Introduction: Patients that are being treated in the intensive care units are life-threatened due to the termination of one or more of their organs. Therefore a continuous monitoring of their hemodynamic state including invasive measuring of blood pressure by using an arterial catheter is of an utmost importance. Arterial catheter, inserted into one of the selected arteries, enables direct measurement of arterial pressure as well as repeated arterial blood sampling needed for laboratory tests. It thus serves as quick and successful way to solving patient's health condition but on the other hand it poses a risk of creating additional complications. Purpose: The purpose of this diploma thesis is to present the direct method of measuring blood pressure on the theoretical level as well as highlight the role of a nurse before, during and after the insertion of the arterial catheter. The safety of the patient who has had a catheter inserted in the femoral artery is also being emphasized. Methods: The thesis is based on the descriptive research method using systematic review and analysis of scientific literature in English and Slovenian language in the period between 2007 and 2018. The literature and data needed was obtained through remote access to University of Ljubljana Digital Library's databases CINAHL and PubMed. Results: Nurse takes active part in preparing the patient subjected to insertion and removal of arterial catheter, assists while insertion is being performed, keeps observing the patient, oversees the operation of the measurement system, carries out the necessary measurements and changes the dressing of the insertion site when needed. Nurse also makes sure that the procedure is being implemented safely and offers psychological support to the patient. In order for the direct method of measuring blood pressure using arterial catheter to be carried out in a safe and efficient way the patient, personnel, material and space must be prepared according to the relevant requirements. By sticking to aseptic working conditions at all time and constantly monitoring the patient nurse plays a significant role in preventing complications that may occur in any of the three phases of the procedure. The most common complications are bleeding, infection and thrombosis. While inserting the catheter into the femoral artery the leg subjected to the insertion must be observed continuously and accurately due to an increased risk of ischemia being developed. Discussion and conclusion: When treatment of life-threatened patients is concerned the use of arterial catheters is indispensable. Because this invasive blood pressure measurement method can create dangerous and life-threatening complications it is very important that a nurse involved in a process has extensive theoretical knowledge as well as a lot of practical experiences with this procedure. Professionally qualified nurse therefore contributes significantly to the successful and save implementation of intervention. By creating and strictly following the protocol that includes a checklist stating exactly how the patient and material had to be prepared, the patient's safety would be greatly improved and the costs of hospital treatment as well as the time spent in hospital significantly reduced.