Download - DNB OSCE ON ABG
![Page 1: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/1.jpg)
APPROACH TO BLOOD GAS ANALYSIS
Dr. MANDAR HAVAL D.C.H D.N.B
![Page 2: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/2.jpg)
![Page 3: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/3.jpg)
How does the kidney do it?
• The kidney does it in three ways:
– Total reabsorption of filtered bicarbonate (proximal).
– Controlled secretion of H+ into filtrate (distal).
– Judicious use of urinary buffers.
![Page 4: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/4.jpg)
TUBULAR CELL BLOODFILTRATE
![Page 5: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/5.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
H2CO3
H+ + HCO3-
CA II
![Page 6: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/6.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
H2CO3
H+ + HCO3-
CA II
![Page 7: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/7.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
H2CO3
H+ + HCO3-
CA II
Na K ATPase
Na
KNa+
Na+
![Page 8: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/8.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
H2CO3
H+ + HCO3-
CA II
Na K ATPase
Na
KNa+
Na+
H+
Na+ / H+
Antiporter
HCO3-H+ATPase
![Page 9: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/9.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
H2CO3
CA II
Na K ATPase
Na
KNa+
Na+
H+
Na+ / H+ Antiporter
HCO3-
Na / KH+ATPase
![Page 10: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/10.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
H2CO3
CA II
Na K ATPase
Na
KNa+
Na+
H+
Na+ / H+ Antiporter
HCO3-
Na / KHCO3
-
H2CO3
H2O + CO2
CA IV
H+ATPase
![Page 11: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/11.jpg)
TUBULAR CELL BLOODFILTRATE
H2O + CO2
CA II
H2O
CA IV
HCO3-H+
![Page 12: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/12.jpg)
COLLECTING TUBULE CELL FILTRATEBLOOD
H2O + CO2
H2CO3
HCO3-
CA II
H+ ATPase
Cl- / HCO3-
ExchangerCl-
H+
![Page 13: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/13.jpg)
COLLECTING TUBULE CELL FILTRATEBLOOD
H2O + CO2
H2CO3
HCO3-
CA II
H+ ATPase
Cl- / HCO3-
ExchangerCl-
H+
![Page 14: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/14.jpg)
COLLECTING TUBULE CELL FILTRATE
BLOOD
H+ ATPase H+
HPO4=
![Page 15: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/15.jpg)
COLLECTING TUBULE CELL FILTRATE
BLOOD
H+ ATPase H+ HPO4
=H2PO4-
![Page 16: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/16.jpg)
COLLECTING TUBULE CELL FILTRATE
BLOOD
H+ ATPase H+
SO4=
HSO4-
![Page 17: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/17.jpg)
COLLECTING TUBULE CELL FILTRATE
BLOOD
H+ ATPase H+
NH3 NH3
NH4+
![Page 18: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/18.jpg)
Evaluation of Systemic Acid Base Disorders
1. Comprehensive history and physical examination.
2. Evaluate simultaneously performed ABG & serum electrolytes.
3. Identification of the dominant disorder.
4. Calculation of compensation.
5. Calculate the anion gap and the Δ.1. Anion Gap
2. Δ AG
3. Δ Bicarbonate
![Page 19: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/19.jpg)
Step 3:
Identification of the dominant disorder
Primary disorder
pH Initial change
Compensatory change
Metabolic acidosis
↓ ↓ HCO3 ↓ PCO2
![Page 20: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/20.jpg)
Step 3:
Identification of the dominant disorder
Primary disorder
pH Initial change
Compensatory change
Metabolic acidosis
↓ ↓ HCO3 ↓ PCO2
Metabolic alkalosis
↑ ↑ HCO3 ↑ PCO2
![Page 21: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/21.jpg)
Step 3:
Identification of the dominant disorder
Primary disorder
pH Initial change
Compensatory change
Metabolic acidosis
↓ ↓ HCO3 ↓ PCO2
Metabolic alkalosis
↑ ↑ HCO3 ↑ PCO2
Respiratory acidosis
↓ ↑ PCO2 ↑ HCO3
Respiratory alkalosis
↑ ↓ PCO2 ↓ HCO3
![Page 22: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/22.jpg)
• WHERE THE PROBLEM START
![Page 23: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/23.jpg)
Calculation of compensationMean "whole body" response equations for simple acid-base disturbances.
Note: The formula calculates the change in the compensatory parameter.
