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Basic ABG Interpretation
Jose Socrates ‘DEE’ Evardone
Year Level I
Department of Internal Medicine
Cebu Doctors University...
arterial blood gas (ABG)
• test that measures the:
–1) oxygen tension (PaO2),
–2) carbon dioxide tension (PaCO2),
–3) acid...
ARTERIAL BLOOD GASES
• ARTERIAL SAMPLING
• Needle puncture
– - Site selection
– - Collateral circulation
– - Technique
– -...
ARTERIAL BLOOD GASES
• ARTERIAL SAMPLING:
• Common sites include:
– 1) radial,
– 2) femoral,
– 3) brachial,
– 4) dorsalis ...
ARTERIAL BLOOD GASES
Technique
●Local analgesia
●The seal of a heparinized syringe should be
broken by pulling its plunger...
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
ARTERIAL BLOOD GASES
SPECIMEN CARE
Gas diffusion through the plastic syringe is a
potential source of error.
- Using a gla...
ARTERIAL BLOOD GASES
SPECIMEN CARE
The HEPARIN
decrease in the pH
dilute the PaCO2
heparin solution should be minimized an...
ARTERIAL BLOOD GASES
SPECIMEN CARE
Air bubbles that exceed 1 to 2 percent of the
blood volume
falsely high PaO2
falsely lo...
ARTERIAL BLOOD GASES
INTERPRETATION
"Oxygenation and mechanisms of hypoxemia“
and
"Simple and mixed acid-base disorders"
ARTERIAL BLOOD GASES
"Oxygenation and mechanisms of
hypoxemia“
MEASURES OF OXYGENATION:
1) Arterial oxygen saturation (SaO...
ARTERIAL BLOOD GASES
Arterial oxygen
saturation
(SaO2)
ARTERIAL BLOOD GASES
Arterial oxygen
tension
(PaO2)
ARTERIAL BLOOD GASES
A-a oxygen gradient
A-a oxygen gradient = PAO2 - PaO2
A-a gradient = 2.5 + 0.21 x age in years
ARTERIAL BLOOD GASES
PaO2/FiO2 ratio
A normal PaO2/FiO2 ratio is 300 to 500
mmHg
less than 300 mmHg indicating
abnormal ga...
ARTERIAL BLOOD GASES
a-A oxygen ratio
a-A oxygen ratio = PaO2 ÷ PAO2
lower limit of normal is 0.77-0.82
most reliable when...
ARTERIAL BLOOD GASES
Oxygenation index
OI = [mean airway pressure x
FiO2 ÷ PaO2] x 100
ARTERIAL BLOOD GASES
MECHANISMS OF HYPOXEMIA
Hypoventilation
V/Q mismatch
Right-to-left shunt
Diffusion limitation
Reduced...
ARTERIAL BLOOD GASES
"Simple and mixed
acid-base
disorders"
ARTERIAL BLOOD GASES
Normal Values
(Harrisons)
Normal Values
• pH = 7.35 – 7.45
• pCO2 = 35 – 45 mmHg lungs
(Reference Value = 40)
• HCO3 = 22 – 26 mmol/L kidneys
(Refer...
Definition Of Terms
• Acidemia- Arterial pH < 7.56
• Alkalemia- Arterial pH > 7.45
• Acidosis- A process that tends to low...
Definition Of Terms
• Metabolic acidosis- A disorder that reduces
the serum Hc03 and pH
• Metabolic Alkalosis- A disorder ...
Definition Of Terms
• Simple Acid Base Disorder- Appropriate
Respiratory or Renal Compensation for the
Disorder
• Mixed Ac...
ARTERIAL BLOOD GAS ANALYSIS
• 1) Look at the pH
– Acidemia or alkalemia
– The cause is in the same direction
• 2) Look at ...
ARTERIAL BLOOD GAS ANALYSIS
• 1) Look at the pH
– Acidemia or alkalemia
– The cause is in the same direction
• 2) Look at ...
ARTERIAL BLOOD GAS ANALYSIS
• 1) Look at the pH
– Acidemia or alkalemia
– The cause is in the same direction
• 2) Look at ...
ARTERIAL BLOOD GAS ANALYSIS
• 1) Look at the pH
– Acidemia or alkalemia
– The cause is in the same direction
• 2) Look at ...
ARTERIAL BLOOD GAS ANALYSIS
• 1) Look at the pH
– Acidemia or alkalemia
– The cause is in the same direction
• 2) Look at ...
