Discrimination of Pain Intensity Level and Side Effects of Postoperative Pain using Parameters Extracted from Evoked Pain Pattern

The value of evoked potentials (EPs) in the clinical assessment of physiological function has been recognized for some time by those with specialized neurophysiological interests. Based on this concept, we have applied this novel technique for discrimination of pain intensity level and side effects using time-domain parameters extracted from the evoked pain pattern (EPP) in postoperative pain via patient-controlled analgesia (PCA). In conventional PCA systems, each delivery is similar to evoked pain stimulation, and we then count the following demands in a lockout interval. Therefore, the EPP is calculated and averaged from several lockout intervals in a period of time. From this calculation, the evoked parameters of area, latency, and amplitude of each period of time can be easily extracted. A total of 741 cases from 1519 patients at a medical centre have been screened and compared with these three parameters using different visual analog scales (VAS) and side effects (SE). The results indicate that the area parameter is a good indicator for higher VAS patients and the variance of latency parameter is a better outcome for interpreting the patients with side effects. However, the amplitude parameter shows no significant differences in both VAS and SE groups.