Study tests ultrasound-guided leg raise for fluid response in pigs: full analysis
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A newly published swine study points to a potentially practical way to assess fluid responsiveness without immediately reaching for a fluid bolus. In research published in the Journal of Veterinary Emergency and Critical Care on February 10, 2026, investigators reported that a modified passive leg-raising maneuver, interpreted with transthoracic echocardiography, identified fluid-responsive healthy pigs under sevoflurane anesthesia. The key signal was a rise in aortic velocity-time integral, with the authors reporting a predictive cutoff of 11.2% or greater. (deepdyve.com)
The work fits into a longer effort to adapt dynamic fluid assessment tools from human critical care into veterinary medicine. Passive leg raising has been used in people as a reversible “self-volume challenge,” temporarily shifting venous blood toward the thorax to see whether stroke volume rises. Reviews in human critical care have found good diagnostic performance when the maneuver is paired with real-time cardiac output surrogates, including echocardiographic measures, though they also emphasize that the test is technically sensitive and not foolproof. (ccforum.biomedcentral.com)
In veterinary medicine, this group’s 2026 paper appears to extend earlier experimental pig work rather than start from scratch. A 2019 American Journal of Veterinary Research study in healthy isoflurane-anesthetized pigs found that a modified passive leg-raising maneuver increased cardiac output during experimentally induced hypovolemia, but not during normovolemia or hypervolemia. That earlier study concluded the maneuver might help identify animals likely to respond to fluids, while also calling for validation in clinically ill patients. (pubmed.ncbi.nlm.nih.gov)
The new study adds transthoracic ultrasound guidance to that concept. Based on the available abstracting and indexing records, the investigators prospectively evaluated healthy, mechanically ventilated pigs anesthetized with sevoflurane and assessed whether the aortic velocity-time integral increased after the maneuver in fluid responders. Their reported finding — that a VTIAo increase of at least 11.2% could predict responsiveness — is important because it suggests a noninvasive echocardiographic readout may substitute for a direct fluid challenge in this tightly controlled setting. (deepdyve.com)
Independent expert reaction specific to this paper was limited in publicly accessible sources, but the broader literature helps frame its significance. Human critical care reviews describe passive leg raising as one of the more versatile dynamic tests for preload responsiveness, particularly because it is reversible and avoids committing the patient to fluid administration. Those same sources also note common caveats: echocardiographic measurement requires training, the hemodynamic response is transient, and accuracy can be affected by ventilation strategy, arrhythmias, and how precisely the maneuver is performed. (ccforum.biomedcentral.com)
Why it matters: For veterinary teams, especially those in anesthesia, emergency, and critical care, the study adds to a growing case for ultrasound-based hemodynamic assessment instead of relying on static measures or empiric fluid loading alone. If the signal holds up in clinical populations, a modified passive leg raise plus transthoracic echocardiography could become a useful way to identify which patients may actually benefit from fluids, and which may not. That matters because both under-resuscitation and over-resuscitation carry risk, and many practices are already investing in point-of-care ultrasound skills. Still, the current evidence remains preclinical: healthy pigs, controlled ventilation, and anesthesia are not the same as unstable dogs and cats with sepsis, hemorrhage, cardiac disease, or spontaneous breathing. (researchgate.net)
There’s also a practical implementation question. Even if the physiology translates, routine use will depend on whether general practitioners and ER clinicians can obtain reproducible aortic flow measurements quickly enough for the test to be useful at the bedside. That may make this more immediately relevant to referral hospitals, academic centers, and advanced anesthesia services than to every primary care clinic. That’s an inference based on the technical demands described in the echocardiography literature, rather than a conclusion stated directly by the study authors. (ccforum.biomedcentral.com)
What to watch: The real milestone will be follow-up studies in clinical veterinary patients, across species and disease states, that test whether this cutoff performs reliably outside the laboratory and whether it changes fluid therapy decisions or outcomes. Related veterinary work in dogs suggests the modified passive leg-raise concept is already being explored beyond pigs, so the translational pathway is clearly active. (pubmed.ncbi.nlm.nih.gov)