Lumboperitoneal Adjustable Pressure Shunts
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Lumboperitoneal Adjustable Pressure Shunts
The PS Medical® Strata® NSC lumboperitoneal valve allows the physician to noninvasively adjust the pressure/flow performance level pre- and post-implantation without the need for radiographic confirmation by using magnetic adjustment tools in order to address changing patient needs. The design helps ensure that the valve’s performance level resists inadvertent changes.
The Strata NSC lumboperitoneal shunt system provides continued cerebrospinal fluid flow from the subarachnoid space into the peritoneal cavity. The Strata NSC lumboperitoneal 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. The Strata NSC Lumboperitoneal Shunt System is designed for management of communicating hydrocephalus.
The small lumen peritoneal catheter is designed as a distal component of a cerebrospinal fluid shunt system for use in shunting cerebrospinal fluid into the peritoneal cavity.
CSF shunt devices should not be implanted if there is infection in any areas in which the various components of the shunt system will be implanted. These include infections of the skin areas through which the shunt system will traverse, the meninges and subarachnoid space, peritoneum and intraperitoneal and retroperitoneal organs, pleura and blood stream.
Shunting of CSF from the lumbar subarachnoid space into the peritoneal cavity is contraindicated in patients with obstructive hydrocephalus, i.e., where there is no free communication between the ventricles and the subarachnoid space. Medtronic Neurosurgery’s PS Medical Strata NSC LP shunt products are not appropriate for the treatment of obstructive or noncommunicating hydrocephalus unless the patient has had prior surgery establishing a functioning pathway between the cerebral ventricles and the subarachnoid space.
Since the lumbar catheter is inserted into the subarachnoid space via a 14-gauge Tuohy needle or laminectomy, the technique should not be used if there is a congenital or acquired spinal deformity at the implantation site.
The long-term use of LP shunts in infants and young children with hydrocephalus is not recommended. In this age group, technical difficulties may be experienced due to the smallness of the lumbar subarachnoid space, the more caudal position of the conus, and the likelihood of repeated revisions necessitated by the growth of the patient.
The small lumen peritoneal catheter should not be implanted in situations requiring high flow rates or very low differential pressures. Its flow limiting properties may lead to underdrainage under these conditions.
Performance of the small lumen peritoneal catheter with high-resistance shunting components such as the Integra NPH™ low flow valve, Integra OSV II® valve or Codman® SiphonGuard®device has not been characterized. Excessive resistance to flow in the complete shunt system may lead to underdrainage complications. Therefore, use of these devices with the small lumen peritoneal catheter is contraindicated.
The valve pressure level setting should always be verified following patient exposure to high magnetic fields.
The adjustment tools contain 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. Ferromagnetic substances may impede the ability of the adjustment tools to change and confirm the performance level setting. Refer to adjustment tool insert for instructions, warnings, precautions and complications.
The adjustment tools should NOT be sterilized.
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 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.
After valve implantation, do not use the PS Medical Strata II adjustment kit.
The performance characteristics of this device may be altered if components or devices of other manufacturers are used in conjunction with this device.
Valve function and performance level setting should be checked in the event that the valve is subjected to significant mechanical shock or trauma.
The appropriate product, size, or performance characteristics must be chosen for the specific patient’s needs, based on diagnostic tests and physician experience. Product labeling specifies applicable product performance and indications.
From a diagnostic standpoint, the presence of the valve in a patient may disrupt or impair the use of MRI if the area of interest is near the location of the valve.
Handling or the use of instruments when implanting these products may result in the cutting, slitting, crushing, or breaking of components.
Use of sharp instruments while handling these devices can nick or cut the silicone elastomer, resulting in leakage and necessitating revision. Care must also be taken when closing incisions to ensure that the devices are not cut or nicked by suture needles. Such damage may lead to loss of product integrity, and necessitate surgical revision of the implanted system.
Care must be taken to avoid stretching or kinking the catheters at any point along their course or damaging the tubing or slit valves during handling or passing the catheter with a catheter passer.
Care must be taken during the procedure to avoid putting cuts, punctures and holes in the catheter. When applying the fixation tabs to the catheter, take care to ensure that the catheter is positioned in the recessed groove of the tab.
