Adjustable Pressure Valve
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Adjustable Pressure Valve
The Strata NSC valve is a shunt component designed to provide continued Cerebrospinal Fluid (CSF) flow from the ventricles of the brain into the right atrium of the heart or the peritoneal cavity. The Strata NSC valve allows the physician to non-invasively adjust the pressure/flow performance level pre- and post-implantation without the need for radiographic confirmation in order to address changing patient needs.
Shunting of CSF into the peritoneal cavity or other areas of the body should not be carried out if there is infection in any areas in which the various components of the shunt system will be implanted. These include infections of the scalp and other skin area through which the shunt system will traverse, the meninges and cerebral ventricles, peritoneum and intraperitoneal and retroperitoneal organs, pleura and blood stream. CSF shunting is contraindicated if there is infection present in any area of the body. Additionally, shunting into the atrium of patients with congenital heart disease or other serious cardiopulmonary abnormalities is contraindicated.
The valve pressure level setting should always be verified following patient exposure to high magnetic fields.
Devices known to contain magnets should be kept away from the immediate valve implant location, as they may have an effect on the performance level setting of the Strata-type valve. All magnets have an exponentially decreasing effect on the valve the further away they are located. Common environmental levels of electromagnetic (radio frequency) radiation generated by security scanners, metal detectors, microwave ovens, mobile telephones, high voltage lines, and transformers should not affect the performance level settings.
Valve function and performance level setting should be checked in the event that the valve is subjected to significant mechanical shock or trauma.
The Adjustment Tool contains strong magnets. Care should be taken when using the tool near magnetically sensitive medical implants (e.g. pacemakers and vagal nerve stimulators), electronic equipment, data storage devices such as computer diskettes or credit cards. The Locator Tool, Indicator Tool, and Adjustment Tool should NOT be sterilized.
Ferromagnetic substances may impede the ability of the adjustment tools to change and confirm the Performance Level setting.
Refer to Adjustment Kit insert for Instructions, warnings, precautions and complications.
The appropriate product and size must be chosen for the specific patient's needs, based on diagnostic tests and physician experience. Product labeling specifies applicable product performance levels or ranges.
Lint, fingerprints, talc, other surface contaminants, or residues from latex gloves can cause foreign body or allergic reactions.
Improper use of instruments in the handling or implantation of shunt products may result in the cutting, slitting or crushing of components.
Such damage may lead to loss of shunt integrity, and necessitate premature surgical revision of the shunt system.
Care must be taken to ensure that particulate contaminants are not introduced into shunt components during preimplantation testing or handling. Introduction of contaminants could result in improper performance of the shunt system. Particulate matter that enters the shunt system may result in shunt occlusion, or may also hold pressure/flow controlling mechanisms open, resulting in overdrainage.
In securing catheters to connectors, the encircling ligatures should be securely, but not too tightly, fastened, lest they eventually cut through the silicone tubing.
Care must be taken in the routing of catheters to prevent kinking and needless abrasion along their course. Abrasion can result in premature catheter failure (fracture). The rim of the twist drill or burr hole may be trimmed to provide a beveled notch where the ventricular catheter emerges and is curved to lie adjacent to the skull.
“Small” size catheters have thinner walls and lower overall strength as compared with “Standard” size catheters. These characteristics result in a comparatively greater potential failure (fracture) rate and, therefore, shorter life expectancy for “Small” size catheters.
Physicians who implant “Small” size catheters for cosmetic reasons must acknowledge the potentially higher rate of catheter revision and weight this against the cosmetic benefit.
Patients with hydrocephalus shunt systems must be kept under close observation in the postoperative period for signs and symptoms that suggest shunt malfunction. The clinical findings may indicate shunt malfunction. The clinical findings may indicate shunt obstruction or overdrainage of CSF.
Shunt obstruction may occur in any of the components of the shunt system. The system may become occluded internally due to tissue fragments, blood clots, tumor cell aggregates, bacterial colonization or other debris. Catheters which contact internal body structures can become kinked or blocked at their tips (e.g., investment of a ventricular catheter tip into the choroid plexus or of the distal catheter tip into the greater omentum or loops of the bowel). Finally, shunt obstruction may occur due to growth of an infant or child, or physical activities which result in disconnection of the shunt components or withdrawal of a distal catheter from its intended drainage site.
Shunt obstruction may occur in any of the components of the shunt system. The ventricular catheter may become occluded by particulate matter such as blood clots or brain fragments, by investment of the catheter tip in choroid plexus, by embedding of the catheter in brain tissue, or by coaptation of the ventricular walls in the presence of overdrainage (“slit ventricle”).
Disconnected shunt components may further migrate.
Shunt systems may fail due to mechanical malfunction, leading to under- or overdrainage.
Malfunction or obstruction of the shunt system may lead to signs and symptoms of increased intracranial pressure if the hydrocephalus is not compensated. In the infant, the common symptoms are increased tension of the anterior fontanelle, congestion of scalp veins, listlessness, drowsiness and irritability, vomiting and nuchal rigidity. In older children and adults, the common symptoms are headaches, vomiting, blurring of vision, nuchal rigidity, deterioration of consciousness, and various abnormal neurological findings.
Overdrainage of CSF may predispose development of a subdural hematoma or hydroma or collapse of the lateral ventricular walls leading to obstruction of the ventricular catheter.
