[Fluid therapy in the dog and the cat]

Underlying principle for fluid therapy is the knowledge about distribution of body water (60% of body weight) into compartments: intra- and extracellular fluid (ICF, ECF) cover respectively one half, one sixth of the latter fills the intravascular system. According to the concentration of ions and molecules in the lost fluids, dehydration is classified into hypertone, hypotone and isotone. Clinical assessment and laboratory examination (PCV, hemoglobin, total protein, urine analysis, electrolyte and blood gas evaluation) are crucial features for determination of dehydration rate, acid-base and electrolyte imbalances. Derangements of body-fluid and electrolyte metabolism and their treatment are discussed. The quantity of fluids necessary for rehydration of the patient is calculated on the basis of clinical findings. Overhydration risk has to be considered more seriously in cats than dogs. Intravenous, subcutaneous, oral and intraperitoneal infusions are feasible. A survey to technical aspects and required instruments is presented in conclusion.