Second Example - ABG Report of the Patient

Example: (2)

ABG Report of the patient

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 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.