Ultrasound-guided Axillary Artery vs Femoral Artery Cannulation.

Inclusion Criteria: mechanically ventilated critically ill patients with indications for artery cannulation: * in whom radial artery cannulation is unable to perform or * in order to conduct hemodynamic monitoring using transpulmonary thermodilution Exclusion Criteria: * age less than 18 years * trauma and hematoma at the catheterization site * clinically significant coagulation disorders * infection at the catheterization site * lack of patients or closest relatives contents * precedent surgery operation into the femoral and axillary arteries * clinically significant ischemia of the limb at the cannulation side