If the ventricular catheter becomes bound to the choroid plexus or adjacent brain tissue by fibrous tissue adhesions, it is suggested that it should not be forcibly removed. It is suggested that gentle rotation of the catheter may help to free it. It is advised that the catheter be left in place rather than risk intraventricular hemorrhage which may be caused by forcible removal.
Subcutaneous catheter passers can break at welds or component assembly points, or due to extreme deformation of the malleable shaft.
Sudden breakage can lead to trauma of tissues or organs, and damage to the shunt system. Instruments must be inspected prior to use to ensure continued integrity and functionality. Disposable instruments must never be reused, or injury to the patient and physician is possible.
The Strata NSC valve is considered Magnetic Resonance Conditional in accordance with ASTM F2503.
MRI systems of up to 3.0 Tesla may be used any time after implantation and will not damage the Strata® II valve mechanism, but can change the performance level setting. The performance level setting should always be checked before and after MRI exposure.
The results of the tests performed to assess magnetic field interactions, artifacts, and heating, indicated the presence of the valves evaluated should present no substantial risk to a patient undergoing an MRI procedure using the following conditions:
Using the GE 3.0T Excite® HD Magnetic Resonance Imaging System, the valve experienced a maximum temperature change of 0.4°C over a 15-minute exposure period.
The table provides maximum signal voids (artifact sizes) for standard imaging pulse sequences at 3.0 Tesla per ASTM F2119.
|Valve||Pulse Sequence||Plane Imagine||Max. Signal Void (Artifact), cm2|
Do NOT take the Adjustment Tool into an MRI facility as these magnets could potentially be a safety hazard to the patient and/or user.
Proximity to MRI suite may impede the mechanism in the Indicator Tool due to the field strength of an MRI magnet. Move out of the vicinity prior to attempting to verify a valve setting.
Complications associated with ventriculoperitoneal CSF shunting systems may be similar to those experienced in any surgical procedure carried out under local and/or general anesthesia. These include reactions to drugs and anesthetic agents, electrolyte imbalance and excessive blood loss, particularly in infants. A patient may rarely exhibit a reaction due to sensitivity to the implant.
In CSF shunting procedures, the most common complications are due to obstruction of the system as described under “Warnings.” Obstruction may occur in any component of the system due to plugging by brain fragments, blood clots, and/or tumor cell aggregates at some point along its course. Obstruction may also occur because of separation of the system components or kinking and/or coiling of the catheter. This may predispose migration of the ventricular catheter into the lateral ventricle and the distal catheter into the peritoneum, or other structure in which the catheter is implanted. As noted previously, growth of the infant or child may cause the distal catheter to be withdrawn from the atrium into the internal jugular vein or from the peritoneum into tissue planes where the fluid cannot be absorbed.
There are other potentially serious complications. Local and systemic infections are not uncommon with shunting procedures. Usually, they are due to organisms inhabiting the skin, particularly Staphylococcus epidermidis. Other pathogens circulating in the blood stream may colonize the shunt and, in the majority of patients, require its removal.
In 1973, Robertson et al. summarized the incidence of infection in ventriculoperitoneal shunts reported up to that time. Infection in ventriculoperitoneal shunting occurred in 5 to 10% of the patients in most of the reports.
In 1993, Kestle et al. reported significant reductions in infection (less than 4%) with the use of antibiotics, short duration of surgery (surgical experience) and control of the operating room environment (e.g., designated operating room, limited personnel and traffic, covered skin surfaces). The article states that results can also be obtained without the use of antibiotics, but with rigorous perioperative control of the environment.
Using prophylactic antibiotics in shunted patients is somewhat controversial as their use may predispose infection by more resistant organisms. Therefore, the decision to use antibiotics prophylactically rests with the attending physician and/or surgeon.
Shunting into the peritoneum may fail because of investments of the catheter in loops of bowel or in the greater omentum. Perforation of the bowel by the peritoneal catheter with subsequent development of peritonitis has been described.
CSF overdrainage may result in excessive reduction of CSF pressure and predispose the development of a subdural hematoma or hygroma, and excessive reduction of ventricular size leading to obstruction because of impingement of the ventricular walls on the inlet holes in the catheter. In the infant, this excessive pressure reduction will cause marked depression of the anterior fontanelle, overriding of cranial bones and may convert communicating into obstructive hydrocephalus.
The incidence of epilepsy after ventricular shunting procedures has been reported. This study also indicated that the incidence of seizures increased with multiple catheter revisions.
StrataVarius is intended for use by physicians, to non-invasively identify the Strata-type valve Performance Level (PL) setting and display that information numerically in terms of PL level and the equivalent pressure reading in millimeters of water (mm H2O).
The StrataVarius allows the user to change the pressure setting of the valve non-invasively without the need for radiographic confirmation.
The Medtronic Neurosurgery StrataVarius system should not be used as a diagnostic tool, but rather only for confirmation of, or to change a pressure level in, a Strata-type valve.
StrataVarius should not be used on any fixed pressure valve. Use only on PS Medical Strata-type adjustable valves.
StrataVarius should not be used in a sterile environment.
Although no known complications have been reported, the StrataVarius system should be used at the discretion of the attending physician.
This therapy is not for everyone. Please consult your physician. A prescription is required.
For further information, please contact your Medtronic NT sales representative.
Caution: Swedish law restricts this device to be ordered by, and sold to, a physician or medical institution only. Refer to product package insert for instructions, warnings, precautions and complications.