This document provides an overview of acid-base imbalances, including the key components of pH, PCO2, and base excess. It discusses respiratory and metabolic acid-base disorders, how the body controls acid-base balance through buffers, lungs, and kidneys, and the symptoms and treatments of common acid-base imbalances like metabolic acidosis, metabolic alkalosis, respiratory acidosis, and respiratory alkalosis.

1. Acid Base Imbalance Peggy D. Johndrow 2009

2. Must it be so complicated! Key concepts pH PC02 Base Excess

3. What I need to know Components Two Components Respiratory Metabolic

4. What I need to know Respiratory Respiratory When breathing is inadequate carbon dioxide (respiratory acid) accumulates. Extra C02 combines with water to form carbonic acid which leads to an acid PH Evaluate PC02

5. What I need to know Metabolic Metabolic When metabolism is impaired acid forms , poor blood supply stop oxidative metabolism and lactic acid forms. “Metabolic Acid”

6. Why do we care? Variations in pH or PC02 are not causes of pathology (lab values) Both may be well tolerated when circulation and oxygenation maintained Abnormal levels of pH and PC02 are best indicators of trouble

7. Let’s Review pH represents degree of acidity of fluid Major concern pH of blood Normal range 7.35-7.45 Incompatible with life value 6.8-7.8

8. Normal Blood pH Keeping pH within normal range involves balancing acids and bases in body fluids Normal pH for arterial blood: 7.35 to 7.45 Normal pH for venous blood: 7.31 to 7.41 Changes from normal blood pH interfere with many normal functions by: Changing shape of hormones & enzymes Changing distribution of other electrolytes, causing fluid & electrolyte imbalances. Changing of excitable membranes Decreasing effectiveness of many hormones & medications

9. Acid-Base Chemistry Acids Bases Buffers Body fluid chemistry: Bicarbonate ions Relationship between carbon dioxide and hydrogen ions Calculation of free hydrogen ion level

10. pH Control Controlled precisely because even minor deviation from normal can affect body organs Hydrogen ion concentration directly relates to pH

11. Acid pH Higher hydrogen ion concentration more acid the fluid More acid solution lower the pH

12. Sources of Acids Incomplete breakdown of glucose Destruction of cells Bicarbonate

13. Alkaline pH Lower hydrogen ion concentration more alkaline the pH More alkaline fluid higher the pH

14. Acid Base Balance Table

15. Mechanisms Regulate Acid Base Balance pH Buffers: Bicarbonate-Carbonic Acid Buffer System Lungs Kidneys

16. Bicarbonate-Carbonic Acid Buffer System Normal ratio 20 to 1 20 parts HC03- to 1 part H2C03 If alter 20:1 ratio pH will change (not value but ratio that determines pH)

17. What is carbonic acid? Carbon dioxide(C02) potential acid when dissolved in H20 becomes carbonic acid (C02 + H20 = H2C03) Key : When C02 the H2C03 When C02 the H2C03 If either changes so the 20:1 ratio is no longer maintained results in acid base imbalance

18. Respiratory Acid-Base Control Mechanisms Chemical buffers alone cannot prevent changes in blood pH, respiratory system second line of defense against changes: Hyperventilation Hypoventilation

19. Respiratory Mechanism Diagram

20. Lungs Alkaline Excretion of carbon dioxide(C02) Respiratory center regulates amount of C02 exhaled by controlling speed and depth of respirations Increased respiration (tachypnea) C02 level decreases and blood pH becomes more base

21. Lungs Acid Decreased respirations (bradypnea) C02 increases and the blood becomes more acidic. By adjusting the speed and depth of respirations; the respiratory center and lungs are able to regulate blood pH minute to minute

22. Renal Acid-Base Control Mechanisms Kidneys third line of defense against wide changes in body fluid pH Stronger for regulating acid-base balance but take longer to completely respond than chemical & respiratory mechanisms Kidney movement of bicarbonate Formation of acids Formation of ammonium

23. Kidneys Excess acid excreted by kidneys Have ability to alter amount of acid or base excreted but generally process takes hours to days Can retain or excrete hydrogen(H+) and Bicarbonate(HC03-) to restore balance Kidneys can’t compensate with renal failure or severe impairment

24. Compensation Body attempts correct changes in blood pH pH below 6.9 or higher than 7.8 usually fatal Respiratory system more sensitive to acid-base changes; can begin compensation efforts within seconds to minutes Renal compensatory mechanisms much more powerful & result in rapid changes in ECF composition not fully triggered unless imbalance continues for several hours to days

25. Respiratory Compensation Lungs compensate for acid-base imbalances of metabolic origin Example: Prolonged running causes buildup of lactic acid, hydrogen ion levels in ECF increase, pH drops; breathing triggered in response to increased carbon dioxide levels to bring pH level back to normal

