Cannula: Applications & Health Benefits

A cannula represents a hollow needle used as part of a syringe to penetrate human or animal tissue to inject or withdraw fluids. In medicine, it is used for diagnostic and therapeutic purposes. Needles are now almost exclusively used only once for routine procedures for hygienic reasons.

What is a cannula?

Cannulas are hollow needles through which injections or blood samples are taken. They can also be used as mandrins to insert catheters. Cannulas play an indispensable role in medicine. They are hollow needles through which injections or blood samples are taken. They can also be used as mandrins for the introduction of catheters. Depending on the intended use, the length, outer diameter and cut of the cannulae vary. In most cases, there is an oblique cut at the end of the cannula. This causes it to make a small incision as it enters the tissue. This cut causes the puncture (piercing into the tissue) to be less painful. When injecting into existing body orifices or body cavities, blunt cannulas are used. This does not injure the tissue. These cannulas are bluntly ground and cut vertically. Button cannulas still have a bead-shaped thickened head. Their use is mainly in dentistry.

Shapes, types and styles

Cannulas can be classified by indication, by characteristics, or by use. Depending on the purpose for which they are indicated, there are biopsy cannulas, tracheal cannulas, injection cannulas, puncture cannulas, or irrigation cannulas. The length, diameter and vessel play a role in the characteristics. The size of cannulas can be specified in various measurements. Thus, the outer diameter is represented in millimeters. For the fineness of the outer diameter, the representation is in gauge (G). The larger the gauge value, the thinner the cannula. Furthermore, the cannula can be pointed or blunt ground. According to use, there are single-use cannulas or multiple-use cannulas. For hygienic reasons, only disposable cannulas are used in Germany today for blood sampling and injections. Cannulas often have to be inserted into blood vessels for injections or blood sampling. These require a sharp cut to open the tissue of the blood vessel through an incision. For some applications, such as dentistry, cannulas are often used only to introduce irrigation fluids or medications into an existing body opening (body cavity). In this case, no tissue needs to be opened. Cannulas with a blunt cut or with a bead-like thickened head are used. These cannulas are also used for the treatment of wounds with medication. A cannula can also be used as a stylet. In this case, it serves as an aid for inserting catheters or tubes. When the catheter or tube is positioned in the correct place, the stylet is removed.

Structure and mode of operation

Very commonly, cannulas are used to open blood vessels. Blood sampling and injections are among the routine procedures in medical use. Here, cannulas with a sharpened oblique grind must always be used. This makes an incision. If this oblique grinding were not present, only painful displacement of the tissue would occur. To keep the injection as painless as possible, some needles are additionally coated. After puncturing the tissue, the sharpness of the grinding disappears again. The next application would be much more painful. For this reason, the cannula is disposed of immediately after a single use. When blood or tissue is collected, the samples are aspirated through the narrow channel of the hollow needle. In contrast, injection involves injecting the material to be injected (blood, electrolyte solution, nutrient solution, medication, and more) into the target tissue or blood vessel. In both cases, the cannula is attached to a reservoir of the syringe, which either contains the injection solution or is filled during blood as well as sample collection. Cannulas also provide as mandrins for opening blood vessels or other tissue parts for insertion of catheters or tubes. Biopsies by puncturing certain organs can also be performed using cannulas. Cannulas are also used in a wide range of applications for the treatment of wounds with medication.

Medical and health benefits

Cannulas have great medical importance. For example, they serve diagnostic purposes in blood sampling and the removal of tissue in biopsies. Injections occupy a large space. For example, blood transfusions, electrolyte administration, injections of nutrient solutions, hormone replacement therapies and much more would not be possible without cannulas. Another major field of application for cannulas is the treatment of wounds with medication in medicine and dentistry. The insertion of catheters and tubes is often ensured by cannulas. In emergency medicine, many life-saving measures would not be possible without cannulas. Of course, their proper use is important. Thus, cannulas can also be the source of disease. In the past, it was more common for infectious diseases to be transmitted via syringes. Often the needles were used several times, and even their disinfection failed in some cases. That is why today the strict rules of single use of needles apply. However, even at present, adverse health effects due to improper use of needles and syringes cannot be ruled out. For example, they must always be sterilized before use. When carrying out infusions, care must always be taken to ensure that no air can enter the blood vessels. This is a serious emergency that can lead to air embolism. Overall, the medical importance of cannulas cannot be overestimated. They found medical application even in ancient times.