Hello, This is dr Shoukat Memon, working as a consultant Nephrologist in the Indus Hospital and Health Network Karachi.
Email: drshoukatmemon@gamail.com We will discuss following: I have highlighted the following areas in discussion in this video: 1. What is AG, how is it calculated, and its significance? 2. Seeing Anion Gap from a different angle. It is an increase in Anions or a decrease in Cations that both give rise to raised AG. 3. Unmeasured Cations when subtracted from Unmeasured Anions give as same gap. 4. Reviewing the range of AG from a study done on thousands of patients. The currently commonly used range of AG is 8 to 12. 5. Metabolic acidosis with rasied AG and Normal AG. 6. How to Get Corrected Anion Gap. Under normal circumstances, the body is based on neutrality which means whatever number of Aations are there, they are balanced with Anions. Examples of Cations: Na, K, Ca, Mg, Globulin; And Anions: Cl, HCO3, Albumin, So4, Po4 For the sack of understanding to manage patients, Anion Gap (AG) has been devised arbitrarily by Substracting sodium ions minus Cloride+Bicarbonate In other words, we can say, Anion Gap is the Unmeasured Anions minus unmeasured cations. Typically AG value has been set as 8 - 12. When we find raised AG, It suggests some unknown anions have been accumulated. To see this from a different angle, we can say either increase in unmeasured anions or a decrease in unmeasured cations, both can give rise to raised AG. Now from a practical perspective, if we take the example of Renal/Kidney Failure, we find raised AG and that is because of the accumulation of sulfate and phosphate anions. In uncomplicated or simple acid base disorder , we find same amount of accumulated (anions which is raised above 12 ) is the decrease in Bicarbonate from 24. For example if anion is increased 8 from cut-off 12 (AG:20) , Bicarbonate would be 16 (24 - 8). In condition where we find normal AG metabolic acidosis i.e. Diarrhea, Renal tubular acidosis. In these condition decrease in bicarbonate is compensated by accumulation of chloride anions and this keep the AG unchanged but metabolic acidosis is there. We need to see AG always in the setting of serum albumin value as we know AG is mainly contributed by serum albumin. If we find serum serum albumin 1 lower than 4 (s.albumin 3 mg/dl) then we need to add 2.5 in calculated AG of that particular patient.