Cannulae

Cannulae are slender tubes inserted into a vessel, duct, or body cavity to allow drainage or the delivery of fluids, medications, or gases. The term originates from the Latin canna, meaning reed, and is used across medical specialties to describe a range of devices that share the function of creating and maintaining a channel for passage.

In vascular access, intravenous cannulae are commonly placed into peripheral veins to infuse fluids, administer drugs, or draw blood for testing. Arterial cannulae are designed for placement in an artery to provide continuous blood pressure monitoring or frequent sampling in critical care settings. Nasal cannulae, used in respiratory therapy, deliver supplemental oxygen through a soft tube with prongs placed in the nostrils. Surgical drains may incorporate cannulae to evacuate fluids from a wound or body cavity. Some cannulae act as introducers to facilitate placement of larger catheters or instruments.

Materials and sizing vary by application. Cannulae may be made from flexible plastics such as polyurethane or PVC, silicone for biocompatibility and comfort, or stainless steel for certain reusable applications. Sizes are described using gauge or French units, chosen according to the target vessel, required flow, and patient factors.

Safety and maintenance emphasize sterile technique during insertion and observation for complications such as infection, phlebitis, thrombosis, vessel injury, or air embolism. Removal is performed when therapy ends or if complications occur, with appropriate monitoring and follow-up as needed.