1. Acid Base Disorders

2. Acid Base -Basic Concepts
Hydrogen Ion [H+] is tightly controlled
[H+] is determined by the balance between PaCO2 and serum HCO3 (bicarbonate)
Henderson-Hasselbalch Equation
[H+] = 24 (PaCO2 / HCO3-)

3. Normal Values
[H+] = 40 nEq/L
pH = ( )
PaCO2 = 40 mm Hg (35-45)
HCO3 = 24 mEq/L (22-26)

4. Keep It Simple PaCO2 = Acid HCO3 = Base  PaCO2 =  pH (Acidemia)
 PaCO2 =  pH (Alkalemia)
HCO3 = Base
 HCO3 =  pH (Alkalemia)
 HCO3 =  pH (Acidemia)

5. In Numbers Acidosis: pH < 7.35 Alkalosis: pH > 7.45
Respiratory PaCO > 40 mmHg
Metabolic HCO3 < 24 mEq/L
Alkalosis: pH > 7.45
Respiratory PaCO2 < 40 mmHg
Metabolic HCO3 >24 mEq/L

6. Simple Acid-Base Disorders

7. Acid-Base Analysis What do You Need?
Arterial Blood gases (pH, CO2)
Serum chemistry (Na, K, Cl, HCO3)

8. Simple Vs. Mixed Compensation Concept [H+] = 24 (PaCO2 / HCO3-)
Is compensation appropriate?
Must know “rules of thumb” of compensation

9. Respiratory Compensation
Compensate for metabolic disorders
Prompt response
Metabolic acidosis
Hyperventilation - ↓ PaCO2
Metabolic alkalosis
Hypoventilation - ↑ PaCO2

10. Metabolic Compensation
Compensation for respiratory disorders
Slow response
Starts in 6-12 hours
Steady state in few days
Respiratory acidosis
Stimulates HCO3 reabsorption --↑ HCO3
Respiratory alkalosis
Inhibits HCO3 reabsorption -- ↓ HCO3

11. Metabolic Acidosis Anion Gap
Metabolic acidosis is grouped according to the anion gap
Anion Gap (AG)
The difference between measured cations and measured anions in the serum
AG= Na+ - [Cl- + HCO3-]
Normal ( mEq/L)

12. Wide Anion Gap Acidosis
Methanol
Uremia
Diabetic Ketoacidosis, Ketoacidosis
Paraldehyde
Iron, Isoniazid (INH)
Lactic Acidosis
Ethanol, Ethylene glycol
Salicylates

13. Non (normal) Anion Gap Acidosis
Hyperalimentation
Acetazolamide, amphotericin
RTA –Renal Tubular Acidosis
Diarrhea
Ureteral Diversions
Pancreatic fistula
Saline resuscitation

14. Metabolic Alkalosis Characterized by
Primary  in HCO3 concentration
Compensatory  in PaCO2
Classified according to urinary chloride
Chloride responsive
Chloride resistant

15. Metabolic Alkalosis Chloride Responsive
Urine Cl- >20 mEq/L
Volume Contraction:
Nasogastric suctioning
Vomiting
Diuretics
Post Hypercapnia
Hypokalemia
Hypomagnesemia
Penicillin

16. Metabolic Alkalosis Chloride Unresponsive
Urine Cl- < 20 mEq/L
Mineralcorticoid excess
Exogenous steroids
Alkali Ingestion
Licorice
Too much wine
Tobacco chewers
Bartter’s Syndrome