An implantable infusion system may be indicated for patients who have tolerated an intrathecal trial and whose life expectancy and analgesic needs are greater than 3 months. For details on patient selection and screening go to the Medtronic website.
Medtronic's intrathecal drug delivery systems are composed of two implantable components: an infusion pump and an intraspinal catheter. The pump is placed abdominally in a subcutaneous pocket, while the catheter is inserted into the intrathecal space of the spine, tunneled under the skin and connected to the pump. Medication can be delivered at constant or variable flow rates. The pumps weigh approximatley 4 ounces and are approximately 3 inches in diameter and one inch thick. The primary differences between the pump models are the size of the reservoir and the presence of a side catheter access port. The most commonly implanted pump model holds a maximum of 18ml of medication. To avoid the need for frequent pump refills the medicine is concentrated so that the required amount of medication can be delivered.
Common Concentrations for Implanted Drug Delievery Systems (IDDS)
- Local Anesthetics bupivacaine 3% (30mg/ml) or 2% (20mg/ml)
- Fentanyl 1000mcg/ml
- Morphine (available in solution up to 50mg/ml)
- Hydromorphone (available in solution up to 10mg/ml, powder can be diluted up to 60mg/ml)
- Clonidine varies (available in solution to 500mcg/ml)
Preparation of concentrated solutions for internally implanted pumps requires a minimum of 24 hours notice. Please contact Dave Wegner RPh (265-0327) as soon as possible (preferrably a week in advance) to assure necessary powders are in stock. Concentrated solution need to compounded by UWHC Pharmacy or Chartwell from powder increasing risk for infection. Patients should be consented [consent form to be developed] about the risk of infection when administered compounded medications via the neuraxial route.
Prior to surgery, it is critical to screen for the presence of infection. Laboratory testing (e.g., complete blood count differential and urinalysis) should be conducted one to two days prior to surgery. If the patient shows any sign of infection, the implant should be postponed until the infection is resolved. The patient may also be treated with pre- and perioperative prophylactic antibiotics.
Patient Informed Consent [Consent form under development]
During preoperative care, the patient should be instructed on his/her treatment and personal responsibilities. Informed Consent Form is required including providing the patient with information about additional risks of using compounded medications. Primary areas to be covered during preoperative education and the Informed Consent process include:
- Preoperative procedures
- Implant procedure
- Postoperative pain or discomfort
- Risk of infection and other surgery/therapy complications
- Postoperative precautions and self-care responsibilities
- Refill schedules and procedures
- Follow-up care
Routine postoperative care includes regular assessment of vital signs, recovery from general anesthesia, pain, side effects, and complications, and routine incision line care. The patient will have two suture lines;
- abdominal incision on the abdomen where the pump is placed and
- a 2-3 inch incision on the back where the catheter was inserted into the intrathecal space.
Once the incisions are healed the pump and catheter insertion sites requires no special care.
Management of Complications
Potential postoperative complications can be organized into surgical, system, adverse drug events and other.
Potential surgical complications include: infection, spinal headache, CSF hygroma, CSF leakage around catheter insertion site, bleeding, pain and discomfort, pump pocket seroma, and hematoma.
Postop care involves regular assessments for signs and symptoms of all of the above potential complications. Should any of signs and symptoms of complications occur, they should be reported immediately to the designated responsible physician.
Please refer to the SynchroMed® Infusion System: Clinical Reference Guide for Pain Therapy-Part Two for Patient Management information related to specific surgical complications (available in the online Library).
Complications with the SynchroMed Infusion System may occur, including: catheter kink, catheter obstruction, catheter dislodgement, disconnection or breaks, programming errors, or pump failure.
System complications may present as drug overdose, loss of drug effect, or withdrawal symptoms. When investigating loss of drug effect, evaluate factors such as disease progression, drug tolerance or concurrent illness.
Consult the drug package insert for additional information. If there are no patient-related factors present, then investigate system problems.
Adverse Drug Events
Monitor the patient until you are confident that the patient's response to the drug is acceptable. Watch for adverse drug events and signs of drug overdose. Please consult the drug package insert for additional information.
