Use of a heated anesthetic circuit decreases heat loss compared to a nonwarmed circuit in anesthetized New Zealand white rabbits (Oryctolagus cuniculus)

Objective: To evaluate the effect of a commercially available heated anesthetic circuit (HAC; Heated ZDS Qube; Darvall) on body temperature in anesthetized New Zealand white rabbits (Oryctolagus cuniculus). Methods: Rabbits were anesthetized in a research facility over approximately 2 weeks in a randomized, complete crossover design (June 4 to 13, 2024). Each animal was sedated, then anesthetized with isoflurane twice (7-day washout) with a warmed (W) or nonwarmed (NW) HAC. Once intubated, the HAC was connected and preheated (43.3 °C) for W or off (room temperature) for NW events. Temperature (rectal and 2 esophageal modalities) was recorded every 5 minutes under anesthesia. At 60 minutes, anesthesia was discontinued. Once responsive, the animal was moved to an incubator (29.4 °C). Rectal temperature was recorded every 30 minutes until normothermic (≥ 38 °C). Statistical analysis included descriptive statistics, paired t tests, and a linear mixed-effects model, with significance at P < .05. Results: 10 healthy approximately 4-month-old intact male rabbits were included. Hypothermia (≤ 37.9 °C) occurred in 10 of 10 NW and 7 of 10 W events. Temperature decreased linearly with anesthesia time in all events. Mean W temperatures were significantly higher than NW at all time points; rectal (regression coefficient, -0.19; 95% CI, -0.26, -0.12), Darvall esophageal (-0.40; 95% CI, -0.49, -0.31), and Vmed esophageal temperature (-0.31; 95% CI, -0.38, -0.23). Conclusions: This HAC may be useful for minimizing perianesthetic hypothermia in rabbits. Clinical Relevance: Hypothermia is a common anesthetic complication in rabbits. Determining effective methods to minimize perianesthetic heat loss is critical.