abg analysis

1. DEPARTMENT OF INTERNAL MEDICINE
AIIMS
ABG AND ACID BASE DISORDERS
Preceptors
Presenter
Moderator

2. Overview
Sample Collection And Handling
Basic steps in ABG interpretation
Simple and Mixed acid base disorders
Interpretation of other ABG parameters
Approach to hypoxemia

3. SAMPLE COLLECTION AND HANDLING

4. Heparinisation of Syringe
0.05 ml heparin is taken for 1ml of blood
Chhapola et al., Use of liquid heparin for blood gas sampling in pediatric intensive care unit: A comparative study of effects of varying volumes of
heparin on blood gas parameters. Indian J Crit Care Med. 2013 Nov 1;17(6):350.
↑PO2, ↓pH,
↓PCO2
Sample Clotted
Correct Dilution
0.1 ml for 1 ml Blood
0.05 ml for 1 ml Blood
[Hub]
Flushed with
Heparin

5. Modified Allen’s test
• Limited studies, variable accuracy
• Rarely performed in clinical practice
• Important during Radial. A cannulation

6. Positioning of hand

7. Local Anesthesia?
 Randomized Control Trial
 Pain rated on a 10 cm Visual Analog Scale
 Subcutaneously injected lidocaine anesthesia did not
reduce the median pain of radial artery puncture
(Control 1.8 cm vs. Intervention 1.6 cm, P = 0.938).
Wade et al., Radial artery blood gas sampling: a randomized controlled trial of lidocaine local anesthesia. J Evid-Based Med. 2015

8. Positioning of the Needle
• 23-25 gauge needle
• For radial artery sampling the skin is
punctured at 30 – 45 degree
• After withdrawal of syringe firm
pressure should be applied for at least
5 minutes
Dev SP, Hillmer MD, Ferri M. Arterial Puncture for Blood Gas Analysis. N Engl J Med. 2011 Feb 3;364(5):e7.

9. Place the cap on a flat
surface, then remove your
hand from the cap
With one hand, hold the
syringe and use the needle to
scoop up the cap
 When the cap covers the
needle completely, use the
other hand to secure the cap
on the needle hub. Be careful
to handle the cap at the bottom
only
One Hand Scoop Technique for Capping of the
Needle

10. Air Bubbles
• Air bubbles - ↑Po2, ↓Pco2,
↓pH
• Should be removed by gently
tapping
the side of the syringe

11. ABG vs. VBG
 Colour
 Pulsatile movement of blood
 Compare SO2 in ABG value with
saturation in Pulse oximeter

12. ABG vs. VBG
Studies show that VBG from a central line blood is more reliable
than peripheral line VBG
Byrne et al., Peripheral venous and arterial blood gas analysis in adults: are they
comparable? A systematic review and meta-analysis. Respirol Carlton Vic. 2014
Decrease in pH Increase in
PCO2
VBG from central
line
0.03 – 0.05 4-5 mmHg
VBG from
peripheral line
0.02 – 0.4 3-8 mmHg
A comparison of VBG values with ABG
values

13. Effect of temperature on ABG
values
Ideally ABG sample should be transported in ice
Better to analyze ABG within 10 minutes
ABG should be analysed 30 minutes after making changes in ventilator p
PARAMETER 37OC (CHANGE
EVERY 10 MINUTES
4OC (CHANGE EVERY
10 MINUTES)
pH 0.001 0.001
PCO2 1 mm Hg 0.1 mm Hg
PO2 0.1% 0.001%

14. ABG Analyzer
 Cobas b221
Measured values Derived values
PO2 – Clark electrode HCO3
PCO2 – Severinghaus
electrode
Base excess
pH – Sanz electrode A-a gradient
K, Na, Glucose , Lactate
For calculating an accurate A-a gradient by ABG machine a correct FiO2
value has to be given
A-a gradient: Alveolar- arterial gradient

