2nd Example – ABG Report of the Patient

Example: (2)

A patient of constrictive pericarditis, who had breathlessness on slight movement from one month admitted in stuporosed condition in emergency department of DMCH on 15/01/15.

ABG Report of the patient

ABG was done on 15/01/15 at 9.39 PM.

ABG Analysis:

 (i) Gas Analysis

Step:1
PaO₂ – 49.8 mm of Hg–Moderate hypoxemia
SPo₂ – 70.5 % – Severe hypoxemia

There is slight  left shift of the oxygen dissociation curve, most probably due to decrease in temperature.

Step:2
PAO₂ – 49.8 mm Hg – low
So, either Fio2 low or PaCo2 high.

Step:3
P(A-a)O2 = (49.8 – 49.8) mm Hg.
= 0 mm of Hg – normal

Step:4
PaCo2 – 122.5 – Hypercapnea – hypoventilation
So, the patient has hypoxemia with Hypercapnea
i.e. Type 2 Respiratory failure.

Due to advanced stage of LVF.

Step:5
Here PaCo2 is increased, and P(A-a)O2 is not increased , so the cause is hypoventilation alone  and since the patient had no neuromuscular disease , so it is due to decreased respiratory drive due to critical illness.

Step:6
P/F index or hypoxemia index = 237.3
x-ray finding does not suggest progressive diffuse pulmonary infiltration , feature of pneumonia . So it can be due to heart failure or arterial hypoxemia.

Step:7
There is slight mismatch in the relation between SPo2 and PaO2.
Cause of mismatch is left shift of the oxygen dissociation curve most probably due to low temperature.

Step:8
Hemoglobin and HCT value are high indicating polycythaemia mosr probably due to hypercapnea . we calculate arterial oxygen content
CaO2= 16.4X10(gm/L) X 1.34 X 70.5 / 100 + 0.003 X 49.8
= 154.93 + 0.149
= 155.08 ml/L
Expected CaO2 in a 70 Kg person is 194.44 ml/L.

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(ii) Electrolyte Analysis
S.Na₊  – 130.7 mmol/L  – low
S.Cl_–   – 86.5      mmol/l  – low
S.iCa – 0.915 mmol/L  – normal
S.K₊   – 5.31      mmol/L    – high
Decrease level of   s.Na+ and Cl-is due to fluid retention.high level of K+ matches with the change  in pH due to acidosis.

Anion Gap :-
AG = [130.7]-[86.5+43.4]
= 130.7-129.9
= 0.8 mmol/l
Derived AG is 6.1 mmol/L
This increased level of AG is due to increased in unmeasured anion.

Delta Gap :-
= 6.1-12
=  -5.9
Delta gap + HCo3 = -5.9+43.4
= 37.5 – metabolic alkalosis.

Gap-Gap Ratio :-
= -5.9 /(24-43.4)
= -5.9/-19.4
= 0.30 <1

BE :-
BE= 43.4 – 24=19.4
So,metabolic alkalosis.

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(iii) Acid Base Analysis

Step:1

 

 

Step:2
Hco3 – 43.4 mmol/L – Metabolic alkalosis

Step:3
PaCo2- 122.5 – Respiratory acidosis

Step:4

Step:5

Expected cause of Acid-Base change in simple.
So, respiratory acidosis with compensated metabolic alkalosis.
Compensation of Hco3 In chronic condition
= 2.62 X 122.5/7.50 kpa=42.79
So, expected value of Hco3  = 24+42.79=66.70
Compensation of Hco3 In acute condition
= 0.75X 122.5/7.5 = 12.25
So, expected value of Hco3 = 24+12.25=36.25

So,respiratory acidosis with chronic compensated metabolic alkalosis.

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Final diagnosis
Respiratory acidosis with chronic compensated metabolic alkalosis with hypoxemia and dilutional huponatremia

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Causes of Respiratory Acidosis
In this case it is ventilatory failure due to decreased respiratory drive or due to respiratory muscle weakness.