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Acid-Base Disturbances Clinical Approach 2006 Pravit Cadnapaphornchai.

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Presentation on theme: "Acid-Base Disturbances Clinical Approach 2006 Pravit Cadnapaphornchai."— Presentation transcript:

1 Acid-Base Disturbances Clinical Approach 2006 Pravit Cadnapaphornchai

2 Simple vs Mixed Simple Simple When compensation is appropriate When compensation is appropriate Mixed Mixed When compensation is inappropriate When compensation is inappropriate

3 Simple Acid-Base Disturbances When compensation is appropriate When compensation is appropriate Metabolic acidosis (↓ HCO 3, ↓ pCO 2 ) Metabolic alkalosis (↑ HCO 3, ↑ pCO 2 ) Respiratory acidosis (↑ pCO 2, ↑ HCO 3 ) Respiratory alkalosis (↓ pCO 2, ↓ HCO 3 )

4 Stepwise Approaches History & physical examination History & physical examination Arterial blood gas for pH, pCO 2, (HCO 3 ) Arterial blood gas for pH, pCO 2, (HCO 3 ) Use the HCO 3 from ABG to determine compensation Use the HCO 3 from ABG to determine compensation Serum Na, K, Cl, CO 2 content Serum Na, K, Cl, CO 2 content Use CO 2 content to calculate anion gap Use CO 2 content to calculate anion gap Calculate anion gap Calculate anion gap Anion gap = {Na - (Cl + CO 2 content)} Anion gap = {Na - (Cl + CO 2 content)} Determine appropriate compensation Determine appropriate compensation Determine the primary cause Determine the primary cause

5 Organ dysfunction CNS – respiratory acidosis (suppression) and alkalosis (stimulation) CNS – respiratory acidosis (suppression) and alkalosis (stimulation) Pulmonary – respiratory acidosis (COPD) and alkalosis (hypoxia, pulmonary embolism) Pulmonary – respiratory acidosis (COPD) and alkalosis (hypoxia, pulmonary embolism) Cardiac – respiratory alkalosis, respiratory acidosis, metabolic acidosis (pulmonary edema) Cardiac – respiratory alkalosis, respiratory acidosis, metabolic acidosis (pulmonary edema) GI – metabolic alkalosis (vomiting) and acidosis (diarrhea) GI – metabolic alkalosis (vomiting) and acidosis (diarrhea) Liver – respiratory alkalosis, metabolic acidosis (liver failure) Liver – respiratory alkalosis, metabolic acidosis (liver failure) Kidney – metabolic acidosis (RTA) and alkalosis (1 st aldosteone) Kidney – metabolic acidosis (RTA) and alkalosis (1 st aldosteone)

6 Organ Dysfunction Endocrine Endocrine Diabetes mellitus – metabolic acidosis Diabetes mellitus – metabolic acidosis Adrenal insufficiency – metabolic acidosis Adrenal insufficiency – metabolic acidosis Cushing’s – metabolic alkalosis Cushing’s – metabolic alkalosis Primary aldosteronism – metabolic alkalosis Primary aldosteronism – metabolic alkalosis Drugs/toxins Drugs/toxins Toxic alcohols – metabolic acidosis Toxic alcohols – metabolic acidosis ASA – metabolic acidosis and respiratory alkalosis ASA – metabolic acidosis and respiratory alkalosis Theophylline overdose – respiratory alkalosis Theophylline overdose – respiratory alkalosis

7 Stepwise Approaches History & physical examination History & physical examination Arterial blood gas for pH, pCO 2, (HCO 3 ) Arterial blood gas for pH, pCO 2, (HCO 3 ) Use the HCO 3 from ABG to determine compensation Use the HCO 3 from ABG to determine compensation Serum Na, K, Cl, CO 2 content Serum Na, K, Cl, CO 2 content Use CO 2 content to calculate anion gap Use CO 2 content to calculate anion gap Calculate anion gap Calculate anion gap Anion gap = {Na - (Cl + CO 2 content)} Anion gap = {Na - (Cl + CO 2 content)} Determine appropriate compensation Determine appropriate compensation Determine the primary cause Determine the primary cause

