paediGAV Valve: Instructions for Use

1. CAUTION

Federal law restricts this device to sale by or on order of a physician!

2. INDICATION

The paediGAV is intended to shunt cerebrospinal fluid (CSF) from the lateral ventricles of the brain into the peritoneum.

3. TECHNICAL DESCRIPTION

The paediGAV is a site-specific shunt valve for the treatment of pediatric hydrocephalus. It consists of a ball-cone valve and a gravity valve, ensuring physiological drainage in all body positions.

Diagram Description (Fig. 1): Schematic cross-section of the paediGAV, detailing the ball-cone unit (comprising a coding ring and spiral spring) and the gravitational unit (comprising a tantalum ball and a sapphire ball).

The paediGAV features a robust titanium casing. The proximal end contains a ball-cone valve controlled by a spiral spring, which determines the opening pressure. The distal end has a gravity valve with a tantalum ball to control its opening pressure and a sapphire ball for reliable sealing. Connectors or silicone catheters can be optionally installed at the distal end.

4. OPERATING MODES OF THE paediGAV

The paediGAV operates in two principal modes, depending on body position:

• Horizontal Body Position (Fig. 2): In this position, the ball-cone valve is open, and the gravity valve remains open, allowing drainage without counteracting force.
• Vertical Body Position (Fig. 3): When the patient stands, the gravity valve closes. Drainage resumes only when the sum of intraventricular pressure and hydrostatic pressure exceeds the opening pressure of the ball-cone valve and the force exerted by the tantalum ball in the gravity valve.

Diagram Description (Fig. 2): paediGAV in horizontal body position, showing the ball-cone valve open and the gravity valve open.

Diagram Description (Fig. 3): paediGAV in vertical body position, illustrating the gravity valve closed and the ball-cone valve potentially open under pressure.

5. PHYSICS BACKGROUND

In a horizontal position, intraventricular pressure (IVP) is typically positive. Drainage is regulated by the pressure in the abdominal cavity.

In a standing position, ventricular pressure should ideally be slightly negative. To achieve this with shunt drainage, the valve's opening pressure must be set higher to compensate for reduced hydrostatic pressure and prevent overdrainage. Conventional valves may cause critical overdrainage when the patient stands.

Diagram Description (Fig. 4): Diagram illustrating the calculation of intraventricular pressure (IVP) for horizontal and standing body positions. It shows how IVP is influenced by opening pressures (PL, Ps) and hydrostatic pressure (PH), with abdominal cavity pressure (PB) also noted.

Selecting a suitable paediGAV: The paediGAV is site-dependent, offering two distinct opening pressures: one for horizontal and one for vertical body positions. This eliminates the need for percutaneous adjustments.

• Horizontal Body Position: Available pressure settings are 4 cmH2O and 9 cmH2O, chosen based on patient indication and age.
• Vertical Body Position: The opening pressure depends on the patient's hydrostatic parameter (size). Infants typically require a low pressure rating, while larger children may need a higher rating.

6. PRESSURE RATING

Each paediGAV is calibrated to strict quality control standards. Available pressure combinations (horizontal/vertical) and their corresponding coding are as follows:

These pressure ratings represent the pressure drop at a drainage rate of 5 ml/h. Postoperative identification of selected pressure ratings is possible via radiography using their codes.

Diagram Description (Fig. 5): Radiographic image of a paediGAV, showing its internal structure and indicating a specific pressure rating (9/24 cmH2O).

7. SHUNT VARIANTS AVAILABLE

The paediGAV is available in several variants, incorporating different components:

• Burrhole Reservoir: Positioned in the cranial burrhole for IVP measurement, medication injection, and fluid siphoning. Features a robust titanium floor for protection. Available with integrated catheters or connectors.
• Prechamber: Positioned on the cranium for IVP measurement, medication injection, fluid siphoning, and shunt status checking. Also features a robust titanium floor. Available with integrated catheters or connectors.
• Burrhole Deflector: Used to adjust the length of the ventricular catheter to be inserted into the skull. The ventricular catheter is typically placed at a 90-degree angle in the burrhole.

8. TUBE SYSTEMS

The paediGAV is designed for optimal ventricular pressure. It is available as a shunt system or as an individual shunt valve, with or without an integrated distal catheter (1.2 mm inner diameter, 2.5 mm outer diameter). Individual valves require a catheter with approximately 1.2 mm inner diameter and 25 mm outer diameter. The shunt valve connector accommodates catheters with inner diameters from 1.0 mm to 15 mm. The catheter's outer diameter should be roughly twice its inner diameter. Catheters must be securely fixed to the valve connector with a ligature, avoiding kinks.

