The Effects of Sedation with Dexmedetomidine–Butorphanol and Anesthesia with Propofol–Isoflurane on Feline Grimace Scale(©) Scores

SIMPLE SUMMARY: A pain assessment is essential to provide appropriate pain relief. The Feline Grimace Scale(©) (FGS) is a facial expression-based acute pain scale used in feline medicine; increased FGS scores could indicate acute pain in cats requiring analgesia. However, it is unknown if some sedatives and/or anesthetics can bias pain assessment using the FGS. This study aimed to investigate the effects of sedation with dexmedetomidine-butorphanol followed by anesthesia with propofol-isoflurane on the FGS scores of healthy cats. The cats were video-recorded before and up to 24 h after sedation and general anesthesia. Images collected from the videos were randomized and scored independently by four raters who were masked to the treatments. Dexmedetomidine and butorphanol significantly increased the FGS scores at 20 min after administration. General anesthesia with propofol and isoflurane significantly increased the FGS scores at 0.5 h post-anesthesia, but not after. There were no other statistically significant findings. In conclusion, sedation with dexmedetomidine and butorphanol and general anesthesia with propofol and isoflurane increase FGS scores and may bias clinical pain assessment. Although the effects were short-lived, they should be taken into account during acute pain assessment. ABSTRACT: This study aimed to evaluate the effects of sedation and anesthesia on Feline Grimace Scale(©) (FGS) scores. Twelve healthy cats were included in a prospective, blinded and randomized, cross-over study with a 14 day wash-out. Saline or dexmedetomidine-butorphanol (Dex-But) was administered intramuscularly before an anesthetic induction with propofol and maintenance with isoflurane. Saline or atipamezole (Dex-But) was administered at the end of the general anesthesia. Video-filming/image capturing was performed before and up to 24 h post-anesthesia. A total of 125 images were evaluated by four raters blinded to the treatment groups using the FGS (ear position/orbital tightening/muzzle tension/whiskers change/head position; action units (AU); scores 0–2 for each AU). The effects of the sedation/anesthesia were analyzed (p < 0.05). The total FGS and each AU scores were significantly higher with Dex-But than with saline 20 min post-sedation. In the saline group, the total FGS, orbital tightening, and whiskers and head position scores were significantly higher than baseline at 0.5 h post-anesthesia. In the Dex-But group, the total FGS and each AU scores were significantly higher after sedation, whereas the orbital tightening scores were significantly higher at 0.5 h post-anesthesia when compared with the baseline. None of the other comparisons between or within the groups was significantly different. The sedation with dexmedetomidine-butorphanol and anesthesia with propofol-isoflurane changed the FGS scores on a short-term basis; consequently, they may bias acute pain assessment.