ABG interpretation Dr Ayman Sabri

2. Case • A 50-Year old woman underwent intestinal bypass for morbid obesity . She has 10-15 watery stool motion per day , she was treated by tincture of opium . Next day she was found somnolent and hypotensive. The plasma value were: • A 50-Year old woman underwent intestinal bypass for morbid obesity . She has 10-15 watery stool motion per day , she was treated by tincture of opium . Next day she was found somnolent and hypotensive. The plasma value were: 2

3. Laboratory data PH 7.02 PaCO2 30 HCO3 (mEq/L) 10 What is your Diagnosis ? HCO3 (mEq/L) Na (mEq/L) 130 K (mEq/L) 3.2 CL (mEq/L) 102 3 What is your Diagnosis ?

6. 1. History taking and physical examination 2. Assess accuracy of data (validity). 3. Identify the primary disturbance 1. Check arterial pH-------- acidosis or alkalosis 2. HCO3 - & pCO2 analysis---primary disorder. 4. Compensatory responses 5. Calculate AG 6. Assess delta ratio 7. Urine anion gab 8. Formulate acid-base diagnosis 1. History taking and physical examination 2. Assess accuracy of data (validity). 3. Identify the primary disturbance 1. Check arterial pH-------- acidosis or alkalosis 2. HCO3 - & pCO2 analysis---primary disorder. 4. Compensatory responses 5. Calculate AG 6. Assess delta ratio 7. Urine anion gab 8. Formulate acid-base diagnosis

8. • Step 1. History taking and physical examination Comprehensive history taking and physical examination can often give clues as to the underlying acid-base disorder • Step 1. History taking and physical examination Comprehensive history taking and physical examination can often give clues as to the underlying acid-base disorder

9. Respiratory alkalosisPulmonary embolus Respiratory acidosisCOPD Metabolic acidosis Dehydration or shock Hyperkalaemia Metabolic alkalosisVomiting , Hypokalaemia Metabolic alkalosisVomiting , Hypokalaemia Metabolic acidosis Severe diarrhea salisylates or alcohol intoxication Metabolic acidosisRenal failure metabolic acidosis Hyperglycaemia (DKA? if ketones present Respiratory alkalosisCirrhosis

13. ValidityValidity

16. 1.Arterial pH 2.Look at PCO2, HCO3

17. • Principle – The body does not fully compensate for primary acid-base disorders. i.e. PH < 7.4 ……. acidosis PH > 7.4 ……. alkalosis • Principle – The body does not fully compensate for primary acid-base disorders. i.e. PH < 7.4 ……. acidosis PH > 7.4 ……. alkalosis

18. Acidosis AlkalosisAcidosis

19. - If PCO2 is the initial chemical change, then process is respiratory. - if HCO3- is the initial chemical change, then process is metabolic. - If PCO2 is the initial chemical change, then process is respiratory. - if HCO3- is the initial chemical change, then process is metabolic.

20. PCO2HCO3PH     AcidosisAcidosis AlkalosisAlkalosis MetabolicMetabolic MetabolicMetabolic        AcidosisAcidosis AlkalosisAlkalosis AlkalosisAlkalosis MetabolicMetabolic RespiratoryRespiratory RespiratoryRespiratory

23. Metabolic acidosis Expected pCO2 = 1.5 x [HCO3] + 8 (range: +/- 2) Metabolic alkalosis Expected pCO2 = 0.7 [HCO3] + 20 (range: +/- 5) “If the actual pCO2 or [HCO3 -] is different from the predicted values, You must suspect a 2nd acid-base disorder” Metabolic acidosis Expected pCO2 = 1.5 x [HCO3] + 8 (range: +/- 2) Metabolic alkalosis Expected pCO2 = 0.7 [HCO3] + 20 (range: +/- 5) “If the actual pCO2 or [HCO3 -] is different from the predicted values, You must suspect a 2nd acid-base disorder”

24. • Acute Respiratory : The [HCO3] will increase by 1 mmol/l for every 10 mmHg elevation in pCO2 above 40 mmHg. Expected [HCO3] = 24 + { (Actual pCO2 - 40) / 10 } • Chronic Respiratory : The [HCO3] will increase by 4 mmol/l for every 10 mmHg elevation in pCO2 above 40mmHg. Expected [HCO3] = 24 + 4 { (Actual pCO2 - 40) / 10} • Acute Respiratory : The [HCO3] will increase by 1 mmol/l for every 10 mmHg elevation in pCO2 above 40 mmHg. Expected [HCO3] = 24 + { (Actual pCO2 - 40) / 10 } • Chronic Respiratory : The [HCO3] will increase by 4 mmol/l for every 10 mmHg elevation in pCO2 above 40mmHg. Expected [HCO3] = 24 + 4 { (Actual pCO2 - 40) / 10}

