acid base balance

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acid base balance
2010-10-22 14:17:44

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  1. pH
    power of hydrogen (-)
  2. [H+]
    hydrogen ion concentration
  3. body fluid pH
    7 10^-7 .0000001 mg/l
  4. lower pH
    more acidic ([H+] high)
  5. Higher pH
    more basic ([H+] low)
  6. body acids
    formed as end products of metabolism
  7. Volatile body acids
    can be eliminated as CO2 gas (carbonic acid h2co3 -> h2o+co2)
  8. Nonvolatile body acids
    can be eliminated by kidney ( sulpuric, phosporic, organic acids secreted in urine)
  9. Buffers
    • occur in response to acid base status
    • Absorb excessive hydrogen or hydroxyl ion to prevent significant changes in pH
  10. Carbonic Acid-Bicarbonate Buffering
    • Operates in lungs and kidneys
    • lungs h2co3>h2o+co2
    • kidneys h2c03>h+hco3
  11. Protein buffering
    • intracellular buffer system
    • Hemoglobin attaches to hydrogen and releases when needed for pH
  12. Renal Buffering
    secrete hydrogen into urine and reabsorb bicarbonate
  13. Normal and abnormal pH levels
    • 7.35-7.45
    • death <6.9 or 7.8<
  14. PaCO2 normal
    Arterial CO2 partial pressure: normal 35-45 mmHg
  15. HCO3-
    • bicarbonate
    • 22-26 mEq/L
  16. Acidemia
    • too much acid pH< normal 7.35
    • systemic increase in [H+] is acidosis
    • respiratory acidosis: excess co2
    • Metabolic acidosis: loss of HCO3-
  17. alkalemia
    • Too much base; pH > normal 7.45
    • systemic decrease in [H+] is alkalois
    • metabolic alkalosis: excess HCO3-
    • Respiratory alkalosis: loss of CO2
  18. Compensation
    • body adjustments to maintain normal pH
    • resp compensates by changing ventiliation (increase/decrease CO2)
    • Renal compensates by changing urine pH (takes days)
  19. Respiratory Acidosis
    • breathing rate doesnt get rid of all CO2 resulting in hypercapnia
    • COPD, drug overdose, head injury, pulmonary edema
    • s&s: High PaCO2, high HCO3-, low pH, headache blurred vision breathlessness, restlessness, coma
    • Compensation: kidney conserves HCO3- and eliminates H+
  20. Metabolic acidosis
    • causes: loss of metabolic base (HCO3-) (diarrhea), or gain of acid (starvation, alcoholism, diabetes)
    • S&s: low HCO3-, low PaCO2, low pH, headache confusion coma n&v
    • Compensation: faster resp rate to blow of CO2
  21. Respiratory Alkalosis
    • Causes: excessive reduction in CO2 levels (hyperventilation, Hypoxemia (altitudes), Brain stem over stimulation
    • s&s: low PaCO2, low HCo3-, pH high, diaphoresis, dizziness, tingling coma
    • compensation: kidney conserves H+ and excretes HCO3-
  22. Metabolic alkalosis
    • Causes: loss of metabolic acid (emesis, gastric suctioning) or gain of metabolic base (excess antacid ingestion, diuretic therapy causing hypokalemia shifting H+ into cells)
    • S&s: High HCO3-, high PaCO2, high pH neuromuscular irritibility, coma, + signs of causal cond
    • Compensation: lungs "save" CO2 to offset increased base (slow breathing)
  23. mixed acid base imblance
    • seriously ill
    • ex: resp acidosis from bacterial pneumonia combined wit severe diarrhea metabolic acidosis
  24. Process
    • Define (pH, PaCO2, HCO3-) acidotic, alkalotic or normal
    • Determine what type (respiratory PaCO2 matches pH, Metabolic HCO3- Matches pH)
    • Does either PaCO2 or HCO3- go the opposite direction of pH (yes compensated, no uncompensated
    • PaO2 below limits hypoxemia