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ACID BASE BALANCE

ACID BASE BALANCE. ACID BASE BALANCE . General Principles Dynamic relationship which reflects the concentration of hydrogen (H+) ions Hydrogen ions are acids which must be maintained within strict limits Any deviation from norm affects biochemical events

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ACID BASE BALANCE

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  1. ACID BASE BALANCE

  2. ACID BASE BALANCE • General Principles • Dynamic relationship which reflects the concentration of hydrogen (H+) ions • Hydrogen ions are acids which must be maintained within strict limits • Any deviation from norm affects biochemical events • Measured in a negative log (pH) which is inversely proportional to the hydrogen ion concentration • High H+ ion concentration = Low pH • Low H+ ion concentration = High pH

  3. THE pH SCALE • Most frequently used measure of acid base balance • Ranges from 1-14 • 1 means only hydrogen ions present • 14 means no hydrogen ions present • pH of water is 7.0 (neutral) • pH of human body is 7.35-7.45 • pH compatible with life = 6.9-7.8 • pH of < 7.35 indicates a state of acidosis • pH of > 7.45 indicates a state of alkalosis • Variation of 0.4 in either direction can be fatal

  4. Acid-Base Balance • A pH below 7.35 is referred to as acidosis • A pH above 7.45 is referred to as alkalosis

  5. ACID NEUTRALIZATION • Body constantly produces acids through metabolism • Carbon dioxide • Metabolic acids (lactic and pyruvic acid) • Acids must be constantly eliminated from the body • As acids increase, bodily functions decrease • Example • Diminishes myocardial contractility • Reduces vascular response to catecholamines • Interferes with the actions of pharmacological agents

  6. BUFFER SYSTEM • Fastest acting defense mechanism (seconds) • Chief buffer is bicarbonate • Bicarbonate combines with excess hydrogen ions to form carbonic acid in a dynamic relationship: HCO3 + H+ <--------> H2CO3 • For every molecule of carbonic acid, there are 20 molecules of bicarbonate • Any change in 20:1 ratio is immediately corrected to maintain pH • An increase in H+ causes an increase in H2CO3 • A decrease in H+ causes a decrease in H2CO3

  7. Bicarbonate Buffer System • Fastest mechanism • Hydrogen will bind with bicarbonate • Results in formation of carbonic acid

  8. Carbonate Buffer System • An increase in hydrogen ions leads to an increase in carbonic acid. • A deficit in hydrogen ions (alkalosis); carbonic acid will dissociate into bicarbonate ion and hydrogen ion

  9. BUFFER SYSTEM (CONT.) • Carbonic acid is a weak, volatile acid which must be eliminated • Enzyme carbonic anhydrase catalyzes the carbonic acid to convert to carbon dioxide and water: H2CO3--------->CO2 + H2O • CO2 and H2O are easily eliminated by the lungs and kidneys

  10. RESPIRATORY SYSTEM • Functions within minutes (1-3) • Lungs eliminate excess CO2 by increasing respirations, causing a decrease in H+ ion and an increase in pH • Lungs can retain more CO2 by decreasing respirations, causing an increase in H+ ions and a decrease in pH

  11. Respiratory Mechanisms • Increased respirations cause increased elimination of CO2 and H2O. • An increase in pH • Decreased respirations cause retention of CO2 and H2O. • Decreasing pH

  12. RENAL SYSTEM • Slowest onset and generally important in long term maintenance of acid-base balance (hours to days) • Function • Kidneys retain bicarbonate, causing a decrease in H+ ions and an increase in pH • Kidneys excrete bicarbonate, causing an increase in H+ ions and a decrease in pH

  13. Respiration = CO2 + H2O H2CO3 H+ + HCO3- Respiratory Acidosis • Caused by abnormal retention of CO2 from impaired ventilation due to problems occurring in the lungs or respiratory center of the brain

  14. Respiration = CO2 + H2O H2CO3 H+ + HCO3- Respiratory Alkalosis • Caused by increased respiration and excessive elimination of CO2 • The CO2 level is decreased and the pH is increased.

  15. ACID-BASE DERANGEMENTS (CONT.) • Metabolic acidosis • Increased production of acids (lactic and pyruvic) • Can also result from diarrhea, vomiting, diabetes and medications (ASA) • pH is decreased and CO2 level is normal • Treatment is aimed at improving ventilations to eliminate CO2 • Sodium bicarbonate with documented metabolic acidosis • Rarely administered during initial resuscitative strategies

  16. ACID-BASE DERANGEMENTS (CONT.) • Metabolic alkalosis • Caused by increased vomiting, overdosing on antiacids, diuretics • pH is increased and CO2 remains normal • Treatment is aimed at underlying cause • Combinations • Any combination of acid-base derangements • Only ABG can accurately diagnose problem

  17. Thank you!

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