The clinical utility of shock index in hospitalised patients requiring activation of the rapid response team.

Background: The systolic shock index (SSI) is used to direct management and predict outcomes, but its utility in patients requiring rapid response team (RRT) activation is unclear.

Objectives: We explored whether SSI can predict the outcomes of ward patients experiencing clinical deterioration and compared its performance with other parameters.

Methods: This retrospective study included adult patients in medical/surgical wards who required RRT activation. We calculated SSI (heart rate/systolic blood pressure [BP]), diastolic shock index (DSI, heart rate/diastolic BP), modified shock index (heart rate/mean BP), and quick Sequential Organ Failure Assessment (qSOFA) score at activation. We categorised patients into two groups (SSI: ≥1.0 and <1.0). We performed univariate and multivariable logistic regression analyses to evaluate the association of SSI with intensive care unit (ICU) admission, vasopressor therapy, and in-hospital mortality. The covariates included demographics, comorbidities, and reasons for RRT activation.

Results: Among the 837 study patients, 297 (35.5%) had an SSI ≥1.0. On univariate analysis, SSI was associated with vasopressor therapy (odds ratio [OR]: 2.04, 95% confidence interval [CI]: 1.40-2.99) but not ICU admission or in-hospital mortality. On multivariable logistic regression analysis, an SSI ≥1.0 was associated with ICU admission (adjusted OR: 1.55, 95% CI: 1.05-2.28), vasopressor therapy (adjusted OR: 3.05, 95% CI: 1.86-5.00), and in-hospital mortality (adjusted OR: 2.18, 95% CI: 1.42-3.33). A systolic BP <90 mmHg, mean BP < 65 mmHg, and qSOFA score ≥2 were associated with these outcomes in univariate and multivariable regression analyses (adjusted ORs close to those of SSI). Separate receiver operating characteristic curve analysis found that SSI, diastolic shock index, and modified shock index poorly discriminated between survivors and nonsurvivors (area under the curve: <0.60 for all).

Conclusions: In ward patients experiencing clinical deterioration, an SSI ≥1.0 was associated with adverse outcomes but did not perform better than systolic and mean BP and qSOFA. This limits its standalone clinical utility in these patients.