An observational study investigating the efficacy of heated general anaesthetic circuits during feline flank ovariohysterectomies

BACKGROUND: This pilot observational study evaluated the efficacy of the Humphrey ADE-heated general anaesthetic circuit (HGAC) in reducing perioperative inadvertent hypothermia (PIH) by assessing its mitigation of thermal decline in feline patients undergoing flank ovariohysterectomies (OVHs) under general anaesthesia (GA). METHODS: Perioperative rectal temperatures (RTemps) were collected from 20 cats undergoing OVH, with randomised allocation to either the standard general anaesthetic circuit (SGAC; control group) or the HGAC (experimental group). Statistical analyses were conducted using SPSS. RESULTS: The mean perioperative RTemps did not differ significantly between the HGAC and SGAC groups across the entire perioperative period. However, from 35 minutes onwards, RTemps were higher in the HGAC group than in the SGAC group, although the difference was not significant (p = 0.066). RTemps in the HGAC group fluctuated less and increased significantly and gradually as GA progressed (phase 2-3: p = 0.016; phase 1-3: p = 0.011), whereas RTemps in the SGAC group decreased significantly (phase 1-3: p = 0.034), becoming borderline hypothermic at approximately 50 minutes of operating time. LIMITATIONS: The study was limited by its small sample size, which is consistent with a pilot study, and by the involvement of multiple veterinary surgeons in performing the procedures. CONCLUSION: HGACs may be beneficial tools warranting further investigation in modern veterinary practice, with the potential to improve patient welfare standards by promoting normothermia.