ARTERIAL BLOOD GAS ANALYSIS
• 1) Look at the pH
– Acidemia or alkalemia
– The cause is in the same direction
• 2) Look at ...
Calculations for the
Medicine Floors
Normal Values
(Harrisons)
A 45 y.o. doctor ran a 6:12
mile, then fell down on all 4’s
A 45 y.o. doctor ran a 6:12 mile, then fell
down on all 4’s
ACIDOSIS ALKALOSIS
Metabolic
Respiratory
CHRONIC RESP
METABOLIC ACIDOSIS
Winter’s Formula
DETERMINE PRIMARY
DISORDER
• Check the trend of the pH, HCO3, pCO2
• The change that produces the pH is the
primary disord...
DETERMINE PRIMARY
DISORDER
• Check the trend of the pH, HCO3, pCO2
• The change that produces the pH is the
primary disord...
DETERMINE PRIMARY
DISORDER
• Check the trend of the pH, HCO3, pCO2
• The change that produces the pH is the
primary disord...
DETERMINE PRIMARY
DISORDER
• If the trend is the same, check the percent
difference
• The bigger %difference is the 10 dis...
DETERMINE PRIMARY
DISORDER
• If the trend is the same, check the percent
difference
• The bigger %difference is the 10 dis...
CHECK THE
COMPENSATORY RESPONSE
• PREDICTION OF COMPENSATORY RESPONSES
ON SIMPLE ACID BASE DISORDERS
• Metabolic Acidosis PaCO2 = (1.5 X HCO3) + 8
• Metab...
COMPENSATORY RESPONSE
METABOLIC ACIDOSIS
PaCO2 = (1.5 X HCO3) + 8
HCO3 =12 pCO2 =1.5 X 12 + 8 = 26
pCO2 = 1.5 X 7 + 8 = 18...
COMPENSATORY RESPONSE
HCO3 =35 pCO2 =11 X 0.75 = 8.25
= 8.25 + 40 = 48
pCO2 = 52HCO3 =40
METABOLIC ALKALOSIS
PaCO2 will in...
COMPENSATORY RESPONSE
pCO2 =55 HCO3 = 25.5
HCO3 = 28pCO2 =80
ACUTE RESPIRATORY ACIDOSIS
HCO3 will increase 1 meq/L per 10 ...
COMPENSATORY RESPONSE
RESPIRATORY ALKALOSIS
Acute: HCO3 will decrease 2 meq/L per 10 mmHg
decrease in PaCO2
Check for Secondary Acid Base
Disorders
Primary Acid Base
Disorder
Compensation Secondary Base Disorder
Metabolic Acidosis...
Check for Secondary Acid Base
Disorders
Primary Acid Base
Disorder
Compensation Secondary Base Disorder
Metabolic Alkalosi...
Check for Secondary Acid Base
Disorders
Primary Acid Base
Disorder
Compensation Secondary Base Disorder
Respiratory
Acidos...
Check for Secondary Acid Base
Disorders
Primary Acid Base
Disorder
Compensation Secondary Base Disorder
Respiratory
Alkalo...
ANION GAP
Na – (HCO3 + Cl) = 10-12 mmol/L
Na = 135 HCO3 = 15
Cl = 97 RBS = 100 mg%
AG = 135 – 112 = 23
ANION GAP
Na – (HCO3 + Cl) = 10-12
Na = 135 HCO3 = 15
Cl = 97 RBS = 500 mg%
Corrected AG = Na + RBS mg% -100 x 1.4
100
AG ...
DETERMINE CLUES
FROM THE
CLINICAL SETTING
CLUES FROM CLINICAL SETTING
HIGH ANION GAP METABOLIC ACIDOSIS
(HAGMA)
M Methanol
U Uremia
D Diabetic Ketoacidosis
P Parald...
CLUES FROM CLINICAL SETTING
NORMAL ANION GAP METABOLIC ACIDOSIS
(NAGMA)
H Hyperalimentation
A Acetazolamide
R Renal Tubula...
CLUES FROM CLINICAL SETTING
METABOLIC ALKALOSIS
Vomiting
Remote diuretic use
Post hypercapnea
Chronic diarrhea
Cystic fibr...
CLUES FROM CLINICAL SETTING
METABOLIC ALKALOSIS
Bartter’s syndrome
Severe potassium depletion
Current diuretic use
Hyperca...