Lint, fingerprints, talc, other surface contaminants, or residues from latex gloves can cause foreign body or allergic reactions.
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 over-drainage.
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). “Small” size peritoneal catheters have thinner walls and lower overall strength as compared with “Standard” size peritoneal 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 CSF 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 infection or other complications such as CSF leaks due to the puncture of the dura. The clinical findings may indicate shunt obstruction, underdrainage or overdrainage of CSF.
If the shunt components are not adequately secured, migration of the catheters may occur. The entire distal catheter may migrate into the peritoneal cavity, and the lumbar catheter may migrate into or out of the spine.
Disconnected shunt components may further migrate.
Shunt systems may fail due to mechanical malfunction, leading to under- or overdrainage.
Obesity may pose difficulties for the surgeon. Caution must also be exerted if the patient has had previous abdominal surgery.
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 flow-limiting properties of the small lumen peritoneal catheter may increase the risk of shunt underdrainage in some circumstances.
To minimize the possibility of underdrainage in patients confined to a supine position (i.e., bedridden patients), these patients should be elevated at a 45° angle for several hours a day (using a pillow, etc.) until they can sit or stand independently.
The PS Medical Strata NSC lumboperitoneal 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 adjustment tools into an MRI facility, as these magnets could potentially be a safety hazard to the patient and/or user.
Proximity of MRI suite may impede the mechanism in adjustment tools 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 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.
Underdrainage may occur due to obstruction or inadequate performance level setting. Shunt obstruction may occur in any of the components of the shunt system due to plugging by brain fragments, blood clots, bacterial colonization, tumor cell aggregates or other debris at some point along its course. Less commonly, the lumbar end of the shunt may be sealed off by arachnoiditis. Arachnoiditis may give rise to radiculopathy.
Shunt obstruction can require immediate treatment with either revision of the existing system or institution of other techniques.
Catheters that contact internal body structures can become kinked or blocked at their tips (e.g., investment of the distal catheter tip into the greater omentum or loops of the bowel). 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.
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 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 peritoneum into tissue planes where the fluid cannot be absorbed.
Malfunction, underdrainage, or obstruction of the shunt system may lead to signs and symptoms of increased intracranial pressure if the hydrocephalus is not compensated. Underdrainage or obstruction may give rise to a variety of complications. If the hydrocephalus is not compensated, intracranial hypertension will recur with the resultant clinical signs and symptoms. 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. Leakage of CSF into the wounds and along the course of the catheters may be noted.
If the shunt components become separated, the catheters may migrate into the peritoneal cavity, spinal canal or other location.
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, minimal manual shunt handling, limited personnel and traffic, covered skin surfaces, double-gloving). 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 organisms that are more resistant. Therefore, the decision to use antibiotics prophylactically rests with the attending physician and/or surgeon.
The incidence of infection associated with LP shunting has been reported to be comparable to ventriculoperitoneal shunting.
Intra-abdominal complications associated with peritoneal shunting include perforation of the small or large bowel with resultant peritonitis, perforation of other viscera, ureteral obstruction, bizarre migrations of the catheter into the bladder, rectum, vagina and scrotum, and development of ascites and pseudocysts.
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.16
CSF overdrainage, including inadequate performance level setting, may result in excessive reduction of CSF pressure and predispose the development of a subdural hematoma or hygroma. Overdrainage may convert communicating into obstructive hydrocephalus due to occlusion of the aqueduct of Sylvius and postural headache. 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.
LP shunting has been reported to predispose the development of scoliosis, kyphoscoliosis and hyperlordosis and the development of tonsillar herniation. This complication has been found in a high percent of cases in a pediatric age group. Although this has generally been asymptomatic, symptomatic cases and death have also been reported.
Although rare in occurrence, ophthalmological abnormalities have been reported due to shortening of the lumbar catheter associated with child’s growth.
Subarachnoid hemorrhage, intra-abdominal hemorrhage, sinus thrombosis, convulsions and deformities of the lower limbs have been reported following LP shunting.
It has been reported that a very small population of patients may show an acute allergic-type reaction to the shunt system. This may be due to its materials of fabrication, and can lead to patient discomfort, tissue irritation or erosion of any of the components, or other complications.
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.