In rare instances, the development of an inflammatory mass at the tip of the implanted catheter may occur that can result in progressive clinical signs that bear monitoring. These signs include a progressive change in the character, quality, or intensity of pain; an increase in the level and degree of pain despite dose escalation; sensory changes, i.e., numbness, tingling, burning, hyperesthesia and/or hyperalgesia.
Presentations that require immediate diagnosis include bowel and/or bladder dysfunction; myelopathy, conus syndrome, gait disturbances or difficulty ambulating; and paraparesis or paralysis.
If inflammatory mass is suspected, recommended evaluation should include a review of the patient history and neurological evaluation, radiological diagnostic procedures (such as an MRI with contrast), and an appropriate clinical consultation.
Magnetic Resonance Imaging (MRI)
MRI will temporarily stop the SynchroMed Pump motor and suspend drug infusion for the duration of the MRI exposure. The SynchroMed Pump should resume normal operation upon termination of MRI exposure. Exposure of IsoMed Pumps to MRI fileds of 1.5 T(Tesla) has demonstrated no impact to pump performance and limited effect on the quality of the diagnostic information.
During an MRI scan, the patient may experience heating of peripheral nerve stimulation at or near the pump implant site. In the unlikely event that this happens, the MRI scan parameters should be adjusted to reduce Specific Absorption Rate (SAR) for heating or dB/dt for nerve stimulation or both.
Upon completion of an MRI scan, the SynchroMed Pump parameters should be confirmed using a SynchroMed Programmer. SynchroMed Pump Performance has not been established in >2.0 T(Tesla) MR scanners nor has IsoMed Pump performance been established in >1.5 T(Tesla) MR scanners — it is not recommended that patients have MRI scans using these scanners.
Electrical Devices and Electromagnectic Field Interference (EMI) and Radio Frequency Field Interference (RFI)
Large amounts of EMI or RFI could potentially alter information stored in the pump’s memory. It also may affect operation of one or more of the pump’s internal components, but it will not damage the device. The microprocessor inside the SynchroMed Pump contains a self-test that checks the pump program a few times each minute. If the pump memory is compromised, the self-test will sound a memory error alarm. If a memory alarm occurs, the pump will need to be reprogrammed before it will start again. For a complete list of activities (weld, automobile, electric substation, power tools, cell phones, and microwaves, etc) refer to Medtronic book.
The pump may set off metal detectors. A patient identification card should be brought to airports for security clearance. Metal detectors will not interfere with therapy.
Pump interogation and rate adjustments in hospital
The Medtronic SynchroMed programmer is the external component of the SynchroMed Infusion System. The programmer, which controls the drug administration activities of the pump, transmits instructions through the programming head to the pump via coded radio-frequency signals. There are several units located with the hospital. Contact Stephen Deutsch, MD or Miroslav Backonja, MD for assistance.
The programmer is used to noninvasively interrogate and program an implanted SynchroMed pump. The programmer uses a programming head to establish a two-way radio-frequency link with the implanted pump. Through the programming head, the programmer transmits interrogation and programming signals to the pump and receives status information from the pump. This interchange of information and programming instructions is referred to as telemetry.
Medtronic hotline for problem solving
For detailed programming instructions, refer to the SynchroMed® Software and Programmer Technical Manuals, or contact Medtronic Technical Services at 1-800-328-0810.
Patient education booklet and video
- Copies of a patient information video can be obtained through Deb Gordon 263-6488.
The frequency of pump refills varies from weeks to months depending on the medication. Pumps are refilled by inserting a needle through the skin into the pump’s self-sealing silicone septum. Pumps are scheduled to be refilled in an outpatient clinic in advance of the pump’s expected low volume alarm.
Medtronic recommends that clinicians refrain from depending solely on the pump alarm to determine refill intervals or remaining battery life. Some hearing-impaired patients may not hear the alarm, or the pump may be implanted too deep to adequately hear the alarm
The refill procedure involves a specific set of tasks that must be followed precisely to help ensure patient safety. Before clinicians perform refills, they must be well trained in the correct procedures.
Morphine remains stable in the pump for up to 90 days following refill.