Disorder pH Primary change
Compensatory Response
Equation
Metabolic Acidosis
[HCO3-] PCO2 ΔPCO2 1.2 ΔHCO3
Metabolic Alkalosis
[HCO3-] PCO2 ΔPCO2 0.7 ΔHCO3
Respiratory Acidosis
PCO2 [HCO3-] Acute:
ΔHCO3- 0.1 ΔPCO2
Chronic:ΔHCO3
- 0.3 ΔPCO2
Respiratory Alkalosis
PCO2 [HCO3-] Acute:
ΔHCO3- 0.2 ΔPCO2
Chronic:ΔHCO3
- 0.5 ΔPCO2
![Page 24: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/24.jpg)
Simple compensation Disorder pH Primary problem Compensation
Metabolic acidosis ↓ ↓ in HCO3- PaCO2
=1.5xHCO3+8(+/-2)
Metabolic alkalosis ↑ 10↑ in HCO3- 7↑ in PaCO2
Respiratory acidosis ↓ ACUTE -10↑ in PaCO2
CHRONIC -10↑ in PaCO2
1↑ in [HCO3-]3.5↑ in [HCO3-]
Respiratory alkalosis ↑ ACUTE-10↓ in PaCO2
CHRONIC-10↓ in PaCO2
2↓ in [HCO3-]4↓ in [HCO3-]
![Page 25: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/25.jpg)
Calculate the “gaps”
Anion gap = Na+ − [Cl− + HCO3−]
Δ AG = Anion gap − 12
Δ HCO3 = 24 − HCO3
Δ AG = Δ HCO3 −, then Pure high AG Met. Acidosis
Δ AG > Δ HCO3 −, then High AG Met Acidosis + Met. Alkalosis
Δ AG < Δ HCO3 −, then High AG Met Acidosis + Normal AG Met ANote:
Add Δ AG to measured HCO3− to obtain bicarbonate level
that would have existed IF the high AG metabolic acidosis were to be absent, i.e., “Pre-existing Bicarbonate.”
Bicarbexistinge
BicarbCurrent
AGDelta
__Pr
_
_
![Page 26: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/26.jpg)
SOME FORMULA
•THAT YOU SHOULD KNOW
![Page 27: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/27.jpg)
CALCULATION OF H+
20 – 7.70 30 – 7.50 40(H+) – 7.40 (PH) 50 – 7.30 65 – 7.20
3
2
24HCO
PaCOH
![Page 28: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/28.jpg)
pH H+ pH H+6.70 200 7.40 40
6.75 178 7.45 35
6.80 158 7.50 32
6.85 141 7.55 28
6.90 126 7.60 25
6.95 112 7.65 22
7.00 100 7.70 20
7.05 89 7.75 18
7.10 79 7.80 16
7.15 71 7.85 14
7.20 63 7.90 13
7.25 56 7.95 11
7.30 50 8.00 10
7.35 45
![Page 29: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/29.jpg)
CAO2= directly reflects the total number of oxygen molecules in arterial blood, both bound and unbound to hemoglobin
• CaO2 = (1.34 x HB x SPO2) +(0.003 x PaO2)
Normal CaO2 ranges from 16 to 22 ml O2/dl
![Page 30: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/30.jpg)
Which patient is more hypoxemic, and why?
• Patient A: pH 7.48PaCO2 34 mm Hg
PaO2 85 mm Hg
SaO2 95%
Hemoglobin 7 gm%
• Patient B: pH 7.32PaCO2 74 mm Hg
PaO255 mm Hg
SaO2 85%
Hemoglobin 15 gm% www.dnbpediatrics.com
![Page 31: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/31.jpg)
ANS CONT…..
• Patient A: Arterial oxygen content = .95 x 7 x 1.34 = 8.9 ml O2/dl
• Patient B: Arterial oxygen content = .85 x 15 x 1.34 = 17.1 ml O2/dl
• Patient A, with the higher PaO2 but the lower hemoglobin content, is more hypoxemic
www.dnbpediatrics.com
![Page 32: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/32.jpg)
PaO2• Factors affecting the PaO2 include alveolar
ventilation, FIO2, altitude, age, and the oxyhemoglobin dissociation curve
• Relation between PaO2 and SaO2:PaO2 corresponds to SaO2
60mm Hg 90%
50mm Hg 80%
40mm Hg 70%
30mm Hg 60%
![Page 33: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/33.jpg)
True or False: The pO2 in a cup of water open to the
atmosphere is always higher than the arterial pO2 in a healthy person (breathing room air) who is holding the cup
www.dnbpediatrics.com
![Page 34: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/34.jpg)
ANS • The PO2 in the cup of water is always higher. This is for several
reasons. First, there is no barrier to oxygen diffusing into the water; thus the PO2 in the cup will be the same as the atmosphere, at sea level approximately 160 mm Hg.
