How much fluid is too much during anesthesia?

Routine anesthesia fluid plans are getting a more explicit reality check. In a dvm360 article, Lydia Love, DVM, DACVAA, argues that clinicians should think in terms of plasma volume, not just hourly drip rates, when deciding how much IV fluid is enough during anesthesia. Her practical benchmark: plasma volume is roughly 45 to 50 mL/kg in dogs and cats, so once a patient has received about 15 to 20 mL/kg, it's worth reassessing whether more fluid is actually needed, and approaching 30 mL/kg should raise concern for overexpansion and hemodilution in routine cases. That framing aligns with the 2024 AAHA Fluid Therapy Guidelines, which recommend lower starting intraoperative crystalloid rates, 5 mL/kg/hr in dogs and 3 to 5 mL/kg/hr in cats, and advise reevaluation if total fluids exceed 20 mL/kg during a single anesthetic episode. (aaha.org)

Why it matters: For veterinary teams, this is less about a new rule than a shift in mindset. The older default of “surgical fluids” at 10 mL/kg/hr has been steadily moving out of favor because evidence hasn't supported routine high-volume administration in healthy patients, and excessive crystalloid use can contribute to tissue edema, chemosis, nasal discharge, pulmonary crackles, lower oxygen saturation, and misleading assumptions that hypotension is a volume problem instead of an anesthetic-depth or vasodilation problem. In day-to-day practice, the takeaway is to track cumulative volume during the procedure, match fluids to the patient's actual deficits and losses, and reassess earlier, especially in cats and small dogs with less room for error. (aaha.org)

What to watch: Expect this plasma-volume framing to show up more often in anesthesia protocols, CE, and monitoring discussions as practices continue aligning with AAHA's 2024 fluid guidance and newer anesthesia-monitoring recommendations. (aaha.org)