthesia. Previous studies reported that, for evaluating volume status, some ultrasonographic measurements such as inferior vena cava collapsibility index (IVCCI) could be used. Also some studies stated that measurement of aorta diameter index (IVC : Ao index) is reliable to predict hypotension after induction of spinal anesthesia. At the study, the investigators aimed to investigate the predictive values of the inferior vena cava collapsibility index and caval aorta index under ultrasound guidance in predicting post-induction hypotension in patients under general anesthesia.

Inclusion Criteria:

• patients more than 18 years of age
• American Society of Anesthesiologists' (ASA) physical status 1 or 2

Exclusion Criteria:

• BMI more than 30 kg/m²
• Use of angiotensin converting enzyme inhibitors
• pregnancy,
• emergency operations
• baseline arterial systolic blood pressure less than 90 mmHg
• mean arterial blood pressure less than 70 mmHg

patients who scheduled for elective non-cardiac surgery under general anesthesia