• Second, there is no CO2 coming from the cup to dilute the oxygen, as there is in people.
• Third, there is no V-Q inequality or shunt; even healthy people have a difference between alveolar PO2 and arterial PO2 for this reason. Thus a healthy person and a cup of water exposed to the atmosphere at sea level would have PO2 values of about 100 mm Hg and 160 mm Hg, respectively.
www.dnbpediatrics.com
![Page 35: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/35.jpg)
A-a Gradient• Determines the degree of lung function
impairment• The A-a gradient is the partial pressure of
alveolar oxygen minus the partial pressure of arterial oxygen (PAO2-PaO2)
• Normal is 2-10mm Hg or 10 plus one tenth the person’s age
![Page 36: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/36.jpg)
A-a Gradient
• [(713*FIO2)-(PaCO2/0.8)] – PaO2
INTERPRETATION NORMAL – 10-20 (>30 is SINGNIFICANT)Seen in – Shunt Low V/Q Hypoventilation
![Page 37: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/37.jpg)
A-a Gradient• PAO2-PaO2 of 20-30mm Hg on room air
indicates mild pulmonary dysfunction, and greater than 50mm Hg on room air indicates severe pulmonary dysfunction
• The causes of increased gradient include intrapulmonary shunt, intracardiac shunt, and diffusion abnormalities
![Page 38: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/38.jpg)
![Page 39: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/39.jpg)
a/A Ratio
• Pao2/PAo2 NAORMAL LEVEL IS >0.75
• <0.60 IS INCOMPATIBLE WITH SPONTANIOUS BREATHING
![Page 40: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/40.jpg)
PaO2/FIO2 Ratio• To estimate the impairment of oxygenation, calculate
the PaO2/FIO2 ratio• Normally, this ratio is 500-600• Below 300 is acute lung injury*• Below 200 is ARDS*
*Along with diffuse infiltrates, normal PCWP, and appropriate mechanism
![Page 41: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/41.jpg)
OXYGEN INDEX
• OI =MAP X FIO2 x 100 POST DUCTAL PAO2
![Page 42: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/42.jpg)
INTERPRETATION
• OI >40 that is unresponsive to iNO predict a high mortality rate (>80%) and are indications for ECMO.
![Page 43: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/43.jpg)
VENTILATORY INDEX
• VI =PIP X PCO2 X RR 1000
VI > 65% INDICATE PREDICTIVE DEATH IN ARDS
![Page 44: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/44.jpg)
RELATION OF ALBUMIN IN ABG
AG corrected = AG + 2.5[4 – albumin] (AG= Anion gap)
![Page 45: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/45.jpg)
DELTA GAP
Delta gap = (actual AG – 12) + HCO3 Adjusted HCO3 should be 24 (+_ 6) {18-30} If delta gap > 30 -> additional metabolic alkalosis If delta gap < 18 -> additional non-gap metabolic acidosis If delta gap 18 – 30 -> no additional metabolic disorders
![Page 46: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/46.jpg)
SOME CASE DISCUSSION
![Page 47: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/47.jpg)
Case 1• A 15 yr old juvenile diabetic presents with abdominal
pain, vomiting, fever & tiredness for 1 day. He had stopped taking insulin 3 days ago. Examination revealed tachycardia, BP- 100/60, signs of dehydration. Abdominal examination was normal.
• ABG:pH 7.31PaCO2 26 mmHgHCO3 12 mEq/LPaO2 92 mm Hg
• Evaluate the acid-base disturbance(s)?
