The shock index is used clinically to determine the presence and severity of shock. The shock index is calculated by dividing the patient’s pulse rate by the systolic blood pressure. An increase in pulse rate occurs before a decrease in blood pressure; it is an early diagnostic indicator of shock. After treatment of a patient in shock. Although the blood pressure is still low, but if the pulse rate has fallen to near normal and limb warmth, often indicates that the shock has tended to improve. Shock index, to help determine the presence or absence of shock and the severity of shock. <0.5 mostly indicates no shock; >1.0-1.5 has shock; >2.0 is severe shock.