1. Arterial Blood Gases Mark Carpenter January 2013

2. Can I use anonymised data from this presentation for future teaching/Research? 1.Yes 2.No

6. Objectives Develop an organised system for looking at blood gasesDevelop an organised system for looking at blood gases Be able to comment on the arterial pO2 in relation to the FiO2Be able to comment on the arterial pO2 in relation to the FiO2 Detect metabolic acidosis and it’s significance in the acutely unwellDetect metabolic acidosis and it’s significance in the acutely unwell

7. 6-step approach 1.Assess Oxygenation –Is the patient hypoxic –Is there a problem with oxygenation? 2.Determine Acid-Base Deficit –pH>7.45 (H + 7.45 (H + < 35) alkalaemia –pH 45) acidaemia 3.Determine the respiratory component, and does this explain the acid-base deficit –PaCO 2 :>6.0 kPa - respiratory acidosis <4.7kPa - respiratory alkalosis <4.7kPa - respiratory alkalosis

8. 6-step approach 4.Determine the metabolic component, and does this explain the acid-base deficit –HCO 3 -: <22 mmol/l - metabolic acidosis >26 mmol/l - metabolic alkalosis 5.Which is the primary problem : remember compensation never (rarely) completely restores pH to the normal range, and a mixed picture may be present 6.Is there any compensation and if so what is it?

9. Different metabolic processes, of different magnitudeDifferent metabolic processes, of different magnitude Net effect is what determines pHNet effect is what determines pH “Like a bath”“Like a bath” Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9

10. Respiratory Acidosis Any cause of hypoventilation –CNS depression –Neuromuscular disease –Acute or chronic lung disease –Cardiac arrest –Ventilator malfunction

11. Respiratory Alkalosis Any cause of hyperventilation –Hypoxia –Acute lung conditions –Anxiety –Fever –Pregnancy –Hepatic failure –Some central CNS lesions

12. Metabolic Acidosis Increased anion gap (added acid)Increased anion gap (added acid) –Renal failure –Ketoacidosis –Lactic acidosis –Salicylate/Tricyclic overdose

13. Metabolic Acidosis Decreased anion gap (loss of bicarbonate)Decreased anion gap (loss of bicarbonate) –Renal tubular acidosis –Diarrhoea –Carbonic anhydrase inhibitors –Ureteral diversion –Chloride administration

14. Metabolic Alkalosis Loss of acid or gaining alkali –Vomiting –Diarrhoea –Diuretics (and hypokalaemia generally) –Ingestion of alkali

15. Reminder of normal values pH = 7.35 – 7.45pH = 7.35 – 7.45 pO 2 = 10 -13 kPa on airpO 2 = 10 -13 kPa on air pCO 2 = 4.6 – 6.0 kPapCO 2 = 4.6 – 6.0 kPa HCO 3 = 25 – 35 mmols/lHCO 3 = 25 – 35 mmols/l Base excess ± 2.0Base excess ± 2.0 Anion gap 10 -18Anion gap 10 -18

16. Case 1 Young female admitted with overdose of unknown tablets pO 2 15 kPa on air pH7.24 PaCO 2 2.5 HCO 3 8

17. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

18. 1: Is there a problem with Oxygenation? 1.Yes 2.No

19. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

20. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

21. 3b: Does this explain the pH? 1.Yes 2.No

22. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

23. 4b: Does this explain the pH? 1.Yes 2.No

24. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

25. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

26. Case 1 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.24

27. Case 2 Elderly male admitted from nursing home with one week history of fever and vomiting pO 2 12 kPa on 4l by mask pH7.49 PaCO 2 6.3 HCO 3 35

28. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

29. 1: Is there a problem with Oxygenation? 1.Yes 2.No

30. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

31. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

32. 3b: Does this explain the pH? 1.Yes 2.No

33. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

34. 4b: Does this explain the pH? 1.Yes 2.No

35. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

36. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

37. Case 2 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.49

38. Case 3a Middle aged man admitted with cough sputum and haemoptysis. Life-long smoker pO 2 4 on air pH7.19 PaCO 2 9.7 HCO 3 28

39. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

40. 1: Is there a problem with Oxygenation? 1.Yes 2.No

41. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

42. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

43. 3b: Does this explain the pH? 1.Yes 2.No

44. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

45. 4b: Does this explain the pH? 1.Yes 2.No

46. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

47. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

48. Case 3a Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.19

49. Case 3b Middle aged man admitted with cough sputum and haemoptysis. Life-long smoker pO 2 6 on airSpO2 92% pH7.32 PaCO 2 10.0 HCO 3 39

50. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

51. 1: Is there a problem with Oxygenation? 1.Yes 2.No

52. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

53. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

54. 3b: Does this explain the pH? 1.Yes 2.No

55. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

56. 4b: Does this explain the pH? 1.Yes 2.No

57. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

58. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

59. Case 3b Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.32

60. Case 4 Middle aged man awake and breathing spontaneously on ET tube following cardiac arrest pO 2 35 FiO2 0.8 pH6.9 PaCO 2 8.9 HCO 3 13

61. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

62. 1: Is there a problem with Oxygenation? 1.Yes 2.No

63. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

64. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

65. 3b: Does this explain the pH? 1.Yes 2.No

66. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

67. 4b: Does this explain the pH? 1.Yes 2.No

68. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

69. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

70. Case 4 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9

71. Case 5 Elderly lady with congestive cardiac failure pO 2 9 on 40% oxygen pH7.64 PaCO 2 3.5 HCO 3 29

72. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis

73. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

74. 1: Is there a problem with Oxygenation? 1.Yes 2.No

75. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

76. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

77. 3b: Does this explain the pH? 1.Yes 2.No

78. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

79. 4b: Does this explain the pH? 1.Yes 2.No

80. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

81. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

82. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis

83. Did you change your answer?? 1.Yes 2.No Be Honest!!

84. Case 5 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.64

85. Case 6 Young diabetic male admitted with chest infection, vomiting and drowsiness pO 2 12 on air pH7.31 PaCO 2 1.6 HCO 3 6.0

86. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis

87. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

88. 1: Is there a problem with Oxygenation? 1.Yes 2.No

89. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

90. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

91. 3b: Does this explain the pH? 1.Yes 2.No

92. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

93. 4b: Does this explain the pH? 1.Yes 2.No

94. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

95. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

96. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis

97. Did you change your answer?? 1.Yes 2.No Be Honest!!

98. Case 6 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.31

99. Case 7 54 yr-old lady post MI. Acutely unwell, cold, clammy, hypotensive and oliguric pO 2 10 on 60% oxygen pH6.99 PaCO 2 7.8 HCO 3 14

100. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis

101. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

102. 1: Is there a problem with Oxygenation? 1.Yes 2.No

103. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

104. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

105. 3b: Does this explain the pH? 1.Yes 2.No

106. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

107. 4b: Does this explain the pH? 1.Yes 2.No

108. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

109. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

110. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis

111. Did you change your answer?? 1.Yes 2.No Be Honest!!

112. Case 7 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 6.99

113. Case 8 50 yr-old man admitted with exacerbation of long-standing bronchial asthma. Respiratory rate of 30 pO 2 5.1 on 60% oxygen pH7.39 PaCO 2 5.8 HCO 3 26

114. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid–Base issue

115. 1: Assess Oxygenation: Is the patient Hypoxaemic? 1.Yes 2.No

116. 1: Is there a problem with Oxygenation? 1.Yes 2.No

117. 2: Assess Acid-Base Status 1.Acidaemic 2.Neutral 3.Alkalaemic

118. 3: Assess Metabolic Component… 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Neither

119. 3b: Does this explain the pH? 1.Yes 2.No

120. 4: Assess the Respiratory Component 1.Resp Acidosis 2.Resp Alkalosis 3.Neither

121. 4b: Does this explain the pH? 1.Yes 2.No

122. 5: Which is Primary? 1.Metabolic Acidosis 2.Metabolic Alkalosis 3.Respiratory Acidosis 4.Respiratory Alkalosis 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid/Base problem

123. 6: Is there any compensation? 1.No it’s mixed 2.No 3.Resp Acidosis 4.Resp Alkalosis 5.Met Acidosis 6.Met Alkalosis

124. So what is it?? 1.Resp Acidosis with compensation 2.Met Alkalosis with compensation 3.Resp Alkalosis with compensation 4.Met Alkalosis with compensation 5.Mixed Acidosis 6.Mixed Alkalosis 7.No Acid–Base issue

125. Did you change your answer?? 1.Yes 2.No Be Honest!!

126. Case 8 Alkalaemia normal Acidaemia 7.6 7.4 5 7.3 5 6.9 7.39

127. Questions ?

128. Summary Develop an organised system for looking at blood gases Develop an organised system for looking at blood gases Be able to comment on the arterial pO2 in relation to the FiO 2 Be able to comment on the arterial pO2 in relation to the FiO 2 Detect metabolic acidosis and it’s significance in the acutely unwell Detect metabolic acidosis and it’s significance in the acutely unwell