8 pH 7.45 Acidosis Metabolic Respiratory Mixed Alkalosis Metabolic Respiratory

9 Stepwise Approaches History & physical examination History & physical examination Arterial blood gas for pH, pCO 2, (HCO 3 ) Arterial blood gas for pH, pCO 2, (HCO 3 ) Use the HCO 3 from ABG to determine compensation Use the HCO 3 from ABG to determine compensation Serum Na, K, Cl, CO 2 content Serum Na, K, Cl, CO 2 content Use CO 2 content to calculate anion gap Use CO 2 content to calculate anion gap Calculate anion gap Calculate anion gap Anion gap = {Na - (Cl + CO 2 content)} Anion gap = {Na - (Cl + CO 2 content)} Determine appropriate compensation Determine appropriate compensation Determine the primary cause Determine the primary cause

10 CO 2 content Low Normal High Metabolic acidosis Normal Metabolic alkalosis Resp alkalosis Mixed Resp acidosis A normal CO 2 content + high anion gap = metabolic acidosis + Metabolic alkalosis or metabolic ac + compensatory respiratory ac.

11 Stepwise Approaches History & physical examination History & physical examination Arterial blood gas for pH, pCO 2, (HCO 3 ) Arterial blood gas for pH, pCO 2, (HCO 3 ) Use the HCO 3 from ABG to determine compensation Use the HCO 3 from ABG to determine compensation Serum Na, K, Cl, CO 2 content Serum Na, K, Cl, CO 2 content Use CO 2 content to calculate anion gap Use CO 2 content to calculate anion gap Calculate anion gap Calculate anion gap Anion gap = {Na - (Cl + CO 2 content)} Anion gap = {Na - (Cl + CO 2 content)} Determine appropriate compensation Determine appropriate compensation Determine the primary cause Determine the primary cause

12 Calculation of Anion Gap in Metabolic Acidosis Anion gap = Na – (Cl + HCO 3 ) Normal 8 ± 2 Correction for low serum albumin Add (4-serum albumin g/dL) X 2.5 to the anion gap

13 Stepwise Approaches History & physical examination History & physical examination Arterial blood gas for pH, pCO 2, (HCO 3 ) Arterial blood gas for pH, pCO 2, (HCO 3 ) Use the HCO 3 from ABG to determine compensation Use the HCO 3 from ABG to determine compensation Serum Na, K, Cl, CO 2 content Serum Na, K, Cl, CO 2 content Use CO 2 content to calculate anion gap Use CO 2 content to calculate anion gap Calculate anion gap Calculate anion gap Anion gap = {Na - (Cl + CO 2 content)} Anion gap = {Na - (Cl + CO 2 content)} Determine appropriate compensation Determine appropriate compensation Determine the primary cause Determine the primary cause

14 Compensations for Metabolic Disturbances Metabolic acidosis Metabolic acidosis pCO 2 = 1.5 x HCO ( ± 2) pCO 2 = 1.5 x HCO ( ± 2) Metabolic alkalosis Metabolic alkalosis pCO 2 increases by 7 for every 10 mEq increases in HCO 3 pCO 2 increases by 7 for every 10 mEq increases in HCO 3

15 How does the kidney compensate for metabolic acidosis?

16 By reabsorbing all filtered HCO 3 By reabsorbing all filtered HCO 3 By excreting H + as NH 4 + (and H 2 PO 4 - ) By excreting H + as NH 4 + (and H 2 PO 4 - )Interpretations Urine pH < 5.5 Urine anion gap Negative

17 Compensations for Respiratory Acidosis Acute respiratory acidosis Acute respiratory acidosis HCO 3 increases by 1 for every 10 mm increases in pCO 2 HCO 3 increases by 1 for every 10 mm increases in pCO 2 Chronic respiratory acidosis Chronic respiratory acidosis HCO 3 increases by 3 for every 10 mm increases in pCO 2 HCO 3 increases by 3 for every 10 mm increases in pCO 2 If you don’t have kidneys, can you have chronic respiratory acidosis?

