Effects of general anesthesia on plasma colloid oncotic pressure in dogs

Abstract

OBJECTIVE: To determine the magnitude of the change in colloid oncotic pressure (COP) associated with general anesthesia in dogs undergoing a variety of elective procedures. DESIGN: Cohort study. ANIMALS: 50 client-owned dogs. PROCEDURES: For each dog, preanesthetic and postanesthetic PCV, plasma total solids (TS) concentration, and COP were determined. The procedures requiring anesthesia, volume of crystalloid fluids administered IV, duration of anesthesia, age, weight, and sex were recorded. RESULTS: Postanesthetic PCV (mean +/- SD, 41.8 +/- 5.4%), TS concentration (6.3 +/- 0.8 g/dL), and COP (19.4 +/- 3.6 mm Hg) were significantly decreased, compared with preanesthetic values (48.8 +/- 5.9%, 7.2 +/- 0.7 g/dL, and 24.4 +/- 4.2 mm Hg, respectively). None of the variables tested could be used to reliably predict changes in COP. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that COP in healthy dogs may decrease by 5 mm Hg on average after general anesthesia and that this decrease may not be reliably predicted by the volume of fluids administered IV during anesthesia or by the concurrent measured decrease in TS concentration.