Antisiphon Device in Shunt Kits: How It Counters the Siphon Effect

An antisiphon device is a shunt component that counters the extra suction created when the peritoneal catheter moves from a horizontal to a vertical position, for example when a patient sits up or stands. The DESU antisiphon device is designed to close immediately when the siphon effect occurs, helping prevent overdrainage. It is an option on Defit, Decurve and Depus VP kits, whose codes end in “-ASD”.

Neurosurgeons, theatre nurses and purchasing teams need to know where siphoning comes from, what the device does and does not do, and how the option appears on an order for DESU shunt systems.

What is the siphon effect in a shunt?

A ventriculoperitoneal (VP) shunt carries cerebrospinal fluid (CSF) from the ventricles, through a valve, into the peritoneal cavity. The valve is chosen to open at a given pressure difference between its inlet and outlet. When the patient lies flat, the ventricles, the valve and most of the peritoneal catheter sit at roughly the same height, and the valve does the regulating.

When the patient sits up or stands, the picture changes. The peritoneal catheter now runs downward from the valve to the abdomen, and the column of fluid inside it hangs below the valve. The weight of that column pulls on the outlet side. The valve therefore sees a larger pressure difference than the one it was selected for, and more CSF can flow than the setting alone would suggest. This posture-dependent pull is the siphon effect.

• It is driven by posture: the change from horizontal to vertical is what creates it.
• It acts on the outlet side of the valve, through the peritoneal catheter.
• It is not a fault of the valve; a pressure setting simply does not account for the patient’s position on its own.

Why does siphoning matter?

Overdrainage is a recognised problem in shunt management. If CSF leaves the ventricles faster than intended, patients may describe symptoms that change with position, such as headache when upright that eases when lying down. How much of a concern this is for an individual patient, and how to manage it, is a clinical judgement for the treating team.

For families and patients, our guide to living with a shunt explains in plain language why symptoms that change with position are worth reporting. For a related discussion in external drainage, where the drainage level is set at the bedside, see CSF overdrainage and underdrainage in the EVD setup.

How does the DESU antisiphon device work?

The principle is simple: the device creates an immediate closure effect when the siphon effect occurs, so that excess drainage is prevented. It is used to avoid the siphoning that may occur when the peritoneal catheter turns from a horizontal to a vertical position while CSF is being drained or shunted.

• Purpose: to counter the siphon effect that can occur when the peritoneal catheter moves from horizontal to vertical.
• Response: immediate closure when siphoning occurs.
• Aim: to help prevent overdrainage and to help control siphoning during posture changes.
• Quality: CE marked and manufactured under ISO 13485.

The device does not set the valve’s opening pressure. That remains the job of the valve: low, medium or high fixed pressure on Defit and Decurve, and fixed or adjustable pressure on Depus. The antisiphon device addresses the posture-related pull on the outlet side, which is a separate question from the pressure setting.

Which DESU shunt kits can include an antisiphon device?

The antisiphon device is an option on all three DESU ventriculoperitoneal shunt families. The table summarises the valves it can be combined with.

Each family has its own page with the full specifications: Defit shunts, Decurve shunts and Depus shunts.

How do you recognise an ASD kit when ordering?

When the antisiphon device is supplied inside a kit, the reference code ends with the suffix “-ASD”. That suffix is the simplest check at every step of the supply chain.

• On the quotation and purchase order, list ASD and non-ASD kits as separate line items, even when the valve and pressure are the same.
• At goods receipt, compare the code suffix on the label with the order line.
• On the shelf, keep ASD kits in a clearly labelled position so the theatre team picks the configuration the surgeon asked for.
• Treat the antibiotic configuration as a separate choice from the antisiphon option, and confirm the exact combination you need with our product specialists before ordering.

A mix-up between an ASD and a non-ASD kit is easy to avoid but awkward to correct once a case has started, so the suffix deserves a line on any receiving checklist.

When might a surgeon choose an ASD kit?

The antisiphon device is optional and not part of every kit. The choice is made by the surgeon, following the instructions for use. The questions surgeons weigh include how much time the patient is expected to spend upright, which valve and pressure have been selected, and whether there is any history suggesting overdrainage.

For the hospital, the practical consequence is planning. If some surgeons routinely use ASD kits and others do not, both configurations need to be stocked in the valve sizes and pressures in use, so that the decision can follow the patient rather than whatever happens to be on the shelf.

Does the antisiphon option change the rest of the kit?

The core of the kit stays the same. A DESU VP shunt kit contains the valve, a 23 cm ventricular catheter (1.3 mm inner, 2.5 mm outer diameter), a 120 cm peritoneal catheter (1.1 mm inner, 2.5 mm outer diameter), a stylet and a right-angled connector. Shunt systems are supplied for single use and sterilised by ethylene oxide. The antisiphon device is an addition to that set, not a replacement for any part of it.

Talk to a DESU product specialist

If you are setting up a shunt formulary, comparing ASD and non-ASD configurations or checking a code before ordering, DESU’s product specialists can help. Write to sales@desu.tr, use the contact page, or request a quote for the kits you need.