By starting a peripheral IV you are gaining access to the peripheral circulation of a patient which will enable you to sample blood as well as infuse fluids and IV medications. IV access is essential to manage problems in critically ill patients. High volume fluid resuscitation may be required for the trauma patient, in which case large bore (#16) IV catheters are usually inserted. The patient with cardiac ischemia is at risk for numerous complications such as arrythmias, a peripheral IV is usually started in anticipation of problems.