Acid-Base Balance

1. Acid-Base Balance

2. Normal Acid-Base Balance • Normal pH 7.35-7.45 • Narrow normal range • Compatible with life 6.8 – 7.8 • < 6.8 or > 7.8 incompatible with life ___/______/___/______/___ 6.8 <7.35 7.45˃ 7.8 Acid Acidosis Alkalosis Alkaline

3. Acid- Base balance Balance maintained by: • Buffering systems • Lungs • Kidneys H2CO3…..HCO3

4. Buffer Systems • Prevent major changes in pH • Act as sponges… • 3 main systems Bicarbonate-carbonic acid buffer Phosphate buffer Protein buffer H+ H+ H+

5. Buffer Systems • Bicarbonate buffer - most important Active in ECF and ICF • Phosphate buffer Active in intracelluar (ICF) fluid • Protein buffer - Largest buffer store Albumins and globulins (ECF) Hemoglobin (ICF)

6. Bicarbonate-Carbonic Acid • Body’s major buffer • Carbonic acid - H2CO3 (Acid) • Bicarbonate - HCO3 (Base) 1 20 pH = 7.4 24 mEq/L 1.2 mEq/L H2CO3 ……………… HCO3

7. Acid Substance that contains H+ ions that can be released (H2CO3) Carbonic acid releases H+ ions Base Substance that can accept H+ ions (HCO3) Bicarbonate accepts H+ ions

8. As CO2 increases, carbonic acid increases, H+ ions increase pH drops….. becomes more acidic CO2 +H2O H2CO3 H+ + HCO3 Carbonic Bicarbonate Acid CO2H2CO3H+ HCO3 (pH Acidic <7.35)

9. As HCO3 increases, H+ decreases • pH rises, becomes more alkaline CO2 +H2O H2CO3 H+ + HCO3 Carbonic Bicarbonate Acid CO2H2CO3H+ HCO3 (pH Basic >7.45)

10. Body pH • pH = (bicarbonate) (carbon dioxide) At a normal pH of 7.4 the ratio is 20 :1

11. Respiratory Regulation Mechanisms of control … • Hyperventilation -- blow off CO2 • Hypoventilation -- retain CO2 Regulation rapid... • Seconds to minutes Measured by PaCO2 - Normal 35-45 mm Hg

12. Renal Regulation Mechanism of control • Excretion or retention of H+ or HCO3 Regulation….. Slow • Hours to days to change pH Normal serum HCO3 • 22-26 mEq/L

13. Pathophysiologic changes in Acid-Base Imbalances Acidosis, Acidemia, Alkalosis, Alkalemia The term ending in "OSIS" is a description on what is occuring. The term ending in "emia" is the actual medical condition of the occurence of "osis" 

14. Acidosis refers to disorders that lower arterial pH to < 7.35. • Acidemia refers to a arterial pH < 7.35. • Alkalosis refers to disorders that elevate arterial pH to > 7.45. • Alkalemia refers to a arterial pH > 7.45.

15. Acidosis (acidemia) • pH falls below 7.35 • Increase in blood carbonic acid or • Decrease in bicarbonate

16. Alkalosis (alkalemia) • pH greater than 7.45 • Increase in bicarbonate or • Decrease in carbonic acid

17. Acid-Base Imbalances Primary cause or origin: • Metabolic Changes brought about by systemic alterations • Respiratory Changes brought about by respiratory alterations

18. METABOLIC VERSUS RESPIRATORY ACID-BASE DISORDERS • Metabolic disorders produce an alteration in the plasma bicarbonateconcentration and result from the addition or loss of nonvolatile acid or alkali to or from the extracellular fluid. • Respiratory disorders involve an alteration in the PCO2, reflecting an increase or decrease in alveolar ventilation.

19. Acid-Base Imbalances Compensation • Corrective response of kidneys and/or lungs Compensated • Restoration of pH and 20 : 1 ratio Uncompensated • Inability to adjust pH or 20 : 1 ratio

20. Disorder of Acid- Base balanceFour Basic Types of Imbalance • Respiratory Acidosis • Respiratory Alkalosis • Metabolic Acidosis • Metabolic Alkalosis

21. Respiratory Acidosis • Carbonic acid excess • Exhaling of CO2 inhibited • Carbonic acid builds up • pH falls below 7.35 • Cause = Hypoventilation H2CO3

22. Acid-Base Imbalances • Normal 1 20 7.4 1.2 mEq/L 24 mEq/L H2CO3 ……………… HCO3

23. Respiratory Acidosis 1 13 7.21 24 mEq/L 1.84 mEq/L H2CO3 ……………… HCO3

24. Respiratory Acidosis • Compensation: How? • Opposite regulating mechanism • Problem = depressed breathing, build up of CO2 in blood • Response - Kidney retains HCO3 (Response ….. Slow)