15. Electrodes

16. BASIC STEPS IN ABG INTERPRETATION

18. Normal ABG values
pH 7.35 – 7.45
PaCO2 35 – 45 mmHg
PaO2 80 – 100 mmHg
HCO3 22 – 26 mmol/L
BE -2 to +2
SaO2 >95%

19. Basic Steps to Identify Acid Base
Disorders
1. History
2. Validation of ABG
3. Identification of primary disorder
4. Calculation of compensation
5. Calculation of anion gap and delta gap if
primary disorder is metabolic acidosis

20. Case Scenario
 A 28 year old female with history of Sjogren’s syndrome
with h/o diarrhea for 2 days. Examination shows no
signs of dehydration with stable vitals and normal
systemic examination.
 Her ABG report showed
pH : 7.31
PCO2 : 33
HCO3
- : 16
Na+ : 138
Cl- : 114
Urine Na+ :100
Urine K+ : 31
Urine Cl- : 105
How can you come to a diagnosis with this report ?

21. Validation of an ABG report
• Calculated H+ = 24(CO2)/HCO3
-
Actual H+ = (7.80- pH) x 100
 Compare these two
• Example
Calculated H+ = 24(33)/16 = 49
Actual H+ = (7.80 – 7.31) (100) = 49
pH : 7.31
PCO2 : 33
HCO3
- : 16
Na+ : 138
Cl- : 114
Urine Na+
:100
Urine K+ :
31
Urine Cl- :
105

22. Identification of Primary Disorder
pH : 7.31
PCO2 : 33
HCO3
- : 16
Na+ : 138
Cl- : 114
Urine Na+
:100
Urine K+ : 31
Urine Cl- :
105
Is pH and
PCO2 both
normal?
Yes
Stop. No acid
base disorder
No
Some
disorder
present. Keep
evaluating

23. Identification of Primary Disorder
Current knowledge:
An acid base disorder is
present
Primary disorder – Metabolic Acidos
pH : 7.31
PCO2 : 33
HCO3
- : 16
Na+ : 138
Cl- : 114
Urine Na+
:100
Urine K+ :
31
Urine Cl- :
105
What is the
direction of
pH and
PCO2?
Same
direction
Primary
metabolic
Opposite
direction
Primary
respiratory

24. DISORDER PRIMARY
RESPONSES
COMPENSATORY
RESPONSE
Metabolic
acidosis
 [H+]  pH  HCO3
-  PCO2
Metabolic
alkalosis
 [H+]  pH  HCO3
-  PCO2
Respiratory
acidosis
 [H+]  pH  pCO2  HCO3
-
Respiratory
alkalosis
 [H+]  pH  pCO2  HCO3
-
Kassirer-Bleich Equation : H+ = 24 X [PCO2]
[HCO3
-]
Characteristics of  Acid-Base disorders

25. Calculation of Compensation
Current knowledge:
An acid base disorder is
present
We know the primary
disorder
Calculate expected
compensation using
the equations
pH : 7.31
PCO2 : 33
HCO3
- : 16
Na+ : 138
Cl- : 114
Urine Na+
:100
Urine K+ : 31
Urine Cl- :
105

26. Expected Compensation
Metabolic
Acidosis
PaCO2= (1.5 x HCO3
-) + 8 ± 2
(Winter’s formula)
PaCO2=[HCO3
-]+15
Metabolic
Alkalosis
PaCO2= (0.7 x HCO3-) + 21
± 2
PaCO2=[HCO3
-]+15

27. Respiratory Disease – Acute/Chronic
 ΔH+/ΔPaCO2
 <0.3 – Chronic
 >0.8 – Acute
 0.3 to 0.8 – Acute on chronic
In simple terms if the patient has a chronic
respiratory acidosis there will be associated
mild to moderate increase in bicarbonate levels
due to chronic renal compensation
In acute and acute on chronic the pH will be low
In chronic pH will be normal or near normal

28. Expected Compensations
For 10 mm Hg change in PCO2 change in HCO3
- is
given by
Respiratory
acidosis
Respiratory
alkalosis
Acute 1 2
Chronic 4 5

