1st Example – 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:

ABG Report of the patient
ABG Report of the patient

(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.

*********************************************************************************************

(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.

*********************************************************************************************

(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.
Cause of Type 1 RF

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.

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