Evaluation of tissue oxygen saturation in naturally occurring canine shock patients

Objective: To measure tissue oxygen saturation (StO ₂ ) in a population of dogs with naturally occurring shock and to evaluate the relationship of StO ₂ with an established veterinary severity scoring system (Acute Patient Physiologic and Laboratory Evaluation) and patient survival. Design: Prospective observational study. Setting: University teaching hospital. Animals: Twenty-five adult dogs presenting in shock, as determined by the presence of hypotension, the calculated shock index, and hyperlactatemia. Interventions: StO ₂ was measured prior to any therapeutic interventions. Blood samples were also collected for measurement of plasma lactate, complete blood count, and a serum biochemical profile. Abdominal and thoracic focused assessment with sonography was also performed. Measurements and Main Results: Dogs enrolled in this study had lower mean (±SD) StO ₂ values (65.12 ± 17.7%) than previously reported in experimental models of canine hemorrhagic shock. There was a moderate correlation between lower StO ₂ and increasing Acute Patient Physiologic and Laboratory Evaluation scores. A single StO ₂ value, assessed prior to therapeutic intervention, was not a sensitive predictor of mortality in this population. Conclusions: Dogs with naturally occurring shock have lower mean StO ₂ values than those previously reported in dogs with experimentally induced shock. A lower initial StO ₂ was associated with worse disease severity but was not a significant predictor of survival in this population.