Fuzzy Pain Demand Index from an I-Pain System for Assessment of Postoperative Pain Via Patient-Controlled Analgesia Using Different Amounts and Combination Drugs

Abstract

In our previous study, a novel fuzzy pain demand (FPD) derived from the interval of each bolus of patient- controlled analgesia (PCA) according to a fuzzy modeling algorithm can show the patients' dynamic demand and past efforts to overcome the postoperative pain. Hence, this study investigated whether FPD index can distinguish the analgesic efficacy using different amounts and combination drugs. Six hundred and seventy- nine patients with upper and lower abdominal, spinal, and extremity procedures receiving intravenous PCA were compared between morphine (1mg/ ml) alone and a combination of morphine (1mg/ml) and ketorolac ( 1.2mg/ml) in the postoperative setting of pain management. Moreover, we also compared the effect of dosage (1 ml versus 2 ml per delivery). The conventional parameters, standard mean drug consumption (MDC), demand/ delivery ratio (D/D ratio), and clinical observation pain using the visual analog scale (VAS) measured at rest and during movements, were compared with the FPD index. The FPD index demonstrated a better sensitivity than the D/D ratio in the morphine and ketorolac combination group than morphine alone, regardless of the dosage (1 versus 2 ml per delivery). Moreover, it also demonstrated a better sensitivity than the MDC at 1 ml per delivery but similar results at 2 ml per delivery. However, when the FPD index is compared with the VAS score in terms of most pain and rest pain, there is no any relationship between these two parameters' pattern. This result indicates that the FPD index can only assess the intensity of pain better than the D/D ratio and MDC but it cannot replace the VAS which is not entirely determined by the nociceptive stimuli but rather as a result of both sensory-discriminative and emotional-cognitive components of patient's suffering.