Acid Base Balance

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Acid Base Balance

  1. 1. Acid-Base Balance<br />C Washington RN, MSNEd<br />
  2. 2. Acid-Base Balance<br />Homeostasis & optimal cellular function<br />Hydrogen ion concentration of body fluids wnl<br />Hydrogen ion concentration falls<br />pH rises<br />solution become more alkaline or basic<br />
  3. 3. 3 Systems that maintenance pH<br />Buffers<br /><ul><li>Moves or release hydrogen ions</li></ul>Respiratory system<br /><ul><li>Regulate carbonic acid by eliminating or retaining CO2</li></ul>Renal system<br /><ul><li>Long term regulation of acid-base in body</li></li></ul><li>ABG Interpretation: 1st Step<br />Determine if the pH represents acidosis or alkalosis or is perfectly normal<br />
  4. 4. Acid-Base Disorders<br />Hydrogen ions (H+) determines acidity of body fluids<br />Acids release H+ ions in solution<br />Bases accepts H+ ions in solution<br />
  5. 5. Acid-Base Disorders<br />H+ ions concentration of a solution is measured by its pH<br />Normal pH<br />7.35-7.45 (pH of 7 is neutral)<br />
  6. 6. Relationship between H+ ions & pH <br /><ul><li>H+ ion concentration increases
  7. 7. pH falls
  8. 8. Solution becomes more acid
  9. 9. H+ ions concentration falls
  10. 10. pH rises
  11. 11. Solution becomes more alkaline</li></li></ul><li>
  12. 12. Acidic or Alkalotic<br />pH 7.0<br />pH 7.9<br />pH 7.4<br />pH 7.5<br />pH 7.3<br />
  13. 13. Note:<br /><ul><li>pH alone is not sufficient to tell us whether an imbalance is due to a respiratory or metabolic problem
  14. 14. Evaluate other values of ABGs to determine the primary problem
  15. 15. Or whether the body is attempting to compensate for the imbalance</li></li></ul><li>Regulation of Acid-Base Balance<br /><ul><li>Buffer Systems
  16. 16. Protein molecules, phosphate
  17. 17. Helps to maintain a stable pH
  18. 18. Removes or release H+ ions
  19. 19. Excess acid (acidosis) pH <7.35
  20. 20. buffers bind with H+ ions
  21. 21. To alkaline (alkaline) pH >7.45
  22. 22. buffers release H+ ions</li></li></ul><li>Most Important Buffer system<br />Bicarbonate-carbonic acid buffer system<br />Controlled by lungs & kidneys<br />Aeorobic metabolism = to forms of acid<br /> respiratory acid (carbonic acid)<br /> metabolic acids<br />In order to maintain proper pH balance, the<br />body attempts to maintain a ratio of 20:1 (bicarb to carbonic acid)<br />
  23. 23. Regulation of Acid-Base Balance<br /><ul><li>Respiratory System
  24. 24. Eliminates or retains carbon dioxide
  25. 25. ↑ carbon dioxide (acid) stimulate respiration
  26. 26. ↑rate & depth of resp↓ pH to normal range
  27. 27. Alkalosis depresses respiration
  28. 28. ↓ rate & depth of resp retains carbon dioxide</li></ul>Normal PaCO2 = 35- 45 mmHg<br />
  29. 29. ABG Interpretation: 2nd Step<br /><ul><li>Evaluate the pCO2
  30. 30. Determine if it falls within the acceptable range
  31. 31. If pCO2 falls below the lower limit (resp alkalosis)
  32. 32. Id pCO2 falls above the upper limit (respiratory acidosis)
  33. 33. High pCO2 represents acidosis (retention of CO2)
  34. 34. Note: High value in pH represents alkalosis.