CLUES FROM CLINICAL SETTING
RESPIRATORY ACIDOSIS
CHRONIC: COPD, intracranial tumors
ACUTE: pneumonia, head trauma, general...
CASE 1
56F with vomiting and diarrhea 3 days ago
despite intake of loperamide. Her last urine
output was 12 hours ago.
PE ...
CASE 1
serum Na = 130 pH = 7.30
K = 2.5 pCO2 = 30
Cl = 105 HCO3 = 15
BUN = 42 pO2 = 90
crea = 2.0
RBS = 100
BCR = BUN / cr...
CASE 1
serum Na = 130 pH = 7.30
K = 2.5 pCO2 = 30
Cl = 105 HCO3 = 15
BUN = 42 pO2 = 90
crea = 2.0
RBS = 100
pH = acidosis...
CASE 1
serum Na = 130 pH = 7.30
K = 2.5 pCO2 = 30
Cl = 105 HCO3 = 15
BUN = 42 pO2 = 90
crea = 2.0
RBS = 100
pCO2 = 15 x 1....
CASE 1
serum Na = 130 pH = 7.30
K = 2.5 pCO2 = 30
Cl = 105 HCO3 = 15
BUN = 42 pO2 = 90
crea = 2.0
RBS = 100
AG= 130 – (105...
CASE 2
19F, fashion model, is surprised to find her K=2.7
mmol/L because she was normokalemic 6
months ago. She admits to ...
CASE 2
serum Na 138 63
K 2.7 34
Cl 96 0
HCO3 30 0
pH 7.45 5.6
pCO2 45
Metabolic
Alkalosis
Plasma Urine
pH = alk, pCO2 =a...
COMPENSATORY RESPONSE
HCO3 =35 pCO2 =11 X 0.75 = 8.25
= 8.25 + 40 = 48
pCO2 = 52HCO3 =40
METABOLIC ALKALOSIS
PaCO2 will in...
CASE 3
AG= 138 – (96+30) = 12 NAG
Plasma Urine
serum Na 138 63
K 2.7 34
Cl 96 0
HCO3 30 0
pH 7.45 5.6
pCO2 45
CASE 3
Plasma Urine
serum Na 138 63
K 2.7 34
Cl 96 0
HCO3 30 0
pH 7.45 5.6
pCO2 45
What is the cause of the acid base diso...
CASE 4
73M with long standing COPD (pCO2 stable at
52-58 mmHg), cor pulmonale, and peripheral
edema had been taking furose...
CASE 4
PE: BP 110/70, HR 110, RR 24, T=40
respiratory distress
prolonged expiratory phase
postural drop in BP
drowsy, diso...
CASE 4
admission after 48 hrs
pH = acidosis
pCO2 =acidosis, HCO3 = alk
Respiratory
Acidosis
serum Na 136 139
K 3.2 3.9
...
COMPENSATORY RESPONSE
pCO2 =55 HCO3 = 25.5
HCO3 = 28pCO2 =80
ACUTE RESPIRATORY ACIDOSIS
HCO3 will increase 1 mmol/L per 10...
serum Na 136 139
K 3.2 3.9
Cl 78 86
HCO3 40 38
pH 7.33 7.42
pCO2 78 61
pO2 43 56
CASE 4
admission after 48 hrs
HCO3 = 25.5...
Check for Secondary Acid Base
Disorders
Primary Acid Base
Disorder
Compensation Secondary Base Disorder
Respiratory
Acidos...
CASE 5
42M, alcoholic, brought to the ER intoxicated.
He was found at Rizal park in a pool of
vomitus. PE showed unkempt a...
serum Na = 130 pH = 7.53
K = 2.9 pCO2 = 25
Cl = 80 HCO3 = 20
BUN = 34 pO2 = 60
crea = 1.4 alb = 38
RBS = 15 mmol/L
CASE 5
...
serum Na = 130 pH = 7.53
K = 2.9 pCO2 = 25
Cl = 80 HCO3 = 20
BUN = 12 pO2 = 60
crea = 120 alb = 38
RBS = 15 mmol/L
CASE 5
...
COMPENSATORY RESPONSE
RESPIRATORY ALKALOSIS
Acute: HCO3 will decrease 2 mmol/L per 10 mmHg
decrease in PaCO2
serum Na = 130 pH = 7.53
K = 2.9 pCO2 = 25
Cl = 80 HCO3 = 20
BUN = 12 pO2 = 60
crea = 120 alb = 38
RBS = 15 mmol/L
CASE 5
...
serum Na = 130 pH = 7.53
K = 2.9 pCO2 = 25
Cl = 80 HCO3 = 20
BUN = 12 pO2 = 60
crea = 120 alb = 38
RBS = 15 mmol/L
CASE 5
...
