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ABG INTERPRETATION Teaching file.

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1 ABG INTERPRETATION Teaching file

2 STEPWISE APPROACH Obtain clues from the clinical setting
Determine primary disorder Check the compensatory response Calculate the anion gap Calculate the delta/deltas Identify specific etiologies for the acid-base disorder Prescribe treatment

3 DETERMINE CLUES FROM THE CLINICAL SETTING

4 CLUES FROM CLINICAL SETTING
HIGH ANION GAP METABOLIC ACIDOSIS: AG, normal Cl Lactic acidosis Ketoacidosis Ingestions; alcohol, INH, methanol, ethylene glycol Renal failure Massive rhabdomyolysis

5 CLUES FROM CLINICAL SETTING
NORMAL ANION GAP METABOLIC ACIDOSIS Normal AG, Cl Diarrhea- GI loss of HCO3 RTA- renal loss of HCO3 Ingestion of ammonium chloride or hyperalimentation fluids Acetazolamide therapy

6 CLUES FROM CLINICAL SETTING
METABOLIC ALKALOSIS (urine Cl < 10 mEq/d) Vomiting Remote diuretic use Post hypercapnea Chronic diarrhea Cystic fibrosis

7 CLUES FROM CLINICAL SETTING
METABOLIC ALKALOSIS (urine Cl > 10 mEq/d) Bartter’s syndrome Severe potassium depletion Current diuretic use Hypercalcemia Hyperaldosteronism Cushing’s syndrome

8 CLUES FROM CLINICAL SETTING
RESPIRATORY ACIDOSIS CHRONIC: COPD ACUTE: pneumonia RESPIRATORY ALKALOSIS Hyperventilation

9 DETERMINE THE PRIMARY DISORDER

10 Important values at normal physiologic state
HCO3= 24 mmol/L (18-26 mmol/L) pCO2= 40 mmHg ( mmHg)

11 Characteristics of primary acid base disturbances
disorder pH (H+) Primary disturb Compensa-tory response Met Acidosis Dec inc Dec (HCO3) Dec PCO2 Met Alkalosis dec Inc (HCO3) Inc PCO2 Resp acid Inc (PCO2) Inc HCO3 Resp alkalosis Dec (PCO2) Dec HCO3

12 HCO3 generation- kidneys
Moving on… disorder Primary abnormality Secondary response Resp acidosis hypoventilation HCO3 generation- kidneys Resp alkalosis hyperventilation HCO3 consumption Metabolic acidosis Loss of HCO3 or gain H+ Hyperventilation Metabolic alkalosis Gain of HCO3 or lose H+

13 Moving on… Metabolic acidosis Dec HCO3
1.2 mmHg dec in PCO2 foe every 1 meq/L fall in HCO3 Metabolic alkalosis Inc HCO3 0.7 mmHg inc in CO2 for every 1 meq/L rise in HCO3 Respiratory acidosis Inc PCO2 1 meq/L inc in HCO3 for every 10 mmHg rise in PCO2 Respiratory alkalosis Dec PCO2 2 meq/L dec in HCO3 for every 10 mmHg fall in PCO2

14 DETERMINE PRIMARY DISORDER
Check the trend of the pH, HCO3, pCO2 The change that produces the pH is the primary disorder pH = HCO3 = 12 pCO2 = 30 ACIDOSIS ACIDOSIS ALKALOSIS METABOLIC ACIDOSIS

15 DETERMINE PRIMARY DISORDER
Check the trend of the pH, HCO3, pCO2 The change that produces the pH is the primary disorder pH = HCO3 = 28 pCO2 = 60 ACIDOSIS ALKALOSIS ACIDOSIS RESPIRATORY ACIDOSIS

16 DETERMINE PRIMARY DISORDER
Check the trend of the pH, HCO3, pCO2 The change that produces the pH is the primary disorder pH = HCO3 = 19 pCO2 = 20 ALKALOSIS ACIDOSIS ALKALOSIS RESPIRATORY ALKALOSIS

