How much is too much during anesthesia fluid therapy?

Version 2

A dvm360 clinical article by Lydia Love, DVM, DACVAA, is putting a sharper point on a familiar anesthesia question: when does routine IV fluid support become too much? Love recommends using estimated plasma volume, about 45 to 50 mL/kg in dogs and cats, as a practical reference during anesthesia. In that framework, total delivered volumes above roughly 15 to 20 mL/kg should trigger a reassessment, and totals nearing 30 mL/kg deserve particular scrutiny for possible overhydration rather than automatic continuation. (cvm.ncsu.edu)

The article lands in a profession that has already been moving away from older, more liberal fluid practices. The 2024 AAHA Fluid Therapy Guidelines say the once-common 10 mL/kg/hr anesthesia rate lacked a strong evidence base, and point to the lower rates introduced in the 2013 guidance, 5 mL/kg/hr in dogs and 3 mL/kg/hr in cats, as the current starting point for patients with normal cardiac and renal function. AAHA also stresses that some short, uncomplicated anesthetic events in euhydrated, euvolemic patients receiving injectable anesthesia may not require IV fluids at all beyond catheter support. (aaha.org)

That context helps explain why Love’s plasma-volume framing is useful. It gives teams a simple mental model for total exposure over the course of a procedure, rather than focusing only on an hourly rate. A cat on fluids for a long dental, for example, can accumulate a clinically meaningful intravascular load even if the hourly rate seems modest. AAHA now explicitly recommends monitoring both anesthesia duration and total fluid volume, and says fluid plans should be reevaluated if rates surpass 20 mL/kg during a single anesthetic episode. (aaha.org)

The wider literature supports that caution. A review in Frontiers in Veterinary Science found that species-specific evidence remains limited, but concluded that goal-directed fluid therapy is preferable to rules of thumb or standardized formulas. The authors note that balanced crystalloids are generally the best first choice, that boluses should not exceed 20 to 30 mL/kg, and that treating anesthetic-associated hypotension with fluids alone is often ineffective, especially when vasodilation from anesthetic drugs is the real driver. In those cases, adjusting the anesthetic plan and considering vasoactive or inotropic support may be more rational than continuing to increase fluid volume. (pmc.ncbi.nlm.nih.gov)

AAHA’s updated guidance also gives clinicians a clearer checklist for identifying when “routine” fluid therapy is becoming excessive. Signs of overload include a gallop sound or new murmur, especially in cats, edematous tissues, chemosis, paw swelling, clear nasal discharge, pulmonary crackles, low oxygen saturation, pleural effusion, and ascites. If those signs appear, the guideline recommends stopping fluids or reducing them to catheter-patency levels, with furosemide considered in patients showing pulmonary edema or pleural effusion. (aaha.org)

Why it matters: For general practice, ER, and specialty teams, this is a practical reminder that fluid therapy during anesthesia should be treated like any other drug: it needs an indication, a dose, a monitoring plan, and a stopping point. That matters most in cats, geriatric patients, and animals with occult cardiac or renal disease, but it also applies to healthy routine surgery patients who can accumulate surprisingly large volumes over time. The larger shift here is cultural as much as clinical, away from “default fluids” and toward documenting cumulative volume, reassessing after each bolus or threshold, and teaching the whole perioperative team to recognize early signs of overload. (aaha.org)

There wasn’t clear standalone expert reaction tied specifically to Love’s dvm360 article in the public record I reviewed, but the direction of travel is consistent across major veterinary guidance and review literature: use lower starting rates, personalize the plan, and don’t assume hypotension equals fluid responsiveness. AAHA’s task force has similarly emphasized that fluid therapy should be tailored to clinical context, rather than applied with one-size-fits-all formulas. (aaha.org)

What to watch: The next step is likely not a single new cutoff, but broader adoption of perioperative protocols that track total mL/kg delivered, incorporate fluid-responsiveness monitoring where available, and prompt earlier anesthetic adjustment when blood pressure falls without clear evidence of hypovolemia. As the evidence base grows, expect more scrutiny of long-standing anesthesia fluid habits, particularly in cats and in longer “routine” procedures. (aaha.org)