Work out shock index instantly with clear inputs, formula shown and shareable results.
Divides heart rate by systolic pressure to give the shock index, and by mean arterial pressure for the modified index.
Shock index
SI = heart rate / systolic BP; modified SI = heart rate / mean arterial pressure; normal SI is about 0.5 to 0.7
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
It rises before blood pressure falls, so it can flag occult hypoperfusion earlier than systolic pressure alone.
Obstetric haemorrhage work uses higher thresholds, commonly 0.9 to 1.7, because baseline physiology differs.