Hypodermic needle

A cannula, hollow needle or the injection needle is a hollow needle which is used in medicine to introduce fluids through a syringe into a human or animal body ( to be injected ), or ( puncturing ) of this can be seen.

The end of the cannula is usually sharpened with an inclined cut, in order to place a small incision in the tissue upon penetration. If the fabric is not cut, but merely suppressed as with a simple needle puncture would be painful.

Very fine needles may be used for the injection of insulin. Some products are also coated to allow pain-free as possible injection.

By puncturing tissue or material, the sharpness of the needle tip is lost to some extent, so that the injection is painful. For this reason, needles should be changed after removal of drugs from so-called vials ( to -piercing rubber closure ) before the actual injection.

A special form of the cannula, the cannula button ( also referred to as irrigation cannula ), in which the tip is not sharp sharpened, but with a small head / knob. Button cannulas are used to inject medication into existing openings ( body cavity ) without hurting the fabric. They are often used in the treatment of chronic wounds.

Button cannulas are used for accurate dosing and application of liquid and viscous material and in this case called application tips. Here, the bead- head thickening is without bevel grinding to protect against puncture wounds. You will find attached to syringes widespread use in dentistry, dental technology and crafts. The industry often uses with automatically controlled air-powered syringes.

To avoid needlestick injuries and a possibly resulting disease medically used needles are disposed of in so-called sharps boxes. A Back Plug into the protective sheath ( recapping ) is usually prohibited.

Units for injection needles

The specification of the cannula size can be done in several ways, are commonly expressed in millimeters (mm ) gauge, after Pravaz system ( Gr. ) or in Charriere or French ( Charr., Ch, Fr.)

Pravaz system ( Gr. )

Named after the French orthopedic surgeon Charles Gabriel Pravaz ( 1791-1853 ). The marking of the Pravaz system is "Gr. " ( For size).

Gauge (G)

The unit G is the outer diameter. The higher the gauge value, the smaller the outer diameter of the cannula. The unit is borrowed from the U.S. unit for wires. This corresponds to the number of the gauge value of the number of operations, ie, the more a wire running through the wire drawing machine, the thinner it is ( and the bigger the gauge value ). The conversion into millimeters outside diameter and the color coding is standardized in EN ISO 6009 and EN ISO 9626.

Overview and comparison chart for the color codes, dimensions and sizes of cannulas

* The ISO standards organize the size indicated in gauge to the outside diameter and the color. So once no measure in gauge is specified, the corresponding data in the row are not taken from the ISO standard, they are included only for clarity.

Use in chemical laboratories

In chemical laboratories cannulas are used to remove fluids from blood vessels with the aid of needles or fill them. For this purpose, a septum ( puncture membrane ) is often pierced.

A special form of needle is the so-called transfer cannula. It is an obliquely cut at both sides of a steel capillary, which is used to transfer large amounts of liquid under the exclusion of air by a piston to another. To this end, both pistons are sealed with a septum. The pistons are connected to the transfer needle so that it is immersed in the liquid to be transferred. Must be connected to the piston with the liquid, for example, an inert gas-filled balloon, an overpressure is established. Thus, the liquid can now access the other piston, the pressure must be there to break down. To this end, stung by the septum simply a cannula. In this type of working the exclusion of air often Schlenk flask may be used.

Modern production of cannulas

For the production of the hollow needles steel sheet is wound around a mandrel and welded metal. The resulting steel tube is then repeatedly drawn into the length, diameter and wall thickness decrease steadily until finally the desired values ​​are reached. Then, the resulting fine steel tube is cut into individual needles. Now the sharpening is done. Then the tips are carefully deburred, chamfered ( gechamfert ) and sterilized.

Touches the needle tip

  • Lancets cut
  • Facet cut
  • Simply cut
  • V- Bevel -cut
  • Pencil Point
  • Huber point
  • Quinckeschliff ( for Quincke - Babcock needle)
  • Relief ( Seldinger technique )
  • Menghini -cut
Gauge (engineering)
177831
de