18 Compensations for Respiratory Alkalosis Acute respiratory alkalosis Acute respiratory alkalosis HCO 3 decreases by 2 for every 10 mm decrease in pCO 2 HCO 3 decreases by 2 for every 10 mm decrease in pCO 2 Chronic respiratory alkalosis Chronic respiratory alkalosis HCO 3 decreases by 4 for every 10 mm decrease in pCO 2 HCO 3 decreases by 4 for every 10 mm decrease in pCO 2 If you don’t have kidneys can you have chronic respiratory alkalosis?

19 Mixed Acid-Base Disorders Mixed respiratory alkalosis & metabolic acidosis Mixed respiratory alkalosis & metabolic acidosis ASA overdose ASA overdose Sepsis Sepsis Liver failure Liver failure Mixed respiratory acidosis & metabolic alkalosis Mixed respiratory acidosis & metabolic alkalosis COPD with excessive use of diuretics COPD with excessive use of diuretics

20 Mixed Acid-Base Disorders Mixed respiratory acidosis & metabolic acidosis Mixed respiratory acidosis & metabolic acidosis Cardiopulmonary arrest Cardiopulmonary arrest Severe pulmonary edema Severe pulmonary edema Mixed high gap metabolic acidosis & metabolic alkalosis Mixed high gap metabolic acidosis & metabolic alkalosis Renal failure with vomiting Renal failure with vomiting DKA with severe vomiting DKA with severe vomiting

21 Stepwise Approaches History & physical examination History & physical examination Arterial blood gas for pH, pCO 2, (HCO 3 ) Arterial blood gas for pH, pCO 2, (HCO 3 ) Use the HCO 3 from ABG to determine compensation Use the HCO 3 from ABG to determine compensation Serum Na, K, Cl, CO 2 content Serum Na, K, Cl, CO 2 content Use CO 2 content to calculate anion gap Use CO 2 content to calculate anion gap Calculate anion gap Calculate anion gap Anion gap = {Na - (Cl + CO 2 content)} Anion gap = {Na - (Cl + CO 2 content)} Determine appropriate compensation Determine appropriate compensation Determine the primary cause Determine the primary cause

22 Generation of Metabolic Acidosis H + HCO 3 - Exogenous acids ASA Toxic alcohol Endogenous acids ketoacids DKA starvation alcoholic Lactic acid L-lactic D-lactate Administration of HCl, NH 4 + Cl, CaCl 2, lysine HCl Loss of HCO 3 diarrhea Compensations Buffers Lungs Kidneys High gapNormal gap If kidney function is normal, urine anion gap Neg

23 H HCO 3 Loss of H + from GI Vomiting, NG suction Congenital Cl diarrhea Loss of H + from kidney 1 st & 2 nd aldosterone ACTH Diuretics Bartter’s, Gitelman’s, Liddle’s Inhibition of β – OH steroid deh Gain of HCO 3 Administered HCO 3, Acetate, citrate, lactate Plasma protein products Compensations Buffer Respiratory Forget the kidney

24 CASE 1 A 24 year old diabetic was admitted for weakness. Serum Na 140, K 1.8, Cl 125, CO 2 6, anion gap 9. pH 6.84 (H + 144) pCO 2 30, HCO 3 5

25 Interpretation of Case 1 Patient has normal gap metabolic acidosis

26 Interpretation of Case 1 Next determine the appropriateness of respiratory compensation Next determine the appropriateness of respiratory compensation pCO 2 = 1.5 x HCO ( ± 2) pCO 2 = 1.5 x HCO ( ± 2) pCO 2 = 1.5 x = 17.5 pCO 2 = 1.5 x = 17.5 The patient’s pCO 2 is 30 The patient’s pCO 2 is 30 The respiratory compensation is inappropriate The respiratory compensation is inappropriate

27 Interpretation of Case 1 This patient has normal anion gap metabolic acidosis with inappropriate respiratory compensation This patient has normal anion gap metabolic acidosis with inappropriate respiratory compensation The finding does not fit DKA but is consistent with HCO 3 loss from the GI tract or kidney The finding does not fit DKA but is consistent with HCO 3 loss from the GI tract or kidney