  35. 35. High CO2 =CO2 retention or hypoventilation
  36. 36. CO2 is acidotic in the blood=respiratory acidosis</li></li></ul><li>Interpreting pCO2 values<br />pCO2 of 22<br />pCO2 of 32<br />pCO2 of 35<br />pCO2 of 40<br />pCO2 of 45<br />pCO2 of 50<br />pCO2 of 60<br />
  37. 37. Regulation of Acid-Base Balance<br /><ul><li>Renal System
  38. 38. Normal bicarbonate 22-26 mEq/L
  39. 39. Acidosis
  40. 40. Excess H+ ions
  41. 41. pH falls
  42. 42. kidneys excrete H+ and retain bicarbonate
  43. 43. Alkalosis
  44. 44. Kidneys retains H+ ions
  45. 45. excrete bicarbonate</li></li></ul><li>Metabolic Components<br /><ul><li>When there is a loss of acid in the body or
  46. 46. An excess base
  47. 47. HCO3 will be greater than 26
  48. 48. Resulting in metabolic alkalosis
  49. 49. When there is an excess of metabolic acid
  50. 50. Or not enough base
  51. 51. HCO3 will be less than 22
  52. 52. Causing metabolic acidosis</li></li></ul><li>ABG Interpretation: 3rd Step<br /><ul><li>Determine the direction of the the metabolic component HCO#
  53. 53. Whether it is within normal limits
  54. 54. High (metabolic alkalosis)
  55. 55. Low (metabolic acidosis)</li></ul>Think of HCO3 as a base <br /> *too much causes metabolic alkalosis<br /> *too little causes metabolic acidosis<br />
  56. 56. Interpreting HCO3 Values<br />HCO3 of 22<br />HCO3 of 16<br />HCO3 of 30<br />HCO3 of 25<br />HCO3 of 12<br />HCO3 of 27<br />
  57. 57. Base Excess (BE)<br /><ul><li>Metabolic component
  58. 58. Calculation of circulating buffer/base
  59. 59. Normal range BE is -2 to +2</li></ul> BE of -8 represents a deficit of base=metabolic acidosis<br /> BE of +10 representsan excess of base=metabolic alkalosis<br />
  60. 60. Metabolic Acidosis<br />Deficit HCO3<br />Common in cases of kidney disease and diabetes<br />Respiratory Acidosis<br />Excess HCO3<br />Caused by hypoventilation<br />Metabolic Alkalosis<br />Excess HCO3<br />Caused by diarrhea, steroid or diuretic therapy.<br />Respiratory Alkalosis<br />Deficit HCO3<br />Caused by hyperventilation<br />Acid-Base Imbalances<br />
  61. 61.
  62. 62. Acid-Base Imbalances<br /><ul><li>Metabolic Acidosis
  63. 63. Ph < 7.35
  64. 64. HCO3- < 22 mEq/L
  65. 65. Respiratory Acidosis
  66. 66. pH <7.35
  67. 67. PaCO2 > 45 mmHg</li></li></ul><li>
  68. 68.
  69. 69. Acid Base Imbalances<br /><ul><li>Metabolic Alkalosis
  70. 70. pH > 7.45
  71. 71. HCO3- > 26 mEq/L
  72. 72. Respiratory Alkalosis
  73. 73. pH >7.45
  74. 74. PaCO2 <35 mmHg</li></li></ul><li>
  75. 75. Acid Base Imbalance<br />
  76. 76. Practice: Analyzing ABGs<br />
  77. 77. Compensation<br />When there is an imbalance in one parameter of the buffer system (bicarbonate-kidneys) – carbonic acid (lungs) the other tries to compensate for it by causing the opposite imbalance<br />Goal: Restore the 20:1 ratio & return the pH back to the acceptable range 7.35-7.45<br />
  78. 78. ABG Interpretation: Final Step<br />Determine if compensation is present and to what extent<br />When compensation is present, you will see two imbalances<br />The question-Which is the primary problem & which imbalance is due to compensation<br />
  79. 79. Compensation<br />The Clue: pH<br />If the pH is leaning toward acidosis or alkalosis then the parameter with the matching imbalance is the primary problem & the other is due to compensation<br />
  80. 80. Compensation: Example<br />Pt has chronic pulmonary problems & is in a chronic respiratory acidosis.<br />His kidneys will compensate by retaining bicarbonate<br />Creating a metabolic alkalosis to balance his chronic respiratory acidosis<br />
  81. 81. Compensation<br />pH 7.30 acidosis<br />PCO2 70 respiratory acidosis<br />HCO3 30 mild metabolic alkalosis<br />Interpretation<br />Respiratory acidosis with partial compensation by the kidneys. <br />The kidneys have only begun to compensate, because the pH is not back to acceptable limits yet<br />
  82. 82. Supplementary Resources<br />Handout: <br /> “Interpreting Arterial Blood Gases”<br />Nursing Article<br /> ”Perfecting your acid-base balancing act: How to detect and correct acid-base disorders”<br />
  83. 83. <ul><li>The nursing caring for a patient undergoing several days of gastric decompression recognizes that the patient is at risk for which of the following acid-base imbalances?