Serum Electrolytes:Na 140 mEq/LK 5.0 mEq/LCl 100 mEq/L
![Page 48: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/48.jpg)
Case 1: Solution
• Dominant disorder is Metabolic Acidosis• Compensation formula:
Δ PaCO2 = 1.2 × Δ HCO3
= 1.2 × 12= 14.4
PaCO2 = 40 – 14 = 26 Compensation is appropriate. • Anion Gap = 140 – (100 + 12)
= 28 AG is high.
pH 7.31PaCO2 26 HCO3 12 PaO2 92
Na 140 K 5.0 Cl 100
![Page 49: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/49.jpg)
Case 1: Solution
• Δ AG = 28 – 12= 16
• Δ HCO3 = 24 – 12= 12
• Δ AG > Δ HCO3-
• Final Diagnosis:High AG Met. Acidosis + Met. Alkalosis
pH 7.31PaCO2 26 HCO3 12 PaO2 92
Na 140 K 5.0 Cl 100
![Page 50: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/50.jpg)
Case 2• A 14 yr old boy presents with continuous vomiting of
3 days duration, mental confusion, giddiness, and tiredness for 1 day.
• Examination revealed tachycardia, hypotension and dehydration.
• ABGpH 7.50PaCO2 48HCO3 32PaO2 90
• Evaluate the acid-base disturbance(s)?
Serum Electrolytes:Na 139K 3.9Cl 85
![Page 51: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/51.jpg)
Case 2: Solution
• Dominant disorder is Metabolic Alkalosis• Compensation formula:
Δ PaCO2 = 0.7 × Δ HCO3
= 0.7 × 8= 5.6
PaCO2 = 40 + 6 = 46 Compensation is appropriate. • Anion Gap = 139 – (85 + 32)
= 22 AG is high.
pH 7.50PaCO2 48 HCO3 32 PaO2 90
Na 139 K 3.9 Cl 85
![Page 52: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/52.jpg)
Case 2: Solution
• Δ AG = 22 – 12= 10
• High AG metabolic acidosis
• Final Diagnosis:
Metabolic Alkalosis + High AG Met. Acidosis
pH 7.50PaCO2 48 HCO3 32 PaO2 90
Na 139 K 3.9 Cl 85
![Page 53: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/53.jpg)
Case 3: Varieties of Metabolic Acidosis
Patient A B CECF volume Low Low NormalGlucose 600 120 120pH 7.20 7.20 7.20Na 140 140 140Cl 103 118 118
HCO3- 10 10 10
AG 27 12 12Ketones 4+ 0 0
High-AG Met.
Acidosis
Non-AG Met.
Acidosis
Non-AG Met.
Acidosis
![Page 54: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/54.jpg)
Renal handling of Hydrogen in Metabolic Acidosis
• In the setting of metabolic acidosis, normal kidneys try to increase H+ excretion by increasing titratable acidity and ammonia. The latter is excreted as NH4
+.
• When NH4+ is excreted, it also causes increased chloride loss,
to maintain electrical neutrality.
• Chloride loss, therefore, will be in excess of Na and K.
• Urine Anion-Gap = Na + K – Cl
• In metabolic acidosis, if Urine anion gap is negative, it suggests that the kidneys are excreting H+ effectively.
![Page 55: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/55.jpg)
Urine Electrolytes in Metabolic Acidosis
Patient A B CU. Na 10 50U. K 14 47U. Cl 74 28Urine AG –50 +69
Dx: Diarrhea RTA
In Normal anion gap Metabolic Acidosis, Positive Urine AG suggests distal Renal Tubular Acidosis
Negative Urine AG suggests non-renal cause for Metabolic Acidosis.
Urine Anion Gap = (U. Na + U. K – U. Cl)
![Page 56: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/56.jpg)
Case 4
• A 17 yr old boy presented with history of progressive dyspnoea with wheezing for 4 days.
• He also had fever, cough with yellowish expectoration.
• He had increased sleepiness for 1 day. • On examination, he was tachypnoeic, pulse-
100/min bounding, BP-160/96, central cyanosis +, drowsy, asterixis +, RS – B/L extensive wheezing +.
• CXR- hyperinflated lung fields with tubular heart.
![Page 57: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/57.jpg)
Case 4: Laboratory data
• ABG:pH 7.30PaCO2 60 mmHg
HCO3 28 mEq/L
PaO2 68 mm Hg
• Serum Electrolytes:Na 136 mEq/L
K 4.5 mEq/L
Cl 98 mEq/L
• Evaluate the acid-base disturbance(s)?
![Page 58: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/58.jpg)
Case 4: Solution
• Dominant disorder is Respiratory Acidosis• Compensation formula:
Δ HCO3 = 0.3 × Δ PaCO2 = 0.3 × 20= 6
HCO3 = 24 + 6 = 30
Compensation is appropriate. • Anion Gap = 136 – (98 + 28)
= 10 AG is normal.
pH 7.30PaCO2 60 HCO3 28 PaO2 68
Na 136 K 4.5 Cl 98
![Page 59: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/59.jpg)
Case 5
• 12 year old girl presented with complaints of difficulty in breathing and upper abdominal discomfort for the past 1 hr.