28 How to differentiate normal gap acidosis resulting from GI HCO 3 loss (diarrhea) vs dRTA?

29 Diarrhea vs RTA Diarrhea Diarrhea History History Urine pH < 5.5 Urine pH < 5.5 Negative urine anion gap Negative urine anion gap dRTA History Urine pH > 5.5 Positive urine anion gap

30 Case 2 A 26 year old woman, complains of weakness. She denies vomiting or taking medications. P.E. A thin woman with contracted ECF. Serum Na 133, K 3.1, Cl 90, CO 2 content 32, anion gap11. pH 7.48 (H + 32), pCO 2 43, HCO UNa 52, UK 50, UCl 0, UpH 8

31 Interpretation of Case 2 Determine the appropriateness of respiratory compensation Determine the appropriateness of respiratory compensation For every increase of HCO 3 by 1, pCO 2 should increase by 0.7 For every increase of HCO 3 by 1, pCO 2 should increase by 0.7 pCO 2 = 40 + (32-25) x 0.7 = 44.9 pCO 2 = 40 + (32-25) x 0.7 = 44.9 The patient’s pCO 2 = 43 The patient’s pCO 2 = 43

32 Interpretation of Case 2 This patient has metabolic alkalosis with appropriate respiratory compensation This patient has metabolic alkalosis with appropriate respiratory compensation

33 Interpretation of Case 2 Urine Na + 52, UK + 50, Cl - 0, pH 8 Urine Na + 52, UK + 50, Cl - 0, pH 8 Urine pH = 8 suggests presence of large amount of HCO 3. The increased UNa and UK are to accompany HCO 3 excretion. The kidney conserves Cl Urine pH = 8 suggests presence of large amount of HCO 3. The increased UNa and UK are to accompany HCO 3 excretion. The kidney conserves Cl The findings are consistent with loss of HCl from the GI tract The findings are consistent with loss of HCl from the GI tract Final diagnosis = Self-induced vomiting Final diagnosis = Self-induced vomiting

34 Vomiting vs Diuretic Active vomiting Active vomiting ECF depletion ECF depletion Metabolic alkalosis Metabolic alkalosis High UNa, UK, low UCl High UNa, UK, low UCl Urine pH > 6.5 Urine pH > 6.5 Remote vomiting Remote vomiting ECF depletion ECF depletion Metabolic alkalosis Metabolic alkalosis Low UNa, high UK, low Cl Low UNa, high UK, low Cl Urine pH 6 Urine pH 6 Active diuretic ECF depletion Metabolic alkalosis High UNa, UK and Cl Urine pH Remote diuretic ECF depletion Metabolic alkalosis Low UNa, high UK, low Cl Urine pH 5-6

35 Case 3 A 40 year old man developed pleuritic chest pain and hemoptysis. His BP 80/50. pH 7.4, pCO 2 25, HCO 3 15 and pO 2 50 A 40 year old man developed pleuritic chest pain and hemoptysis. His BP 80/50. pH 7.4, pCO 2 25, HCO 3 15 and pO 2 50

36 Interpretation of Case 3 A normal pH suggests mixed disturbances A normal pH suggests mixed disturbances

37 Interpretation of Case 3 His pCO 2 is 25, his HCO 3 15 His pCO 2 is 25, his HCO 3 15 If this is acute respiratory alkalosis his HCO 3 should have been 25-{(40-25) x 2/10}= 22 If this is acute respiratory alkalosis his HCO 3 should have been 25-{(40-25) x 2/10}= 22 If this is chronic respiratory alkalosis, his HCO 3 should have been 25 – {(40-25) x 4/10} = 19 If this is chronic respiratory alkalosis, his HCO 3 should have been 25 – {(40-25) x 4/10} = 19 If this is metabolic acidosis, his pCO 2 should have been 1.5 x = If this is metabolic acidosis, his pCO 2 should have been 1.5 x = 30-31