QUESTIONS?
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
Acid Base, Arterial Blood Gas
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Acid Base, Arterial Blood Gas

ABG, CDUH, IM, Internal Medicine, Arterial Blood Gas, Interpretation

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Acid Base, Arterial Blood Gas

  1. 1. Basic ABG Interpretation Jose Socrates ‘DEE’ Evardone Year Level I Department of Internal Medicine Cebu Doctors University Hospital
  2. 2. arterial blood gas (ABG) • test that measures the: –1) oxygen tension (PaO2), –2) carbon dioxide tension (PaCO2), –3) acidity (pH), –4) oxyhemoglobin saturation (SaO2), and –5) bicarbonate (HCO3) concentration in arterial blood. • Some blood gas analyzers also measure the methemoglobin, carboxyhemoglobin levels
  3. 3. ARTERIAL BLOOD GASES • ARTERIAL SAMPLING • Needle puncture – - Site selection – - Collateral circulation – - Technique – - Complications • Indwelling catheters • SPECIMEN CARE • TRANSPORT • ANALYSIS • INTERPRETATION – Normal values
  4. 4. ARTERIAL BLOOD GASES • ARTERIAL SAMPLING: • Common sites include: – 1) radial, – 2) femoral, – 3) brachial, – 4) dorsalis pedis, or – 5) axillary artery • the radial artery is used most often because it is – accessible, – easily positioned, and – more comfortable for the patient than the alternative sites
  5. 5. ARTERIAL BLOOD GASES Technique ●Local analgesia ●The seal of a heparinized syringe should be broken by pulling its plunger. ●the artery should be punctured with the needle at a 30 to 45 degree angle relative to the skin ●rolled between the hands ●pressure applied to the puncture site for five to ten minutes to achieve hemostasis. 30-45-degree angle (for radial artery), 45-60-degree angle (for brachial artery), 45-90-degree angle (for femoral artery) with the bevel of the needle turned up
  6. 6. ARTERIAL BLOOD GASES
  7. 7. ARTERIAL BLOOD GASES
  8. 8. ARTERIAL BLOOD GASES
  9. 9. ARTERIAL BLOOD GASES
  10. 10. ARTERIAL BLOOD GASES
  11. 11. ARTERIAL BLOOD GASES
  12. 12. ARTERIAL BLOOD GASES
  13. 13. ARTERIAL BLOOD GASES
  14. 14. ARTERIAL BLOOD GASES
  15. 15. ARTERIAL BLOOD GASES
  16. 16. ARTERIAL BLOOD GASES
  17. 17. ARTERIAL BLOOD GASES SPECIMEN CARE Gas diffusion through the plastic syringe is a potential source of error. - Using a glass syringe - placed on ice and analyzed within 15 minutes
  18. 18. ARTERIAL BLOOD GASES SPECIMEN CARE The HEPARIN decrease in the pH dilute the PaCO2 heparin solution should be minimized and at least 2 mL of blood should be obtained
  19. 19. ARTERIAL BLOOD GASES SPECIMEN CARE Air bubbles that exceed 1 to 2 percent of the blood volume falsely high PaO2 falsely low PaCO2 gently removing the bubbles without agitation and analyzing the sample as soon as possible
  20. 20. ARTERIAL BLOOD GASES INTERPRETATION "Oxygenation and mechanisms of hypoxemia“ and "Simple and mixed acid-base disorders"
  21. 21. ARTERIAL BLOOD GASES "Oxygenation and mechanisms of hypoxemia“ MEASURES OF OXYGENATION: 1) Arterial oxygen saturation (SaO2) 2) Arterial oxygen tension (PaO2) 3) A-a oxygen gradient 4) PaO2/FiO2 ratio 5) a-A oxygen ratio 6) Oxygenation index
  22. 22. ARTERIAL BLOOD GASES Arterial oxygen saturation (SaO2)