17 DETERMINE PRIMARY DISORDER
If the trend is the same, check the percent difference The bigger %difference is the 10 disorder (16-24)/24 = 0.33 (60-40)/40 = 0.5 pH = HCO3 = 16 pCO2 = 60 ACIDOSIS ACIDOSIS ACIDOSIS RESPIRATORY ACIDOSIS

18 DETERMINE PRIMARY DISORDER
If the trend is the same, check the percent difference The bigger %difference is the 10 disorder (38-24)/24 = 0.58 (30-40)/40 = 0.25 pH = HCO3 = 38 pCO2 = 30 ALKALOSIS ALKALOSIS ALKALOSIS METABOLIC ALKALOSIS

19 CHECK THE COMPENSATORY RESPONSE

20 Examples: in simple metabolic acidosis
If patient presents with pH=7.2 and HCO3=16, what is the normal compensated value for pCO2? 24-16= 8 meq/L  8 x 1.2 = 9.6 mmHg fall in PCO2 40 mmHg-9.6 mmHg = 30.4 mmHg Normal compensation PCO2 = 30.4 mmHg

21 Example 2 If patient presents with pH= HCO3= 22 meq/L, and pCO2= 9, what is your interpretation? Note the pH and tell whether it is acidosis or alkalosis? Note the HCO3 and pCO2 values to determine which causes the primary disturbance? Determine the compensatory response What is our diagnosis?

22 CALCULATE THE ANION GAP

23 ANION GAP Na – (HCO3 + Cl) = 12 + 4 Na = 135 HCO3 = 15
Cl = RBS = 100 mg% AG = 135 – 112 = 23

24 Corrected Na = Na + RBS mg% -100 x 1.6
ANION GAP Na – (HCO3 + Cl) = Na = HCO3 = 15 Cl = RBS = 500 mg% Corrected Na = Na + RBS mg% x 1.6 100 AG = – 112 = 29.4

25 CHECK THE DELTA / DELTA

26 Delta-delta Cl HCO3 NAGMA

27 Delta-delta HCO3 AG HAGMA

28 Delta values HCO3 = HCO3 patient – HCO3 normal
HCO3 patient – 24 mmol/L AG = AG patient – AG normal AG patient – 12 meq/L Cl= Cl patient – Cl normal Cl patient – 105 mmol/L

29 NAGMA with metabolic alkalosis
Pure NAGMA HCO3 = Cl HCO3 <  Cl >  Cl NAGMA with metabolic alkalosis NAGMA plus HAGMA

30 HAGMA with metabolic alkalosis
Pure HAGMA HCO3 = AG HCO3 <  AG >  AG HAGMA with metabolic alkalosis HAGMA plus NAGMA

31 Confused?... Sample problems
ABG: HCO3 = 15 mmol/L AG= 21 meq/L What type of metabolic acidosis are we dealing? Calculate your delta values Determine any underlying metabolic disorder based on the comparison of delta values?

32 Solution Step 1 The anion gap is elevated ( N value is 12), chloride values are not given so we assume them to be normal. Therefore we have HAGMA Step 2 HCO3 = 24 mmol/L – 15 mmol/L = 9 mmol/L AG = 21 meq/L – 12 meq/L = 9 mmol/L

33 solution Step 3: Compare your delta values HCO3 AG 9 mmol/L 9mmol/L
The values are equal Diagnosis: Pure HAGMA

34 Isa pa… Problem No 2 ABG: HCO3 = 15 mmol/L AG = 30 meq/L
Step 1: what type of metabolic acidosis Step 2: calculate your delta waves Step 3: compare your delta values Step 4: diagnosis

35 Problem 3 ABG: HCO3 = 15 mmol/L Cl = 114 meq/L
Step 1: we have a Cl elevation instead of an anion gap elevation therefore we have a NAGMA Step 2: HCO3: 24-15= 9 mmol/L Cl: meq/L = 9 mmol/L Step 3: Compare 9 mmol/L mmol/L Step 4: Pure NAGMA

36 PE showed BP = 80/60, HR = 110, RR = 28. There is poor skin turgor.
CASE 1 56F with vomiting and diarrhea 3 days ago despite intake of loperamide. Her last urine output was 12 hours ago. PE showed BP = 80/60, HR = 110, RR = 28. There is poor skin turgor.

