Section 1: Introduction and Fluid Therapy Definitions
Fluid therapy is a common aspect of veterinary patient care, required for a wide range of clinical conditions spanning from relatively mild cases (e.g., short-term inadequate voluntary intake from acute gastritis) to more moderate conditions (e.g., chronic kidney disease) to life-threatening emergencies (e.g., substantial volume loss and shock).
When prescribed and administered correctly, fluid therapy can be one of the most beneficial treatments available in veterinary medicine. However, achieving desired therapeutic outcomes, rather than administering fluids with no effect or that worsen the problem, requires an understanding of the physiologic factors that influence body fluid movement and electrolyte balance. Refining this knowledge to create tailored therapeutic plans for each patient can be challenging, yet it proves to be a satisfying endeavor in enhancing patient recovery.
These guidelines offer an overview of the body’s fluid dynamics and provide practical recommendations for selecting fluids, calculating administration rates, and choosing administration routes in dogs and cats for the purposes of resuscitation, rehydration, and maintenance.
The guidelines also cover fluid therapy recommendations for anesthetized patients, patients with common conditions, and those with disorders presenting special fluid therapy challenges. Additionally, these guidelines detail patient monitoring parameters, highlight methods to prevent fluid overload, describe fluid delivery options, and address controversies and misconceptions in fluid therapy. Online resources include case examples and answers to frequently asked questions.
Fluid Therapy Definitions
Dehydration—A condition in which the body loses more fluids than it takes in, resulting in an imbalance of water and electrolytes.
Euvolemia/euvolemic—Normal balance and distribution of total body water.
Fluid overload/fluid intolerance—A clinical spectrum that spans from hypervolemia to life-threatening edema and cavitary effusions.
The guidelines task force has proposed that fluid intolerance may be the more appropriate term for this condition, as this term more accurately describes how the amount of fluid needed to overload a patient is dependent on their tolerance for a given amount of fluids. “Fluid intolerance” thus encompasses both iatrogenic overload and overload due to underlying comorbidities. However, given that “fluid overload” is still widely used and recognized within the veterinary medical profession, it will be the primary term used in these guidelines to refer to this condition.
Hypervolemia/hypervolemic—Increased fluid volume within the vascular space. Hypertension is not usually an indication of hypervolemia (except when renal disease is present).
Hypovolemia/hypovolemic—Decreased fluid volume within the vascular space.
Maintenance fluids—Crystalloid solutions formulated with electrolyte concentrations to meet a patient’s daily requirements.
Replacement fluids—Crystalloid fluids intended to replace lost body fluids and electrolytes.
Total body water—The total amount of water contained in three mammalian body compartments: intracellular (67%) and extracellular
(33%), which is further divided into interstitial (25%) and vascular (or intravascular) (8%) spaces.