  23. 23. ARTERIAL BLOOD GASES Arterial oxygen tension (PaO2)
  24. 24. ARTERIAL BLOOD GASES A-a oxygen gradient A-a oxygen gradient = PAO2 - PaO2 A-a gradient = 2.5 + 0.21 x age in years
  25. 25. ARTERIAL BLOOD GASES PaO2/FiO2 ratio A normal PaO2/FiO2 ratio is 300 to 500 mmHg less than 300 mmHg indicating abnormal gas exchange less than 200 mmHg indicates severe hypoxemia
  26. 26. ARTERIAL BLOOD GASES a-A oxygen ratio a-A oxygen ratio = PaO2 ÷ PAO2 lower limit of normal is 0.77-0.82 most reliable when the FiO2 is less than 0.55
  27. 27. ARTERIAL BLOOD GASES Oxygenation index OI = [mean airway pressure x FiO2 ÷ PaO2] x 100
  28. 28. ARTERIAL BLOOD GASES MECHANISMS OF HYPOXEMIA Hypoventilation V/Q mismatch Right-to-left shunt Diffusion limitation Reduced inspired oxygen tension
  29. 29. ARTERIAL BLOOD GASES "Simple and mixed acid-base disorders"
  30. 30. ARTERIAL BLOOD GASES Normal Values (Harrisons)
  31. 31. Normal Values • pH = 7.35 – 7.45 • pCO2 = 35 – 45 mmHg lungs (Reference Value = 40) • HCO3 = 22 – 26 mmol/L kidneys (Reference value = 24)
  32. 32. Definition Of Terms • Acidemia- Arterial pH < 7.56 • Alkalemia- Arterial pH > 7.45 • Acidosis- A process that tends to lower the extracellular pH (Hydrogen ion concentration increases) • Alkalosis- A process that tends to raise the extracellular pH (hydrogen ion concentration decreases)
  33. 33. Definition Of Terms • Metabolic acidosis- A disorder that reduces the serum Hc03 and pH • Metabolic Alkalosis- A disorder that elevates serum Hc03 and pH • Respiratory Acidosis- A disorder that elevates the arterial pC02 and reduces the pH • Respiratory Alkalosis- A disorder that reduces the arterial pC02 and elevates the pH
  34. 34. Definition Of Terms • Simple Acid Base Disorder- Appropriate Respiratory or Renal Compensation for the Disorder • Mixed Acid Base Disorder- Presence of More than one acid base Disorder
  35. 35. ARTERIAL BLOOD GAS ANALYSIS • 1) Look at the pH – Acidemia or alkalemia – The cause is in the same direction • 2) Look at pCO2 – Decreased in alkalosis – Increased in acidosis • 3) Look at HCO3 – Decreased in acidosis – Increased in alkalosis • 4) Remember, the body does NOT overcompensate • 5) Compensation can be COMPLETE or INCOMPLETE Example # 1 PH – 7.34 pCO2 – 52 HCO3 - 19
  36. 36. ARTERIAL BLOOD GAS ANALYSIS • 1) Look at the pH – Acidemia or alkalemia – The cause is in the same direction • 2) Look at pCO2 – Decreased in alkalosis – Increased in acidosis • 3) Look at HCO3 – Decreased in acidosis – Increased in alkalosis • 4) Remember, the body does NOT overcompensate • 5) Compensation can be COMPLETE or INCOMPLETE Example # 2 PH – 7.34 pCO2 – 50 HCO3 - 31
  37. 37. ARTERIAL BLOOD GAS ANALYSIS • 1) Look at the pH – Acidemia or alkalemia – The cause is in the same direction • 2) Look at pCO2 – Decreased in alkalosis – Increased in acidosis • 3) Look at HCO3 – Decreased in acidosis – Increased in alkalosis • 4) Remember, the body does NOT overcompensate • 5) Compensation can be COMPLETE or INCOMPLETE Example # 3 PH – 7.38 pCO2 – 24 HCO3 - 19
  38. 38. ARTERIAL BLOOD GAS ANALYSIS • 1) Look at the pH – Acidemia or alkalemia – The cause is in the same direction • 2) Look at pCO2 – Decreased in alkalosis – Increased in acidosis • 3) Look at HCO3 – Decreased in acidosis – Increased in alkalosis • 4) Remember, the body does NOT overcompensate • 5) Compensation can be COMPLETE or INCOMPLETE Example # 4 PH – 7.46 pCO2 – 42 HCO3 - 31
