METABOLIC ACIDOSIS

1. METABOLICACIDOSIS III-D2 Rodriguez, Jan Gayl – Sahagun, Marie Janice

2. SALIENT FEATURES

3. SALIENT FEATURES (LAB DATA)

4. WHAT IS THE ACID BASE DISTURBANCE PRESENT IN THIS CASE?

5. METABOLIC ACIDOSIS

6. METABOLIC ACIDOSIS • Infection  Increased plasma lactate: 3.0 meq/L • Severe diarrhea  Decreased serum bicarbonate: 10 meq/L • Increased serum chloride: 108 meq/L • Kussmaul respiration • Decreased PCO2 : 17 mmHg (compensated) • Normal blood pH: 7.39 (compensated)

7. ALGORITHM FOR THE DIAGNOSIS OF THE ACID BASE DISORDER

8. 1. Establish database 2. Identify the main disorder: 3. Evaluate compensation (using the formulas)

9. 4. Determine the anion gap (AG, normal = 12).  * If the AG is >20 = metabolic acidosis * If there is an AG,   Calculate the gap-gap (delta-gap) = patient’s anion gap – 12 (normal anion gap).   Calculate the delta HCO3 = normal HCO3 (use 25) – the patient's HCO3.   delta-gap ÷ delta HCO3 should normally be between 1-2 If < 1 = combined non-gap and gap acidosis   If > 2 suggests = metabolic alkalosis.

10. RULE OF THUMB IN BEDSIDE INTERPRETATION OF ACID BASE DISORDER

11. RULE OF THUMB Metabolic acidosis • PaCO2 should fall by 1.0 to 1.5 X the fall in plasma HCO3- concentration • pCO2 should rarely be < 20 mmHg. • Bicarbonate deficit (mEq/L) = [0.5 x BW(kg)] x (24 - HCO3) Metabolic alkalosis • PsCO2 should rise by 0.25 to 1.0 X the rise in plasma HCO3- concentration

12. RULE OF THUMB Acute respiratory acidosis • Plasma HCO3- concentration should rise by about 1 mmole per liter for each 10 mm Hg increment in PaCO2 ( 3 mmoles per liter). • Acute change pH/pCO2 = 0.008 Chronic respiratory acidosis • Plasma HCO3- concentration should rise by about 4 mmoles per liter for each 10 mm Hg increment in PaCO2 ( 4 mmoles per liter). • Chronic change pH/pCO2 = 0.003

13. RULE OF THUMB Acute respiratory alkalosis • Plasma HCO3- concentration should fall by about 1 to 3 mmoles per liter for each 10 mm Hg decrement in the PaCO2, usually not to less than 18 mmoles per liter • Acute change pH/pCO2 = 0.008 Chronic respiratory alkalosis • Plasma HCO3- concentration should fall by about 2 to 5 mmoles per liter per 10 mm Hg decrement in PaCO2 but usually not to less than 14 mmoles per liter. • Chronic change pH/pCO2 = 0.003

14. HOW DO YOU COMPUTE FOR THE ANION GAP?WHAT IS ITS SIGNIFICANCE?COMPUTE FOR THE ANION GAP OF THIS PATIENT

15. AG = [Na+] – ([Cl-] + [HCO3-]) ANION GAP COMPUTATION • Anion Gap  represents the difference between the concentration of the major plasma cation (Na+) and the major plasma anions (Cl- and HCO3-) • Formula

16. SIGNIFICANCE OF AG • Nonvolatile acid added to body fluids  ↑ [H+], ↓ pH, ↓ [HCO3-]  ↑ Anion Concentration • Change in Anion - provides convenient way to analyze and help determine the cause of metabolic acidosis • NV 10-12 mmol/L • Normal AG - Anion of nonvolatile acid  Cl- • High AG - Anion of nonvolatile acid  Lactate, β-hydroxybutyrate Calculation of AG is a useful way to identify the causeof ametabolic acidosis

17. AG COMPUTATION (Case) AG = [Na+] – ([Cl-] + [HCO3-]) = [138] – ([108) + [10]) = 20 meq/L(High AG)

18. ANION GAP • Normal Anion Gap • Loss of bicarbonate • Addition of HCl • Renal Tubular Dysfunction • High Anion Gap • Overproduction of organic acids • Failure of the kidneys to maintain bicarbonate levels

19. Normal Anion Gap • Diarrhea • Renal Tubular Acidosis • Carbonic Anhydrase Inhibition

20. High Anion Gap • Lactic Acidosis • Ketoacidosis • Drug and Toxin Induced • Advanced Renal Failure

21. Prediction of Compensatory Responses on Simple Acid Base Disturbances • Acid-Base Nomogram • Shaded areas show 95% confidence limits for normal compensation • Finding acid-base values within the shaded areas does not rule out a mixed disturbance • Not a substitute for computation

22. Prediction of Compensatory Responses on Simple Acid Base Disturbances • Acid-Base Nomogram • pH 7.39 • HCO3 10 mEq/L • PCO2 17 mmHg

23. TREATMENT • Antibiotic • IVF/Vasopressors

24. Thank you!