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Shock index: a re-evaluation in acute circulatory failure
M Y Rady1, P Nightingale, R A Little
1Intensive Care Unit, University Hospital of South Manchester, UK.
Resuscitation
|June 1, 1992
Summary
The shock index (SI) effectively monitors left ventricular stroke work in hypovolemic and septic shock. However, SI has limited value for assessing oxygen transport in clinical septic shock.
Area of Science:
- Critical Care Medicine
- Hemodynamics
- Shock Pathophysiology
Background:
- The shock index (SI), a ratio of heart rate to systolic arterial pressure, is a simple yet informative hemodynamic parameter.
- Understanding its correlation with cardiac function and oxygen transport is crucial for managing circulatory failure.
Purpose of the Study:
- To evaluate the relationship between the shock index (SI) and cardiac function and oxygen transport.
- To assess SI's utility in experimental hemorrhage and clinical septic shock models.
Main Methods:
- Utilized an experimental model of 40% hemorrhage in anesthetized pigs.
- Analyzed hemodynamic and oxygen transport variables in normovolemic hyperdynamic septic patients in the ICU.
- Examined the correlation between SI and various physiological parameters.
Main Results:
- In hemorrhage, SI inversely correlated with cardiac index (CI), stroke volume (SV), mean arterial pressure (MAP), and left ventricular stroke work (LVSW).
- Oxygen delivery (DO2) and mixed venous oxygen saturation (SvO2) were also inversely related to SI during hemorrhage.
- In clinical septic shock, SI showed an inverse relationship with LVSW but not with CI, MAP, or oxygen transport variables.
Conclusions:
- SI serves as a valuable non-invasive tool for monitoring left ventricular stroke work changes during acute hypovolemic and normovolemic circulatory failure.
- The utility of SI in assessing systemic oxygen transport and therapeutic response in clinical septic shock appears limited.