29. Calculation of compensation
Current knowledge:
An acid base disorder is
present
We know the primary
disorder
Expected compensation – 30 -34
Calculate
compensation
using the
equations
Compensatio
n accounts for
the observed
values
Diagnosis of
acid base
state
achieved.
Observed
values do not
match
calculated
compensation
Mixed
disorder
present, find
the additional
disorder!
pH : 7.31
PCO2 : 33
HCO3
- : 16
Na+ : 138
Cl- : 114
Urine Na+ :100
Urine K+ : 31
Urine Cl- : 105
Compensated Metabolic
Acidosis

30. CONCEPTS IN METABOLIC ACIDOSIS

31. Anion Gap Concept
Anion gap= Unmeasured Anions-
Unmeasured Cations
(Normal Anion gap = 10 ± 2)
 For every 1g/dl reduction in plasma albumin concentration the AG
decreases by 2.5
 Corrected AG = Calculated AG + [2.5 × (4 – albumin)]
Increased UA Decreased UC
Ketoacidosis Hypocalcemia
Lactic
Acidosis
Hypomagnesemia
Renal Failure Hypogammaglobulin
emia
Poisoning by
alcohol,
salicylates
Alkalosis

32. Urine Anion Gap Concept
Diarrhoea RTA
Compensato
ry
reabsorption
of
chloride
Defective
excretion of
H+
↑ Urinary chloride ↓ Urinary chloride
Urine anion gap = Urine [(Na + K) –
Cl]
Negative Urinary anion gap – Diarrhea
Positive Urinary anion gap - RTA

33. Delta Gap
 Delta gap = HCO3
- + (Calculated AG* – 12)
* No need to correct AG for Albumin while calculating delta
gap
Delta Gap
<24 Non anion gap metabolic
acidosis
>24 Metabolic alkalosis

34. Delta Ratio
ΔAG/ΔHCO3- = (AG-12)/(24-HCO3-)
 ΔAG/ΔHCO3- = (Increase in AG)/ (Decrease in bicarbonate)
Delta Ratio
1-2 Pure High AG Metabolic Acidosis
>2 Associated Metabolic Alkalosis
<2 Associated Non Anion Gap
Metabolic Acidosis

35. Approach to Metabolic Acidosis -
Summary
Metabolic
Acidosis
Normal anion
gap
Positive
urine anion
gap
Renal
tubular
acidosis
Negative
urine anion
gap
Diarrhea
Increased
anion gap
Ketones
positive
Ketoacidosis
Increased
serum
lactate
Lactic
acidosis

36. Systemic Effects of Acidemia and
Alkalemia
SYSTEM ACIDEMIA ALKALEMIA
Cardiovascu
lar system
↓Cardiac Output,
Hypotension ,
↓ Threshold for VF,
↓Response to catecholamines
Arteriolar constriction,
Angina, VT/VF, SVT
Respiratory
system
Respiratory muscle
weakness, dyspnoea
Hypoventilation, Reversal
of hypoxic pulmonary
vasoconstriction → V/Q
mismatch
Metabolic Inhibition of anaerobic
glycolysis, ↓ATP production,
↑Insulin resistance, ↑K,
Anaerobic Glycolysis, ↓K,
iCa, Mg
Cerebral Inhibition of cell volume
regulation , coma
Cerebral vasoconstriction

37.  A 28 year old female with history of Sjogren’s syndrome
with h/o diarrhea for 2 days. ABG was as follows:
pH – 7.31 Na+ - 138 Urine Na+ -100
PCO2 – 33 Cl- – 114 K+ - 31
HCO3
- – 16 Cl- – 105
Diagnosis : Compensated Metabolic Acidosis
Further evaluation:
Final Diagnosis:
Compensated Normal
Anion Gap Metabolic
Acidosis due to Renal
Tubular Acidosis
Case Scenario Cont…
Anion Gap Calculation : Na+ – [(HCO3- + Cl-)]
= 138- (16 + 114)
= 138 – 130 = 8 (Normal AG)
Next step : Urine Anion Gap : Urine [(Na + K) – Cl]
= [(100 + 31)- 105]
= 131 – 105 = 26 (Positive
UAG)

