Shock index:
Shock index is defined as the heart rate divided by systolic blood
pressure. It has been studied in patients either at risk of or
experiencing shock from a variety of causes such as trauma, myocardial
infarction, hemorrhage, pulmonary embolism, sepsis, and obstetric
haemorrhage. Schroll R. Et al reported Shock Index ≥1 had a sensitivity
of 67.7% (95% CI 49.5%-82.6%) and specificity of 81.3% (95% CI
78.0%-84.3%) for predicting massive transfusion in trauma patients. In
obstetrics, Nathan et al reported that SI ≥ 1.7 had 25.0% sensitivity
(95% CI 5.5-57.2) and 97.7% specificity (CI 94.8-99.3), for predicting
ICU admission in postpartum haemorrhage.(13). Welsh et al reported SI de
0.9 as a good predictor of necessity for transfusion in postpartum
haemorrhage (14). This study determined that the value of the shock
index, dynamically evaluated, at the time of diagnosis, and 30 minutes
after diagnosis, allows early identification of those patients who
present massive bleeding with the sensitivity of 0.43 and specificity of
0.98 and 0.64 sensitivity and specificity 0.7 respectively. Our study’s
cut point did not differ much from other studies. As a general rule SI
> 1 is the predictor of adverse effects in most of the
clinical scenarios independent of the moment of its determination. At
initial phases of shock, the compensatory mechanism of the
cardiovascular system responds by increasing the heart rate, increasing
myocardial contractility and constricting peripheral blood vessels as a
result of the direct stimulation via the sympathetic system although
this compensatory mechanism makes the shock index an early indicator of
severe haemorrhage.