26. Renal Compensation Healthy kidney can correct or compensate for changes in blood pH when respiratory system either overwhelmed or unhealthy Example: Person has chronic obstructive pulmonary disease, retains carbon dioxide in blood, blood pH level falls (becomes more acidic); kidney excretes more hydrogen ions & increases re-absorption of bicarbonate back into blood

27. Acidosis and Alkalosis Metabolic caused by an imbalance in production and excretion of acids or bases by kidney Respiratory caused primarily by lung or breathing disorders which affect CO2

28. Normal Arterial Values Parameter Arterial Sample pH 7.35-7.45 PaC02 35-45 mmHg Pa02 80-100 mmHG Oxygen Saturation 95-100% Base Excess + or - 2 HC03- 22-26 mEq/L

29. Acid Base Guide Disorder Initial Event Compensation Respiratory Acidosis PaC02 or normal HC03 pH Kidneys eliminate H+ and retain HCO3- Respiratory Alkalosis PaC02 or normal HC03 pH Kidneys conserve H+ and excrete HC03- Metabolic Acidosis or normal PaC02 HC03- pH Lungs eliminate C02 conserve HC03- Metabolic Alkalosis or normal Pac02 HCO3- pH Lungs ventilation to PC02 kidneys conserve H+ to excrete HC03-

30. Acid Base Key Concept With Respiratory reverse relationship Increase PaC02/HC02 Decrease pH Decrease PaC02/HC02 Increase pH Metabolic acidosis all values decreased (equal) alkalosis all values increased (equal)

31. Metabolic Acidosis Excessive blood acidity characterized by inappropriate low level of bicarbonate Increase in acid and blood becomes acidic

32. Metabolic Acidosis Causes Kidney Failure Diabetic Ketoacidosis Lactic Acidosis Poison: Salicylate(overdose), Methanol(wood alcohol), paraldehyde, ethylene glycol (antifreeze),acetazolamide, ammonia chloride Loss of base through GI tract (diarrhea, ileostomy or colostomy)

33. Metabolic Acidosis Symptoms Mild Nausea, vomiting , fatigue, tachypnea Moderate Extreme weakness, sleepy, confusion, increased nausea Severe Severe drop in BP, shock, coma, death

34. Metabolic Acidosis Treatment Depends on cause Treat underlying cause such as control diabetes or remove toxin from blood Occasionally dialysis Direct treatment Mild: IV fluids and underlying disorder Severe: bicarbonate IV (used with caution)

35. Metabolic Alkalosis Condition in which the blood is alkaline because of an inappropriately high level of bicarbonate

36. Metabolic Alkalosis Causes Body loses too much acid or ingest too much alkali from substance like bicarbonate of soda(baking soda for indigestion) Excessive loss of Na or K affects kidneys ability to control blood acid-base balance Diuretics (thiazides, furosemide, loop diuretics) Loss of acid from vomiting or GI suction Overactivity of adrenal gland (Cushing's or use of steroids)

37. Metabolic Alkalosis Symptoms Mild Can have no symptoms at all Irritably, muscle twitching and muscle cramps Severe Prolonged contraction of and spasms of muscle tetany

38. Metabolic Alkalosis Treatment Replace water and electrolytes (NA and K) Treat underlying cause Severe occasionally dilute acid in the form of ammonium chloride is given IV

39. Respiratory Acidosis Excessive blood acidity caused by build up of carbon dioxide

40. Respiratory Acidosis Causes Anything that interferes with lungs ability to expel carbon dioxide adequately Emphysema, Chronic bronchitis, Asthma Severe pneumonia Pulmonary edema Over-sedation with narcotics sleeping medication or overdose Also with impairment of nerves or muscles that impair mechanics of breathing

41. Respiratory Acidosis Treatment Improve lung function Medications to improve lung function Artificial respirations with a mechanical ventilator

42. Respiratory Alkalosis Condition in which blood is alkaline because of rapid or deep breathing results in a low blood carbon dioxide

43. Respiratory Alkalosis Causes Hyperventilation Anxiety Pain Cirrhosis of the liver Low oxygen levels in the blood Fever Aspirin(salicylate) overdose

44. Respiratory Alkalosis Treatment Slow rate of breathing Administer pain medication Breathe into paper bag helps raise C02 level, person rebreathes C02 back in after breathing out. Hold the breath as long as possible and repeat the sequence 6 to 10 times

45. Let’s Practice http://www.mhhe.com/biosci/ap/ap_casestudies/cases/ap_case14.html http://www.rnceus.com/abgs/abgframe.html

46. Acid Base References http://www.tmc.tulane.edu/departments/anesthesiology/acid/default.html http://qldanaesthesia.com/AcidBaseBook/Abindex.htm Or type in acid base and see what helps you