Complementary value of the Shock Index v. the Modified Shock Index in the prediction of in-hospital intensive care unit admission and mortality: A single-centre experience

BACKGROUND: Shock is a state of circulatory insufficiency that creates an imbalance between tissue oxygen supply and demand, resulting in end-organ dysfunction and hypodynamic circulatory failure. Most patients with infectious and trauma-related illnesses present to the emergency department (ED) in shock. OBJECTIVES: To study the usefulness of the shock index (SI) and modified shock index (MSI) in identifying and triaging patients in shock presenting to the ED. METHODS: This was a year-long observational, cross-sectional study of 290 patients presenting to the ED of a tertiary hospital in compensated or overt shock. The SI and MSI were calculated at the time of first contact, and then hourly for the initial 3 hours. Relevant background investigations targeting the cause of shock and prognostic markers were done. The outcome measures of mortality and intensive care unit admission were documented for each participant. RESULTS: The mean age of the participants was 49 years, and 67% of them were men. In consensus with local and national data, the major medical comorbidities were hypertension (20%) and diabetes mellitus (16%). An SI ≥0.9 and an MSI ≥1.3 predicted in-hospital mortality (p<0.05) and ICU admission (p<0.05) with no significant superiority of the MSI over the SI in terms of mortality, although the MSI was a better surrogate marker for critical care admission. CONCLUSION: The study showed the complementary value of the SI and MSI in triage in a busy tertiary hospital ED, surpassing their components such as blood pressure, heart rate and pulse pressure. We determined useful cut-offs for these tools for early risk assessment in the ED, and larger multicentre studies are needed to support our findings. STUDY SYNOPSIS: What the study adds. The study highlights the usefulness of clinical bedside tools such as the shock index (SI) and modified shock index (MSI) in triaging patients in the emergency department, and their role in predicting morbidity and mortality. Implications of the findings. Compared with systolic blood pressure, diastolic blood pressure and mean arterial pressure, alone or in combination, the SI and MSI had higher sensitivity and specificity in terms of outcome prediction. While both an elevated SI and an elevated MSI predicted in-hospital mortality, the MSI was a better surrogate marker for ICU admission.