Study adds feline data on IV ephedrine during anesthesia

A newly published study in Veterinary Sciences offers fresh clinical data on intravenous ephedrine for cats that become hypotensive during general anesthesia for radiation therapy, a setting where repeated anesthetic events are common and blood pressure support matters. In 10 client-owned cats treated at Nihon University between April 2025 and April 2026, investigators found that IV ephedrine significantly increased systolic, mean, and diastolic arterial pressure. They also found no significant hemodynamic difference between cats given saline before ephedrine and those given atropine before ephedrine. (mdpi.com)

That matters because ephedrine is familiar in small animal anesthesia, but feline-specific evidence has been thin. The AAFP feline anesthesia guidelines define hypotension in cats at roughly mean arterial pressure below 60 mmHg, emphasize that blood pressure should be monitored closely, and note that ephedrine can be used when hypotension persists despite addressing anesthetic depth and giving appropriate fluids. Those same guidelines also caution that ephedrine may be less effective than some continuous-rate inotropes and can promote arrhythmias, underscoring the need for better species-specific data. (pmc.ncbi.nlm.nih.gov)

The new paper helps address that gap with a prospective crossover design in a real clinical population. According to the article summary, the cats were referred for radiation therapy and experienced hypotension during anesthesia. Each cat later received the alternate pretreatment in a second session, allowing the investigators to compare ephedrine’s effects with and without atropine in the same general cohort. The study reported a significant main effect of ephedrine on systolic, mean, and diastolic arterial pressure, while atropine pretreatment did not significantly alter that response. (mdpi.com)

The findings also line up with a related 2025 JAVMA retrospective analysis from the same research group. In that larger dataset of 1,679 dogs and cats, IV ephedrine increased mean arterial pressure in cats without decreasing heart rate, and the response rate did not change significantly with or without atropine premedication. By contrast, in dogs, atropine helped prevent ephedrine-associated heart rate decreases and improved the blood pressure response. Taken together, the newer prospective feline study appears to reinforce the idea that cats may respond differently from dogs when ephedrine is used to treat anesthetic hypotension. (pubmed.ncbi.nlm.nih.gov)

There’s also some useful historical context. An older study on prophylactic intramuscular ephedrine in cats and dogs found that ephedrine delayed, but did not prevent, anesthesia-induced hypotension in cats. That earlier work was about prevention rather than rescue treatment, so it doesn’t answer the same clinical question as the new IV study, but it shows how limited the feline evidence base has been for years. Meanwhile, broader feline anesthesia guidance has continued to rely on practical algorithms that start with reducing inhalant dose when possible, giving balanced fluids when appropriate, and then adding vasoactive support such as dopamine, dobutamine, or ephedrine if hypotension persists. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, the biggest value here is not that ephedrine is new, but that the evidence is becoming more cat-specific. Many anesthesia decisions in cats still depend on extrapolation from canine data, expert habit, or institutional protocol. This study suggests that if a hypotensive anesthetized cat needs IV ephedrine, atropine pretreatment may not be necessary just to preserve the pressor effect, unlike in dogs. That could matter in radiation therapy services, referral anesthesia, and any practice managing repeated anesthetic events in feline patients. At the same time, the study is small, single-center, and focused on a narrow clinical scenario, so it’s better viewed as practice-informing than practice-settling. (mdpi.com)

The study also arrives as feline anesthesia monitoring standards continue to emphasize tighter blood pressure surveillance and earlier intervention. The AAFP guidelines note that direct arterial pressure monitoring is the most reliable method, though often not practical in routine care, and recommend structured responses when mean arterial pressure drops below target. In that context, better evidence on how fast and how reliably common rescue drugs work in cats could improve protocol design, staff training, and case selection, especially for older cats or those with cardiac or renal comorbidities where fluid boluses may be less straightforward. (pmc.ncbi.nlm.nih.gov)

What to watch: The next step is external validation. Larger multicenter studies could clarify dose-response, duration of benefit, heart rate effects, arrhythmia risk, and how ephedrine compares with dopamine, dobutamine, phenylephrine, or epinephrine in different feline case types. For now, this paper strengthens the case that IV ephedrine can raise blood pressure in hypotensive anesthetized cats, and that atropine’s role in that response may be much smaller in cats than in dogs. (mdpi.com)