| Pain Medicine Essay, Research Paper
IMPLANTABLE INFUSION DEVICES FOR LONG TERM PAIN MANAGEMENT;
EXAMINATION OF ITS EFFECTIVENESS AGAINST OTHER MEASURES
I reviewed 36 available articles up to date in order to answer the above question. In my presentation I will start by giving background information about chronic pain. I will discuss different types of delivery systems available, their benefits to the patient, as well as disbenefits, and cost.
Chronic pain reduces the quality of life in many patients and restricts their ability to engage in normal daily activities. Although many pain patients may be managed in the long term on oral medications, there is percentage of this population that needs additional or alternative means of treatment. Many side effects of the medications themselves, such as depression, drowsiness, confusion may contribute to the intractable nature of the problem. For the past 18 years, administration of opiates by the spinal route has been one of the palliative treatments available for intractable cancer pain or non-malignant pain, which is resistant to other methods. The goal of the morphine pump is not to deal with the underlying disease but to control the pain symptoms. Intrathecal and epidural administration of narcotics relieves pain by stimulation of stereospecific opiate receptors in the spinal cord and brain stem. Several types of intraspinal opioid delivery systems are now in use, and they are selected based on the patient?s life expectancy.
Less than 5% of cancer patients require invasive approaches for the treatment of cancer pain. However, it is theoretically possible to use these technologies for all chronic pain patients, and the market could be enormous.
Patient management guidelines that were published in 1993 in the Journal of Pain and Symptom Management suggest that patients with cancer related pain who have undergone sequential strong opioid drug trials, who have intractable, unmanageable side effects, and who have undergone a successful spinal opioid efficacy trial and patients with none cancer related chronic pain who failed all conventional syndrome specific therapies before neuroablative surgical procedures, including sequential strong opioid drug trials, who have intractable, unmanageable side effects, and who have undergone a successful spinal opioid efficacy trial, ?are? candidates for implantable spinal infusional therapy.
During my literature review, I was surprised to discover that there are no controlled research data available on this technology; all reports to date have been case reports or studies of relatively small series of patients. Many studies do not give information about disease status or progression during the trial. There is very little information regarding patients who discontinued treatment. There are no direct comparisons of effectiveness of intraspinal morphine vs. other delivery systems in matched subjects. Little discussion is present regarding patient satisfaction data nor the incidence of side effects.
In terms of patient benefits IIPs have been stated to offer a number of possible advantages over other therapies: enhanced activities of daily living and increased activity level, the therapy can be easily tailored (non invasively) to meet changing patient needs, reversible therapies (non destructive), and long term cost effectiveness. Chodekiewitz has suggested in 1995, that with better pain control, patients are likely to return to a more active life and decrease their use of ineffective alternative treatments.
In terms of disbenefits, there are problems that can arise after the implantation of a pump. These problems can be broadly categorized into surgical, mechanical and pharmacological. Long term, and immediate follow up are required in regard to infection, CSF leakage, neural damage and perhaps tolerance, dependence and safety aspects; in my literature search I found that two patients have died from overdose.
The cost of the implantable infusion devices is high. There is also the cost of the operation to implant the system, plus the cost of repeated filling and trouble shooting. It could also mean an outpatient visit at least every three months until the pain resolves. Only one attempt has been made to estimate the likely cost of using pumps for long term pain management and this was a very small case series of nine patients (Horisberger et al. Socioeconomic aspects of an implantable drug delivery device. Recent Results in Cancer Research 1991; 121: 223-232.)
To summarize, implantable infusion devices are used to administer drugs to treat chronic malignant or non-malignant pain. They have been developed primarily to promote patient independence from the hospital setting during chronic infusion therapy, as many patients? chronic pain reduces their quality of life and restricts their ability to engage in normal daily activities. Currently, there are no controlled research data available on this technology; all reports to date have been either case reports or case series. Approximately 30-50% of patients report ?excellent? pain relief. There are significant risks and complications associated with these devices. Studies to date have been of a small number of patients and lacking objective long-term outcome data. Proper patient selection via preselection screening programs are necessary. Further information on the relative benefits such as quality of life improvement of permanent and external infusion pumps is required.
Thus, in conclusion, further studies comparing chronic systemic treatment to spinal infusion would be necessary. Of interest, the National Standing Group on Health Technology has identified intrathecal pump systems for giving opioids in chronic pain as a NHS research priority in 1995.
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