Careful preoperative screening of candidates for indwelling drug administration systems for the relief of intractable pain can help to exclude patients who will not benefit from this technology and predict efficacy in others. Unfortunately, bias on the part of both the treating physician and the patient can inappropriately skew the results of subjective or improperly controlled trials and lead to the implantation of drug administration systems in patients who will not benefit from chronic intrathecal narcotic administration.
The author and his coworkers have designed a quantitative, crossover, double-blind paradigm for screening patients who might otherwise be deemed eligible for chronic intraspinal narcotic administration. This paradigm has been used 31 times in 30 patients; based on the outcome of this testing, 22 patients (73%) underwent implantation of chronic infusion systems. Sixteen (80%) of 20 patients with pain related to cancer underwent pump implantation, whereas only six (60%) of the 10 patients with pain of nonmalignant origin were so treated. Sixteen of the patients (72%) have reported good to excellent relief after pump implantation; this includes 12 (75%) of the 16 patients with pain related to cancer and four (66%) of the six patients with pain of nonmalignant origin.
This screening paradigm thus appears to be both reliable and easily applied and promises to be of assistance in the selection of patients appropriate for this mode of therapy.
