Intravenous Cannulas – Sizes, Types, and How to Use

What is an IV Cannulas?

An Intravenous Cannula is a flexible catheter device that is temporarily placed in a vein using a puncture technique. Its special design allows for repeated use of the vascular access. The needle's lumen size varies according to clinical needs. Larger bore iv cannulas are used for rapid fluid infusion or high-viscosity drug administration, while smaller sizes are used for long-term, slow infusion, ensuring iv patency and reducing vascular irritation.

Parts of an IV Cannula

The components of the Intravenous Cannula include a stainless steel puncture needle core, a soft catheter, fixing wings, and a connecting port. The catheter is made of biocompatible materials with a smooth surface to reduce thrombosis formation. It is transparent for easy observation of blood return, and the use of sealing fluid helps maintain the catheter's patency.

Uses of the Intravenous Cannula

Fluid delivery:

The scientific selection of needle lumen sizes can meet large-volume fluid infusion requirements and, with precise adjustment devices, enable controlled infusion. This ensures smooth intravenous infusion for critically ill patients and allows for accurate control when paired with an electronic infusion pump.

Drug delivery:

Suitable for irritating drugs, hypertonic solutions, or long-term antibiotic therapy. It significantly reduces the risk of vascular damage compared to traditional steel needles. The specially designed catheter material is compatible with various drug requirements, preventing the formation of precipitates that could block the catheter.

Monitoring and diagnosis:

Connected to pressure sensors, it can monitor central venous pressure in real-time, providing data for cardiac function evaluation. Blood samples can be collected through the same access during indwelling, reducing the need for repeated punctures and minimizing vascular trauma.

Emergency situations:

In disaster rescue or shock conditions, larger diameter Intravenous Cannulas are preferred to establish access, along with pressure devices to achieve rapid volume expansion. In special cases, it is necessary to recognize vascular features and strictly distinguish between arteries and veins to avoid causing ischemia by mistakenly infusing into an artery.

The Best IV Sites for Intravenous Cannulas

When selecting the insertion point for the Intravenous Cannula, factors such as the patient's vascular condition, treatment duration, and the characteristics of the drug must be considered. Non-joint areas with good elasticity and superficial veins are usually preferred, ensuring that the catheter is fixed stably and does not interfere with daily activities.

IV in Hand

The dorsal hand vein network is a commonly used puncture site, especially for short-term infusion or low-flow drug administration. The superficial location of the veins makes them easy to locate, but frequent movement may cause catheter displacement, requiring reinforcement of the dressing. It is best to avoid puncturing near the metacarpophalangeal joints to prevent friction and leakage during flexion and extension.

IV in Forearm

The cephalic vein or basilic vein branch in the forearm has a thick vessel wall and a straight course, making it suitable for medium to long-term indwelling. Adequate blood flow helps maintain smooth venous access and reduces the risk of thrombosis. This site experiences less muscle activity than the hand, making the catheter more stable, and is suitable for large-diameter Intravenous Cannulas used in long-term, high-flow applications.

IV in Upper arm

The brachial vein above the elbow or the high-positioned cephalic vein is suitable for critically ill patients needing large-volume infusion or long-term high-concentration nutritional fluid administration. These veins are deeper, requiring skilled technique, and after insertion, an elastic bandage should be used to limit excessive joint flexion.

IV in External Jugular Vein

This site is often used for infants or patients with extremely poor vascular conditions, and it can serve as an alternative access in emergency situations. The external jugular vein has a large diameter and high blood flow, allowing for rapid infusion of resuscitation fluids. However, it is close to the carotid artery and nerves, requiring precise operation to avoid arterialization of the venous infusion, and the neck's limited mobility increases nursing difficulty.

IV Cannula Sizes and Uses

The above data comes from CN MEDITECH. For more detailed information, please contact us.

Note:

o The flow rate is based on water-soluble solutions, which may be affected by fluid viscosity, catheter length, and infusion pressure.

o Selection of lumen size should prioritize treatment requirements (e.g., drug viscosity, infusion duration) and vascular conditions.

o For infants or those with vascular sclerosis, the "minimum effective lumen" principle is recommended to reduce the incidence of phlebitis.

Intravenous Cannula Types

Pen-shaped IV Cannula

The main body is straight and lacks side wings. It can be used for one-handed injection, suitable for veins with good conditions requiring rapid access. Its simple structure reduces infection risk and is commonly used in emergency or short-term infusion scenarios.

Butterfly IV Cannula

The wings extend symmetrically like a butterfly, making it easier to stabilize the needle and distribute skin pressure during puncture. It is commonly used in small or slippery veins (e.g., dorsal hand veins), reducing the risk of vessel damage from repeated adjustments.

