This document discusses acid-base disorders and interpretation of arterial blood gases (ABGs). It defines acidosis and alkalosis, and describes respiratory and metabolic causes. Simple and mixed acid-base disorders are explained. Compensation by the lungs and kidneys in response to primary disorders is discussed. A stepwise approach to ABG interpretation is provided, including determining the primary disorder, checking for compensation, calculating the anion gap, and identifying specific etiologies. Characteristics of simple acid-base disturbances and combined disorders are summarized.

1. ACIDOSIS & ALKALOSIS ABG INTERPRETATION CRISBERT I. CUALTEROS, M.D.

8. Characteristics of the simple acid-base disturbances  [HCO3-]  Pco2  Respiratory alkalosis  [HCO3-]  Pco2  Respiratory acidosis  Pco2  [HCO3-]  Metabolic alkalosis  Pco2  [HCO3-]  Metabolic acidosis Compensated response Primary Primary pH Disorder

9. Combined Alkalosis Alk Respiratory Alkalosis Acid Alkalotic Metabolic Alkalosis Alk Acidotic Alkali Metabolic Acidosis Acid Alkalotic Combined respiratory and metabolic Acidosis Acid Respiratory Acidosis Alk Acidotic Acid Interpretation HCO3 PCO 2 pH

12. DETERMINE THE PRIMARY DISORDER

19. CHECK THE COMPENSATORY RESPONSE

24. COMPENSATORY RESPONSE HCO 3 = 35 pCO 2 =11 X 0.75 = 8.25 = 8.25 + 40 = 48.25 pCO 2 = 16 x 0.75 = 12 = 12 + 40 = 52 HCO 3 = 40 METABOLIC ALKALOSIS PaCO2 will increase 0.75 mmHg per 1 mmol/L increase in HCO3

25. COMPENSATORY RESPONSE pCO 2 = 55 HCO 3 = 55-40/10= 1.5 1.5 + 24 = 25.5 HCO 3 = 80-40/10= 4 4+24 = 28 pCO 2 =80 ACUTE RESPIRATORY ACIDOSIS HCO3 will increase 1 mmol/L per 10 mmHg increase in PaCO2

26. COMPENSATORY RESPONSE pCO 3 = 55 HCO 3 = 55-40/10 x 4 = 1.5 x 4 = 6 6 + 24 = 30 CHRONIC RESPIRATORY ACIDOSIS HCO3 will increase 4 mmol/L per 10 mmHg increase in PaCO2

27. COMPENSATORY RESPONSE HCO 3 = 80-40/10 x 4 = 16 + 24 = 40 pCO 3 = 80 CHRONIC RESPIRATORY ACIDOSIS HCO3 will increase 4 mmol/L per 10 mmHg increase in PaCO2

28. COMPENSATORY RESPONSE RESPIRATORY ALKALOSIS Acute: HCO3 will decrease 2 mmol/L per 10 mmHg decrease in PaCO2 Chronic: HCO3 will decrease 4 mmol/L per 10 mmHg decrease in PaCO2

29. CALCULATE THE ANION GAP

32. CHECK THE DELTA / DELTA

60. CASE 3 Expected PCO 2 = 6 x 0.75 = 4.5+40 = 44.5 CompensatedMetabolic Alkalosis serum Na 138 63 K 2.7 34 Cl 96 0 HCO 3 30 0 pH 7.45 5.6 pCO 2 45 Plasma Urine PaCO2 will increase 0.75 mmHg per 1 mmol/L increase in HCO3 from 24

61. CASE 3 Anion Gap = Na – (HCO3+Cl) 138 – (30+96) = 12 NAG Plasma Urine serum Na 138 63 K 2.7 34 Cl 96 0 HCO 3 30 0 pH 7.45 5.6 pCO 2 45

62. CASE 3 Plasma Urine serum Na 138 63 K 2.7 34 Cl 96 0 HCO 3 30 0 pH 7.45 5.6 pCO 2 45 What is the cause of the acid base disorder?

63. CASE 3 What is the cause of the acid base disorder? 1) diuretic intake 2) surreptitious vomiting 3) Bartter’s syndrome 4) Adrenal tumor 5) nonreabsorbable anion

64. CASE 3 How should her acid-base disorder be managed? 1) correct hypokalemia 2) hydrate with NSS 3) administer acidyfing agent 4) give carbonic anhydrase inhibitor

72. CASE 4 admission after 48 hrs  pH = acidosis  pCO 2 =acidosis,  HCO 3 = alk Respiratory Acidosis serum Na 136 139 K 3.2 3.9 Cl 78 86 HCO 3 40 38 pH 7.33 7.42 pCO 2 78 61 pO 2 43 56

74. CASE 4 serum Na 136 139 K 3.2 3.9 Cl 78 86 HCO 3 40 38 pH 7.33 7.42 pCO 2 78 61 pO 2 43 56 admission after 48 hrs Expected HCO 3 = 78-40/10 = 3.8 + 24 = 27.8 Respiratory Acidosis & M. Alkalosis

75. CASE 4 serum Na 136 139 K 3.2 3.9 Cl 78 86 HCO 3 40 38 pH 7.33 7.42 pCO 2 78 61 pO 2 43 56 How should this patient be managed? admission after 48 hrs

76. CASE 4 1) intubation and mechanical ventilation 2) low flow oxygenation by nasal prong 3) oxygen by face mask 4) sodium bicarbonate infusion with KCl How should this patient be managed?

88. QUESTIONS?

89. Thank You