Modified shock index formula is:

Shock Index(SI) Modified Shock Index (MSI) SI is defined as hea rate divided by systolic BP Better marker for assessing severity of shock than hea rate & BP alone. Utility in trauma patients , sepsis, obstetrics, myocardial infarction, stroke & other acute critical illnesses. Correlated with need for interventions such as blood transfusion & invasive procedures including operations SI is known as a hemodynamic stability indicator Si does not take into account the diastolic BP MSI is defined as hea rate divided by mean aerial pressure High MSI indicates a value of stroke volume & low systemic vascular resistance, a sign of hypodynamic circulation Low MSI indicates a hyperdynamic state. MSI has been considered a better marker than SI for moality rate prediction. Ref: Sabiston 20th edition Pgno: 52