• On examination, vitals normal, patient hyperventilating, RS – normal, Abdomen – normal.
![Page 60: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/60.jpg)
Case 5: Laboratory data• ABG:
pH 7.50PaCO2 25 mmHg
HCO3 21 mEq/L
PaO2 100 mm Hg
• Serum Electrolytes:Na 137 mEq/L
K 3.9 mEq/L
Cl 99 mEq/L Calcium 9.0 mEq/L
• Evaluate the acid-base disturbance(s)?
![Page 61: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/61.jpg)
Case 5: Solution
• Dominant disorder is Respiratory Alkalosis• Compensation formula:
Δ HCO3 = 0.2 × Δ PaCO2 = 0.2 × 15= 3
HCO3 = 24 – 3 = 21 Compensation is appropriate. • Anion Gap = 137 – (99 + 21)
= 17 AG is slightly high which can be seen in respiratory
alkalosis.
pH 7.50PaCO2 25 HCO3 21 PaO2 100
Na 137 K 3.9 Cl 99Calcium 9.0
![Page 62: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/62.jpg)
Case 7
• Explain the acid-base status of a 18-year-old boy with history of chronic renal failure treated with high dose diuretics admitted to hospital with pneumonia and the following lab values:
ABG Serum Electrolytes
pH 7.52 Na+ 145 mEq/L
PaCO2 30 mm Hg K+ 2.9 mEq/L
PaO2 62 mm Hg Cl- 98 mEq/L
HCO3- 21 mEq/L
![Page 63: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/63.jpg)
Case 7: Solution
• Dominant disorder is Respiratory Alkalosis• Compensation formula:
Δ HCO3 = 0.2 × Δ PaCO2 = 0.2 × 10= 2
HCO3 = 24 – 2 = 22 Compensation is appropriate. • Anion Gap = 145 – (98 + 21)
= 26 AG is very high suggestive of metabolic acidosis.
pH 7.52PaCO2 30 HCO3 21 PaO2 62
Na 145 K 2.9 Cl 98
![Page 64: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/64.jpg)
Case 7: Solution• Δ AG = 26 – 12
= 14
• Δ HCO3 = 24 – 21= 3
• Δ AG > Δ HCO3-
High AG Met Acidosis + Met. Alkalosis
• Final Diagnosis:Respiratory Alkalosis +
High AG Metabolic Acidosis + Metabolic Alkalosis
pH 7.52PaCO2 30 HCO3 21 PaO2 62
Na 145 K 2.9 Cl 98
![Page 65: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/65.jpg)
Case 8
• The following values are found in a 65-year-old patient. Evaluate this patient's acid-base status?
ABG Serum Chemistry
pH 7.51 Na + 155 mEq/L
PaCO2 50 mm Hg K+ 5.5 mEq/L
HCO3- 40 mEq/L Cl- 90 mEq/L
CO2 40 mEq/L
BUN 121 mg/dl
Glucose 77 mg/dl
![Page 66: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/66.jpg)
Case 8: Solution• Dominant disorder is Metabolic Alkalosis• Compensation formula:
Δ PaCO2 = 0.7 × Δ HCO3= 0.7 × 16= 11.2
PaCO2 = 40 + 11 = 51 Compensation is appropriate.
• Anion Gap = 155 – (90 + 40)= 25
AG is high.
pH 7.51PaCO2 50 HCO3 40 PaO2 62
Na 155 K 5.5 Cl 90BUN 121
![Page 67: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/67.jpg)
Case 8: Solution
• Δ AG = 25 – 12= 13
• High AG metabolic acidosis
• Final Diagnosis:
Metabolic Alkalosis + High AG Metabolic Acidosis
pH 7.51PaCO2 50 HCO3 40 PaO2 62
Na 155 K 5.5 Cl 90BUN 121
![Page 68: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/68.jpg)
Case 9
• A 52-year-old woman has been mechanically ventilated for two days following a drug overdose. Her arterial blood gas values and electrolytes, stable for the past 12 hours, show:
ABG Serum ChemistrypH 7.45 Na + 142 mEq/L
PaCO2 25 mm Hg K+ 4.0 mEq/L
Cl- 100 mEq/L HCO3- 18 mEq/L
![Page 69: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/69.jpg)
Case 9: Solution
• Dominant disorder is Chronic Respiratory Alkalosis• Compensation formula:
Δ HCO3 = 0.5 × Δ PaCO2 = 0.5 × 15= 7.5
HCO3 = 24 – 8 = 16 Compensation is appropriate.
