Peripheral venous catheters are special cannulas that can remain in the patient’s vein for extended periods of time. They are used for multiple or prolonged administration of intravenous medications or short infusions and are most commonly used in hospital or emergency medicine settings. Peripheral venous catheters exist in sizes that are easily distinguished by color and can be selected according to the nature of the vessels and the indication.
What is a peripheral venous catheter?
Peripheral venous catheters are special cannulas that can remain in the patient’s vein for an extended period of time. Peripheral venous catheters are also called indwelling venous catheters and are distinct from central venous catheters. They are small catheters that, as the name suggests, can be inserted into the peripheral veins of the body. In practice, this special form of catheter is used very frequently. Peripheral venous catheters are not only frequently used in emergency situations. Peripheral venous catheters are primarily used for fluid therapy. Peripheral venous catheters can be used to administer multiple intravenous drugs or infusions to a patient, and blood transfusions are also possible. Suitable body sites for placing a peripheral venous catheter are the vein on the back of the hand, the vein on the forearm, or the vein in the crook of the elbow. Each of these sites has individual advantages but also disadvantages. What these body sites have in common, however, is that the veins run superficially here and are therefore easily accessible. The peripheral venous catheter was invented in 1950 by David J. Massa. It was established in Germany in 1962 by the physician and chemist Bernhard Braun. He gave rise to the colloquial name Braunüle for the peripheral venous catheter.
Forms, types, and styles
Peripheral venous catheters exist in a variety of sizes that can be easily distinguished by their respective colors. The smallest peripheral venous catheters have a yellow plastic element, followed in increasing size by blue, pink, green or green-white, white, gray, and orange. The unit of size for peripheral venous catheters is the gauge (G). The larger the gauge, the smaller the diameter of the venous catheter and the smaller the gauge, the larger the diameter of the catheter. It is also referred to as the flow rate of the catheter: the smaller the gauge, the higher the flow rate of the catheter; the same principle applies in reverse. Accordingly, for children, a yellow, blue or even pink peripheral venous catheter with a high Gaugen value of 24 to 20 is used, which corresponds to an outer diameter of 0.7 to 1.1mm and an inner diameter of 0.4 to 0.8mm. For adults, the size is chosen according to the nature of the vessels and according to the indication. For infusions, catheters with a gauge of 18 to 17 are considered common, corresponding to an outer diameter of 1.3 to 1.5mm and an inner diameter of 1.0 to 1.1mm. In the event of shock or a similar emergency situation where a lot of volume needs to enter the veins quickly through the peripheral venous catheter, catheters with a larger diameter are usually used, corresponding to a size of 16 to 14 G with an outer diameter of 1.7 to 2.2mm and an inner diameter of 1.3 to 1.7. Not only the diameter but also the length of the plastic catheter increases as the Gauge value decreases.
Structure and mode of operation
The peripheral venous catheter consists essentially of two parts: A cannula made of steel and a catheter surrounding it made of plastic, more precisely Teflon. The part of the peripheral venous catheter that remains in the vein is made of tissue-friendly plastic. At the plastic element, which is located outside the puncture site, the venous catheter can be connected to infusions or, when not in use, can be sealed airtight. For some time now, the use of a safety catheter has been mandatory. With this, when the cannula is pulled out, a small, clamp-like metal structure is slipped over the needle, which greatly reduces the risk of infection from needlestick injuries for physicians and nurses.
Medical and health benefits
There are several health benefits for the peripheral venous catheter. Most commonly, it is used to administer intravenous medications or infusions.Blood can also be drawn through a peripheral venous catheter, and blood transfusions are possible with sufficiently large peripheral venous catheters. Peripheral venous catheters may only be inserted by physicians or, following their instructions, by specialized personnel such as nurses. Emergency paramedics are also authorized to do so without a physician’s authorization in appropriate situations. The size of the peripheral venous catheter is chosen primarily according to the indication, as is the puncture site. In emergency situations in particular, a large volume must often be able to pass through the catheter in a short time. The great advantage of the peripheral venous catheter is that the patient only has to be punctured once and the catheter can then remain in the vein for several days. This means that intravenous drugs do not always have to be administered via a new puncture site. A sealable chamber on the outer part of the peripheral venous catheter prevents blood clotting in the same. For longer dwell times, a venous port or central venous catheter is usually used. A peripheral venous catheter should not remain in the vein for more than 72 to 96 hours. If it is still needed after that time, it can be easily changed.
