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ANALGESIA

Patient-Controlled-Analgesia Analgesimetry and Its Problems

From the Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.

Address correspondence and reprint requests to Igor Kissin, MD, PhD, Pain Research Center, Brigham and Women's Hospital, 75 Francis St., MRB611, Boston, MA 02115. Address e-mail to kissin{at}zeus.bwh.harvard.edu.

Abstract

In addition to providing pain relief, patient-controlled-analgesia (PCA) is also extensively used in clinical research for the assay of analgesic effectiveness of new drugs and methods of pain treatment. The main outcome measure of PCA analgesimetry is the difference in opioid requirements between the control (placebo) group and the new drug (or treatment) group. The following potential problems of PCA analgesimetry are analyzed: 1) weak correlation between pain intensity and opioid consumption, 2) interference of nonanalgesic effects of opioids, 3) role of acute tolerance to the analgesic effect of opioids, 4) problems of the patient's training, 5) interaction between main outcome measures, and 6) sample size and negative outcome problems. Knowledge of the pitfalls of PCA analgesimetry should decrease the risk of errors in its use.