Warmed IV fluids may slow heat loss in anesthetized horses

A new Equine Veterinary Journal report adds some much-needed evidence to a familiar equine anesthesia practice: warming intravenous fluids. Researchers led by Miranda Starr and colleagues at the University of Pennsylvania’s New Bolton Center found that warmed IV fluid administration attenuated body temperature loss in anesthetized horses, even though it didn’t fully prevent hypothermia. The study suggests fluid warming may offer a modest but measurable benefit in a species where preventing peri-anesthetic heat loss remains challenging. (beva.onlinelibrary.wiley.com)

That matters because peri-anesthetic hypothermia is a well-recognized complication of general anesthesia in horses, and it’s associated with prolonged recovery, delayed coagulation, and impaired wound healing. Existing evidence for equine warming strategies is relatively sparse. The EVJ paper notes that low operating theater temperatures, cold surfaces, and body surface wetness all contribute to heat loss in horses, while prior equine work has shown some benefit from forced-air warming and limb bandaging, but not a broad menu of well-validated options. (beva.onlinelibrary.wiley.com)

In the new study, six healthy adult horses underwent anesthesia twice in a prospective, randomized crossover design. Investigators compared fluids delivered through an activated versus inactivated HOTLINE blood and fluid warmer, while recording core temperature at four anatomic sites and measuring fluid temperature at multiple points in the delivery system. Overall core temperature differences between groups were statistically significant but not clinically meaningful on their own. The more important finding was the time-by-warmer interaction: warmed fluid administration significantly reduced the rate of temperature decline, with a reported beta coefficient of 0.0033°C per minute and a p value of 0.0004. The authors concluded that the device increased delivered fluid temperature and provided a modest protective effect against hypothermia. (d197for5662m48.cloudfront.net)

The study also comes with important caveats. The authors list a small sample size, environmental variability, and the absence of a surgical procedure among the main limitations. That means the findings are best read as proof of physiologic effect, not yet proof that warmed fluids alone will materially change recovery quality or complication rates in a broader surgical population. Even in the warmed-fluid setting, horses still became hypothermic over time. (beva.onlinelibrary.wiley.com)

The broader literature supports that interpretation. The EVJ authors note that warmed fluids alone are generally insufficient to maintain normothermia in anesthetized patients, which aligns with findings in human and small animal medicine. In equine practice, fluid administration is routine for hemodynamic support during anesthesia, and adult horses may receive substantial volumes, making fluid temperature a relevant variable. Reference sources in equine medicine also note that fluids warmed at the bag can cool substantially through the administration set, which helps explain why distance-independent in-line warming systems may be more useful than simply starting with a warm bag. (beva.onlinelibrary.wiley.com)

Why it matters: For equine veterinarians, anesthesiologists, and technicians, this study gives some evidence to support a common but lightly validated intervention. The practical message isn’t that fluid warmers solve peri-anesthetic hypothermia. It’s that they may slightly slow heat loss and fit best as part of a multimodal warming plan, particularly in referral hospitals managing longer procedures or higher fluid volumes. At New Bolton Center, where the large animal anesthesia service reports anesthetizing about 1,500 cases per year, the work also reflects the kind of operational questions large equine hospitals are trying to answer with data rather than habit. (beva.onlinelibrary.wiley.com)

No outside expert commentary or industry statement tied specifically to this paper was readily available in public sources at the time of writing. Still, the study’s framing is consistent with established anesthesia guidance: active warming methods can help, but logistics, patient size, and procedure setup often limit what’s feasible in horses. That makes incremental gains meaningful, even when they’re modest. (beva.onlinelibrary.wiley.com)

What to watch: The next step is likely larger clinical studies in surgical horses, ideally testing warmed IV fluids in combination with forced-air warming or passive insulation and tracking outcomes such as recovery quality, coagulation measures, wound healing, and time to normothermia. For now, this paper strengthens the case for fluid warming as an adjunctive tool, not a standalone answer. (beva.onlinelibrary.wiley.com)