When the rapid detection of haemodynamic change is imperative, the ‘gold standard’ is direct arterial pressure monitoring. Other indications for invasive arterial pressure monitoring include severe underlying cardiovascular disease, the 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 the femoral, brachial, axillary and dorsalis pedis arteries. Complications of arterial cannulation include haemorrhage, thrombosis, vasospasm, distal ischaemia, dissection, infection, unintentional arterial drug administration, pseudoaneurysm and arteriovenous fistula formation.