Assessment of shock index in healthy cats and in cats presenting to an emergency room with shock.

Abstract

OBJECTIVE: To prospectively compare the shock index (SI) in a population of healthy cats with a population of cats presenting to the emergency room (ER) deemed to be in a state of shock. DESIGN: Prospective cohort study of cats. SETTING: University teaching hospital. ANIMALS: Twenty-seven healthy control cats were enrolled to establish a reference interval, and 27 cats were enrolled that were presented to the ER with clinical signs of shock. Shock was defined as abnormalities in at least 2 of the following inclusion criteria: plasma lactate concentration > 2.5&#xa0;mmol/L; peripheral vasoconstriction (at least 2 of the following parameters: capillary refill time >3&#xa0;s, rectal-interdigital temperature gradient [RITG] >8&#xb0;C, femoral pulse not palpable, pale mucous membranes); or systolic blood pressure (SBP) < 100&#xa0;mm&#xa0;Hg. INTERVENTIONS: Upon presentation, SI (SI&#xa0;=&#xa0;heart rate [HR]/SBP), HR, SBP, and RITG were recorded in both groups, along with peripheral venous blood sampling for lactate measurement. MEASUREMENTS AND MAIN RESULTS: The mean SI in the control group was 1.47&#xa0;&#xb1;&#xa0;0.2 and was 1.87&#xa0;&#xb1;&#xa0;0.47 in the shock group (P&#xa0;=&#xa0;0.001). Using equality in sensitivity and specificity of 0.7, an SI cutoff point of 1.54 (95% confidence interval [CI]: 0.49-0.86) was determined with an estimated area under the receiver operating characteristic curve of 0.78 (95% CI: 0.65-0.90). HR, plasma lactate concentration, and RITG did not differ between the groups. Systolic arterial blood pressure (P&#xa0;=&#xa0;0.01), rectal temperature (P&#xa0;=&#xa0;0.02), and interdigital temperature (P&#xa0;=&#xa0;0.04) differed significantly. CONCLUSIONS: The SI is a noninvasive, easy, and reliable parameter for distinguishing cats in shock from normal cats.