Medication Injection IV Cannula

The catheter's tail has an additional port for drug injection, allowing for temporary drug infusion without interrupting the main infusion line. This type is especially suitable for critically ill patients requiring frequent rescue medication injections, but strict disinfection protocols are necessary to prevent contamination of the catheter.

Small Wing IV Cannula

The needle wings are small and flat, and the catheter's flexibility is optimized. This type is suitable for long-term indwelling or for patients who move frequently (e.g., children or restless patients). It balances stability with comfort and requires additional adhesive pads for catheter protection.

Different types should be selected based on the puncture site, treatment duration, and patient cooperation: Butterfly/small-wing types are preferred for poor vascular conditions or difficult puncture sites; the medication-injection type is preferred for frequent drug interventions; the pen-shaped type is suitable for standardized infusion.

Benefits and Risks of Using Intravenous Cannulas

Benefits

· Speed: Quickly establishes a stable venous access, avoiding delays caused by repeated punctures during emergency treatment or ongoing drug administration.

· Efficiency: Reduces the frequency of healthcare worker operations. One needle can be used for blood collection, drug administration, and dynamic monitoring, optimizing clinical workflows.

· Convenience: Reduces patient discomfort from repeated punctures and, during long-term treatments, allows for continued infusion through the same access, facilitating daily care adjustments.

Risks

· IV Infection: The catheter may cause local or systemic infections due to skin microorganism invasion or line contamination during indwelling. Strict aseptic techniques and regular maintenance are required.

· Phlebitis and Thrombotic Phlebitis: Mechanical irritation, chemical damage from drugs, or poor blood flow may lead to vascular inflammation or thrombosis, manifesting as redness, swelling, and pain. Timely removal is necessary.

· Extravasation: Leakage of fluid into surrounding tissues can cause swelling and necrosis, often due to incorrect catheter placement or poor fixation. Abnormalities at the injection site should be monitored and intervened promptly.

· Displacement or Accidental Removal: Excessive patient movement or inadequate adhesive strength may cause the catheter to dislodge or become displaced, affecting treatment or requiring re-puncture.

· Allergic Reactions: Some materials or dressings may cause skin contact allergies, such as itching or rashes, and require the use of low-allergy materials.

· Limitations on Long-Term Use: Repeated or long-term catheterization in the same vein may increase the risk of sclerosis or blockage, necessitating regular evaluation of vascular condition and puncture site rotation.

How to Place an IV Catheter

IV Insertion Step by Step

1.Patient Assessment and Preparation

Confirm the medical orders and the puncture site, evaluate vascular elasticity, fullness, and orientation. Explain the procedure to the patient to alleviate anxiety, position them comfortably, and expose the puncture area.

2.Aseptic Technique

Wear gloves and disinfect the skin around the puncture site in a spiral motion, covering an area with a diameter greater than 5 cm. Allow the disinfectant to dry naturally and avoid re-touching the disinfected area.

3.Puncture and Catheter Insertion

Stretch the skin and stabilize the vein, holding the indwelling needle at a 15-30 degree angle. Once blood return is observed, lower the angle and continue inserting the needle 1-2 mm to ensure the catheter tip is inside the vessel.

4.Advancing the Catheter and Removing the Needle Core

One hand holds the needle wings steady while the other advances the catheter fully into the vein. Once no resistance is felt, apply light pressure to the puncture point to prevent blood leakage and slowly withdraw the needle core.

5.Fixing and Connecting

Use a sterile transparent dressing to cover the puncture point without tension. Fix the iv catheter's tail in a "U" or "Ω" shape, connect the infusion device, and observe for smooth infusion.

Intravenous Insertion Tips

· Prioritize veins that are large, straight, and elastic, avoiding joint areas. For children, consider hand or scalp veins, and for adults, forearm or elbow veins. Avoid scars or venous sinuses.

· Lightly tap or let the limb hang to increase vein fullness before puncture. In elderly or dehydrated patients, warm compresses can improve vein visibility.

· If blood return is not clear, slightly withdraw the needle and adjust the angle before re-advancing. If there is significant resistance, the catheter may be adhering to the vessel wall or mistakenly entering a branch, requiring catheter re-insertion.

· Avoid repeated punctures at the same site. Keep the catheter parallel to the vein when advancing. If the patient experiences severe pain, be cautious of vessel perforation or leakage risks.

· Extend the fixation dressing at joint areas and use elastic bandages for restless patients to prevent catheter pressure or twisting. Mark the catheter insertion date for later maintenance.

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