Medical procedure – Peripheral Intravenous Cannulation

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Introduction
Obtaining peripheral intravenous access is an essential skill for all physicians. Although it is considered one of the simplest invasive procedures, mastering this potentially lifesaving intervention requires refined skills and experience.

Indications
Peripheral intravenous catheterization is required in a broad range of clinical applications, including intravenous drug administration, intravenous hydration, and transfusions of blood or blood components, as well as during surgery, during emergency care, and in other situations in which direct access to the bloodstream is needed.

Contraindications
Relative contraindications to insertion of a peripheral catheter at a specific site in the body may include infection, phlebitis, sclerosed veins, previous intravenous infiltration, burns or traumatic injury proximal to the insertion site, arteriovenous fistula in an extremity, and surgical procedures affecting an extremity. Other situations may preclude obtaining peripheral intravenous access. For instance, extreme dehydration or shock may render cannulation of collapsed peripheral veins impossible. When access to peripheral veins is impossible and in situations in which accessing peripheral veins may take too long, insertion of a central venous or intraosseous catheter or peripheral venous cutdown may be required.

Anatomy
A detailed understanding of the venous systems of the upper and lower extremities will facilitate successful cannulation. The upper extremities have two primary venous systems: the cephalic and the basilic veins. The venous system of the lower extremities consists of the greater and lesser saphenous veins.

Site Selection
The choice of a site for intravenous cannulation depends on many factors, including the intended use of the catheter, accessibility of the vein given the position of the patient, the patient’s age and comfort, and the urgency of the situation. In general, upper-extremity veins are preferred, since they are more durable and are associated with fewer complications than are lower-extremity veins. The preferred cannulation sites are the veins of the forearm. The median cubital vein, which crosses the antecubital fossa, is frequently cannulated in urgent situations, because it accommodates large-bore catheters and may be easier to cannulate than other veins in the forearm. However, caution is warranted to avoid inadvertent cannulation of the brachial artery, which usually lies just medial to the median cubital vein. The same applies for the radial and ulnar arteries at the level of the wrist — careful palpation to identify arterial pulsations should minimize the possibility of this complication.

When upper-extremity veins are inaccessible, the dorsal veins of the foot or the saphenous veins of the lower extremity may be used. Cannulation in these veins is associated with a higher incidence of thrombosis and embolism. However, this risk is lower in children and infants than in adults; therefore, the veins of the legs and feet are an acceptable alternative when cannulation of the upper extremities has failed in a child or infant. Other alternative intravenous cannulation sites include the scalp veins, used in neonates and young infants, and the external jugular vein.

Equipment
Gather the equipment and have it ready at the bedside before beginning the procedure. You will need gloves, eye protection, a nonlatex tourniquet, chlorhexidine-based antiseptic solution, sterile 2-by-2 gauze, a saline flush, a transparent occlusive dressing and tape, a catheter of an appropriate size, ranging from 14- to 24-gauge, an intravenous fluid bag with tubing, and a sharps container. A local or topical anesthetic may be required if the catheter is 20-gauge or greater.

Catheter Type and Size
There are many catheters, varying in style, length, and safety mechanisms.Different safety mechanisms have been developed to minimize the possibility of inadvertent needle sticks. Needles should always be discarded appropriately in a sharps container.

The size of the catheter used will depend on the clinical situation. The smallest effective catheter should be used, because small catheters allow for less resistance to blood flow around the cannula and are associated with fewer complications. Large catheters, such as 14- and 16-gauge catheters, are used in acute situations for fluid resuscitation. Other variables that may influence the size of the catheter used include age-related vessel size, the need for pressurized boluses for administration of contrast material or medication, and the viscosity of the fluid to be infused.

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