First Example - ABG Report of the Patient

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.