  84. 84. Metabolic acidosis
  85. 85. Metabolic alkalosis
  86. 86. Respiratory acidosis
  87. 87. Respiratory alkalosis</li></li></ul><li><ul><li>A patient is admitted with suspected heroin overdose & a resp rate of 5 to 6 per minute. Which of the following assessment data would the nurse anticipate? (select all that apply)
  88. 88. pH 7.29
  89. 89. Alert & oriented
  90. 90. PaCO2- 54 mmHg
  91. 91. HCO3- 32 mEq/L
  92. 92. Skin warm & flushed</li></li></ul><li>Client diagnosis: bacterial pneumoniaABGs: pH 7.24, PCO2 65 mmHg & HCO3- 24 mEq/L Antibiotics and O2 started. What is a priority nursing intervention?<br />
  93. 93. Mrs. Mendoza<br />Which assessment data indicate that this client has impaired gas exchange?<br />75-years-old<br />H/O emphysema<br />Adm with Pneumonia<br />Decreased urine output<br />Lethargy<br />Decreased chest excursion<br />hypotension<br />
  94. 94. Mrs. Mendoza<br />Which of the following<br />ABG values indicates that<br />this client is a CO2<br />retainer?<br />PaCO2 = 40 mm Hg<br />PaCO2 = 60 mm Hg<br />Bicarbonate = 42<br />PaO2 = 60 mm Hg<br />
  95. 95. Mrs. Mendoza<br />Which of the following ABGs most likely indicate that she is having a negative response to the administration of oxygen. (next slide)<br />Baseline ABG’s<br />pH 7.36<br />PaCO2 60 mm Hg<br />Pa02 52 mmHg<br />Bicarbonate 42 mEq/L<br />
  96. 96. Mrs. Mendoza<br /><ul><li>pH 7.35
  97. 97. PaCO2 64 mm Hg
  98. 98. Pa02 60 mmHg
  99. 99. Bicarbonate 42 mEq/L
  100. 100. pH 7.36
  101. 101. PaCO2 60 mm Hg
  102. 102. Pa02 60 mmHg
  103. 103. Bicarbonate 42 mEq/L
  104. 104. pH 7.36
  105. 105. PaCO2 60 mm Hg
  106. 106. Pa02 58 mmHg
  107. 107. Bicarbonate 38 mEq/L
  108. 108. pH 7.33
  109. 109. PaCO2 66 mm Hg
  110. 110. Pa02 66 mmHg
  111. 111. Bicarbonate 42 mEq/L</li></li></ul><li>Mrs Mendoza<br />Based on your answer from the last slide, is the client’s respiratory acidosis compensated or uncompensated? Explain your answer.<br />Which immediate interventions are needed for this client.<br />
  112. 112. Mrs Mendoza<br />Later in the shift, you note that his oxygen is set at 5 L/minute. <br />The client says that he asked the nursing assistant to turn up his oxygen because he was havng trouble breathing. <br />What actions, if any, should you take at this time<br />
  113. 113. Mr. Henderson: H/O Cellulites<br />What is the patients acid<br />base imbalance?<br />T 101 F 90/60<br />SOB<br />Diarrhea 2 days<br />pH 7.30<br />pCO2 28<br />Pa02 88<br />HCO3 17<br />
  114. 114. Mr Williams HCO3 level of 17 mEq/L is a result<br />of:<br /><ul><li>Respiratory hypoventilation
  115. 115. Overelimination of bicarbonate
  116. 116. Respiratory compromise
  117. 117. Underelimination of hydrogen ions</li></li></ul><li>Mr. Williams<br />Which of the following symptoms would<br />indicate a worsening of the acidotic condition?<br />Increased blood pressure<br />Anxiety<br />Rising PaCO2<br />Increased urinary output<br />
  118. 118. Mr. Williams<br /><ul><li>Which of the following interventions would be critical in reversing the client’s condition?
