Assessment of shock index in healthy dogs and dogs in hemorrhagic shock

Objective To compare the shock index (SI) in a population of healthy dogs to a population of dogs with confirmed hemorrhagic shock. Design Retrospective analysis of data collected prospectively from 2 previous studies. Setting University teaching hospital. Animals Seventy‐eight healthy control dogs enrolled in a study to establish a reference interval for a tissue oxygen monitor; 38 dogs with confirmed hemorrhagic shock enrolled in a study to evaluate the tissue oxygen monitor in hemorrhagic shock. The heart rate and systolic blood pressure obtained during the respective studies were used to calculate the SI. Interventions None. Measurements and Main Results Shock index was significantly higher in the hemorrhage group (median 1.37, range 0.78–4.35) than the control group (median 0.91, range 0.57–1.53); 92% of the dogs in hemorrhagic shock had an SI of >0.91. Compared with controls, dogs in hemorrhagic shock had significantly lower body temperatures (median 38.3°C, range 35.6–39.9°C versus median 38.7°C, range 37.5–39.9°C), higher heart rates (median 150/min, range 120–220/min versus median 110/min range 80–150/min), lower systolic blood pressures (mean 112 mm Hg, SD ±35.8 mm Hg versus mean 125 mm Hg, SD ±21.5 mm Hg), higher lactate concentrations (median 0.51 mmol/L, range 0.078–1.41 mmol/L versus median 0.11 mmol/L, range 0.033–0.33 mmol/L), and lower hemoglobin concentrations (median 81 g/L, range 56–183 g/L versus median 162.5 g/L, range 133–198 g/L). Conclusions Shock index is a simple and easy calculation that can be used as an additional triage tool and should prompt further investigation for hemorrhage if the values are >0.9.