38 Interpretation of Case 3 He has combined respiratory alkalosis and metabolic acidosis He has combined respiratory alkalosis and metabolic acidosis The likely diagnosis is pulmonary embolism with hypotension and lactic acidosis or pneumonia with sepsis and lactic acidosis The likely diagnosis is pulmonary embolism with hypotension and lactic acidosis or pneumonia with sepsis and lactic acidosis Other conditions are ASA overdose, sepsis, liver failure Other conditions are ASA overdose, sepsis, liver failure

39 Case 4 A patient with COPD developed CHF. Prior to treatment his pH 7.35, pCO 2 was 60 and HCO During treatment with diuretics he vomited a few times. His pH after treatment was 7.42, pCO 2 80, HCO A patient with COPD developed CHF. Prior to treatment his pH 7.35, pCO 2 was 60 and HCO During treatment with diuretics he vomited a few times. His pH after treatment was 7.42, pCO 2 80, HCO 3 48.

40 Interpretation of Case 4 Pt’s data pH 7.35, pCO 2 60 and HCO 3 32 Pt’s data pH 7.35, pCO 2 60 and HCO 3 32 For acute respiratory acidosis For acute respiratory acidosis For every 10 mm elevation of pCO 2, HCO 3 increases by 1, his HCO3 should have been 25 + (60-40) x 1/10 = 27 For every 10 mm elevation of pCO 2, HCO 3 increases by 1, his HCO3 should have been 25 + (60-40) x 1/10 = 27 He did not have acute respiratory acidosis He did not have acute respiratory acidosis

41 Interpretation of Case 4 Pt’s data pH 7.35, pCO 2 60 and HCO Pt’s data pH 7.35, pCO 2 60 and HCO For chronic respiratory acidosis For chronic respiratory acidosis For every 10 mm elevation of pCO 2, HCO 3 increases by 3 For every 10 mm elevation of pCO 2, HCO 3 increases by 3 His HCO 3 should have been 25 + (60-40) x 3/10 = 31 His HCO 3 should have been 25 + (60-40) x 3/10 = 31 His HCO 3 is 32 His HCO 3 is 32 He had well compensated chronic respiratory acidosis He had well compensated chronic respiratory acidosis

42 Interpretation of Case 4 His pH is now 7.42, pCO 2 80, HCO 3 48 His pH is now 7.42, pCO 2 80, HCO 3 48 If pCO 2 of 80 is due to chronic respiratory acidosis, HCO 3 should only be 32 +(80-60) x 3/10=38 and not 48 If pCO 2 of 80 is due to chronic respiratory acidosis, HCO 3 should only be 32 +(80-60) x 3/10=38 and not 48 He had combined metabolic alkalosis and respiratory acidosis after treatment of CHF He had combined metabolic alkalosis and respiratory acidosis after treatment of CHF

43 Case 5 A cirrhotic patient was found to be confused. Serum Na 133, K 3.3, Cl 115, CO 2 content 14, anion gap 4 A cirrhotic patient was found to be confused. Serum Na 133, K 3.3, Cl 115, CO 2 content 14, anion gap 4 pH 7.44 (H + 36), pCO 2 20, HCO 3 13 pH 7.44 (H + 36), pCO 2 20, HCO 3 13

44 Interpretation of Case 5 Determine the respiratory compensation Determine the respiratory compensation For chronic respiratory alkalosis, every 10 reduction in pCO 2, HCO 3 should decrease by 4 For chronic respiratory alkalosis, every 10 reduction in pCO 2, HCO 3 should decrease by 4 HCO 3 should be 25 - (40-20) x 4/10=17 HCO 3 should be 25 - (40-20) x 4/10=17 For acute respiratory alkalosis, HCO 3 = 21 For acute respiratory alkalosis, HCO 3 = 21 Patient’s HCO3 is 13, suggesting a metabolic acidotic component is present Patient’s HCO3 is 13, suggesting a metabolic acidotic component is present Anion gap is 4, even corrected for low albumin, is still low suggesting a normal gap metabolic acidosis Anion gap is 4, even corrected for low albumin, is still low suggesting a normal gap metabolic acidosis Patient had combined metabolic acidosis and respiratory alkalosis Patient had combined metabolic acidosis and respiratory alkalosis


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