38. HIGH AG NORMAL AG
Lactic Acidosis GI loss
Ketoacidosis Normal saline infusion
Renal failure (ESRD) RTA
Methanol/Glycol/Salicylate
poisoning
Acetazolamide
Causes of Metabolic Acidosis

39. Metabolic Alkalosis
 History is very important
2 PHASES
GENERATION PHASE MAINTANENCE PHASE
•Loss of H+ through mouth
o Vomiting
o Nasogastric tube
•Loss of H+ through urine
o Diuretic Use
•Iatrogenic HCO3
- infusion
• Decreased intra arterial
blood volume
o Congestive Cardiac
Failure
o Cirrhosis
• Hypokalemia
• Hypochloremia

40. Approach to metabolic alkalosis
Unexplained
Metabolic
Alkalosis
<20
mmol/L
Saline
responsiv
e
Vomiting
NG tube
Certain
diarrhea
Villous
adenoma
Laxative
abuse
Diuretic use
>20
mmol/L
Saline
non
responsi
ve
Hypertensio
n
Hyperaldosteroni
sm
Cushing’s
Liddle’s
Normo/hypotensi
on
Milk alkali
Barter syndrome
Gitelmann
Severe hypokalemia
Urine
Chloride
Diuretics can cause a waxing and waning urinary chloride level

41. Other Causes of Metabolic Alkalosis
 Other causes
Refeeding metabolic alkalosis
Massive blood transfusion
• Symptoms are due to associated electrolyte
disturbance
• Hypokalemia, hypocalcemia, hypochloremia

42. Treatment of Metabolic Alkalosis
 Treat underlying cause , PPI can be used
Saline
responsive
Non
edematous
state
Nacl at
100ml/hr
Edematous
state
KCl/Spirinolacto
ne/Acetazolamid
e

43. Mixed Disorder
 Opposite direction
 Same direction but higher / lower than expected
 PH normal – but change in PCO2 / HCO3
-
 History is very important
 Can produce extremes of pH

44. DISORDER EXAMPLES
Respiratory acidosis
with metabolic acidosis
↓in pH
↓ in HCO3
↑ in PaCO2
Cardiac arrest
Intoxications
Multi-organ failure
Respiratory alkalosis
with metabolic alkalosis
↑in pH
↑ in HCO3-
↓ in PaCO2
Cirrhosis with diuretics
Pregnancy with
vomiting
Over ventilation of
COPD
Respiratory acidosis
with metabolic alkalosis
pH in normal range
↑ in PaCO2,
↑ in HCO3-
COPD with diuretics,
vomiting, NG suction
Severe hypokalemia
Respiratory alkalosis
with metabolic acidosis
pH in normal range
↓ in PaCO2
↓ in HCO3
Sepsis
Salicylate toxicity
Renal failure with CHF
or pneumonia
Advanced liver disease
Metabolic acidosis with
metabolic alkalosis
pH in normal range
HCO - normal
Uremia or ketoacidosis
with vomiting, NG
Examples of Mixed Disorders

45. INTERPRETATION OF OTHER ABG PARAMETER

46. ABG and Electrolytes
 Statistically significant difference were obtained in
measurement of Na and K in arterial and serum
samples.
 Clinicians should be cautious in using these two
values interchangeably
 Critical decisions can be made by values
obtained by both arterial and serum samples.
Gupta et al., Are sodium and potassium results on arterial blood gas analyzer equivalent to those on electrolyte analyzer? Indian J
Crit Care Med. 2016 Apr;20(4):233–7.
Alanazi et al. Correlation between the Measurements of Serum and Arterial Blood Gas (ABG) Electrolytes in Patients Admitted to the
Intensive Care Unit at King Abdul-Aziz Medical City, Riyadh, Saudi Arabia. Am J Clin Med Res. 2015 Sep 16;3(3):55–9.

