Indications for Femoral Artery Cannulation, US-Guided For use in critically ill, unstable patients, especially those with refractory shock and respiratory failure: Continuous blood pressure measurement Repeated blood gas measurements (PO2, PCO2, pH) Continuous cardiac function measurement, in lieu of pulmonary arterial catheterization Repeated blood samples for laboratory tests Arterial cannulation is also used in settings of major fluid shifts or blood loss (eg, major surgery), inotropic support, and hypothermia (including induced) and for angiography and therapeutic embolization.