Intrathecal Pump Therapy
Performed by Top Pain Management Doctors in San Antonio, Texas
An intrathecal pumpis a battery-powered, programmable device implanted in the body in order to control intractable pain and other health conditions. The device works by delivering medication directly into the fluid surrounding the spine. Implantation of an intrathecal pump is an effective way for many people to manage persistent chronic pain that has not responded to other pain management therapies.
An intrathecal pump system consists of a pump, which stores the medication within a reservoir, and a small plastic tube called a catheter. Medication flows from the pump through the catheter through the theca of the spinal cord into the subarachnoid space, or the area beneath the arachnoid membrane that covers the brain and spinal cord. The pump is programmed to release medication gradually over a period of time in a continuous infusion, or to release specific amounts of medication at different times of the day in boluses, depending on the needs of the patient. The pump may also be programmed to permit the patient to self-dose as needed, allowing on-demand pain management.
Delivery of drugs into spinal fluid requires smaller amounts of medication and is often more effective at pain control than oral therapy. In fact, spinal analgesia may be so effective that patients are able to reduce or discontinue oral pain medications, thereby decreasing associated side effects (Corrado et al, 2008).
One of the most common uses for intrathecal pumps is to control intractable, chronic cancer pain. In patients with persistent pain from malignancy, patient-controlled intrathecal drug therapy is associated with improved pain reporting, and reduced use of oral painkillers, according to a recent retrospective chart review (Brogan & Winter, 2011). After initiation of intrathecal drug therapy with patient-controlled dosing, 50% of patients had discontinued all non-intrathecal opioids at follow-up, and 46% of the patients on breakthrough medications no longer required their use. At follow-up, there was a significant reduction in total non-intrathecal opioid use, and pain scores were significantly lower than at baseline.
Intrathecal pump systems are also prescribed for control of many types of non-malignant pain. One such indication is for failed back surgery syndrome, or failure of one or more surgeries to successfully control persistent back or leg pain (Tomycz et al, 2010). Other applications include control of dystonia and pain in complex regional pain syndrome (reflex sympathetic dystrophy), a progressive disease of the nervous system involving constant chronic burning pain (Van Hilten et al, 2000; Zyluk, 2009). Continual pain from chronic pancreatitis is another possible reason for implantation of a pain pump (Kongkam et al, 2009). A pain pump can also be implanted to lessen neuropathic pain, axial spinal pain, diffuse pain, brachial plexitis, central pain, arachnoiditis, poststroke pain, spinal cord injury pain, peripheral neuropathy, pain from postherpetic neuralgia, or as a therapeutic alternative to a spinal cord stimulator (Koulousakis et al, 2007; Zacest et al, 2009).
Spinal analgesia was first discovered in the late 19th century by August Bier, after the discovery of cocaine as a local anesthetic. The potent anesthetic effects of injecting cocaine into the intrathecal space incited increased awareness of the treatment modality (Knight et al, 2007). Later, in the 1940s, the first uses of continuous spinal analgesia with opioids were demonstrated. However, the therapy was not widely accepted until 1973, with the discovery of opiate receptors in the spinal cord (Knight et al, 2007). In 1979, spinal analgesia was introduced clinically for obstetric analgesia, and in 1981 the first clinical use of an implantable intrathecal opioid delivery device was demonstrated for use in chronic cancer pain.
Another major indication for intrathecal pumps is for patients with cerebral palsy or other forms of spasticity who may receive intrathecal baclofen to help manage their condition. Intrathecal baclofen therapy may reduce harmful sensory and motor stimulations caused by spasticity to more optimal levels (Nomura et al, 2012).
Morphine is the drug most commonly used in intraspinal analgesia because of its history, duration of action, and ease of use (Knight et al, 2007). However, during the last 20 years other agents have been incorporated into intraspinal therapy. Alternative opioids such as hydromorphone, alpha adrenergic agents, baclofen for neuropathic pain local anesthetics, adrenergic agonists, N-methyl-D-aspartate receptor agonists, and other agents are currently being used in implantable drug delivery systems (Knight et al, 2007). Muscle relaxants such as baclofen are also used in cases of spasticity, as in cerebral palsy, multiple sclerosis, and spinal injuries.
