• assessment;
  • dehydration;
  • packed cell volume;
  • plasma total solids


Objective: To characterize the relationship between clinical estimates of hydration in dogs and cats admitted to an intensive care unit (ICU) and changes in their body weight following 24–48 hours of fluid therapy.

Design: Outcome study.

Setting: ICU at a veterinary teaching hospital (VTH).

Animals: A total of 151 dogs and 42 cats with various medical disorders that had not had surgery within 48 hours of admission into the ICU were consecutively admitted into the study. Animals with any condition predisposing to excess fluid loss or retention were excluded: heart disease, sepsis, trauma, pancreatitis, pleural or pericardial effusion, ascites, and pathologic oliguria. Animals that acquired any of the following during the observation period were excluded: gastrointestinal fluid loss, edema or diseases predisposing to edema, oliguria, diuretic therapy, and body fluid drainage or hemorrhage. Fluid therapy was ordered based on estimate of hydration at admission. Other treatments were not modified or withheld.

Interventions: Physiologic data were collected at the time of admission and 24–48 hours later.

Measurements and main results: Hydration was estimated on admission to the ICU using clinical judgement with no supporting laboratory data. Each admitting clinician used this estimate to plan fluid therapy. Fluid therapy was defined as the administration of any enteral or parenteral fluids as well as any decision to withhold fluids. Paired measurements taken on admission and at 24–48 hours included packed cell volume (PCV), total plasma solids (TS), and body weight. Amount and type of fluids or blood products administered were noted. Neither clinician estimates of dehydration nor baseline PCV or TS predicted clinically significant changes in body weight following fluid therapy, and there was no relationship between weight change and changes in PCV or TS.

Conclusions: A clinical diagnosis of dehydration in our ICU does not predict weight gain following fluid therapy. Neither baseline PCV/TS nor changes in these measurements following 24–48 hours of fluid therapy predicted changes in body weight.