37 CASE 1 serum Na = 130 pH = 7.30 K = 2.5 pCO2 = 30 Cl = 105 HCO3 = 15
BUN = 15 pO2 = 90 crea = 177 RBS = 100 BCR = BUN / crea x = 21 PRE-RENAL

38 pH = acidosis, pCO2 =alk, HCO3 = acidosis
CASE 1 serum Na = pH = 7.30 K = pCO2 = 30 Cl = HCO3 = 15 BUN = 15 pO2 = 90 crea = 177 RBS = 100 pH = acidosis, pCO2 =alk, HCO3 = acidosis Metabolic Acidosis

39 CompensatedMetabolic Acidosis
CASE 1 serum Na = pH = 7.30 K = pCO2 = 30 Cl = HCO3 = 15 BUN = 15 pO2 = 90 crea = 177 RBS = 100 CompensatedMetabolic Acidosis pCO2 = 9 x 1.2 = 10.8

40 CASE 1 serum Na = 130 pH = 7.30 K = 2.5 pCO2 = 30 Cl = 105 HCO3 = 15
BUN = 15 pO2 = 90 crea = 177 RBS = 100 AG= 130 – (105+15) = 10 NAGMA

41 NAGMA + metabolic alkalosis
CASE 1 serum Na = pH = 7.30 K = pCO2 = 30 Cl = HCO3 = 15 BUN = 15 pO2 = 90 crea = 177 RBS = 100 /= ( )/(24-15) = 0.56 NAGMA + metabolic alkalosis

42 CASE 1 56F with vomiting and diarrhea 3 days ago despite intake of loperamide. Her last urine output was 12 hours ago. PE showed BP = 80/60, HR = 110, RR = 28. There is poor skin turgor. pH 7.30, HCO3=15, pCO2=30, Na=130 K=2.5 How will you correct the acid base disorder?

43 How will you correct the acid base disorder?
CASE 1 1) Hydrate 2) Hydrate + IV NaHCO3 3) Hydrate + oral NaHCO3 4) Hydrate + correct hypokalemia How will you correct the acid base disorder?

44 INDICATIONS FOR HCO3 THERAPY
pH < 7.2 and HCO3 < 5 – 10 mmHg When there is inadequate ventilatory compensation Elderly on beta blockers in severe acidosis with compromised cardiac function Concurrent severe AG and NAGMA Severe acidosis with renal failure or intoxication

45 COMPLICATIONS OF HCO3 THERAPY
Volume overload Hypernatremia Hyperosmolarity Hypokalemia Intracellular acidosis Causes overshoot alkalosis Stimulates organic acid production  tissue O2 delivery NaHCO3 50 ml = 45 mEq Na NaHCO3 gr X tab = 7 mEq Na

46 1 potassium durule = 10 mEq K
POTASSIUM CORRECTION K deficit = (3.5 – K)/0.27 x 100 Give ½ of the deficit in 24 hours K deficit = (3.5 – 2.5)/0.27 x 100 = 370 1 cc oral KCL = 1.33 mEq K 1 potassium durule = 10 mEq K

47 30M with epilepsy has a grand mal seizure. Labs showed:
CASE 2 30M with epilepsy has a grand mal seizure. Labs showed: pH = Na = 140 pCO2= K = 4 HCO3 = 17 Cl = 98 %pCO2 =13, %HCO3 = 29 Metabolic Acidosis

48 CASE 2 30M with epilepsy has a grand mal seizure. Labs showed:
pH = Na = 140 pCO2= K = 4 HCO3 = 17 Cl = 98 Metabolic & Respiratory Acidosis pCO2 =7 x 1.2 = 8.4