9. TESTING THE VALVE PRIOR TO IMPLANTATION

Each paediGAV undergoes testing to verify its performance characteristics. Dynamic characteristics are not assessed in static tests.

Patency Test: The safest method to check patency is to aspirate fluid using a sterile syringe attached to the distal end of a catheter, with the valve's proximal end submerged in sterile saline. Fluid removal indicates patency.

CAUTION: Avoid applying pressure with the syringe. Ensure sterility and prevent particle contamination.

Diagram Description (Fig. 6): Illustration of the patency test setup, showing a sterile syringe connected to the valve's distal end, with the proximal end submerged in sterile saline.

Pre-implantation Test Procedure: Surgeons can verify valve specifications using the following test in the operating room.

CAUTION: Maintain sterility and avoid particle contamination.

Equipment Required: Sterile fluid reservoir or water bath; sterile 60-cm hydrostatic pressure gauge with millimeter grading and a three-way faucet.

Diagram Description (Fig. 7): Diagram of the pre-implantation test setup, including a water bath, a hydrostatic pressure gauge with a three-way faucet, a sterile syringe, and connecting tubing.

Calibrating the Test Set-up:

• Adjust the three-way faucet to fill the pressure gauge to at least 5 cmH2O (Fig. 9).
• Isolate the syringe from the pressure gauge by rotating the three-way faucet with the silicone tube submerged in the water bath (Fig. 10).
• Allow the water column in the pressure gauge to drop to zero, aligning the zero point with the water level if necessary. The gauge is now calibrated.

Diagram Description (Fig. 8): Illustration of the first step in calibrating the test setup.

Diagram Description (Fig. 9): Illustration of the second step in calibrating the test setup.

Diagram Description (Fig. 10): Illustration of the third step in calibrating the test setup.

10. TEST PROCEDURE (Pre-implantation)

NOTE: The valve must be submerged in the water bath during tests. Ensure the pressure gauge's zero point aligns with the water level.

1. Connect the sterile valve to the test setup.
2. Rotate the three-way faucet (Fig. 9) to fill the pressure gauge to 10 cmH2O above the expected opening pressure (e.g., 19 cmH2O for the low pressure side of a 9/29 paediGAV, or 39 cmH2O for the high pressure side).
3. Rotate the three-way faucet (Fig. 8) to isolate the pressure gauge.
4. Remove all air from the valve and setup by rinsing with sterile water from the syringe.
5. Submerge the sterile valve in the water bath, ensuring the distal end is underwater for valid results.
6. To isolate the syringe, maintain flow through the valve while rotating the three-way faucet (Fig. 10). The water column should drop. If it does not, repeat steps 2-6.
7. Allow the water level in the pressure gauge to drop for 2 to 2.5 minutes and record the resulting pressure.

11. Test Results - Pre-implantation Test

The pressure readings from this test should yield the following results:

Prone/Horizontal Valve Position

Upright/Vertical Valve Position

12. PRESSURE-FLOW CHARACTERISTICS

The pressure-flow characteristics for the available paediGAV pressure ratings are presented in the following graphs. These graphs illustrate the relationship between flow rate (ml/h) and pressure (cmH2O) for different valve configurations. Generally, higher pressure ratings accommodate higher flow rates at a given pressure.

[Description of graphs: Multiple graphs are presented, each showing pressure on the y-axis and flow rate on the x-axis. Each graph depicts the pressure-flow curve for a specific paediGAV model, e.g., paediGAV 4/14 cmH2O, paediGAV 4/19 cmH2O, etc., with lines indicating the pressure rating for horizontal and vertical positions.]

13. BACKFLOW PROTECTION TEST

This test uses the pre-implantation test setup. Fill the shunt valve with sterile saline using a single-use syringe, ensuring all air is expelled (Fig. 11). Connect the shunt valve against the direction of flow (indicated by an arrow). The valve outlet port should be at the zero level of the pressure gauge. The pressure gauge is set to 14 cmH2O (Fig. 12).

Open flow to the valve and close flow to the syringe using the three-way faucet. A maximum of two drops per minute (0.1 ccm) should be expelled from the distal end of the shunt valve (Fig. 13).

CAUTION: Maintain sterility and avoid particle contamination.

Diagram Description (Fig. 11): Illustration of the first step in the backflow protection test.

Diagram Description (Fig. 12): Illustration of the second step in the backflow protection test.

Diagram Description (Fig. 13): Illustration of the third step in the backflow protection test, showing minimal fluid expulsion.

