DIFFERENCES AMONG PATIENTS IN OPIOID SELF-ADMINISTRATION DURING BONE-MARROW TRANSPLANTATION

The distinctive features of individual patients, here termed individua l differences, are inescapable aspects of day-to-day patient pain mana gement, but classically designed research studies ignore such differen ces. This paper introduces statistical pattern visualization methodolo gy for the study of complex individual differences in clinical setting s. We demonstrate the application of such methods in patients undergoi ng bone marrow transplantation (BMT) and suffering severe oral mucosit is as a consequence of the aggressive BMT preparative regimen. Oral mu cositis produces severe pain and patients often require parenteral opi oid medication for several weeks. Unfortunately, the opioid can cause side-effects that limit drug use for pain control. Patients differ in severity and duration of oral mucositis, analgesic response to opioids , and side-effects. We identified and classified individual difference s in patterns of drug use, pain control and side-effects in 33 BMT pat ients who received opioid drug via patient-controlled analgesia (PCA) systems for 7 days or more. These systems allowed bolus dosing and als o provided a basic level of analgesic protection through continuous dr ug infusion. Continuous infusion levels increased or decreased in resp onse to patient bolus self-administration. We employed statistical smo othing (moving average) techniques to remove random variation from the individual data sets and created three-way (trivariate) plots of chan ge over time in drug use, pain and an opioid side-effect (impairment o f concentration). The patterns apparent in these plots indicated that 24.2% of patients used PCA optimally (increases in drug use associated with reductions in pain and little or no side-effect), an additional 30.3% manifested a potentially optimal pattern limited by side-effect that worsened with dosing, and 36.4% used PCA suboptimally (modest pai n control plus side-effects). In addition, for each subject we created a summary measure for the simultaneous change in three variables: the distance of each day's trivariate score from the origin of a three di mensional plot. This summary measure correlated significantly with the changing severity of patients' oral mucositis over time (r = 0.502). This study demonstrates how interactive graphic techniques can provide a basis for examining changes over time among multiple, correlated va riables associated with a single individual. It illustrates the applic ation of such techniques and demonstrates that individual subject data sets merit examination in cases where clinical data reflect human per formance. (C) 1997 International Association for the Study of Pain. Pu blished by Elsevier Science B.V.