25. • Acute Respiratory The [HCO3] will decrease by 2 mmol/l for every 10 mmHg decrease in pCO2 below 40 mmHg. Expected [HCO3] = 24 - 2 { ( 40 - Actual pCO2) / 10 } • Chronic Respiratory The [HCO3] will decrease by 5 mmol/l for every 10 mmHg decrease in pCO2 below 40 mmHg. Expected [HCO3] = 24 - 5 { ( 40 - Actual pCO2 ) / 10 } (range: +/- 2) • It takes 2 to 3 days to reach maximal renal compensation • Acute Respiratory The [HCO3] will decrease by 2 mmol/l for every 10 mmHg decrease in pCO2 below 40 mmHg. Expected [HCO3] = 24 - 2 { ( 40 - Actual pCO2) / 10 } • Chronic Respiratory The [HCO3] will decrease by 5 mmol/l for every 10 mmHg decrease in pCO2 below 40 mmHg. Expected [HCO3] = 24 - 5 { ( 40 - Actual pCO2 ) / 10 } (range: +/- 2) • It takes 2 to 3 days to reach maximal renal compensation

28. • The anion gap is defined as the quantity of anions not balanced by cations. • (Na + K) + Unmeasured cations = (Cl + HCO3) + Unmeasured anions • Anion Gap= measured cation- measured anion. • Anion gap = [Na + K] – (Cl + HCO3) • Value: 12 ± 4 meq/L • The anion gap is defined as the quantity of anions not balanced by cations. • (Na + K) + Unmeasured cations = (Cl + HCO3) + Unmeasured anions • Anion Gap= measured cation- measured anion. • Anion gap = [Na + K] – (Cl + HCO3) • Value: 12 ± 4 meq/L

29. Anions and Cations in Serum (Values in mEq/L) CATIONSANIONS Calcium 5Organic acids 5 Magnesium 1.5Sulfates 1 Potassium 4.5Phosphates 2 Actually there is no gap Potassium 4.5Phosphates 2 Sodium 140Proteins 15 Bicarbonates 24 Chlorides 104 Total 151Total 151

31. High Anion Gap Normal anion gap • 1. Ketoacidosis - Diabetic - Alcoholic - Starvation • 2. Lactic acidosis • 3. Toxicosis - Ethylene glycol - Methanol - Salicylates • 4. Advanced renal failure • 1. GIT HCO3 - loss - Diarrhea - External fistulas • 2. Renal HCO3 - loss - Proximal RTA - Distal RTA - Hyperkalemic RTA metabolic acidosis (MUD PILES)(MUD PILES) Methanol Uremia Diabetic ketoacidosis Propylene glycol Isoniazid intoxication Lactic acidosis Ethanol ethylene glycol Salicylates • 1. Ketoacidosis - Diabetic - Alcoholic - Starvation • 2. Lactic acidosis • 3. Toxicosis - Ethylene glycol - Methanol - Salicylates • 4. Advanced renal failure • 1. GIT HCO3 - loss - Diarrhea - External fistulas • 2. Renal HCO3 - loss - Proximal RTA - Distal RTA - Hyperkalemic RTA (MUD PILES)(MUD PILES) Methanol Uremia Diabetic ketoacidosis Propylene glycol Isoniazid intoxication Lactic acidosis Ethanol ethylene glycol Salicylates

32. Osmolal gap Step 1: Calculate Osm = 2[Na+] + glucose/18 + BUN/2.8 Step 2: Measure Osm Step 3: Osmolal gap (measured - calc) should be ≤ 10

