Duration of clinical effects and absence of referred hyperalgesia after femoral vein cannulation in rats

The goal of this study was to assess the duration of pain-related clinical effects and referred hyperalgesia after surgery in rats. Isoflurane anesthesia with or without femoral vein cannulation was performed (n = 6 per group). Body weight and food and water consumption were monitored daily for 48 h, and tail-flick latency was measured twice daily for 24 h after surgery. Water consumption at 24 h after surgery was significantly decreased in the surgical group compared with baseline values and those of the anesthesia group. Body weight change and food consumption showed nonsignificant decreases compared with baseline in both groups 24 h after the procedure. There was a trend toward decreased food consumption after surgery compared with that for the anesthesia-alone group. Tail-flick latency was nonsignificantly decreased the afternoon after surgery compared with baseline values or that after anesthesia alone. Tail-flick latency was similar to baseline and between groups 24 h after surgery. All parameters were similar between groups and compared with baseline by 48 h after surgery. Our results show some changes in postsurgical pain-related parameters only during the initial 24-h period after femoral cannulation surgery, but only the change in water consumption was significant. Although this study involved only a small number of animals, our findings suggest that femoral vein cannulation produces a less painful stimulus than that seen in studies assessing these parameters after abdominal surgery. Hyperalgesia from a distant painful stimulus could not be measured in this model by using the tail-flick assay.