shock index
Also written as: SI
A calculated ratio of heart rate to systolic blood pressure used to assess hemodynamic status in trauma and critically ill patients.
Full Definition
Shock index is a simple physiological parameter calculated by dividing heart rate by systolic blood pressure (HR/SBP). Normal shock index ranges from 0.5 to 0.7, with values greater than 0.9 suggesting significant volume loss or cardiogenic shock. In trauma patients, an elevated shock index may indicate occult shock before traditional vital signs become abnormal, making it a useful early indicator of hemodynamic compromise. The parameter is particularly valuable because it can identify patients at risk for massive transfusion and poor outcomes. Modified shock index incorporates additional factors such as age to improve predictive accuracy. The calculation is simple enough to perform mentally at the bedside, making it practical for rapid clinical assessment.
Usage
Usage note: Values >0.9 are considered abnormal and suggest hemodynamic compromise.
In Context
- "The patient's shock index of 1.2 indicated significant hemodynamic compromise despite normal blood pressure." — Emergency medicine assessment
- "Serial monitoring of shock index can help identify early hemodynamic deterioration in trauma patients." — Critical care documentation