The spinal cord and brain are surrounded by three meninges, or protective membranes. Between the inner two meninges, the arachnoid and the pia mater, is a fluid filled space called the subarachnoid or intrathecal space. CSF flows through this area, bathing and protecting the brain and spinal cord. Pain pumps are designed to deliver medication directly into the intrathecal space.
Delivery of medication into the CSF within the intrathecal space is more efficient than oral dosing as it bypasses the circuitous route that oral medication takes through the body. Delivery directly into the intrathecal space allows medication to take effect more quickly, and requires a significantly smaller dose than when taken orally. Using less medication is beneficial as it typically causes fewer side effects.
Patients with intractable pain must undergo a trial intrathecal injection or infusion before implantation of an intrathecal pump can occur. Trialing for intrathecal pump placement is an essential part of the decision-making process in placing a permanent device, and it has become common practice to perform a temporary neuroaxial infusion before permanent device implantation (Deer et al, 2012). The purpose of the trial is to determine if the system is effective in that individual (Ahmed et al, 2005). Success is usually defined as pain reduction of 50% or more.
A pain pump trial involves a single injection of medicine delivered through lumbar puncture, multiple injections delivered via lumbar puncture or catheter over a period of days, or a continuous trial in which the drug is delivered through an indwelling catheter connected to an external pump placed intrathecally or epidurally. Intrathecal placement of the catheter is preferable in that it more closely approximates the system that the patient will eventually receive; also, intrathecal placement in the spine is easier and requires less medication than an epidural trial (Reisfield & Wilson, n.d.). If the trial is successful, the patient may be approved for implantation of a permanent system.
During installation of a pain pump, the patient is given sterile preparation and anesthesia. The catheter is placed intrathecally through a small incision in the middle of the back and secured with sutures. Once the catheter is placed, an extension catheter is tunneled through the skin to the abdomen, where the pump will be implanted. The pump is introduced into the abdomen through an incision of a few inches and placed into a pocket created between skin and muscle layers, and the extension catheter is attached to the pump. The pump is secured to the layer of fascia overlying the abdominal muscles and both incisions are closed. Most patients are discharged the same day.
Medication refills are scheduled regularly with the patient’s pain management specialist. At each refill appointment, the patient’s treatment plan will be reassessed, and the pump adjusted accordingly. The doctor or nurse refills the pump by injecting medication through the skin and into the fill port on top of the reservoir. This is done with a small needle. The goal of treatment is to deliver enough medication to achieve optimal results while producing as few side effects as possible. Supplemental oral medicine may be prescribed if the patient still experiences periods of breakthrough pain.
Implantation of a pain pump is an effective way for most people to manage persistent chronic pain and reduce reliance on oral medications (Corrado et al, 2008). Continuous intrathecal or epidural infusion eliminates the peaks and valleys of pain relief and patient-controlled analgesia pumps enhance the efficacy of continuous infusions by allowing the patient to administer bolus doses to control acute pain (Kwan, 1990). Further, intrathecal pump systems are fully reversible if the patient opts to discontinue therapy.
A study that sought to demonstrate the effectiveness of the intrathecal pain pump by examining patients’ self-reported pre- and post-implantation pain levels found the perceived success rate for implantation was 68%, when measured by the ability to reduce reliance on oral medication (Corrado et al, 2008). Further, the success rate was calculated as 86% when measured by willingness to undergo the procedure again. Another study comparing outcome measures of a computerized assessment of pain, emotional distress, and quality of life between chronic non-cancer pain patients who received an implantable device and those who did not receive a device found patients with an implantable device reported less emotional distress and improved quality of life compared with those without an implantable device (Jamison et al, 2008).
Complications from implantation of an intrathecal pump can be categorized into surgical, mechanical, medical and pharmacological problems (Knight et al, 2007) and may require corrective measures or even removal of the device.
Some types of surgical complications include intra-operative bleeding, neurological injury, infection, cerebral spinal leaks, shredded catheters, and malpositioned subcutaneous pockets (Knight et al, 2007).
