Is Shock Index a Valid Predictor of Mortality in Emergency Department Patients With Hypertension, Diabetes, High Age, or Receipt of β- or Calcium Channel Blockers?

Study objective: Shock index is a widely reported tool to identify patients at risk for circulatory collapse. We hypothesize that old age, diabetes, hypertension, and beta- or calcium channel blockers weaken the association between shock index and mortality. Methods: This was a cohort study of all first-time emergency department (ED) visits between 1995 and 2011 (n=111,019). We examined whether age 65 years or older, diabetes, hypertension, and use of beta- or calcium channel blockers modified the association between shock index and 30-day mortality. Results: The 30-day mortality was 3.0%. For all patients, with shock index less than 0.7 as reference, a shock index of 0.7 to 1 had an adjusted odds ratio (OR) of 2.9 (95% confidence interval [CI] 2.7 to 3.2) for 30-day mortality, whereas shock index greater than or equal to 1 had an OR of 10.5 (95% CI 9.3 to 11.7). The crude OR for shock index greater than or equal to 1 in patients aged 65 years or older was 8.2 (95% CI 7.2 to 9.4) compared with 18.9 (95% CI 15.6 to 23.0) in younger patients. beta- Or calcium channel-blocked patients had an OR of 6.4 (95% CI 4.9 to 8.3) versus 12.3 (95% CI 11.0 to 13.8) in nonusers and hypertensive patients had an OR of 8.0 (95% CI 6.6 to 9.4) versus 12.9 (95% CI 11.1 to 14.9) in normotensive patients. Diabetic patients had an OR of 9.3 (95% CI 6.7 to 12.9) versus 10.8 (95% CI 9.6 to 12.0) in nondiabetic patients. A shock index of 0.7 to 1 was associated with ORs greater than 1 (range 2.2 to 3.1), with no evident differences within subgroups. The adjusted analyses showed similar ORs. Conclusion: Shock index is independently associated with 30-day mortality in a broad population of ED patients. Old age, hypertension, and beta- or calcium channel blockers weaken this association. However, a shock index greater than or equal to 1 suggests substantial 30-day mortality risk in all ED patients.