<qa>  What is the name of the alternative approach to acid-base balance?Metabolic acidosis is frequently found in patients with shock. Traditional methods of evaluating acid-base status can underestimate and even miss complex acid-base disorders particularly in the setting of hypoalbuminemia, hypohypernatraemia and hypohyperchloraemia .An alternative approach to acid-base balance, based on chemical and physical principles, and was proposed by Peter Stewart more than 30 years ago. Later in 1992 Figge and Fencl modified the strong ion difference, which corresponds with the net charge balance of all strong ions present in a given solution the Fencl-Stewart approach. The strong ion gap SIG which corresponds with the difference between the apparent strong ion difference and the effective strong ion difference was proposed by Kellum. Compared to the Fencl- Stewart approach SIG has more accuracy and bedside practicality. 