Final answer:
Discontinuing an IV site if phlebitis is evident is critical due to the risk of thrombosis and potential life-threatening complications like pulmonary embolism, as well as the possibility of severe bloodstream infections.
Step-by-step explanation:
It is most important to discontinue the IV site if phlebitis is evident because phlebitis can be dangerous due to the risk of blood clots, known as thrombosis, which can occur in the inflamed vein. While phlebitis can cause the patient pain and discomfort, the larger concern is the potential for these clots to break off and travel through the bloodstream, leading to life-threatening complications such as a pulmonary embolism. Furthermore, if the IV site with phlebitis is not discontinued, there is a risk of local infections escalating into bloodstream infections, which have high morbidity and mortality rates, contributing significantly to hospital-related deaths.