Intra-operative bleeding can occur from ineffective local hemostasis during the procedure. In order to prevent bleeding during installment of the device, patients on blood thinners are not candidates for this type of procedure until the coagulation returns to normal (Knight et al, 2007).
Superficial post-operative bleeding around the wound is another potential complication. A seroma or hematoma, a medical complication, can appear at the pump site, presenting with swelling, pressure, and pain, and leakage of sanguinous or serosanguinous fluid from the wound. Postoperative monitoring can help prevent this type of complication from becoming significant.
Neurologic injury, or injury of the spine, nerves and associated tissues, can result from surgical error. This type of injury is rare, however, when the procedure is performed by a skilled practitioner. The development of neurologic symptoms can also be associated with the formation of an inflammatory mass at the tip of the spinal catheter. This inflammatory response leads to the development of an expanding sterile mass known as a granuloma at the tip of the catheter (Zimmerman & Rauck, 2012).
Another cause of neurologic complication is development of a hematoma. One case of bilateral subdural hematoma following implantation of intrathecal drug delivery device has been reported in the literature (Magro et al, 2011). Surgical drainage of the hematoma resulted in full neurologic recovery.
Cerebral spinal fluid leaks represent another form of tissue damage from intrathecal pump implantation. The needle used to access the epidural space can sometimes leave a hole through which CSF may leak. Such leaks may lead to post-dural puncture headaches.
In order to combat infection, strict sterile techniques and antibiotics, and monitoring may be used. The patient may be given pre-operative and intra-operative antibiotics. Intrathecal infections, although rare, are one type of infectious complication and require removal of all implanted hardware.
According to one estimate, mechanical complications may account for nearly two-thirds of problems with intrathecal pump systems (Varhabhatla & Zuo, 2012). Mechanical complications are related to equipment failure. A major type of mechanical complication is malfunction of the catheter, which can become blocked, obstruct, or fracture (Rhee et al, 2012; Wörner et al, 2009). The catheter can also leak where it connects to the pump, migrate outside the thecal sac, or cause the formation of catheter-associated inflammatory masses (Haranhalli et al, 2011; Tomycz et al, 2012). Another type of mechanical problem is failure of the pump, which upon rare occasions can stop working. The pump battery will also need to be replaced every few years, depending on how often the device is used.
Medication errors are another typical category of complications seen with pain pumps. The medications used in these systems can cause accidental intoxication, over- or underdose (Berger at al, 2012; Kramer et al, 2009; Sakaguchi et al, 2008). Further, the analgesics and other drugs used in pain pump therapy are associated with a range of side effects caused by simply taking the medication on a regular basis (e.g., respiratory depression, constipation, nausea, dizziness, anxiety, depression, edema). In order to avoid pharmacological complications, drug refills must be done by trained individuals who are able to accurately assess pain, conduct physical examinations, and evaluate subtle changes in condition (Knight et al, 2007). Refills must also be done in a timely fashion; a case study reports a woman receiving morphine with an intrathecal pump who went into respiratory failure after attending her refill appointment 12 days later than scheduled (Ruan et al, 2010). Her dose had been titrated up to 4 mg/day, and she had been on an empty pump for an extended period. When her pump was finally refilled, 4 mg/day was too strong of a dose given that she had lost her opioid tolerance. This case study underscores the importance of patient compliance in keeping refill appointments given that the strong analgesics used in pain pump therapy can be dangerous.
Results of intrathecal pain pump therapy vary depending on the underlying condition being treated and its severity (Knight et al, 2007). Treatment goals for chronic pain patients may include reduction in pain, reduction in oral medications, improved pain reporting, reduced supplemental oral, around-the-clock, and breakthrough opioid requirements (Brogan et al, 2011), and improvement in activities of daily living. Treatment goals for spastic patients may include reduction in rigidity and muscle spasms, reduction in oral medications, ease of nursing care, improved sitting, improved mood, and improved sleep (Gray et al, 2012).
From the beginnings of spinal analgesia in cord in the late 19th century, this treatment modality has been used as an effective means to treat chronic, severe pain and other serious health conditions. There has been a great deal of advancement in the physiologic and pharmacologic understanding of direct neuromodulation, treatment options, and surgical techniques, resulting in improved safety and efficacy (Belverud et al, 2008).
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