Fifth Example - ABG Report of the Patient

Fifth Example - ABG Report of the Patient

A 55 years obese patient admitted in emergency department of DMCH with the C/O breathlessness, pain abdomen, irritability. She was taking corticosteroid for longer period and had moon facie, obesity, hypertension and pateche. Before ABG she was give O2 inhalation 5 L/min, Diuretics, corticosteroid, nebulisation, Inhalation with salbair I. iv fluid, pantoprazole, antibiotics without improvement. Then after 48 hrs patient was transferred to ICU and ABG was done.

ABG Analysis

1. Gas Analysis :-

Step: 1

Pao₂ = 135.3 mm of Hg – Above normal, due to high Fio_2.

_{Step: 2}

PAo₂ = 135.3 mm of Hg – Above normal, due to high Fio_2.

_{Step: 3}

P(A-a)o₂ = (135.3-135.3) 

                = 0, below normal – no Parenchymal lung 

                                                 disease.

Step: 4

PaCo₂ = 15.7 mm of Hg – low – Hyperventilation.

     No, respiratory failure.

Step: 5

Patient has below normal PaCo₂ with no increase in 

P(A-a)o₂ and The Fio₂ is not less, so no respiratory 

cause of increased respiration.

Step: 6

P/F = 135.3/40X100    (Here Fio₂ = 50%)

      = 338.25                   No ALI

Step:7

The relation between Spo₂ and Pao₂ are normal.

Step: 8

Cao₂ = 5.5X10X1.34X99/100+0.003X135.3

         = 5.5X1.34X0.99+0.003X135.3

         = 72.963+0.4059

         = 73.369

         The weight of the patients is 65 kg.

         So expected normal Cao₂ in this patient = 180.6 ml 

         of O₂/L

         But it is  = 73.369

         So it is one cause of dyspnoea.

2. Electrolyte Analysis

Ca⁺⁺  - 0.166 mmol/L – Low -> Cause of Hypocalcaemia is needed to be 

                                                      searched.  

K⁺     - 1.25 mmol/L – Low  -> i.e. losses in gastrointinal or renal cause 

                                                      here probably due to diuretic  use.

Anion Gap :-

26.4 mmol/L -> So AG>20 mmol/L                                  

                       Support a primary metabolic acid base disturbance.

Delta Gap :-

Delta Gap = 26.4-12

                 = 14.4

Delta gap + HCo₃    = 14.4 + 10.5

                             = 24.9 falls in between 22-26 mmol/L,  Normal

           So no metabolic alkalosis and no non-anion gap metabolic acidosis.

Gap - Gap Ratio :-

Gap-Gap ratio = (26.4-12)/(24-10.5)

                     = 14.4/14.5 =approx 1

            Indication high AG metabolic acidosis.

Base Excess :-

Base Excess (BE) = -12.5 -> Metabolic acidosis.

                                               It also justified.

3. Acid - Base Analysis

Step: 1

Step: 2

HCo₃ = 10.5 mmol/L -> metabolic acidosis .

Step: 3

PaCo₂ = 15.7 mm of Hg (< 40 mm of Hg) so, respiratory alkalosis.

Step: 4

H⁺ & HCo₃^- move in same direction.

So, respiratory cause. So, Respiratory Alkalosis.

Step: 5

So, PaCo₂ & HCo₃^- move in same direction.

So, simple cause (fallacy of the formula, because there is metabolic acidosis confirmed).

So, other way to know about mixed disorder is to evaluate.

              Expected value of PaCo₂ = 46

              Actual value of PaCo₂      = 15.7

So, Expected value and actual value of PaCo₂ do not match -> So, mixed disorder present.

So, High Anion gap Metabolic acidosis with Respiratory alkalosis.

Step: 6     

Compensatory  change

Predicted comparative of PaCo₂ fall = 1.2 X (24-10.5)

                                                     = 1.2 X 13.5 = 16.20

                

So, Expected value of PaCo₂          = 40 - 16.20 = 23.80

The value of PaCo₂ is 15.7

       Much less than 23 – 80

So, Respiratory Alkalosis associated. 

Final diagnosis

The patient has mixed disorder of high anion gap metabolic acidosis with respiratory alkalosis 

with dehydration with hypokalaemia  with hypocalcaemia without ALI/ Parenchymal lung disease.

Causes of Respiratory Alkalosis 

                L – Liver disease – Increase SGPT

                E – Embolism – Not

                D – Drug

                A – Anxiety – Present

                V – Ventilator – Not

                P – Pregnancy – Not

                H – Hyperventilation - Present 

Causes of High Anion gap metabolic acidosis 

                M – Methanol                         - No history in this patient

                U – Uraemia                           - Not present

                D – Diabetes mellitus             - Not present

                P – Paraldehyde                      - No history

                I – Infection (CBC) Present , Ischaemia (ECG) Not Present

                L – S.lactate                            - Not done

                E – Ethanol                             - No history

                S – Starvation, Salicylate