25. Causes • Airway obstruction • Cardiac arrest (acute) • Central nervous system trauma • Chronic bronchitis, extensive pneumonia • Chronic metabolic alkalosis • Drugs ( opioids, general anesthetics, hypnotics, alcohol and sedatives)

26. Signs and symptoms • Restlessness caused by hypoxemia • Change in the level of consciousness • Headache

27. Respiratory Alkalosis • Carbonic acid deficit • Increased exhaling of CO2 • Carbonic acid decreases • pH rises above 7.45 • Cause = hyperventilation H2CO3

28. Acid-Base Imbalances • Normal 1 20 7.4 1.2 mEq/L 24 mEq/L H2CO3 ……………… HCO3

29. Respiratory Alkalosis 1 40 7.70 0.6 mEq/L 24 mEq/L H2CO3 ……………… HCO3

30. Causes • Pulmonary: severe hypoxemia, pneumonia, acute asthma • Nonpulmonary: anxiety, fever, aspirin toxicity, metabolic acidosis, central nervous system disease

31. Signs and symptoms • Deep, rapid breathing, CNS and neuromascular disturbances • Dizziness due to decreased cerebral blood flow

32. Respiratory Alkalosis • Compensation: • Problem = excess “blowing off” of CO2 • Result = decrease in carbonic acid and increase in HCO3 • Response: Kidney excretes excess bicarbonate

33. Metabolic Acidosis • Base-bicarbonate deficit • Low pH (< 7.35) • Low plasma bicarbonate (base) • Cause = relative gain in H+ (lactic acidosis, ketoacidosis) or actual loss of HCO3 (renal failure, diarrhea)

34. Acid-Base Imbalances • Normal 1 20 7.4 1.2 mEq/L 24 mEq/L H2CO3 ……………… HCO3

35. Metabolic Acidosis • Kidney failure (decrease in bicarbonate) 1 10 7.10 12 mEq/L 1.2 mEq/L H2CO3 ……………… HCO3

36. Metabolic Acidosis • Lactic acidosis, keto acidosis (increase acid… no change in bicarbonate) 1 10 7.10 24 mEq/L 2.4 mEq/L H2CO3 ……………… HCO3

37. Causes • Excessive fat metabolism: diabetic ketoacidosis, chronic alcoholism, mal nutrition or a low – carbohydrate, high fat diet producing more ketoacids than the metabolic process can handle. • Anaerobic carbohydrate metabolism causing an increase in lactic acid level • Diarrhea or loss of sodium bicarbonate from the intestine • Salycilate intoxication (overuse of aspirin)

38. Signs and symptoms • Headache and lethargy progressing to drowsiness coma and death if condition is severe and untreated • Deep , rapid breathing • Fruity smelling breath from fat catabolism and excretion of acetone through the lungs in diabetes mellitus

39. Metabolic Acidosis • Compensation: • Problem = low HCO3 (base) or high H+ ion (acid) • Response: Lungs hyperventilate • Get rid of CO2 Renal: increase H+ secretion and reabsorption of HCO3-

40. Metabolic Alkalosis • Bicarbonate excess • High pH (> 7.45) • Loss of H+ ion or gain of HCO3 • Most common causes vomiting, gastric suctioning • Other: Abuse of antacids, K+ wasting diuretics(hypokalemia)

41. Acid-Base Imbalances • Normal 1 20 7.4 1.2 mEq/L 24 mEq/L H2CO3 ……………… HCO3

42. Metabolic Alkalosis 1 30 7.58 1.2 mEq/L 36 mEq/L H2CO3 ……………… HCO3

43. Causes • Chronic vomiting, use of steroids, cushing’s disease (causes of critical acid loss) • Excessive intake of absorbable alkali, bicarbonate of soda or other antacids, IV fluids with high concentration of bicarbonate (causes of bicarbonate retention) • Alteration in extracellular electrolytes level including low chloride, low plasma potassium

44. Signs and symptomes • Clinical features of metabolic alkalosis results from the body’s attempt to correct the acid - base imbalance primarily through hypoventilation • Slow shallow respiration • Cardiovascular abnormalities • Nausea, vomiting

45. Metabolic Alkalosis • Compensation: • Problem = too much base • Response: Lungs compensate by hypoventilating • Retain CO2 • Renal: excrete less acid and more base

46. Interpreting arterial blood gas values (ABGs) • pH 7.35 - 7.45 • PaCO2 35 - 45 mmHg • HCO3 22 - 26 mEq/L

47. Interpreting ABGs 1. Start with pH • Normal? • Acidosis? • Alkalosis? ___/______/___/______/___ 6.8 7.35 7.45 8.0 Acidosis Alkalosis

48. Interpreting ABGs 2. Assess PaCO2 (respiratory value) _____/________/______ 35 45 Respiratory Respiratory AlkalosisAcidosis

49. Interpreting ABGs 3. Evaluate metabolic indicators Bicarbonate (HCO3) 22-26

50. Interpreting ABGs HCO3 _______/_______/________ 22 26 Metabolic Metabolic acidosis alkalosis