Tuohy Needle and Guidewire in Lumbar Catheter Kits

Why lumbar catheter kits include a Tuohy needle and guidewire: what each one does, what 14 G means for a 1.6 mm catheter, and which DESU kits contain them.

A Tuohy needle creates the insertion path for a lumbar catheter, and a guidewire helps guide the catheter along it in a controlled way. DESU supplies both in the lumbar kits of its neurosurgical catheters range and in Depus LP shunt kits, so the placement tools arrive with the catheter they are meant to serve.

Key takeaways

• The Tuohy needle supports creation of the insertion path; the guidewire helps guide the catheter in a controlled way.
• DESU lumbar and lumboperitoneal catheter kits include a 14 G Tuohy needle.
• Depus LP shunt kits include a 0.018” guidewire.
• The lumbar drainage kit adds an angled trocar, a Luer Lock connector, a distal cap and a fixation part.

What is a Tuohy needle?

A Tuohy needle is a hollow needle with a curved tip, so its opening faces partly to the side instead of straight ahead. The design is widely used for spinal and epidural access. A catheter passed through it leaves at an angle, which helps direct it along the spinal canal rather than straight across.

In a lumbar catheter kit, the needle is how the soft catheter gets through the tissue. It is an application component that supports creation of the insertion path during lumbar catheter placement. It is a tool for placement and is not part of what stays in the patient.

Why is the needle 14 G?

Needle gauge runs backwards: the lower the number, the larger the needle. A 14 G needle is a large one, well above the fine spinal needles used for a routine diagnostic lumbar puncture.

The reason is the catheter. A needle used this way has to let the catheter pass through it, and the DESU lumbar catheter has a 1.6 mm outer diameter. A fine spinal needle could not admit a catheter of that size, so the bore of the needle is set by the device it has to deliver and not by the small sample of fluid a diagnostic needle takes.

What does the guidewire do?

The guidewire helps place and guide the lumbar catheter in a controlled way. The need for it comes from the material. Silicone is soft and flexible, which suits a catheter that will sit in the body, but a soft tube is hard to steer and advance on its own over a long distance.

The dimensions show how fine the catheter is. Its inner diameter is 0.8 mm, and the long catheters in these kits run to 100 cm or 80 cm. In Depus LP shunt kits, the guidewire is 0.018”, which is about 0.46 mm.

Which DESU kits include a Tuohy needle and guidewire?

Four products include them, and they are not identical:

The lumbar catheter kit is the simplest of these, and the lumboperitoneal catheter kit adds the peritoneal catheter. The lumbar drainage catheter kit is for external drainage, and Depus shunts supply the valve as well. More on the other parts of these kits is in the guides to lumbar shunt catheter kits and to the lumbar drainage catheter kit.

How is the Tuohy needle different from the angled trocar?

Only the lumbar drainage kit includes an angled trocar, and it should not be confused with the needle. The needle is used during placement of the lumbar catheter; the trocar is an accessory that supports appropriate guidance and placement of the catheter. A team moving from shunt kits to drainage kits will find this one extra instrument in the tray, and its use is set out in the instructions for use.

How do the length marks work with the needle and guidewire?

All the lumbar catheters in these catheter kits have tantalum length marks at each centimetre from 5 to 20 cm, and 24 drainage holes in four rows of six at the proximal end. The silicone is radiopaque, so the position of the catheter can be followed under imaging.

The needle and guidewire get the catheter in. The marks are what tell the team how far it has gone. How far to advance the catheter is the surgeon's decision.

Does the antibiotic-impregnated option change the tools?

The catheter's size does not change. The antibiotic-impregnated lumbar catheter has the same basic dimensions as the standard one: 0.8 mm inner diameter and 1.6 mm outer diameter. The lumboperitoneal kit has the 14 G Tuohy needle and guidewire in both the standard and the impregnated system. The impregnated option of the lumbar catheter kit, code LACK, is offered as a catheter alternative, so our product specialists can confirm its contents for your order. The difference is in the catheter itself, where the antibiotic is impregnated into the material and released in a controlled manner over 28 days. Impregnated catheters are orange and standard ones white.

What should the team check before the case?

• The product code matches the order: lumbar shunt, lumboperitoneal, lumbar drainage or Depus LP.
• The Tuohy needle and the guidewire are both accounted for when the kit is opened.
• The catheter colour matches the order: orange for impregnated, white for standard.
• The fixation part is available where the kit includes one.
• The team has read the instructions for use for that product, including any warnings on moving the catheter once it is in the needle.

A soft catheter can be damaged against a needle tip if it is drawn back through the needle. Technique, and what to do if a catheter has to be repositioned, belong to the surgeon and the instructions for use.

Talk to a DESU product specialist

To confirm the contents of a lumbar kit or get its instructions for use, write to sales@desu.tr, use the contact page or request a quote.

Frequently asked questions

Is the Tuohy needle implanted with the catheter?

No. It is an application component used during placement. Like the guidewire, it is a placement tool, separate from the catheter.

Do the lumbar drainage and lumbar shunt kits use the same catheter length?

No. The lumbar drainage catheter is 80 cm and the lumbar shunt catheter is 100 cm. Both have a 0.8 mm inner and a 1.6 mm outer diameter.

Does DESU sell the Tuohy needle or guidewire on their own?

They are supplied as kit components, with no separate product codes. Tell us if you need something outside these kits.

Is a stylet included in lumbar catheter kits?

The lumbar kits include a Tuohy needle and a guidewire, and no stylet. The stylet comes with the ventricular and ventriculoperitoneal catheter kits.

Related standards

• ISO 13485: Medical devices — Quality management systems
• ISO 10993 series: Biological evaluation of medical devices