The Shock index (SI) is calculated as follows:

𝑺𝑰=𝑯𝑹/𝑺𝑷

HR – Heart rate

SP – Systolic blood pressure

normal range: 0.5 to 0.7

SI upon emergency department arrival may be considered a clinical indicator of hypovolemic shock in respect to transfusion requirements, hemostatic resuscitation and mortality. 

In daily clinical practice, SI may be used to assess the presence of hypovolemic shock.

If SI>=1, lactate (ID 33) should be monitored.

1) https://read.qxmd.com/read/8092595/a-comparison-of-the-shock-index-and-conventional-vital-signs-to-identify-acute-critical-illness-in-the-emergency-department?redirected=slug

2) Shock Index and Early Recognition of Sepsis in the Emergency Department: Pilot Study