  119. 119. Explain whether or not bicarbonate would be given to this client to correct her condition</li></ul>IVFs<br />O2<br />HCO3<br />K+<br />
  120. 120. Mr. Williams<br />What other lab values would be important to monitor at this time? Explain<br />
  121. 121. A patient’s blood pH is decreasing.<br />The nurse realizes that this patient’s hydrogen ion concentration is: <br />
  122. 122. Increasing<br />Decreasing<br />Being affected by oxygen concentration<br />Stabilizing <br />
  123. 123. A patient is admitted with the diagnosis of diabetic ketoacidosis. <br />The nurse realizes that this patient’s body will attempt to attain acid-base balance by:<br />
  124. 124. Decreasing its respiratory rate. <br />Increasing the reabsorption of hydrogen ions.<br />Increasing the secretion of hydrogen ions.<br />Decreasing the reabsorption of bicarbonate.<br />
  125. 125. A patient has a respiratory rate of 20. <br />The nurse calculates this patient’s minute ventilation to be:<br />
  126. 126. 1 L/min<br />2 L/min<br />5 L/min<br />10 L/min<br />
  127. 127. The nurse, admitting a patient with diabetes, believes the patient is attempting to correct an acidotic condition. <br />Which of the following did this nurse most likely observe while assessing this patient?<br />
  128. 128. Slow methodical respirations<br />Deep rapid respirations<br />Change in level of consciousness<br />Intact extraocular movements<br />
  129. 129. The nurse is caring for a patient with metabolic acidosis. <br />The nurse realizes that which of the following laboratory values might be altered for this patient?<br />
  130. 130. Ammonia<br />Blood-urea-nitrogen<br />Creatinine<br />Prothrombin<br />
  131. 131. The nurse is reviewing a patient’s arterial blood gas results. <br />Which of the following values should the nurse study first?<br />
  132. 132. PaCO2<br />HCO3<br />Compensation<br />pH<br />
  133. 133. The nurse is caring for a patient with pneumonia who has arterial blood gas values of: pH 7.20, PaCO2 75, HCO3- 28, PaO2 44.<br />Which of the following would be a priority for this patient? <br />
  134. 134. Assisting the patient to breathe into a paper bag.<br />Preparing to administer Sodium Bicarbonate IV.<br />Placement of the patient in high Fowler’s position.<br />Administration of the prn sedative available.<br />
  135. 135. A patient is admitted in respiratory acidosis secondary to barbiturate overdose. <br />Which of the following will the nurse most likely assess in this patient?<br />
  136. 136. Kussmaul’s respirations <br />Seizures<br />Slow, shallow respirations<br />Increased deep tendon reflexes<br />
  137. 137. The nurse is providing discharge instructions to a patient with respiratory alkalosis. <br />Which of the following statements indicates the patient understands the instructions?<br />
  138. 138. “I will not take my Lasix without a potassium supplement.”<br />“I will not use Mylanta 5-6 times a day like I used to.”<br />“I will take a stress management class or seek counseling.”<br />“I will call my MD the next time I have diarrhea for a few days.”<br />

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