33. ‫ﻻ‬‫ﻳ‬‫ﻤ‬‫ﻜ‬‫ﻦ‬‫ﻋ‬‫ﺮ‬‫ض‬‫ا‬‫ﻟ‬‫ﺼ‬‫ﻮ‬‫ر‬‫ة‬.‫ﻗ‬‫ﺪ‬‫ﻻ‬‫ﺗ‬‫ﻜ‬‫ﻮ‬‫ن‬‫ھ‬‫ﻨ‬‫ﺎ‬‫ك‬‫ﻣ‬‫ﺴ‬‫ﺎ‬‫ﺣ‬‫ﺔ‬‫ﻛ‬‫ﺎ‬‫ﻓ‬‫ﯿ‬‫ﺔ‬‫ﻟ‬‫ﻠ‬‫ﺬ‬‫ا‬‫ﻛ‬‫ﺮ‬‫ة‬‫ﻋ‬‫ﻠ‬‫ﻰ‬‫ا‬‫ﻟ‬‫ﻜ‬‫ﻤ‬‫ﺒ‬‫ﯿ‬‫ﻮ‬‫ﺗ‬‫ﺮ‬‫ﻟ‬‫ﻔ‬‫ﺘ‬‫ﺢ‬‫ا‬‫ﻟ‬‫ﺼ‬‫ﻮ‬‫ر‬‫ة‬‫أ‬‫و‬‫ﻗ‬‫ﺪ‬‫ﺗ‬‫ﻜ‬‫ﻮ‬‫ن‬‫ا‬‫ﻟ‬‫ﺼ‬‫ﻮ‬‫ر‬‫ة‬‫ﺗ‬‫ﺎ‬‫ﻟ‬‫ﻔ‬‫ﺔ‬.‫ﻗ‬‫ﻢ‬‫ﺑ‬‫ﺈ‬‫ﻋ‬‫ﺎ‬‫د‬‫ة‬‫ﺗ‬‫ﺸ‬‫ﻐ‬‫ﯿ‬‫ﻞ‬‫ا‬‫ﻟ‬‫ﻜ‬‫ﻤ‬‫ﺒ‬‫ﯿ‬‫ﻮ‬‫ﺗ‬‫ﺮ‬،‫ﺛ‬‫ﻢ‬‫ا‬‫ﻓ‬‫ﺘ‬‫ﺢ‬‫ا‬‫ﻟ‬‫ﻤ‬‫ﻠ‬‫ﻒ‬‫ﻣ‬‫ﺮ‬‫ة‬‫أ‬‫ﺧ‬‫ﺮ‬‫ى‬.‫إ‬‫ذ‬‫ا‬‫ﻇ‬‫ﻠ‬‫ﺖ‬‫ﻋ‬‫ﻼ‬‫ﻣ‬‫ﺔ‬x‫ا‬‫ﻟ‬‫ﺤ‬‫ﻤ‬‫ﺮ‬‫ا‬‫ء‬‫ﺗ‬‫ﻈ‬‫ﮫ‬‫ﺮ‬،‫ﻗ‬‫ﺪ‬‫ﺗ‬‫ﻀ‬‫ﻄ‬‫ﺮ‬‫إ‬‫ﻟ‬‫ﻰ‬‫ﺣ‬‫ﺬ‬‫ف‬‫ا‬‫ﻟ‬‫ﺼ‬‫ﻮ‬‫ر‬‫ة‬‫ﺛ‬‫ﻢ‬‫إ‬‫د‬‫ر‬‫ا‬‫ﺟ‬‫ﮫ‬‫ﺎ‬‫ﻣ‬‫ﺮ‬‫ة‬‫أ‬‫ﺧ‬‫ﺮ‬‫ى‬.

34. Low Anion Gap - Hypoalbuminemia - Plasma cell dyscrasia - Monoclonal protein - Bromide intoxication - Normal variant Corrected AG= Anion Gap + 2.5 x (4- Albumin) - Hypoalbuminemia - Plasma cell dyscrasia - Monoclonal protein - Bromide intoxication - Normal variant Corrected AG= Anion Gap + 2.5 x (4- Albumin)

37. • If a metabolic acidosis is diagnosed, then the Delta Ratio should be checked Delta ratio= ∆ Anion gap/∆ [HCO3-] ∆ Anion gap = (12-AG) ∆ [HCO3-] = (24 - [HCO3-])

38. Delta ratio Assessment Guidelines < 0.4 Hyperchloremic normal anion gap acidosis < 1 High AG & normal AG acidosis 1 to 2 Pure Anion Gap Acidosis Lactic acidosis: average value 1.6 DKA more likely to have a ratio closer to 1 due to urine ketone loss Pure Anion Gap Acidosis Lactic acidosis: average value 1.6 DKA more likely to have a ratio closer to 1 due to urine ketone loss > 2 High AG acidosis and a concurrent metabolic alkalosis or a pre-existing compensated respiratory acidosis

41. Urine anion gab= (N a +K) -Cl POSITIVE urinary anion gab NEGATIVE urinary anion gab (normal NH(normal NH33 excreationexcreation)) POSITIVE urinary anion gab NEGATIVE urinary anion gab (normal NH(normal NH33 excreationexcreation)) GUT causes NEGATIVEn bowel causes Urinary causes

