Learning Track: 8. Acute Pain Management 
Title: Visual analogue scale cannot measure postoperative pain in an objective fashion, on the contrary, pain vision can measure postoperative pain in an objective way 
Author(s): Uchida M. 
Institute(s): Saitamaseikeikai Hospital, Dept of Anaesthesiology & Pain Medicine, Higashimatsuyama, Japan 
Text: Introduction: Visual analogue scale (VAS) is the common method for evaluating the degree of pain. However, the VAS consists of the patient's own subjective evaluations, so that there are large individual differences, and no quantitative analysis can be readily performed. In experimental trials, ketamine (ket) has been shown to reduce hyperalgesia, prevent opioid tolerance, and lower morphine consumption. However, in clinical trials in humans have shown mixed results in terms of effectiveness. To evaluate postoperative pain by using intravenous patient-controlled (IV-PCA) system with concomitant infusion of fentanyl (fen) and ket, we compared VAS to a pain vision. 
Methods: Anesthesia was performed with AOPRfK (air-oxygen-propofol-remifentanil-low dose ket) in orthopedic surgery. A PCA system was started after extubation. Patients were divided into three groups randomly and received different dosing regimens of co-administration of fen and ket by using PCA system. The infusion rate of fen was 0.5µg/kg/h in all groups. Group K0(n=21): patients were given only fen, Group K0.5 (n=21): fen + ket 0.5 mg/kg/day, Group K1.0(n=21): fen + ket 1.0 mg/kg/day. We evaluated patient´s condition in the night on the day of surgery. Pain was measured by using VAS (0-10, 0: no pain, 10: worst possible unbearable pain), degree of pain was measured by using PainVision® PS-2100 (OSACHI Co., Ltd., Nagano, Japan). Sedation Score was measured by using Richmond Agitation-Sedation Scale (RASS). Statistical analysis was performed by using Wilcoxon Singed-Rank Test in VASs, degrees of pain, and RASSs between GroupK0 vs. GroupK0.5, GroupK0 vs. GroupK1.0, and Groupk0.5 vs. Groupk1.0. p< 0.05 was considered to be statistically significant. 
Results: 
1) VAS: VASs were not significantly different among groups. 
2) pain degree analysis: Group K0 vs. GroupK0.5 p>0.05, Group K0 vs. GroupK1.0, and Groupk0.5 vs. Groupk1.0 p< 0.01. 3) RASS: RASSs were not significantly different among Groups. 
Discussion: Okuda T. et al. (1) reported that VAS expresses factors that include the patient's psychological state and dissatisfactions at a given time, rather than simply evaluating actual pain in the treatment of acute phase of herpes zoster. 
Conclusions: VAS cannot measure postoperative pain in an objective fashion, on the contrary, pain vision can measure postoperative pain in an objective way. 
Reference: The Japanese Journal of Dermatology 2005; 115: 2373-80

Visual analogue scale cannot measure postoperative pain in an objective fashion, on the contrary, pain vision can measure postoperative pain in an objective way