48. Co-Oximeter
MetHb < 1.5%
CarboxyHb <2.5%

49.  A 35 year old female presented with palpitation, easy
fatigability, bleeding gums. CBC showed
pancytopenia. Her SpO2 is98% but her ABG report
showed SaO2-38%; PO2- 28 mmHg
• Faulty pulse oximeter
• Faulty blood gas analyser
• Venous sample
• Sampling from an ischemic limb
• Excessive oxygen consumption following blood
sample collection Massive leukocytosis or
thrombocytosis
Spurious
hypoxemia
Final Diagnosis -
AML
Case Scenario 2

50.  A 55 year old man who is a case of leprosy on
treatment with Dapsone presented with dyspnoea
& cyanosis. His SpO2 was 84 % on 6 litre oxygen.
ABG showed SaO2-99.1%
PO2-180 mmHg.
Final diagnosis -
METHEMOGLOBINEMIA
• SpO2 - SaO2 is called saturation gap
• A saturation gap of >5% is significant
• Seen in methemoglobinemia, carbon monoxide
poisoning, sulfhemoglobin
What is your
inference???
Case Scenario 3

51. APPROACH TO HYPOXEMIA

52. Approach to Hypoxemia
Hypoxemia
Normal
Normal
Low FiO2
Increased
Hypoventilation
PCO2
Increased
100%
FiO2
↑in Po2
V/Q mismatch
No Response
Shunt disorder
Calculate A-a
Gradient
PaO2
Normal 80 – 100 mmHg
Mild hypoxemia 60 – 80 mmHg
Moderate hypoxemia 40 – 60 mmHg
Severe hypoxemia <40 mmHg

53. Alveolar gas equation
 A-a gradient = PAO2 - PaO2
 PAO2= FIO2(PB – PH2O) – PaCO2 X 1/ RQ
= 0.21(760-47) – 40/0.8
= 10
 Normal 12+/- 4
 Needs age and FiO2 correction
 Age/4 + 4
 ↑ 5-7 mm hg every 10% ↑in FiO2
PAO2 – Alveolar partial pressure of oxygen
PB – Barometric pressure
PH2O – Water vapour pressure
FiO2 - Fraction of inspired oxygen
RQ – Respiratory Quotient

54. SHUNT V/Q MISMATCH
 ARDS
Pneumonia
Pulmonary edema
Pulmonary AVM
 Emphysema
 ILD
 Pulmonary vascular
disease
 Positive pressure
ventilation
V/Q vs. Shunt disorder

55. Take Home Message
 Optimal dilution, right technique, correct labeling
of sample important in obtaining ABG report
 Stepwise approach to be followed – importance
to history
 Don’t stop with identification of primary disorder.
Analyse in toto
 Calculation of A-a gradient can give important
clues to lung pathologies

58. FiO2

59. CASE VIGNETTE

60.  A 40 year old female presents to the emergency
with tachypnea, lethargy, vomiting, tinnitus and a
h/o drug overdose. Examination shows no signs of
dehydration with stable vitals and normal systemic
examination.
 Her ABG report is as follows:
 pH: 7.32
 PCO2 : 16
 HCO3-: 8
 PO2 : 95
 Na: 148
 Cl: 112
How can you come to a diagnosis with this report ?

61. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.32, PCO2 : 16, HCO3
- : 8, Na+ :
148,
Cl- : 112
1.Validate:
Calculated H+ = 24(PCO2)/HCO3
-
Actual H+ = (7.80- pH) x 100
Calculated H+ = 24(16)/8 = 48
Actual H+ = (7.80 – 7.32) (100) = 48
2. Is the patient acidemic or alkalemic?
Acidemic
3. Primary Disorder: Metabolic or respiratory?
(pH low, PCO2 low)
Metabolic

62. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.32, PCO2 : 16, HCO3
- : 8, Na+ :
148,
Cl- : 112
4. Is the respiratory system compensating for
the metabolic acidosis?
Expected PCO2 = 1.5 ( 16) + 8 ± 2
= 30 -34
Here PCO2 = 16
Added respiratory alkalosis
5. Is there an increased anion gap?
AG= Na – (HCO3 + Cl)
AG= 148–( 8 + 112) = 28
High anion gap

63. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.32, PCO2 : 16, HCO3
- : 8, Na+ :
148,
Cl- : 112
6. Calculation of delta gap
Delta gap = HCO3
- + (AG – 12)
= 8 + (28 -12)
= 8 + 16
= 24
No added Non anion gap Metabolic acidosis or
Metabolic alkalosis
FINAL DIAGNOSIS :
High anion gap metabolic acidosis with
Respiratory Alkalosis
SALICYLATE INTOXICATION

64.  A 50 year old male with history of CKD presents to the
casualty, he is confused and lethargic. He has vomitus
stains on his clothes.
 His ABG shows
 pH: 7.40
 PCO2 : 40
 HCO3-: 24
 Na: 145
 Cl: 100
Do you think the ABG is normal ? Lets Analyze step
wise

65. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.40, PCO2 : 40, HCO3
- : 24, Na+ :
145,
Cl- : 100
1.Validate:
Calculated H+ = 24(PCO2)/HCO3
-
Actual H+ = (7.80- pH) x 100
Calculated H+ = 24(40)/24 = 40
Actual H+ = (7.80 – 7.40) (100) = 40
2. Is the patient acidemic or alkalemic?
No
3. Primary Disorder: Metabolic or respiratory?
(pH normal, PCO2 Normal)
??

66. pH : 7.40, PCO2 : 40, HCO3
- : 24, Na+ :
145,
Cl- : 100
For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
4. Is there an increased anion gap?
AG= Na – (HCO3 + Cl)
AG= 145–( 24 + 100) = 21
High anion gap
5. Calculation of delta gap
Delta gap = HCO3
- + (AG – 12)
= 24 + (21 -12)
= 24 + 9
= 33
> 24 : Associated Metabolic Alkalosis
< 24 : Non anion gap Metabolic Acidosis
Metabolic Alkalosis

67. pH : 7.40, PCO2 : 40, HCO3
- : 24, Na+ :
145,
Cl- : 100
For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
FINAL DIAGNOSIS :
High anion gap metabolic acidosis with
Metabolic Alkalosis
CAUTION!!
Even with normal pH patient can have
mixed acid base disorder
 Step wise approach important

68.  A 35 year old woman with community acquired
pneumonia, brought with confusion. Her TLC is 24000,
Urea-15mg/dl, Cr-0.8 mg/dl
 Her ABG report is as follows:
 pH: 7.20
 PCO2 : 20
 HCO3-: 8
 PO2 : 90 (FiO2 : 0.21)
 Na: 137
 Cl: 106
How can you come to a diagnosis with this report ?

69. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.20, PCO2 : 20, HCO3
- : 8, Na+ :
137,
Cl- : 106
1.Validate:
Calculated H+ = 24(PCO2)/HCO3
-
Actual H+ = (7.80- pH) x 100
Calculated H+ = 24(20)/8 = 60
Actual H+ = (7.80 – 7.20) (100) = 60
2. Is the patient acidemic or alkalemic?
Acidemic
3. Primary Disorder: Metabolic or respiratory?
(pH low, PCO2 low)
Metabolic

70. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.20, PCO2 : 20, HCO3
- : 8, Na+ :
137,
Cl- : 106
4. Is the respiratory system compensating for
the metabolic acidosis?
Expected PCO2 = 1.5 (8) + 8 ± 2
= 18 - 22
Here PCO2 = 20
Adequate Compensation
5. Is there an increased anion gap?
AG= Na – (HCO3 + Cl)
AG= 137–( 8 + 106) = 23
High anion gap

71. For high-AG metabolic
acidosis: Calculate ΔGap?
Calculate Anion Gap
Expected compensation
If respiratory disorder: Acute or
Chronic ?
Primary disorder : Metabolic or
Respiratory ?
pH: Acidemic or Alkalemic ?
Validate ABG
pH : 7.32, PCO2 : 16, HCO3
- : 8, Na+ :
148,
Cl- : 112
6. Calculation of delta gap
Delta gap = HCO3
- + (AG – 12)
= 8 + (23 -12) = 19
> 24 : Associated Metabolic Alkalosis
< 24 : Non anion gap Metabolic Acidosis
Associated Non anion gap Metabolic acidosis
FINAL DIAGNOSIS :
High Anion gap metabolic acidosis with
Non–anion gap metabolic acidosis