Improved protocols
Traditional methods for monitoring perioperative intravenous fluid administration—measuring heart rate, arterial blood pressure,
and central venous pressure—are poor, generally unpredictable, and late indicators of blood volume changes or of the animal's
response to fluid administration (fluid responsiveness).23-26 Furthermore, differences in intravenous fluid electrolyte concentrations (strong ion difference), colloid composition, and
viscosity are now recognized as producing important acid-base, immunologic, and rheological effects that have important implications
for their therapeutic value.27-34
Anesthetic drugs and anesthetic depth are rarely considered in perioperative fluid protocols, but they are now known to have
a significant influence on factors that determine fluid distribution, elimination, and efficacy.35-37 Isoflurane anesthesia, for example, increases vascular capacitance, decreases urine production, promotes interstitial fluid
accumulation, and inhibits transcapillary refill after either normotensive or hypotensive hemorrhage.35
Four perioperative fluid therapy dilemmas
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These findings, coupled with concerns over the safety of crystalloid and colloid fluids used as replacement fluid therapy,
have led to impassioned debates about optimal perioperative fluid therapy practices.38-41 These debates highlight critical dilemmas (see sidebar "Four perioperative fluid therapy dilemmas") and have prompted the adoption of more "restrictive," " fast-track," "zero balance" (minimal or no weight gain), and "goal-directed"
fluid therapy protocols.3,26,42-46
Conclusion
Perioperative fluid therapy is equivalent to intravenous drug therapy and should be individualized and goal-directed.47-49 As discussed in the next article, each fluid's unique characteristics in relation to the anesthetic and surgical circumstances
for which it is prescribed should be considered.26,50 And, as discussed in the final article, fluid administration and monitoring should be unique to each animal's requirements.
ACKNOWLEDGMENTS
The author thanks Dava Cazzolli, DVM, DACVECC; Jaime Chandler, DVM, DACVECC; Michelle Albino, LVT, CVT (Anesth); and Yukie
Ueyama, DVM, for their assistance in abstracting data.
William W. Muir, DVM, MS, PhD, DACVA, DACVECC
VCPCS
338 W. 7th Ave.
Columbus, OH 43201
For this article's reference citations, go to http://dvm360.com/FluidTherapy1Refs.
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