14. OPERATING PROCEDURE

Positioning the Ventricular Catheter

Various operative techniques can be used. The skin incision should be minimal after drilling the burrhole to prevent CSF leakage. The ventricular catheter is stiffened by a supplied mandrin.

paediGAV Configurations:

• With Burrhole Reservoir: Implant the ventricular catheter first, remove the mandrin, check patency, shorten the catheter, and connect the Burrhole Reservoir. The skin incision should not be directly above the reservoir.
• With Prechamber: Use a Burrhole Deflector to adjust catheter length. Insert the ventricular catheter into the ventricle at a 90-degree angle, then position the Prechamber.

Postoperative verification of catheter position should be done via CT or MRI.

Positioning the paediGAV

The paediGAV is site-dependent and must be implanted parallel to the body axis, typically behind the ear. After incision and tunnelling, the catheter is guided from the reservoir to the valve site, shortened if necessary, and attached with a ligature. Ensure the valve is not directly under the skin incision. An arrow on the valve indicates flow direction (distally and downwards).

Positioning the Peritoneal Catheter

The access site is at the surgeon's discretion (e.g., horizontal, paraumbilical, or transrectal). The catheter is guided from the shunt valve to the selected position using a tunneler or auxiliary incision. It has an open distal end without wall apertures. After entering the peritoneum, the catheter is advanced into the intestinal cavity.

Reimplantation

Shunt components previously implanted in one patient must not be implanted in another.

15. SAFETY MEASURES

Patients require careful monitoring post-implantation. Signs of infection include inflamed skin or tension. Symptoms of shunt dysfunction (headaches, dizziness, confusion, vomiting) necessitate prompt replacement of individual components or the entire system.

16. COMPATIBILITY WITH DIAGNOSTIC PROCEDURES

The paediGAV is made of non-magnetic materials (titanium, sapphire, stainless steel, tantalum), allowing for safe MRI or CT scans without risk to the patient or valve performance.

17. POSTOPERATIVE VALVE TESTS

The paediGAV is designed for reliable function without a pump. Testing is possible for systems with a Prechamber or Burrhole Reservoir, involving rinsing, pressure measurements, or pumping.

18. SAFE FUNCTIONING

The shunt valves are designed for precise and reliable long-term performance. However, replacement may be necessary for technical or medical reasons.

19. STERILIZATION

All products are steam-sterilized and packaged in double-layer sterile bags, ensuring sterility for five years. The expiration date is marked on the package. Do not use if packaging is damaged.

20. RESTERILIZATION

The functional safety and reliability of resterilized products cannot be guaranteed.

21. MEDICAL PRODUCTS CONSULTANTS

In accordance with European law MDD 93/42/EEC, Christoph Miethke GmbH & Co. KG lists the following medical product consultants for product queries:

• Eng. Roland Schulz
• Michaela Funk-Neubarth
• Josefine Kehl
• Eng. Thoralf Knitter
• Dr. Andreas Bunge
• Jan Mugel
• Thammo Weise
• August von Hardenberg

22. MANUFACTURER AND CONTACT INFORMATION

Manufacturer:
Christoph Miethke GmbH & Co. KG
Ulanenweg 2
D-14469 Potsdam, Germany
Phone: +49(0) 331 620 83 0
Fax: +49(0) 331 620 83 40
E-mail: info@miethke.com

Enquiries to:
AESCULAP AG
Am Aesculap Platz
D-78532 Tuttlingen, Germany
Phone: +49 (0) 7461 95-0
Fax: +49 (0) 7461 95-26 00
E-mail: information@aesculap.de

Service address in the US:
AESCULAP Inc.
Attn. AESCULAP Technical Services
615 Lambert Pointe Road
Hazelwood, MO, 63042

AESCULAP Repair Hotline:
Phone: +1 (800) 214-3392
Fax: +1 (314) 895-4420

Distributor in the US / Contact in Canada:
AESCULAP Inc.
3773 Corporate Parkway
Center Valley, PA 18034
Phone: +1-800-282-9000
Website: www.aesculapusa.com

23. REQUIREMENTS OF THE MDD 93/42/EEC

The MDD mandates comprehensive documentation of medical product whereabouts, especially for implants. Individual identification numbers of implanted valves must be recorded in patient records for traceability.

24. NOTE ON THE INSTRUCTIONS FOR USE

The information provided is based on current clinical experience. Surgeons should use their judgment to adapt procedures based on their experience and practice.

25. GENERAL INFORMATION

26. PRODUCT CONFIGURATIONS

The paediGAV is available in the following configurations: