Dr. R. K. Das

ABG Report of the Patient

Example: (1)

A known case of chronic kidney disease admitted in EOPD, D.M.C.H. with the c/o Breathlessness with decreased urine output.

ABG Analysis:

(i) Gas Analysis

Step:1

PaO₂ =36.9 mm of Hg.

SPO₂ =52.4 %

Severe Hypoxemia.

Step: 2

PAO₂ =114.9

Normal.

Step: 3

P(A-a)O₂=(114.9-36.9)

=78 -> increased

Parenchymal lung disease.

Step: 4

PaCo₂=30.2 mm of Hg -> low

So, Type 1 respiratory failure.

Step: 5

O₂ therapy (6 L/m through C-PAP) for 2 hrs

Improved to some extent. So the causes may be

Ventilation / perfusion mismatch i.e.

Airway disease .
Interstitial lung disease.
Alveolar disease.
Pulmary vascular disease.

Step: 6

P/F=36.9/21 X 100

= 175.7 mm Hg.

ALI/ARDS to be decided by excluding, pneumonia or heart failure. There should be (progressive diffuse pulmonary infiltration in x-ray) and arterial hypoxemia.

Step: 7

Relation of PaO₂ and SPO₂ is normal.

Step: 8

CaO₂ = 10X5.6(gm/L)X1.34X52.4/100+0.003X36.9 ml/L

= 39.32+0.11

= 39.43 ml/L

Wt. Of the patient is 58 kg.

So,expected CaO₂ = 161.11 ml/L

Available CaO₂ = 39.43 ml/L

So, Blood transfusion is also indicated.

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(ii) Electrolyte Analysis

S.Na – Normal

S.Cl – raised -> may be due to metabolic acidosis.

S.Ca⁺⁺ - low -> may be due to hypoalbuminemia.

S.K⁺- high -> may be due to acidosis/Renal Dysfunction

Anion Gap :-

AG = 140.5-[110.7+11.4]

= 140.5-122.1

= 18.4 but it is 25.6 as derived by machine. It may be due to hypoalbuminemia.

AG > 20 so, primary metabolic acidosis.

Delta Gap :-

Delta Gap = 25.6-12

= 13.6

Delta Gap + HCo₃^- = 13.6+11.4

= 25 -> Normal range

Gap-Gap Ratio :-

Gap/Gap ratio = 13.6/12.6 >1

But delta gap + HCo₃ is normal.

So their is less chance of associated metabolic alkalosis.

BE :-

BE = 11.4-24

= -12.6 -> Base deficit

So, Metabolic acidosis.

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(iii) Acid-Base Analysis

Step: 1

pH = 7.193

H⁺ = 64.1 nmol/L

So acidemia.

Step: 2

HCo₃ = 11.4 mmol/L

(< 24 mmol/L) so, metabolic acidosis.

Step: 3

PaCo₂ = 30.2 mm of Hg

(< 40 mm of Hg) so, respiratory alkalosis.

Step: 4

Step: 5

Step: 6

Compensation -

Expected, PaCo₂ fall = 1.2 X (24-11.4 )

= 1.2 X 12.6

= 15.12

So, expected PaCo₂ = 40-15.12

= 24.88

So, metabolic acidosis with incomplete compensatory respiratory alkalosis.

Step: 7

AG = 25.6

High anion gap metabolic acidosis.

Delta gap + HCo₃ -> normal.

So, no normal anion gap metabolic acidosis and no metabolic alkalosis.

Step: 8

Final diagnosis – High anion gap metabolic acidosis with incomplete compensatory respiratory alkalosis with type 1 respiratory failure with Hyperkalaemia with Hypocalcaemia.

Causes of High Anion Gap Metabolic Acidosis

M – Methanol - No history in this patient

U – Uraemia - Present

D – Diabetes mellitus - Not present

P – Paraldehyde - No history

I – Infection, Ischaemia, Isoniazide – Infection present, No Ischaemia , No H/O Isoniazide

L – S.lactate - Not done

E – Ethanol - No history

S – Starvation, Salicylate - Starvation present, No H/O Salicylate intoxication

So, Acidosis is most probably due to Infection, Uraemia.

Cause of Type 1 RF

X – Ray chest suggest pneumonia.

Prognosis:-

Since hypoxemia is severe and there is associated Anaemia, hyperkalaemia, pneumonia and uraemia, so prognosis is not good even with haemodialysis, blood transfusion and close monitoring of the patient.