Arterial blood pressure monitoring. Direct arterial pressure monitoring is ideal for beat-to-beat monitoring when rapid detection of hemodynamic changes is imperative. Although the direct technique requires additional expertise, equipment and expense, it is considered the gold standard for blood pressure monitoring and required during all major cardiac surgical procedures. In general terms, indications for arterial cannulation include anticipated major hemodynamic fluctuations or blood loss, presence of severe underlying cardiovascular disease, inability to obtain indirect measurements, and the need for frequent blood sampling. While the radial artery is the most frequently used site, other commonly used arterial cannulation sites include femoral and brachial. The axillary and dorsalis pedis arteries are used less frequently. Complications of arterial cannulation include: hemorrhage, thrombosis, vasospasm, distal ischemia, dissection, infection, inadvertent drug administration, pseudoaneurysm, and arteriovenous fistula formation. Vigilant monitoring of distal perfusion must be maintained and continued for several hours after decannulation to improve the detection of complications.