  39. 39. ARTERIAL BLOOD GAS ANALYSIS • 1) Look at the pH – Acidemia or alkalemia – The cause is in the same direction • 2) Look at pCO2 – Decreased in alkalosis – Increased in acidosis • 3) Look at HCO3 – Decreased in acidosis – Increased in alkalosis • 4) Remember, the body does NOT overcompensate • 5) Compensation can be COMPLETE or INCOMPLETE Example # 5 PH – 7.39 pCO2 – 41 HCO3 - 25
  40. 40. ARTERIAL BLOOD GAS ANALYSIS • 1) Look at the pH – Acidemia or alkalemia – The cause is in the same direction • 2) Look at pCO2 – Decreased in alkalosis – Increased in acidosis • 3) Look at HCO3 – Decreased in acidosis – Increased in alkalosis • 4) Remember, the body does NOT overcompensate • 5) Compensation can be COMPLETE or INCOMPLETE Example # 6 PH – 7.41 pCO2 – 51 HCO3 - 33
  41. 41. Calculations for the Medicine Floors
  42. 42. Normal Values (Harrisons)
  43. 43. A 45 y.o. doctor ran a 6:12 mile, then fell down on all 4’s
  44. 44. A 45 y.o. doctor ran a 6:12 mile, then fell down on all 4’s ACIDOSIS ALKALOSIS Metabolic Respiratory CHRONIC RESP
  45. 45. METABOLIC ACIDOSIS Winter’s Formula
  46. 46. DETERMINE PRIMARY DISORDER • Check the trend of the pH, HCO3, pCO2 • The change that produces the pH is the primary disorder pH = 7.25 HCO3 = 12 pCO2 = 30 ACIDOSIS ACIDOSIS ALKALOSIS METABOLIC ACIDOSIS
  47. 47. DETERMINE PRIMARY DISORDER • Check the trend of the pH, HCO3, pCO2 • The change that produces the pH is the primary disorder pH = 7.25 HCO3 = 28 pCO2 = 60 ACIDOSIS ALKALOSIS ACIDOSIS RESPIRATORY ACIDOSIS
  48. 48. DETERMINE PRIMARY DISORDER • Check the trend of the pH, HCO3, pCO2 • The change that produces the pH is the primary disorder pH = 7.55 HCO3 = 19 pCO2 = 20 ALKALOSIS ACIDOSIS ALKALOSIS RESPIRATORY ALKALOSIS
  49. 49. DETERMINE PRIMARY DISORDER • If the trend is the same, check the percent difference • The bigger %difference is the 10 disorder pH = 7.25 HCO3 = 16 pCO2 = 60 ACIDOSIS ACIDOSIS ACIDOSIS RESPIRATORY ACIDOSIS (24- 16)/24 = 0.33 (60-40)/40 = 0.5
  50. 50. DETERMINE PRIMARY DISORDER • If the trend is the same, check the percent difference • The bigger %difference is the 10 disorder pH = 7.55 HCO3 = 38 pCO2 = 30 ALKALOSIS ALKALOSIS ALKALOSIS METABOLIC ALKALOSIS (38-24)/24 = 0.58 (40-30)/40 = 0.25
  51. 51. CHECK THE COMPENSATORY RESPONSE
  52. 52. • PREDICTION OF COMPENSATORY RESPONSES ON SIMPLE ACID BASE DISORDERS • Metabolic Acidosis PaCO2 = (1.5 X HCO3) + 8 • Metabolic Alkalosis PaCO2 will increase 0.75 mmHg per meq/L increase in HCO3 • Respiratory Acidosis Acute HCO3 will increase 1 meql/L per 10 mmHg increase in PaCO2 Chronic HCO3 will increase 4 meq/L per 10 mmHg increase in PaCO2 • Respiratory Alkalosis Acute HCO3 will decrease 2 meq/L per 10 mmHg decrease in PaCO2 Chronic HCO3 will decrease 4 meq/L per 10 mmHg decrease in PaCO2
  53. 53. COMPENSATORY RESPONSE METABOLIC ACIDOSIS PaCO2 = (1.5 X HCO3) + 8 HCO3 =12 pCO2 =1.5 X 12 + 8 = 26 pCO2 = 1.5 X 7 + 8 = 18.5HCO3 =7
  54. 54. COMPENSATORY RESPONSE HCO3 =35 pCO2 =11 X 0.75 = 8.25 = 8.25 + 40 = 48 pCO2 = 52HCO3 =40 METABOLIC ALKALOSIS PaCO2 will increase 0.75 mmHg per meq/L increase in HCO3
