In medicine, a mandrin is an aid for inserting catheters and tubes . The stylet is located in the hollow instrument to be inserted and is removed when the catheter or tube is in its desired position. The term is derived from the French term mandrin for a mandrel that is used to widen an opening.
Mandrins for intubation (guide rods)
These mandrins are plastic-coated rods (usually with a metal core) that are bent into the desired shape by the user in order to stabilize and shape the endotracheal tube .
As a rule, no stylet is used for endotracheal intubation , as the Magill tube , which is most commonly used, has a shape with which the entrance to the larynx can usually be easily reached.
However, a management staff is used in the following situations:
- The tube used has a low dimensional stability (e.g. Woodbridge spiral tube )
- The tube has an intrinsic shape that must be "stretched" for insertion (intubation) through a stylet ( Oxford tube, double-lumen tube ). (For further information on these special tubes see endotracheal tube )
- Difficult intubation: With the help of the stabilizing effect of the stylet, it is easier to direct the tube into the trachea, if necessary the tube bend can be adapted to the individual shape of the airway, or an epiglottis (larynx) that covers the larynx can be moved under and raised . If you let the guide rod protrude from the tube tip, you can use the slim stylet u. U. it is easier to “feel” through the glottis in order to then “thread” the thicker tube over it. Because of the increased risk of injury to the larynx and windpipe, the “protrusion” of the guide rod is usually avoided.
- Rapid intubation ( Rapid Sequence Induction , e.g. in patients who have not fasted , reduced oxygen deficiency tolerance , pregnancy; generally for emergency intubations): To be on the safe side , a guide rod is used in the tube so that the above-mentioned "tricks" can be used without loss of time in the event of intubation problems .
Stylets in feeding tubes (guidewire)
For long gastric or feeding tubes, particularly soft material is used to prevent pressure necrosis and ulceration of the esophageal wall . If such soft probes are pushed through the nose in the direction of the stomach, they need an internal splint so that they do not kink, roll up or even knot halfway. Such "guide wires" are usually made of hollow metal coils, which enable the correct position by aspiration of gastric juice to control before the stylet is removed.
Stylets in catheters and cannulas
In vascular catheters for veins and arteries, steel cannulas are used as a mandrin, through which blood flows back as a sign of successful vascular puncture (for more information on the technique of placing indwelling catheters see peripheral venous catheter ).
The term “mandrin” is also used for an elongated plastic blind cap that is inserted into indwelling venous cannulas that are temporarily unused . By filling their inner lumen, clogging with blood clots should be avoided. According to the current recommendation (2020), these mandrels should no longer be used for hygienic reasons.
Large vascular catheters are not placed using a stylet, but using the Seldinger technique .
Punctures near the spinal cord
In contrast to vascular puncture, the mandrin of epidural and spinal cannulas is not hollow, but solid. This stylet should completely fill the lumen so that the cannula does not “punch out” a tissue cylinder. Metal and plastic mandrels are used.
- Christine Geffers, Axel Kramer, Simone Scheithauer, Sebastian Schulz-Stübner, Arne Simon (head of the working group), Heidemarie Suger-Wiedeck and Matthias Trautmann: Prevention of infections caused by vascular catheters - Part 2: Peripheral venous indwelling cannulas and arterial catheters recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute . In: Federal Health Gazette - Health Research - Health Protection . Vol. 60, No. 2 . Springer, January 16, 2017, ISSN 1437-1588 , p. 207–215 , doi : 10.1007 / s00103-016-2488-3 ( download from the Robert Koch Institute [PDF; 183 kB ; accessed on August 26, 2020]). Available under Prevention of infections caused by vascular catheters - Part 2 - Peripheral venous indwelling cannulas and arterial catheters Recommendation of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute. In: Publication server of the Robert Koch Institute . Robert Koch Institute