Disease-specific and generic health outcomes: A model for the evaluation of long-term intrathecal opioid therapy in noncancer low back pain patients

Objective: The present study provided comprehensive characterization of the long-term outcomes of intrathecal opioid administration via a drug adminis tration system DAS) in chronic pain patients with predominantly low back pa in. A conceptual framework based on multidimensional outcomes is proposed u sing both disease-specific and generic measures. Design: Pre-post longitudinal data were collected in a retrospective fashio n on 38 patients receiving intraspinal opioid therapy for a minimum of 36 m onths (average = 50 months). Main Outcome Measures: Disease-specific measures included magnitude of infu sed opioid, side effects/complications, pain ratings, McGill Pain Questionn aire, Beck Depression inventory, Oswestry Disability Questionnaire, and pat ient estimated improvement in pain (0-100%). Generic measures of health inc luded the Quality of Well-Being Scale, Medical Outcomes Study MOS) Short Fo rm 36 (SF-36), return to work, patient estimated improvement in functioning , overall patient satisfaction, and family opinion of patient improvement. Results: Disease-specific outcomes. Patients receiving long-term intratheca l opioid administration showed a sixfold increase in morphine equivalents i nfusion rates across dme. DAS patients showed a small but significant decre ase in pain ratings from pre treatment levels. Following 3 years or more of intrathecal opioid infusion, patients endorsed high pain levels on the McG ill Pain Questionnaire, severe levels of disability via the Oswestry Disabi lity Questionnaire, mild levels of depression based on the Beck Depression Inventory, and multiple side effects associated with the intrathecal opioid s and complications related to the infusion system. On retrospective questi oning, patients receiving long-term intrathecal opioid administration repor ted an average of 64% improvement in their pain and 48% improvement in func tioning. Family members of patients reported that they observed on average a 61% improvement in patient's pain. Generic outcome measures. On the Quali ty of Well-Being Scale, patients reported significantly lower health-relate d quality of life than health maintenance organization enrollees with no kn own chronic condition and patients with rheumatoid arthritis (p ( 0.001). O n the MOS SF-36, patients reported significantly lower physical functioning than the U.S. general population, patients with uncomplicated medical cond itions, diabetes-type II patients, and congestive heart failure patients. M ental functioning was comparable to the U.S. general population (p > 0.001) . Fourteen percent of patients were working following implantation. Eighty- nine percent of patients reported good to excellent satisfaction with the l ong-term, intrathecal opioid therapy. Conclusions: Results from this study revealed differences in findings acros s the outcome measures, highlighting die complexity of intrathecal opioid t herapy. Generally, patients after 3 years or more of intrathecal opioid the rapy can be characterized as having substantially impaired physical functio ning with a high prevalence of side effects. Despite poor physical function ing, patients endorsed relatively good mental health status with only mild depressive symptoms. Longitudinal pain ratings showed a modest decrease fro m pretreatment levels. On retrospective evaluation, patients and their fami ly endorsed high levels of pain relief secondary to intrathecal therapy. Ov erall, findings support that intrathecal opioid therapy provides some thera peutic benefit although substantial physical impairment continues to cause debilitation in the patient population.