  55. 55. COMPENSATORY RESPONSE pCO2 =55 HCO3 = 25.5 HCO3 = 28pCO2 =80 ACUTE RESPIRATORY ACIDOSIS HCO3 will increase 1 meq/L per 10 mmHg increase in PaCO2
  56. 56. COMPENSATORY RESPONSE RESPIRATORY ALKALOSIS Acute: HCO3 will decrease 2 meq/L per 10 mmHg decrease in PaCO2
  57. 57. Check for Secondary Acid Base Disorders Primary Acid Base Disorder Compensation Secondary Base Disorder Metabolic Acidosis Actual reduction of pC02 from baseline is HIGHER than that of calculated compensation Secondary RESPIRATORY ALKALOSIS is present Actual reduction of pC02 from baseline is LESS than that of calculated compensation Secondary RESPIRATORY ACIDOSIS is present
  58. 58. Check for Secondary Acid Base Disorders Primary Acid Base Disorder Compensation Secondary Base Disorder Metabolic Alkalosis Actual increase of Pc02 from baseline is HIGHER than that of calculated compensation Secondary RESPIRATORY ACIDOSIS is present Actual reduction of pC02 from baseline is LESS than that of calculated compensation Secondary RESPIRATORY ACIDOSIS is present
  59. 59. Check for Secondary Acid Base Disorders Primary Acid Base Disorder Compensation Secondary Base Disorder Respiratory Acidosis Actual increase of Hc03 from baseline is HIGHER than that of calculated compensation Secondary Metabolic Alkalosis is present Actual increase of Hc03 from baseline is LESS than that of calculated compensation Secondary METABOLIC ACIDOSIS is present
  60. 60. Check for Secondary Acid Base Disorders Primary Acid Base Disorder Compensation Secondary Base Disorder Respiratory Alkalosis Actual decrease of Hc03 from baseline is HIGHER than that of calculated compensation Secondary Metabolic Acidosis is present Actual decrease of Hc03 from baseline is LESS than that of calculated compensation Secondary METABOLIC Alkalosis is present
  61. 61. ANION GAP Na – (HCO3 + Cl) = 10-12 mmol/L Na = 135 HCO3 = 15 Cl = 97 RBS = 100 mg% AG = 135 – 112 = 23
  62. 62. ANION GAP Na – (HCO3 + Cl) = 10-12 Na = 135 HCO3 = 15 Cl = 97 RBS = 500 mg% Corrected AG = Na + RBS mg% -100 x 1.4 100 AG = 135 + 5.6 – 112 = 28.6
  63. 63. DETERMINE CLUES FROM THE CLINICAL SETTING
  64. 64. CLUES FROM CLINICAL SETTING HIGH ANION GAP METABOLIC ACIDOSIS (HAGMA) M Methanol U Uremia D Diabetic Ketoacidosis P Paraldehyde I Isoniazid, Iron L Lactic Acidosis E Ethylene Glycol, Ethanol S Salicylates
  65. 65. CLUES FROM CLINICAL SETTING NORMAL ANION GAP METABOLIC ACIDOSIS (NAGMA) H Hyperalimentation A Acetazolamide R Renal Tubular Acidosis D Diarrhea U Ureteropelvic shunt P Post Hypocapnia
  66. 66. CLUES FROM CLINICAL SETTING METABOLIC ALKALOSIS Vomiting Remote diuretic use Post hypercapnea Chronic diarrhea Cystic fibrosis Acute alkali administration
  67. 67. CLUES FROM CLINICAL SETTING METABOLIC ALKALOSIS Bartter’s syndrome Severe potassium depletion Current diuretic use Hypercalcemia Hyperaldosteronism Cushing’s syndrome Gastric aspiration
  68. 68. CLUES FROM CLINICAL SETTING RESPIRATORY ACIDOSIS CHRONIC: COPD, intracranial tumors ACUTE: pneumonia, head trauma, general anesthetics, sedatives RESPIRATORY ALKALOSIS Hyperventilation, Pregnancy, Liver failure, Methylxanthines
  69. 69. 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.