• Anion Gap = 142 – (100 + 18)= 24
AG is very high suggestive of metabolic acidosis.
pH 7.45PaCO2 25 HCO3 18
Na 142K 4.0 Cl 100
![Page 70: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/70.jpg)
Case 9: Solution
• Δ AG = 24 – 12= 12
• Δ HCO3 = 24 –18= 6
• Δ AG > Δ HCO3-
High AG Met Acidosis + Met. Alkalosis
• Final Diagnosis:
Chronic Respiratory Alkalosis +High AG Metabolic Acidosis +
? Metabolic Alkalosis
![Page 71: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/71.jpg)
Case 11
• A 21 year old male with progressive renal insufficiency is admitted with abdominal cramping. He had congenital obstructive uropathy with creation of ileal loop for diversion. On admission,
ABG Serum ChemistrypH 7.20 Na + 140 mEq/L
PaCO2 24 mm Hg K+ 5.6 mEq/L
Cl- 110 mEq/L HCO3- 10 mEq/L
![Page 72: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/72.jpg)
Case 11: Solution
• Dominant disorder is Metabolic Acidosis
• Compensation formula:Δ PaCO2 = 1.2 × Δ HCO3
= 1.2 × 14= 16.8
PaCO2 = 40 – 17 = 23 Compensation is appropriate.
• Anion Gap = 140 – (110 + 10)= 20
High anion-gap metabolic acidosis.
pH 7.20PaCO2 24 HCO3 10
Na 140 K 5.6 Cl 110
![Page 73: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/73.jpg)
Case 11: Solution
• Δ AG = 20 – 12= 8
• Δ HCO3 = 24 –10= 14
• Δ AG < Δ HCO3-
High AG Met Acidosis + Normal-AG Met. Acidosis
• Final Diagnosis:Mixed Metabolic Acidosis
pH 7.20PaCO2 24 HCO3 10
Na 140 K 5.6 Cl 110
![Page 74: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/74.jpg)
Case 12
• A 15 year old female with hypertension was treated with low salt diet and diuretics. BP 135/85.Otherwise normal.See initial lab values.
• She developed profound watery diarrhea, nausea and weakness.
• On exam, HR = 96, T=100.6 F, BP 115/70. Abdominal tenderness with guarding on palpation.
Parameter InitialSubsequent
Na 137 138
K+ 3.1 2.8
Cl- 90 102
HCO3 35 25
pH 7.51 7.42
PaCO2 47 39
![Page 75: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/75.jpg)
Case 12: Solution• Initally, dominant disorder is Metabolic Alkalosis
• Compensation formula:Δ PaCO2 = 0.7 × Δ HCO3
= 0.7 × 11= 7.7
PaCO2 = 40 + 8 = 48 Compensation is appropriate.
• Anion Gap = 137 – (90 + 35)= 12
AG is normal.
pH 7.51PaCO2 47 HCO3 35
Na 137 K 3.1 Cl 90
![Page 76: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/76.jpg)
Case 12: Solution
• Subsequently, she has developedpH HCO3 PaCO2
↓ ↓ ↓
pH 7.51 7.42PaCO2 47 39 HCO3 35 25
Na 137 138 K 3.1 2.8Cl 90 102
![Page 77: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/77.jpg)
Case 12: Solution
• Subsequently, she has developed
The decrease in bicarbonate is almost same as the rise in chloride.
• Final Diagnosis:
pH HCO3 PaCO2
↓ ↓ ↓ Metabolic acidosis
Metabolic Alkalosis + Hyperchloremic (non-AG) Metabolic Acidosis
![Page 78: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/78.jpg)
Case 13
• A patient with salicylate overdose.pH = 7.45PCO2 = 20 mmHgHCO3 = 13 mEq/L
• Dominant disorder: Respiratory alkalosis• Appropriate Compensation would have been HCO3 of
20 (24 – 4)
• Lower than expected HCO3 suggests presence of metabolic acidosis as well.
![Page 79: DNB OSCE ON ABG](https://reader033.vdocument.in/reader033/viewer/2022061618/554b5681b4c905e9388b4c93/html5/thumbnails/79.jpg)
ALL THE BEST