**7. Base excess approach**

Astrup and Siggaard-Anderson introduced base excess approach, which is close to the traditional approach [22, 23]. Base excess can be calculated from bicarbonate concentration and pH of the body [4]. It can estimate the acid base status of nonrespiratory origin. If base excess is too high, then it is metabolic alkalosis. If base excess is too low, then it is metabolic acidosis. When a deviation of normal blood pH is corrected by administrating base, then it is called base deficit. Which is a characteristic of metabolic acidosis. Base deficit with increase anion gap suggest the addition of acid in the body fluid. If there is a base deficit with normal anion gap, then there is bicarbonate loss from the body.
