Equivalency Between the Shock Index and Subtracting the Systolic Blood Pressure From the Heart Rate: An Observational Cohort Study

Abstract

Background: Although the shock index is known to predict mortality and other severe outcomes, deriving it requires complex calculations. Subtracting the systolic blood pressure from the heart rate may produce a simple shock index that would be a clinically useful substitute for the shock index. In this study, we investigated whether the simple shock index was equivalent to the shock index.Methods: This observational cohort study was conducted at 2 tertiary care hospitals. Patients who were transported by ambulance were recruited for this study and were excluded if they were aged <15 years, had experienced prehospital cardiopulmonary arrest, or had undergone inter-hospital transfer. Pearson’s product-moment correlation coefficient and regression equation were calculated, and two one-sided tests were performed to examine their equivalency. Results: Among 5,429 eligible patients, the correlation coefficient between the shock index and simple shock index was extremely high (0.917, 95% confidence interval 0.912 to 0.921, P <.001). The regression equation was estimated as sSI = 258.55 log SI. The two one-sided tests revealed a very strong equivalency between the shock index and the index estimated by the above equation using the simple shock index (mean difference was 0.004, 90% confidence interval 0.003 to 0.005). Conclusion: The simple shock index strongly correlated with the shock index.

Initial Pulse Pressure and Shock Index Predict Mortality in Burn Patients

“…An abnormal shock index can serve as early identi er of patients that require prioritization for medical care. In fact, studies have demonstrated that SI as compared to traditional vital signs is superior at early identi cation and predicting mortality outcomes in at risk patients 15 . Evidence has shown that normal SI range is 0.5-0.7, with 0.9 accepted as the upper limit of normal 20 .…”

“…SI is calculated by dividing the heart rate (HR) by the systolic blood pressure (SBP), with a normal range currently accepted as 0.5-0.7 in healthy adults with evidence suggesting that values up to 0.9 are within the upper limit of normal; however, poorer outcomes associated with SI values ≥ 1.0 are indicative of worsening hemodynamic status and occult shock. Due to the nature of its linear inverse relationship with hemodynamic parameters including cardiac index, stroke volume, left ventricular stroke work and mean arterial pressure 14 , SI has been demonstrated to predict mortality and other severe outcomes including the necessity of intensive care unit admission and need for blood transfusion in trauma, postpartum hemorrhage, acute myocardial infarction, stroke and septic patients 15 ; however, its role in predicting mortality outcomes in burn victims remains unknown.…”