44. Final DiagnosisFinal DiagnosisFinal DiagnosisFinal Diagnosis

45. Case • A 50-Year old woman underwent intestinal bypass for morbid obesity . She has 10-15 watery stool motion per day , she was treated by tincture of opium . Next day she was found somnolent and hypotensive. The plasma value were: • A 50-Year old woman underwent intestinal bypass for morbid obesity . She has 10-15 watery stool motion per day , she was treated by tincture of opium . Next day she was found somnolent and hypotensive. The plasma value were: 45

46. Laboratory data PH 7.02 PaCO2 30 HCO3 (mEq/L) 10 H = (PCO2/ HCO3) ×24 =PH-7.8 ×100 H= (30/10)X24=7.02-7.8X100 Validity PH= acidosis------Hco3= Met acidosis Primary defect Expected pCO2 = 1.5 x [HCO3] + 8 (range: +/- 2) =1.5X10+8= 22 pco2 30 added respiratory acidosis. CompensationHCO3 (mEq/L) 10 Na (mEq/L) 130 K (mEq/L) 3.2 CL (mEq/L) 102 46 Expected pCO2 = 1.5 x [HCO3] + 8 (range: +/- 2) =1.5X10+8= 22 pco2 30 added respiratory acidosis. Compensation = [Na+] – [HCO3 -] – [Cl-] =130-(10+ 102)= 18 High AG AG Anion gap/∆ [HCO3-] =18-12/24-10= <1 (0.42). High AG & normal AG acidosis Delta ratio

47. Final diagnosis: • Normal Anion gap and high Anion gap metabolic acidosis+ combined respiratory acidosis. – Lactic acidosis (hypotension) – Metabolic acidosis due to HCO3 loss (diarrhea). – Respiratory acidosis due to respiratory depression by opiate. • Normal Anion gap and high Anion gap metabolic acidosis+ combined respiratory acidosis. – Lactic acidosis (hypotension) – Metabolic acidosis due to HCO3 loss (diarrhea). – Respiratory acidosis due to respiratory depression by opiate.

48. Case • A 23y old women with rheumatoid artheritis increased her dose of salicylate because of flare up. She developed epigastric pain and vomiting that persist for 2 days. She went to local hospital where the following blood result obtained: • PH =7.61 Pco2 25mmHg, Hco3 =33mmol/l. • What is your acid base diagnosis? • A 23y old women with rheumatoid artheritis increased her dose of salicylate because of flare up. She developed epigastric pain and vomiting that persist for 2 days. She went to local hospital where the following blood result obtained: • PH =7.61 Pco2 25mmHg, Hco3 =33mmol/l. • What is your acid base diagnosis?

49. Laboratory data PH 7.61 PaCO2 25mmHg. What is your Diagnosis ? PaCO2 25mmHg. HCO3 (mEq/L) 33mmol/l. 49 What is your Diagnosis ?

50. Laboratory data PH 7.61 PaCO2 25mmHg. HCO3 (mEq/L) 33mmol/l. H = (PCO2/ HCO3) ×24 =PH-7.8 ×100 H= (25/33)X24=7.61-7.8X100Validity PH= alkalosis------increased Hco3= Metabolic alkalosis Primary defect Metabolic alkalosis Expected pCO2 = 0.7x [HCO3] + 20 (range: +/- 2) =0.7X33+ 20=43 So compansation is not adaqaute respiratory alkalosis. CompensationHCO3 (mEq/L) 33mmol/l. 50 Metabolic alkalosis Expected pCO2 = 0.7x [HCO3] + 20 (range: +/- 2) =0.7X33+ 20=43 So compansation is not adaqaute respiratory alkalosis. Compensation Final diagnosis Combined Metabolic alkalosis (GIT loss Vomiting ) and respiratory alkalosis with salicylate.

51. Let’s play tic-tac-toe

52. PH 7.26 PaCO2 42 HCO3 17 AlkalineNormalAcidic PH Pa CO2 HCO3 Metabolic acidosis

53. PH 7.49 PaCO2 30 HCO3 23 AlkalineNormalAcidic PHHCO3 Pa CO2 Respiratory alkalosis

54. PH 7.26 PaCO2 52 HCO3 34 AlkalineNormalAcidic PH HCO3 Pa CO2 Respiratory acidosis with compensation (Partial)

55. PH 7.48 PaCO2 51 HCO3 29 AlkalineNormalAcidic PH Pa CO2 HCO3 Metabolic alkalosis with compensation (Partial)

56. PH 7.36 PaCO2 50 HCO3 34 AlkalineNormalAcidic PHPa CO2 HCO3 Respiratory acidosis with compensation (complete)

57. PH 7.43 PaCO2 49 HCO3 30 AlkalineNormalAcidic PHPa CO2 HCO3 Metabolic alkalosis with compensation (complete)

ABG interpretation Dr Ayman Sabri

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