The goal of this observational study is to observe brachial-to-radial pressure gradient in critically-ill patients receiving vasoactive agents. The main questions it aims to answer are:

1. What is the frequency of brachial-to-radial gradient in critically-ill patients receiving vasoactive agents?
2. Is brachial-to-radial gradient greater in patients receiving high doses of vasoactive agents?
3. Is brachial-to-radial gradient associated with worse peripheral perfusion?

Pathological conditions, such as arterial stenosis, use of vasoconstrictive drugs, or massive vasodilatation, can cause significant differences in mean arterial pressure (MAP) in different parts of the arterial system. For example, in the case of stenosis between the brachial and radial arteries, the pressure behind the stenosis is lower than in front of it, which can lead to erroneous conclusions about the actual arterial pressure. The use of vasoconstrictive drugs in patients with circulatory insufficiency can result in reduced peripheral arterial pressure transmission, as evidenced by studies showing lower pressures in the radial artery compared to the femoral artery. Inadequate MAP assessments can lead to excessive use of vasoactive drugs and fluids, increasing the risk of complications such as cardiac ischemia, atrial fibrillation, and renal failure. One method to detect a significant gradient between central MAP (e.g., aorta or femoral artery) and peripheral MAP is non-invasive, oscillometric measurement of MAP on the brachial artery and comparing it to MAP obtained from invasive radial access (known as NIBR-APG). The brachial-radial MAP gradient is highly correlated with the femoral-radial gradient and may be indicative of significantly higher central pressure. The aim of this project is to evaluate the frequency of the brachial-radial gradient phenomenon in patients undergoing vasoconstrictive treatment in intensive care units.

Inclusion Criteria:

• adult (>18 years) patients admitted to the ICU
• must be after initial resuscitation
• invasive blood pressure monitoring in the radial artery
• need for vasoactive drug therapy

Exclusion Criteria:

• pregnancy
• pressure transduction across invasive blood pressure circuit deemed to be inadequate
• mechanical circulatory support
• inability to match non-invasive cuff size to the patient's arm
• need for any hemodynamic intervention during performing study's measurements
• patient's decline to have the measurements done

Adult patients admitted to the intensive care unit, requiring invasive blood pressure monitoring, and undergoing vasoactive therapy.