Comparison of Esophageal and Intranasal Temperature Measurement in Anesthetized Dogs

OBJECTIVE: To compare the accuracy of an intranasal thermometer with an esophageal thermometer for obtaining core body temperature in anesthetized dogs. DESIGN: Prospective single-center observational study. SETTING: Private referral veterinary hospital. ANIMALS: Seventy-three dogs undergoing anesthesia for elective procedures. INTERVENTIONS: Body temperature was measured using an intranasal thermometer and an esophageal thermometer. Results obtained by the two methods were compared. MEASUREMENTS AND MAIN RESULTS: A linear mixed-effects model showed a statistically significant difference between the two methods of measurement, with the intranasal method showing a mean temperature reading 0.2°C (0.3°F) lower than the esophageal method (95% confidence interval [CI]: 0.131-0.225, β = -0.27; p < 0.001). Covariates such as neuter status, body weight, age, or American Society of Anesthesiologists class did not influence temperature readings. A Bland-Altman plot showed a mean difference (bias) of -0.2°C (-0.3°F), with most differences falling within the limits of agreement (±1.3°C [±2°F]), emphasizing the clinically acceptable range of variation between the two methods. Post hoc analysis using a clinically acceptable margin of 0.5°C (0.9°F) showed that the intranasal method was clinically noninferior to the esophageal method, with a 95% CI showing a mean difference of 0.13°C-0.23°C (0.20°F-0.34°F). Equivalence testing confirmed that temperature differences between the two methods were within the clinical margin of ±0.5°C (±0.9°F). CONCLUSIONS: Although intranasal temperature measurement underestimates core body temperature by 0.2°C (0.3°F) (95% CI: 0.131-0.225) compared with esophageal measurement, the difference is generally clinically insignificant. Given that esophageal temperature is indicative of core body temperature, intranasal temperature measurement appears to be another reasonable surrogate for core body temperature measurement in anesthetized dogs.