  70. 70. CASE 1 serum Na = 130 pH = 7.30 K = 2.5 pCO2 = 30 Cl = 105 HCO3 = 15 BUN = 42 pO2 = 90 crea = 2.0 RBS = 100 BCR = BUN / crea = 21 PRE-RENAL
  71. 71. CASE 1 serum Na = 130 pH = 7.30 K = 2.5 pCO2 = 30 Cl = 105 HCO3 = 15 BUN = 42 pO2 = 90 crea = 2.0 RBS = 100 pH = acidosis, pCO2 =alk, HCO3 = acidosis Metabolic Acidosis
  72. 72. CASE 1 serum Na = 130 pH = 7.30 K = 2.5 pCO2 = 30 Cl = 105 HCO3 = 15 BUN = 42 pO2 = 90 crea = 2.0 RBS = 100 pCO2 = 15 x 1.5 + 8 = 30.5 Compensated Metabolic Acidosis
  73. 73. CASE 1 serum Na = 130 pH = 7.30 K = 2.5 pCO2 = 30 Cl = 105 HCO3 = 15 BUN = 42 pO2 = 90 crea = 2.0 RBS = 100 AG= 130 – (105+15) = 10 NAGMA
  74. 74. CASE 2 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.
  75. 75. CASE 2 serum Na 138 63 K 2.7 34 Cl 96 0 HCO3 30 0 pH 7.45 5.6 pCO2 45 Metabolic Alkalosis Plasma Urine pH = alk, pCO2 =acidosis HCO3 = alkalosis
  76. 76. COMPENSATORY RESPONSE HCO3 =35 pCO2 =11 X 0.75 = 8.25 = 8.25 + 40 = 48 pCO2 = 52HCO3 =40 METABOLIC ALKALOSIS PaCO2 will increase 0.75 mmHg per mmol/L increase in HCO3
  77. 77. CASE 3 AG= 138 – (96+30) = 12 NAG Plasma Urine serum Na 138 63 K 2.7 34 Cl 96 0 HCO3 30 0 pH 7.45 5.6 pCO2 45
  78. 78. CASE 3 Plasma Urine serum Na 138 63 K 2.7 34 Cl 96 0 HCO3 30 0 pH 7.45 5.6 pCO2 45 What is the cause of the acid base disorder?
  79. 79. CASE 4 73M with long standing COPD (pCO2 stable at 52-58 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
  80. 80. 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
  81. 81. CASE 4 admission after 48 hrs pH = acidosis pCO2 =acidosis, HCO3 = alk Respiratory Acidosis serum Na 136 139 K 3.2 3.9 Cl 78 86 HCO3 40 38 pH 7.33 7.42 pCO2 78 61 pO2 43 56
  82. 82. COMPENSATORY RESPONSE pCO2 =55 HCO3 = 25.5 HCO3 = 28pCO2 =80 ACUTE RESPIRATORY ACIDOSIS HCO3 will increase 1 mmol/L per 10 mmHg increase in PaCO2
  83. 83. serum Na 136 139 K 3.2 3.9 Cl 78 86 HCO3 40 38 pH 7.33 7.42 pCO2 78 61 pO2 43 56 CASE 4 admission after 48 hrs HCO3 = 25.5 Respiratory Acidosis & M. Alkalosis
  84. 84. Check for Secondary Acid Base Disorders Primary Acid Base Disorder Compensation Secondary Base Disorder Respiratory Acidosis Actual increase of Hc03 from baseline is HIGHER than that of calculated compensation Secondary Metabolic Alkalosis is present Actual increase of Hc03 from baseline is LESS than that of calculated compensation Secondary METABOLIC ACIDOSIS is present
  85. 85. 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=390 C with crackles on the RULF.
  86. 86. serum Na = 130 pH = 7.53 K = 2.9 pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 34 pO2 = 60 crea = 1.4 alb = 38 RBS = 15 mmol/L CASE 5 PRE-RENALBCR = 24
  87. 87. serum Na = 130 pH = 7.53 K = 2.9 pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 12 pO2 = 60 crea = 120 alb = 38 RBS = 15 mmol/L CASE 5 Respiratory Alkalosis %pCO2 =38, %HCO3 = 18
  88. 88. COMPENSATORY RESPONSE RESPIRATORY ALKALOSIS Acute: HCO3 will decrease 2 mmol/L per 10 mmHg decrease in PaCO2
  89. 89. serum Na = 130 pH = 7.53 K = 2.9 pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 12 pO2 = 60 crea = 120 alb = 38 RBS = 15 mmol/L CASE 5 Compensated Respiratory Alkalosis HCO3 = 21
  90. 90. serum Na = 130 pH = 7.53 K = 2.9 pCO2 = 25 Cl = 80 HCO3 = 20 BUN = 12 pO2 = 60 crea = 120 alb = 38 RBS = 15 mmol/L CASE 5 HAGMA + RAlkAG = 130 – (80 + 20) = 30
  91. 91. QUESTIONS?

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