49 30M with epilepsy has a grand mal seizure. Labs showed:
CASE 2 30M with epilepsy has a grand mal seizure. Labs showed: pH = Na = 140 pCO2= K = 4 HCO3 = 17 Cl = 98 AG = 140 – (98+17) = 25 HAGMA + RAc

50 30M with epilepsy has a grand mal seizure. Labs showed:
CASE 2 30M with epilepsy has a grand mal seizure. Labs showed: pH = Na = 140 pCO2= K = 4 HCO3 = 17 Cl = 98 /= (25-12)/(24-17) = 1.9 HAGMA + MAlk + RAc

51 CASE 2 30M with epilepsy has a grand mal seizure. Labs showed:
pH = Na = 140 pCO2= K = 4 HCO3 = 17 Cl = 98 How will you correct the acid base disorder?

52 How will you correct the acid base disorder?
CASE 2 1) IV NaHCO3 using HCO3 deficit 2) oral NaHCO3 at 1 mEq/kg/day 3) intubate 4) no treatment How will you correct the acid base disorder?

53 CASE 2 HCO3 DEFICIT = (D –A) x 0.4 x kg BW
HCO3 deficit = (18 – 17) x 0.4 x 60 = 24 dHCO3 = As HCO3  < 5-10, the Vd increases; hence use 0.7 to 1 Maintenance 1 mEq/day Give ½ as bolus and the other ½ as drip in 24 hrs How will you correct the acid base disorder?

54 PRINCIPLES OF HCO3 THERAPY
LACTIC ACIDOSIS Primary effort should be improving O2 delivery Use NaHCO3 only when HCO3 < 5 mmol/L In states of  CO, raising the CO will have more impact on the pH In cases of low alveolar ventilation,  ventilation to lower the tissue pCO2

55 PRINCIPLES OF HCO3 THERAPY
KETOACIDOSIS Rate of H+ production is slow; NaHCO3 tx may just provoke severe hypokalemia Should be given if… 1) severe hyperkalemia despite insulin 2) HCO3 < 5 mmol/L 3) worsening acidemia inspite of insulin

56 CASE 3 19F, fashion model, is surprised to find her K=2.7 mmol/L because she was normokalemic 6 months ago. She admits to being on a diet of fruit and vegetables but denies vomiting and the use of diuretics or laxatives. She is asymptomatic. BP = 90/55 with subtle signs of volume contraction.

57 pH = alk, pCO2 =acidosis HCO3 = alkalosis
CASE 3 Plasma Urine serum Na K Cl HCO pH pCO2 45 pH = alk, pCO2 =acidosis HCO3 = alkalosis Metabolic Alkalosis

58 CompensatedMetabolic Alkalosis
CASE 3 Plasma Urine serum Na K Cl HCO pH pCO2 45 CompensatedMetabolic Alkalosis pCO2 = 6 x 0.7 = 4.2

59 CASE 3 Plasma Urine serum Na 138 63 K 2.7 34 Cl 96 0 HCO3 30 0
pH pCO2 45 AG= 138 – (96+30) = 12 NAG

60 What is the cause of the acid base disorder?
CASE 3 Plasma Urine serum Na K Cl HCO pH pCO2 45 What is the cause of the acid base disorder?

61 CASE 3 1) diuretic intake 2) surreptitious vomiting 3) diuretic intake
4) Bartter’s syndrome 5) Adrenal tumor 6) nonreabsorbable anion How should her acid-base disorder be managed? What is the cause of the acid base disorder?

