February 6, 2006

NeuroScience Insights for Health Care Professionals

The physicians and staff of The Neuroscience Group are providing this physician and provider communication to help you stay abreast of issues and updates in the dynamic field of neurosciences, with the goal of helping you provide better overall healthcare services to your patients. Based on the level of urgency, emails take the form of Alerts (urgent news within the neurosciences that may impact your practice), Bulletins (important information), or Updates (more general news) and will be noted as such in the topic headline.

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Provider Update: Co-Managing Chronic Pain Pump Patients

Co-managing chronic pain patients with intrathecal pumps is often difficult in the primary care setting because of the complex interactions between systemic diseases and the treatment modality. The risks of intrathecal pumps are usually divided into two main areas of concern: pharmacological side effects related to the medications used and the mechanical complications of the pump systems. Co-managing these complex patients requires ongoing communication between primary care and specialist providers.

Mechanical Complications

Mechanical complications of intrathecal drug delivery include catheter disruption (i.e. disconnection or fracture of the catheter), infections and rarely pump failures. Occasionally, the catheter will become kinked or plugged with sediment from drug precipitation. Catheter tip-associated benign granuloma formation often presents with a sudden loss of analgesia or new neurological symptoms. An MRI ordered by the primary care provider can evaluate catheter disruption. Fluoroscopic evaluation is sometimes needed to assess occlusions. The specialist will order a rotor study under fluoroscopy to assess suspected pump mechanism problems. The pumps are programmed with an audible sound, which alerts the patient when the pump is not functioning correctly. Most often patients will complain that the efficacy of the medication’s effect on their pain level has changed significantly. Infections, either local or systemic, present with the usual signs and symptoms of sepsis (i.e. meningitis). Together, the specialist and primary care provider need to sort out nerve root irritation from benign granuloma formation vs. exacerbation of existing disease processes.

Pharmacological Side Effects

While it may seem that the side effects of intrathecal medication administration is high, these patients have failed other more conservative opioid administration measures. The difficulty lies in sorting out medication side effects from disease-related concerns. The most often reported side effects of intrathecal opioid administration are nausea and vomiting, sedation, urinary retention, pruritis, myoclonic activity and respiratory depression (Williams, Louw, Towlerton, 2000). In our practice, all patients must undergo a trial of intrathecal drug administration through an externally placed catheter prior to implantation of IT pump delivery systems. This allows the specialist and patient to ascertain if intrathecal drug administration can effectively decrease pain levels. During this trial period, some patients experience transient nausea and vomiting which decreases after the first 24-48 hours and are usually dose-related. In our practice, we have noted that catheter position has been associated with increased nerve root irritation. Concurrent use of systemically administered breakthrough opioids may also contribute to the amount of nausea and vomiting. Although rare, sedation and somnolence occurs with both oral and intrathecal opioid medication administration and are usually secondary to delivery rate and potency. This can range from mild disorientation and fatigue to frank psychosis. Careful neuropsychological evaluation can help to evaluate these changes.

Urinary retention is occasionally associated with intrathecal opioid administration. However, this is usually addressed prior to implantation during the trial period. Significant problems are related to the effect of the medication on detrusor and abdominal musculature and the opioid effect on afferent input. Sometimes it is difficult to differentiate between disease-related urodynamic issues and drug-induced effects. For example, MS patients already on Baclofen, may already experience bladder problems. Sometimes the issue is urinary retention and overflow vs. incontinence. In our practice, we frequently refer these patients to urinary incontinence specialists for behavioral and nutritional therapies to help them to deal with urodynamic issues. In MS patients, UTI’s may not present with the usual array of signs and symptoms. The patient may complain instead of increased spasticity or tone. R/O UTI with the appropriate screening tests.

The literature reports that pruritis occurs in about 17% of patients and is one of the more bothersome side effects. In our practice, patients occasionally experience pruritis during the trial period. We have found that narcan .4 mg subQ repeated Q 4-6 hrs. for 24-48 hours during the trial period has decreased pruritis. Myclonic activity is rarely seen with IT drug administration unless extremely high doses of opioid are used for oncology patients. It is a well-known complication of opioid administration, regardless of delivery route. Anticholinergic effects at the spinal level or the effect of morphine metabolites have been linked to myclonic activity. Although usually related to size of the opioid dose, baclofen is used for control. Respiratory depression is a rare but serious side effect. Care must be taken during pump refilling and all reprogramming activity to prevent bolus administration of the opioid.

In our practice, we have frequently seen lower extremity edema, especially with morphine administration, which is a smooth muscle relaxant. Diuretics, support stockings and other strategies to decrease edema help the patient feel more comfortable. Sometimes switching to hydromorphone decreases the amount of edema. Less common side effects of opioid administration include constipation, incontinence, polyarthralgia, sweating, amenorrhea, altered sexual function and altered libido.

Preventing Abuse and Overdose

Assessing tolerance is difficult with IT opioid administration. Tolerance appears more commonly in patients with noncancer pain. Tolerance is defined as IT morphine dose greater than 25 mg per day or concurrent administration of alternate narcotic because of inadequate pain control in the absence of disease progress or other systemic problems. The goal of IT analgesia is to manage not obliterate pain. Most patients with IT pumps do not achieve complete relief of their symptoms. However, significant changes in functional improvement and pain coping have been documented. A thorough neuropsychological evaluation pre-implantation is needed. Candidates for pump implants with psychopathological or substance abuse problems or unresolved issues with secondary gain are not accepted for IT therapy until psychological issues are addressed and re-evaluated. . The specialist monitors incremental dose increases.

One of the advantages of IT drug administration is the potency factor is 1 mg of morphine IT=300 mg. PO. Patients are encouraged to keep a small supply of PO medications on hand for break-through pain or abrupt disruption of IT drug administration (i.e. catheter fracture or kinking)

Collaboration between primary care providers and specialists managing IT drug therapy is a critical component in the selection and ongoing monitoring of patients with IT drug administration. The role of the primary care provider is to assess the use of IT drug administration in concert with other systemic diseases. The role of the specialist is to assure that IT drug therapy is providing significant improvements in function, decreased pain and increased ability to cope with chronic pain with minimal side effects. Careful monitoring and in-depth patient education are necessary to successfully manage chronic pain patients with IT delivery systems. Two-way communication between primary care and specialist providers is an important component of effective patient care.

If you have any questions related to IT therapy, feel free to contact Dr. Phil Yazbak Philip.yazbak@thedacare.org Dr. Randall Johnson. Randall.Johnson@thedacare.org or Diane Vanderlin, APNP diane.vanderlin@thedacare.org. We are planning a Fall 2006 conference for primary care providers.  Please email us with topics that would be of interest to you.