ACID BASE balance and ph buffers medical.pptx

Acid base ppt

1. ACID BASE BALANCE & PH Buffers

2. DISCUSSION HEADINGS BASICS NORMAL PHYSIOLOGY ABNORMALITIES METABOLIC ACID BASE DISORDERS RESPIRATORY ACID BASE DISORDERS ALTERNATIVE CONCEPTS

3. Acid Any compound which forms H⁺ ions in solution (proton donors) eg: Carbonic acid releases H⁺ ions Base Any compound which combines with H⁺ ions in solution (proton acceptors) eg:Bicarbonate(HCO3 ⁻ ) accepts H+ ions

4. Acid – Base Balance Normal pH : 7.35-7.45 Acidosis Physiological state resulting from abnormally low plasma pH Alkalosis Physiological state resulting from abnormally high plasma pH Acidemia : plasma pH < 7.35 Alkalemia : plasma pH > 7.45

5. A CI D S VOLATILE ACIDS: Produced by oxidative metabolism of CHO,Fat,Protein Average 15000-20000 mmol of CO₂ per day Excreted through LUNGS as CO₂ gas FIXED ACIDS (1 mEq/kg/day) Acids that do not leave solution ,once produced they remain in body fluids Until eliminated by KIDNEYS Eg: Sulfuric acid ,phosphoric acid , Organic acids Are most important fixed acids in the body Are generated during catabolism of: amino acids(oxidation of sulfhydryl gps of cystine,methionine) Phospholipids(hydrolysis) nucleic acids

6. Response to ACID BASE challenge Buffering Compensation

7. Bu f f e r s First line of defence (> 50 – 100 mEq/day) Two most common chemical buffer groups Bicarbonate Non bicarbonate (Hb,protein,phosphate) Blood buffer systems act instantaneously Regulate pH by binding or releasing H⁺

8. Carbonic Acid – Bicarbonate Buffer System Carbon Dioxide Most body cells constantly generate carbon dioxide Most carbon dioxide is converted to carbonic acid, which dissociates into H + and a bicarbonate ion Prevents changes in pH caused by organic acids and fixed acids in ECF Cannot protect ECF from changes in pH that result from elevated or depressed levels of CO 2 Functions only when respiratory system and respiratory control centers are working normally Ability to buffer acids is limited by availability of bicarbonate ions

9. Acid – Base Balance The Carbonic Acid – Bicarbonate Buffer System

10. The Hemoglobin Buffer System CO 2 diffuses across RBC membrane No transport mechanism required As carbonic acid dissociates Bicarbonate ions diffuse into plasma In exchange for chloride ions ( chloride shift ) Hydrogen ions are buffered by hemoglobin molecules Is the only intracellular buffer system with an immediate effect on ECF pH 2 Helps prevent major changes in pH when plasma P CO is rising or falling

11. Phosphate Buffer System - Consists of anion H 2 PO 4 (a weak acid)(pKa-6.8) Works like the carbonic acid – bicarbonate buffer system Is important in buffering pH of ICF Limitations of Buffer Systems Provide only temporary solution to acid – base imbalance Do not eliminate H + ions Supply of buffer molecules is limited

12. Acid – Base Balance Disturbances Interactions among the Carbonic Acid – Bicarbonate Buffer System and Compensatory Mechanisms in the Regulation of Plasma pH.

13. Acid – Base Balance Disturbances Interactions among the Carbonic Acid – Bicarbonate Buffer System and Compensatory Mechanisms in the Regulation of Plasma pH. decreased

14. Four Basic Types of Imbalance Metabolic Acidosis Metabolic Alkalosis Respiratory Acidosis Respiratory Alkalosis

15. Acid Base Disorders Disorder pH [H + ] Primary disturbance Seconda r y response Me t abolic acidosis    [HCO 3 - ]  pCO 2 Me t abolic alkalosis    [HCO 3 - ]  pCO 2 Respi r a t ory acidosis    pCO 2  [HCO 3 - ] Respira t ory alkalosis    pCO 2  [HCO 3 - ]

16. Acid – Base Balance Disturbances . Responses to Metabolic Acidosis

17. Acid – Base Balance Disturbances . Metabolic Alkalosis

18. Acid – Base Balance Disturbances Respiratory Acid – Base Regulation.

19. Acid Base Disorders Primary disorder Compensatory response Metabolic acidosis PCO ₂=1.5 X (HCO₃⁻) + 8 +/₋ 2*Winter’s formula+ Metabolic alkalosis 0.6 mm  pCO 2 per 1.0 mEq/L  HCO 3 - Acute respiratory acidosis 1 mEq/L  HCO 3 - per 10 mm  pCO 2 Chronic respiratory acidosis 3.5 mEq/L  HCO 3 - per 10 mm  pCO 2 Acute respiratory alkalosis 2 mEq/L  HCO 3 - per 10 mm  pCO 2 Chronic respiratory alkalosis 5 mEq/L  HCO 3 - per 10 mm  pCO 2

20. MIXED ACID BASE DISORDER Diagnosed by combination of clinical assessment, application of expected compensatory responses , assessment of the anion gap, and application of principles of physiology. Respiratory acidosis and alkalosis never coexist Metabolic disorders can coexist Eg: lactic acidosis/DKA with vomiting Metabolic and respiratory AB disorders can coexist Eg: salicylate poisoning (met.acidosis + resp.alkalosis)