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

63 MANAGEMENT OF METABOLIC ALKALOSIS
Chloride repletion Potassium repletion Tx hypermineralocorticoidism Dialysis Carbonic anhydrase inhibitors Acidifying agents  HCl, NH4Cl

64 INDICATIONS OF HCl pH > 7.55 and HCO3 > 35 with contraindications for NaCl or KCl use Immediate correction of metabolic alkalosis in the presence of hepatic encephalopathy, cardiac arrhythmias, digitalis intoxication When initial response to NaCl, KCl, or acetalozamide is too slow or too little

65 USE OF HCl HCL requirement = (A – D) x 0.5 x kg BW
0.1 – 0.2 N HCl solution = 100 – 200 mEq Do not exceed 0.2 mEq/kg/hour of HCl HCO3 = 70 wt = 60 kg HCl = 1,380 mEq

66 CASE 4 73M with long standing COPD (pCO2 stable at mmHg), cor pulmonale, and peripheral edema had been taking furosemide for 6 months. Five days ago, he had anorexia, malaise, and productive cough. He continued his medications until he developed nausea. Later he was found disoriented and somnolent

67 CASE 4 PE: BP 110/70, HR 110, RR 24, T=40 respiratory distress
prolonged expiratory phase postural drop in BP drowsy, disoriented scattered rhonchi and rales BLFs distant heart sounds trace pitting edema

68 pH = acidosis pCO2 =acidosis, HCO3 = alk
CASE 4 admission after 48 hrs serum Na K Cl HCO pH pCO pO pH = acidosis pCO2 =acidosis, HCO3 = alk Respiratory Acidosis

69 CASE 4 Respiratory Acidosis & M. Alkalosis admission after 48 hrs
serum Na K Cl HCO pH pCO pO HCO3 = = 31.55 HCO3 = (55-40) x 0.35 = HCO3 = (78-55) x 0.1 = 2.3

70 How should this patient be managed?
CASE 4 admission after 48 hrs serum Na K Cl HCO pH pCO pO How should this patient be managed?

71 How should this patient be managed?
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?

72 MANAGEMENT OF RESPIRATORY ACIDOSIS
Correct underlying cause for hypoventilation  effective alveolar ventilation  intubate, mechanically ventilate Antagonize sedative drugs Stimulate respiration (e.g. progesterone) Correct metabolic alkalosis

73 CASE 5 42M, alcoholic, brought to the ER intoxicated. He was found at Rizal park in a pool of vomitus. PE showed unkempt and incoherent patient with a markedly contracted ECF volume. T=39°C with crackles on the RULF.

74 CASE 5 serum Na = 130 pH = 7.53 K = 2.9 pCO2 = 25 Cl = 80 HCO3 = 20
BUN = 12 pO2 = 60 crea = alb = 38 RBS = 15 mmol/L PRE-RENAL BCR = (12/120) x = 24.76

75 Respiratory Alkalosis
CASE 5 serum Na = pH = 7.53 K = pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 12 pO2 = 60 crea = alb = 38 RBS = 15 mmol/L %pCO2 =38, %HCO3 = 18 Respiratory Alkalosis

76 Compensated Respiratory Alkalosis
CASE 5 serum Na = pH = 7.53 K = pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 12 pO2 = 60 crea = alb = 38 RBS = 15 mmol/L Compensated Respiratory Alkalosis HCO3 = (40-25) x 0.2 = 3

77 CASE 5 serum Na = 130 pH = 7.53 K = 2.9 pCO2 = 25 Cl = 80 HCO3 = 20
BUN = 12 pO2 = 60 crea = alb = 38 RBS = 15 mmol/L HAGMA + RAlk AG = 130 – ( ) = 30

78 What are the causes of his acid base disturbance?
CASE 5 serum Na = pH = 7.53 K = pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 12 pO2 = 60 crea = alb = 38 RBS = 15 mmol/L What are the causes of his acid base disturbance?

79 What are the causes of his acid base disturbance?
CASE 5 1) aspiration pneumonia 2) alcohol ketoacidosis 3) vomiting What are the causes of his acid base disturbance?

80 MANAGEMENT OF RESPIRATORY ALKALOSIS
Correct underlying cause of hyperventilation Rebreathe carbon dioxide Mechanical control of ventilation  increase dead space  decrease back up rate  decrease tidal volume  paralyze respiratory muscles

81 The anion gap

82 QUESTIONS?

83 Thank You

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