Intramuscular, intravenous, and intra-arterial cannulation techniques are described. Intramuscular injections deliver medication into large muscles and became popular after World War II. Intravenous cannulation involves inserting a cannula into a vein to deliver fluids or medications and potential complications include extravasation, hematoma, and infection. Intra-arterial cannulation is used for invasive arterial blood pressure monitoring and involves inserting a catheter into an artery like the radial artery. Potential complications of intra-arterial cannulation include thrombosis and pseudoaneurysm.