Intravenous CannulaEdit
An intravenous cannula, commonly referred to as an IV cannula, is a flexible catheter inserted into a vein to provide rapid access for fluids, medications, or blood products. It is a fundamental tool in intravenous therapy and a mainstay in settings ranging from emergency departments to inpatient wards and ambulatory care. Peripheral intravenous cannulas are designed for short- to medium-term use and are distinct from more invasive forms of vascular access such as a central venous catheter. The device enables clinicians to deliver therapies promptly and repeatedly, while allowing easy blood sampling when needed.
The design of an IV cannula prioritizes safety, sterility, and ease of insertion. Most units are made from biocompatible polymers such as polyurethane or polyvinyl chloride, with some newer designs incorporating silicone or other materials to reduce vein irritation. The catheter is typically inserted into a vein via an introducer needle or a needle-over-the-needle assembly; once venous access is achieved, the needle is withdrawn, leaving the flexible catheter in place. The hub or short extension provides a point of connection for syringes, giving sets, or administration sets. Sizes are described by gauge (often abbreviated as G), with common peripheral catheters in a range that balances rapid infusion capability with patient comfort. See gauge (medical) for more detail. Modern systems increasingly use needleless connectors and safety features to minimize risk to both patient and clinician, and they are compatible with standard intravenous administration sets.
Sites for insertion are chosen to maximize dwell time and minimize discomfort and complications. Forearm and antecubital sites are common, though the dorsal hand and other veins may be used. Site selection considers vein condition (patency, palpability, and ease of access), patient activity, and anticipated duration of therapy. Proper skin preparation—often with antiseptics such as chlorhexidine in alcohol or povidone-iodine—is standard to reduce infection risk, and sterile technique is maintained during insertion and maintenance. For difficult access, clinicians may employ technologies such as ultrasound-guided venous access to improve success rates and reduce procedure time. When administering certain fluids, clinicians also rely on normal saline flushes to maintain catheter patency and to prevent clotting within the lumen.
Design and function
- Materials and construction: The catheter portion is typically a flexible tube made from polyurethane or PVC, with some variants using silicone for enhanced biocompatibility or flexibility. The terminal hub or adaptor provides a secure connection to the infusion set. Many systems incorporate safety features to reduce needlestick injuries and accidental dislodgement. See polyurethane; PVC; silicone.
- Sizes and compatibility: Catheter size is described by gauge (G) and length; larger gauges allow rapid fluid administration, while smaller gauges are less traumatic for delicate veins. See gauge (medical) and peripheral venous catheter for related concepts.
- Insertion and maintenance: Insertion uses sterile technique, and proper securing devices (dressings, tape, or stabilizers) help minimize movement. Regular assessment includes inspection for redness, swelling, or pain, and routine flushing with sterile saline to maintain patency. See sterile technique; normal saline; phlebitis.
Clinical use and considerations
- Indications: IV cannulas enable hydration, electrolyte correction, administration of antimicrobials, analgesics, chemotherapy, and parenteral nutrition, as well as rapid blood sampling and transfusion when needed. See intravenous therapy; blood transfusion.
- Durability and dwell time: Short peripheral cannulas are intended for relatively brief courses of therapy and are typically rotated or removed if complications arise. When longer access is needed, clinicians may choose alternatives such as a midline catheter or a central venous catheter. See midline catheter; central venous catheter.
- Complications and monitoring: Potential issues include infiltration, extravasation, phlebitis, infection, catheter occlusion, and rare events such as air embolism. Vigilant monitoring, aseptic technique, and appropriate site care reduce these risks. See phlebitis; infiltration (medicine); extravasation; catheter-related bloodstream infection.
Complications and risk management
- Infiltration and extravasation: Occur when the catheter lumen channels leak fluids into surrounding tissue or when vesicant drugs escape into tissue. Preventive strategies include proper site selection, securement, and timely assessment. See infiltration (medicine); extravasation.
- Infection and thrombophlebitis: Maintaining sterile technique, skin antisepsis, and regular site assessment lowers infection risk and inflammation of the vein. See phlebitis.
- Mechanical issues and occlusion: Catheters can become kinked, displaced, or occluded by clotting; routine flushing with saline helps preserve patency. See catheter occlusion.
- Bloodstream infection risk: While relatively low with proper technique, any indwelling catheter poses a risk; adherence to guidelines on asepsis and line care is essential. See catheter-related bloodstream infection.