Vg Ab

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acid base basics

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Vg Ab

  1. 1. acid base balance Dr venugopal p p Chief-EM Dr vijayaraghavan
  2. 2. What is Acid-base balance <ul><li>Acid-base balance is defined by the concentration of hydrogen ions. </li></ul><ul><li>In order to achieve homeostasis, there must be a balance between the intake or production of hydrogen ions and the net removal of hydrogen ions from the body. </li></ul>
  3. 3. An Acid <ul><li>Molecules containing hydrogen atoms that can release hydrogen ions in solutions are referred to as an acid. </li></ul><ul><li>An example of an acid is hydrochloric acid (HCL) </li></ul>
  4. 4. A Base <ul><li>A base is an ion that can accept a hydrogen ion. </li></ul><ul><li>An example of a base is is the bicarbonate ion.( HCO3 </li></ul>
  5. 5. How is Acid-Base balance measured <ul><li>Hydrogen ion concentration is expressed on a logarithm scale using pH units (part/percentage hydrogen). </li></ul><ul><li>Henderson hesselbach equation (pH=6.1+log[HCO3]/[H2CO3]) </li></ul><ul><li>H2CO3=0.03xpCo2(35-45mmhg) </li></ul><ul><li>HCO3=21-28meq/ </li></ul><ul><li>7.0 being neutral </li></ul><ul><li>Body systems carefully control pH of the body within the range of 7.35-7.45 </li></ul>
  6. 6. pH <ul><li>A low pH corresponds to a high hydrogen ion concentration </li></ul><ul><li>The term “Acidosis” refers to the addition of excess hydrogen ions and the body has a pH that falls below 7.35 </li></ul><ul><li>A high pH corresponds to a low hydrogen concentration </li></ul><ul><li>The term “Alkalosis” refers to excess removal of hydrogen ions from the body and has a pH that rises above 7.45 </li></ul>
  7. 7. How the Body defends against fluctuations in pH <ul><li>Buffers in the blood </li></ul><ul><li>Respiration through the lungs </li></ul><ul><li>Excretion by the kidneys </li></ul><ul><li>Liver </li></ul>
  8. 8. <ul><li>Buffer systems-made of a weak acid or base and its salt. Prevent drastic changes in body fluid pH </li></ul><ul><li>Proteins:the most abundant buffers in body and cells. His and Cys are the two main acids and Hb in RBC’s. </li></ul><ul><li>Carbonic acid-bicarbonate: important regulator of blood pH. The most abundant buffers in the ECF. </li></ul><ul><li>Phosphates:important buffer in ICF and in urine. </li></ul><ul><li>These buffer systems serve as a first line of defense against changes in the acid-base balance </li></ul>Buffers in the Blood
  9. 10. Respiration through the lungs <ul><li>Carbon Dioxide which is formed during cellular metabolism forms carbonic acid in the blood decreasing the pH </li></ul><ul><li>When the pH drops respiration rate increases this hyperventilation increases the amount of CO2 exhaled thereby lowering the carbonic acid concentration and restoring homeostasis </li></ul>
  10. 11. Excretion by the Kidneys <ul><li>The kidneys play the primary role in maintaining long term control of Acid-Base balance </li></ul><ul><li>The kidney does this by selecting which ions to retain and which to excrete </li></ul><ul><li>The kidneys adjust the body’s Acid-Base balance </li></ul>
  11. 12. There are 4 Types of Acid-base Imbalances <ul><li>Respiratory Alkalosis </li></ul><ul><li>Respiratory Acidosis </li></ul><ul><li>Metabolic Alkalosis </li></ul><ul><li>Metabolic Acidosis </li></ul>
  12. 14. ANION GAP <ul><li>To diagnose acid base disorders </li></ul><ul><li>Conc.of anions &cations must be equal to maintain electrical neutrality </li></ul><ul><li>No real ANION GAP in plasma </li></ul><ul><li>AG (only a diagnostic concept) –difference b/w unmeasured anions &unmeasured cations </li></ul><ul><li>Increased AG-UNMA rise or UNMC fall </li></ul><ul><li>UNM cations-ca ,mg,k </li></ul><ul><li>UNM anions-alb,phosphate,sulfate,organic anions </li></ul><ul><li>Usually UNMA>UNMC </li></ul><ul><li>AG range 8-16 meql </li></ul>
  13. 15. =144-24-108=10meql <ul><li>To differentiate MA whether its hyperchloremic (normal anion gap) or hypochloremic (increased anion gap) </li></ul><ul><li>In normal anion gap acidosis-fall in HCO3 accompanied by rise in CL or UNMA to maintain electroneutrality </li></ul><ul><li>In increased anion gap acidosis –fall in HCO3 not accompanied rise in CL but increase in UNMA </li></ul>
  14. 16. ANION GAP <ul><li>Normal (6–12 mEq)   </li></ul><ul><li>   Loss of HCO 3 –   </li></ul><ul><li>     Diarrhea </li></ul><ul><li>     Recovery from diabetic ketoacidosis </li></ul><ul><li>     Pancreatic fluid loss ileostomy (unadapted) </li></ul><ul><li>     Carbonic anhydrase inhibitors </li></ul><ul><li>   Chloride retention </li></ul><ul><li>     Renal tubular acidosis </li></ul><ul><li>     Ileal loop bladder </li></ul><ul><li>   Administration of HCl equivalent or NH 4 Cl   </li></ul><ul><li>     Arginine and lysine in parenteral nutrition </li></ul>
  15. 17. ANION GAP      Ethylene glycol (oxalic acid)      Methanol (formic acid)      Sodium carbenicillin therapy      Salicylate intoxication    Drug or chemical anion      Metabolic alkalosis (increased number of negative charges on protein)      Starvation      Renal insufficiency (PO 4 3– , SO 4 2– )        Lactic acidosis      Alcoholic ketoacidosis      Diabetic ketoacidosis    Metabolic anion Increased (>12 mEq)  
  16. 18. ANION GAP    Bromide intoxication      Monoclonal protein (cationic paraprotein) (accompanied by chloride and bicarbonate)    Plasma cell dyscrasias    Hypoalbuminemia (decreased unmeasured anion) Decreased (< 6 mEq)  
  17. 19. THANK YOU

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