Acid Base Disorders Acid Base Basic Concepts Hydrogen

Acid Base Disorders

Acid Base -Basic Concepts Hydrogen Ion [H+] is tightly controlled n [H+] is determined by the balance between Pa. CO 2 and serum HCO 3 (bicarbonate) n Henderson-Hasselbalch Equation n[H+] = 24 (Pa. CO 2 / HCO 3 -)

Normal Values n[H+] = 40 n. Eq/L np. H = 7. 40 (7. 35 -7. 45) n. Pa. CO 2 = 40 mm Hg (35 -45) n. HCO 3 = 24 m. Eq/L (2226)

Keep It Simple n Pa. CO 2 = Acid Pa. CO 2 = p. H (Acidemia) n Pa. CO 2 = p. H (Alkalemia) n n HCO 3 = Base HCO 3 = p. H (Alkalemia) n HCO 3 = p. H (Acidemia) n

In Numbers n Acidosis: p. H < 7. 35 n Respiratory n Metabolic n Alkalosis: Pa. CO > 40 mm. Hg HCO 3 < 24 m. Eq/L p. H > 7. 45 n Respiratory n Metabolic Pa. CO 2 < 40 mm. Hg HCO 3 >24 m. Eq/L

Simple Acid-Base Disorders

Acid-Base Analysis What do You Need? Arterial Blood gases (p. H, CO 2) n Serum chemistry (Na, K, Cl, HCO 3) n

Simple Vs. Mixed Compensation Concept [H+] = 24 (Pa. CO 2 / HCO 3 -) n Is compensation appropriate? n Must know “rules of thumb” of compensation

Respiratory Compensation n Compensate for metabolic disorders n Prompt response n Metabolic acidosis n Hyperventilation n Metabolic n - ↓ Pa. CO 2 alkalosis Hypoventilation - ↑ Pa. CO 2

Metabolic Compensation for respiratory disorders n Slow response n Starts in 6 -12 hours n Steady state in few days n n Respiratory acidosis n n Stimulates HCO 3 reabsorption --↑ HCO 3 Respiratory alkalosis n Inhibits HCO 3 reabsorption -- ↓ HCO 3

Metabolic Acidosis Anion Gap Metabolic acidosis is grouped according to the anion gap n Anion Gap (AG) n n The difference between measured cations and measured anions in the serum AG= Na+ - [Cl- + HCO 3 -] n Normal (9 - 12 m. Eq/L)

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

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

Metabolic Alkalosis n Characterized by Primary in HCO 3 concentration n Compensatory in Pa. CO 2 n n Classified according to urinary chloride Chloride responsive n Chloride resistant n

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

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