Objective: This study aimed to investigate the effects of IV ephedrine on heart rate (HR) and mean arterial pressure (MAP) in anesthetized hypotensive dogs and cats and whether the presence or absence of preemptive atropine could influence these effects. Methods: This single-center retrospective study collected the data of dogs and cats that received an initial single IV bolus of ephedrine during anesthesia. The cases were analyzed based on the species, presence or absence of preanesthetic atropine administration, and dose of ephedrine. Mean arterial pressure and HR before and after ephedrine administration; response rate to ephedrine (RRE), defined as the probability of MAP > 70 mm Hg after IV ephedrine administration, with/without atropine; and factors contributing to RRE were analyzed. Results: A total of 1,679 dogs and cats were analyzed. In dogs, IV ephedrine decreased the HR, but preanesthetic atropine prevented this decrease and increased the RRE. In cats, IV ephedrine did not decrease the HR and the RRE did not change significantly, regardless of preanesthetic atropine administration. Multivariate logistic regression analysis revealed that the significant factors contributing to RRE were MAP before ephedrine administration and atropine premedication in dogs and MAP before ephedrine administration in cats. Conclusions: In anesthetized dogs, preemptive atropine enhanced the blood pressure–increasing effect of ephedrine by preventing decreases in HR. In anesthetized cats, IV ephedrine with/without atropine increased MAP without decrease in HR. Clinical Relevance: When IV ephedrine is used for treating hypotension during anesthesia, preemptive atropine is recommended in dogs but has less clinical significance in cats.

Objective: To evaluate arterial blood gas analysis (ABGA) findings in dogs with myxomatous mitral valve disease (MMVD), and to examine their association with echocardiographic and thoracic radiographic findings. Methods: In this single-center retrospective study (April 2022 to March 2024), thoracic radiography, echocardiography, ABGA, and blood pressure measurement were compared among 3 groups: the control group (without cardiac disease or with stage B1), stage B2, and stage C. In the stage B2 or C group, severity of MMVD was classified on the basis of the left atrium-to-aortic root ratio (LA:Ao; ≤ 2.0 vs > 2.0) and E-wave peak velocity (E max; ≤ 1.3 vs > 1.3 m/s). The ABGA was compared. Results: Among the enrolled dogs, 22 (90 examinations) were assigned to the stage B2 and C groups and 14 (14 examinations) to the control group. None of the dogs were diagnosed with pulmonary edema. Tracheal collapse and bronchomalacia were observed in many dogs, regardless of the group. Compared with the control group (79 mm Hg; minimum to maximum, 61 to 95 mm Hg), Pa o ₂ was significantly decreased in the stage B2 group (68 mm Hg; 39 to 100 mm Hg) and stage C group (63 mm Hg; 41 to 100 mm Hg). Dogs with E max > 1.3 m/s and LA:Ao > 2.0 (Pa o ₂ , 57 mm Hg; 39 to 84 mm Hg) had lower Pa o ₂ than those with E max < 1.3 m/s and LA:Ao < 2.0 (Pa o ₂ , 67 mm Hg; 51 to 100 mm Hg). Conclusions: Our findings revealed that dogs with stage B2 or C MMVD and concurrent respiratory disease exhibited hypoxemia. Clinical Relevance: ABGA is suitable for detecting hypoxemia that cannot be assessed by thoracic radiography; combined with echocardiography, it may contribute to the assessment of MMVD severity.

Ephedrine is used as a vasopressor in cats, but the hemodynamic effects of intravenous (IV) administration have not been characterized. This study evaluated the hemodynamic effects of IV ephedrine in 10 cats that developed hypotension during anesthesia. Cats received either saline (SE) or atropine (AE) before ephedrine for hypotension (mean arterial pressure < 60 mmHg). Hemodynamic variables were analyzed using a linear mixed-effects model. No significant differences were observed between groups in the response rate (defined as mean arterial pressure ≥ 65 mmHg after ephedrine administration; SE, 70%; AE, 80%) or the duration of the pressor response (SE, 4 [1–10] min; AE, 3 [1–5] min). A significant main effect of ephedrine administration was identified for the systemic vascular resistance index, with increases observed in both groups, reaching statistical significance in the AE group. Significant interaction effects were observed for heart rate and cardiac index, both of which increased significantly in the AE group. These findings indicate that the pressor effect of IV ephedrine in anesthetized hypotensive cats is mediated primarily by increasing systemic vascular resistance index. Ephedrine provides a rapid and reliable pressor response and may be considered an early treatment option for anesthesia-induced hypotension in cats.