To maintain catheter patency throughout the length of a study, the catheter tip should be located in the freely-flowing blood of the aortic arch. Depending on the mouse strain, gender, age and size (weight), the catheter may have to be advanced to different depths. It is recommended, before any survival surgery is performed, to determine the catheter insertion depth for each type of mouse to be implanted. This is done by performing a sternotomy on at least two representative euthanized mice and locating the aortic arch in relation to the carotid bifurcation. More animals may be necessary if there is a high degree of variability in the animal population. Measurements are taken to determine the appropriate length to insert the catheter. Follow the example below for exact steps. 

Note: This process must be performed for every cohort, strain, gender and weight including genetically modified models. See end of document for more details on genetically modified or inbred strains of mice.