1. Anion Gap (AG)
It is a measure of anions other than HCO3 and Chloride Biochemical Basis: Always: CATIONS = ANIONS
11/18/2018 5:41 PM

2. AG (Biochemical Basis)
Major Cat-ions:
Na = mmol/L
K = mmol/L
Ca = mmol/L
Mg = mmol/L
TOTAL CATIONS = mmol/L
11/18/2018 5:41 PM

3. AG (Biochemical Basis)
Major Anions:
Cl = mmol/L
HCO = mmol/L
proteins = mmol/L
PO = mmol/L
SO = mmol/L
Organic Acids = mmol/L
TOTAL ANIONS = mmol/L
11/18/2018 5:41 PM

4. AG =(Na+ K+) - (Cl- + HCO3-) or
=Na+ - (Cl- + HCO3-)
Range : 7 – 18 mmol/l
Cations
Anion Gap = -
It is a measure of anions other than HCO3 and Chloride
Biochemical Basis:
Always:
CATIONS = ANIONS
Anions

5. Anion Gap:
It is only a lab derived index There can Never be an anion gap in any condition because electro- neutrality is always maintained in the plasma
11/18/2018 5:41 PM

6. AG corrected for low albumin (AG corr)
Albumin accounts for about 90% of the mean value AG and albumin is reversely correlated with HCO3
When the level of serum albumin decreases, AG will decrease equally
AG is concealed by hypoalbuminemia
HCO3 will increase accordingly (low Alb alkalosis)

7. * coefficient for converting Alb g/L into Alb mmol/L.
AG corr
Albumin: 40 (35-50) g/L×0.25*
= 10 (9-13) mmol/L
* coefficient for converting Alb g/L into Alb mmol/L.

8. Steps in Diagnosis of a Triple Disorder
Diagnose Double Disorder
Examine AG
Examine [HCO3]
Example:
Double Disorder : Low PCO2+ High [HCO3]
(i.e. Resp Alk + Met Alk)
Triple Disorder : Low PCO2+ High [HCO3] + AG > 16
(i.e. Resp Alk + Met Alk+ High AG Met Acidosis)

9. Diagnosis Triple Disorder
Metabolic Alkalosis
Respiratory Alkalosis
High AG
Metabolic Acidosis

10. Steps in Diagnosis of a Triple Disorder
Diagnose Double Disorder
Examine AG
Examine [HCO3]
Example:
Double Disorder: High PCO2+ [HCO3] higher than the upper limit of compensation
(i.e. Resp Acidosis + Met Alk)
Triple Disorder: High PCO2+ [HCO3] higher than the upper limit of compensation
+ AG > 16
(i.e. Resp Acidosis + Met Alk + High AG Met Acidosis)

11. Diagnosis Triple Disorder
Metabolic Alkalosis
High AG
Metabolic Acidosis
Respiratory Acidosis

12. Other situations of Triple Disorders
Combined High AG and Normal AG Met Acidosis in a patient with Resp Alkalosis
Low Albumin Met Alkalosis with Met Acidosis and Respiratory Alkalosis

13. Important Fact
Respiratory Acidosis and Respiratory Alkalosis never occur together in the same patient !!!

14. Delta Ratio Measured anion gap – Normal anion gap (anion gap – 12)
The delta ratio is used for the determination of a mixed acid base disorder in an elevated anion gap metabolic acidosis
Measured anion gap – Normal anion gap
Normal [HCO3-] – Measured [HCO3-]or
(anion gap – 12)
(24 - [HCO3-])

15. Delta Ratio Assessment Guideline
< 0.4
Hyperchloraemic normal anion gap acidosis
Renal failure
Combined high AG & normal AG acidosis
1 to 2
Uncomplicated high-AG acidosis
Lactic acidosis: 1.6 (average value)
>2
A pre-existing elevated HCO3 level due to:
a concurrent metabolic alkalosis, or
a pre-existing compensated respiratory acidosis

16. Predicted HCO3 If patient's [HCO3] > Predicted [HCO3]
Predicted [HCO3] = 24 -[Anion Gap-12]
If patient's [HCO3] > Predicted [HCO3]
Metabolic acidosis + Metabolic Alkalosis
Compensatory response to resp acidosis

17. If patient's [HCO3] =Predicted [HCO3]
Simple Metabolic acidosis
If patient's [HCO3] < Predicted [HCO3]
Compensatory response to resp alkalosis

18. Example Blood Gases Electrolytes pH 7.58 PCO2 2.1mmHg HCO3 19mmol/L
Na 137 mmol/L
K 5.2 mmol/L
Cl 89 mmol/L
Anion Gap 33 mmol/L
Blood Gases
pH 7.58
PCO mmHg
HCO3 19mmol/L

19. Interpretation of ABG Reports
Look at pH
Step-1
Examine pH and HCO3
Step 2
PCO2 and HCO3
Step 3
Mobile App e.g. Skyscape (or Equations)
Step 4
1. Acidosis, alkalosis, or normal?
primary disturbance respiratory or metabolic?
3. primary respiratory disturbance, is it acute or chronic?
4.If metabolic disturbance, is the respiratory system compensating OK
5. If metabolic acidosis, is there an increased anion gap?
6. an increased anion gap metabolic acidosis, are there other derangements?
Delta Ratio for Triple Disorders
Step 5

20. Thank you