**2. Pathophysiology**

Shock is a state of circulatory insufficiency creating imbalance between oxygen delivery and demand to the tissues, resulting in end-organ dysfunction. At the cellular level, shock first affects the mitochondria. Majority of the aerobic energy comes from combustion of substrates (carbohydrates and fats) along with oxygen, forming carbon dioxide and water. But in shock there is cellular hypoxemia; the tissues enter in anaerobic state and accumulate lactic acid. Lactate starts building up in the blood and acidosis develops [3].

Measurement of serum lactic acid aids in detecting tissue hypoxemia. It is a reliable tool for predicting the outcome and prognosis [4] (**Figure 2**).

**Figure 2.** Pathophysiology of shock [2].
