Intravenous fluid therapy is one of the
most important perioperative treatments veterinarians provide for their
patients. Intravenous fluids are considered a necessary part of the anesthesia protocol because of hypotension and vasodilation that can occur due to the anesthetic drugs.
All animals being prepared for anesthesia and surgery need to be
assessed for hydration status and disorders that create fluid losses, e.g.
vomiting and diarrhea. Intravenous fluid dosages will be influenced by the
animal’s current hydration and ongoing fluid losses. Intravenous fluid dosages
may also be affected by disorders that could predispose the animal to
over-hydration such as cardiac or renal disease.
The traditional intravenous fluid
rate for healthy animals under anesthesia has been 10ml/kg/hour.(1) In the
recent AAHA/AAFP fluid therapy guidelines, this recommendation has been
revised.(2) Table 4 from the paper describes current fluid therapy guidelines
for anesthetized cats and dogs:
Table: Recommendations for Anesthetic
Fluid Rates (from: 2013
AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats. Harold Davis, BA, RVT, VTS (ECC),
Tracey Jensen, DVM, DABVP, Anthony Johnson, DVM, DACVECC, et.al., J
Am Anim Hosp Assoc
2013; 49:149–159)
- Provide
the maintenance rate plus any necessary replacement rate at <10 mL/kg/hr
- Adjust
amount and type of fluids based on patient assessment and monitoring
- The
rate is lower in cats than in dogs, and lower in patients with cardiovascular
and renal disease
- Reduce
fluid administration rate if anesthetic procedure lasts 1 hr
- A
typical guideline would be to reduce the anesthetic fluid rate by 25% q hr
until
maintenance rates are reached, provided the patient remains stable
Rule of thumb for cats for initial
rate: 3 mL/kg/hr
Rule of thumb for dogs for initial
rate: 5 mL/kg/hr
Note that not only are the initial
fluid rates lower than the previously recommended 10ml/kg/hr, but a schedule for
gradual reduction of fluid rates as the anesthetic period progresses is also
recommended. These guidelines are considerably different from what was
previously thought to be necessary fluid rates for anesthetized animals, but
are based on carefully considered factors, evidence based medicine, and
clinical experience of board certified specialists.
References
1. Ann Weil, DVM, DACVAA. Anesthesia
reboot: Erase these myths and misconceptions. Veterinary Medicine, October 2014, pg. 318.
2. Harold Davis, BA, RVT, VTS (ECC),
Tracey Jensen, DVM, DABVP, Anthony Johnson, DVM, DACVECC, et.al. 2013 AAHA/AAFP Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc
2013; 49:149–159.
Questions:
What are your thoughts or opinions
about this change in recommended fluid dosage?
In private practice, in which
anesthetized patients do you typically run intravenous fluids; in all animals
or do you have some kind of selection criteria? In other words, what do you
think the standard of care should be for fluid administration under anesthesia?
Please post comments either here on the blog site or on my
facebook page:
Dr. Stephen Birchard, Veterinary Continuing Education
.
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