Example:- (3)
A young adult of 30 Years suffering from Type 1 Diabetes mellitus from last 5 years, not taking insulin, admitted in emergency department of DMCH with the complain of vomiting, loose motion drowsiness and found tachycardia, hypotension, dehydration , increased rate of respiration (34/m). ABG was done on 12/02/15 at 4.36 PM.
ABG Analysis:
(i) Gas Analysis
Step:1
PaO2 – 139.0 mm of Hg –> High due to use of High Fio2
Step:2
PAO2 – 139.0 mm of Hg –> Above normal alveolar oxygen content due to high Fio2 .
Step:3
P(A-a)O2 = (139.0-139.0) mm of Hg
= 0 mm of Hg –> No Parenchymal
lung disease.
Step:4
PaCo2 -> 11.3 mm of Hg –> Hyperventilation
Step:5
No Hypoxemia/No respiratory failure.
Step:6
P/F = 661.8 –> No ALI/ARDS –> gas exchange is very good.
Step:7
SPO2– = 96.5 –> Probably due to increase H+ there is Rt shift of the Hb dissociation curve. So, PaO2 increase and SpO2 relatively Low.
Step:8
CaO2 = 15.9X10X1.34X96.5/100+0.003X139.0
= 205.60 + 0.417
= 206.01 ml/L
Normal value for this 40 Mg adult man should be approximate 111 ml/L. So oxygen to be avoided to protect from oxygen toxicity.
(ii) Electrolyte Analysis
Upper limit – due to loss of body water content & Cl- is a bit high due to metabolic acidosis.
Ca++ -> 1.172 – High
K+ -> 4.18 – normal , but its value should be high due to decrease blood pH.
For 0.10 decrease of pH.
Increase of K+ should approximate 0.6 mmol/L.
So for 7.029 of pH –> K+ should have increased value upto (N+2.226)mmol/L.
Low level is due to GIT and / or Renal loss.
Anion Gap
AG = 144.9-(116.7+2.9)
=144.9-119.6 = 25.3/29.5 (derived by machine)
Perhaps K+ is also taken in consideration by the machine.
Delta Gap
Delta gap+ measured HCo3 = 17.5 +2.9=20.4 –> low (normal 22-26 mmol/L)
i.e. non anion gap metabolic acidosis.
Gap – Gap Ratio
Gap -gap ratio = (29.5-12) / (24-2.9) = 17.5 / 21.1 = 0.83 <1
i.e. normal AG metabolic acidosis and treatment with N/S (Hyperchloronic).
In this case patient had been gives 3L of N/S before the ABG was done.
Base Excess
BE = 2.9-24 = -21.1 (Derived value by machine -25.8)
Negative value suggestion metabolic acidosis. (So non respiratory cause of Acidosis).
(iii) Acid – Base Analysis
Step:1
pH = 7.029
H+ = 93.6 nmol/L
So acidemia.
Step:2
HCo3 = 2.9 mmol/L (< 24 mmol/L) so, metabolic acidosis.
Step:3
PaCo2 = 11.3 mm of Hg (< 40 mm of Hg) so, respiratory alkalosis.
Step:4
H+ & HCo3– moves in opposite direction.
so, metabolic cause.
Step:5
So, PaCo2 & HCo3– moves in same direction.
so, simple cause.
So, the patient have metabolic acidosis (primary cause) with compensatory respiratory alkalosis.
Step:6
Final Diagnosis
High and normal AG metabolic acidosis with fully compensatory respiratory alkalosis with hyperventilation with low value of K+ is this condition.
Causes of high AG metabolic acidosis
M – Methanol – No history in this patient
U – Uraemia – Blood urea/ s.creatinine/spot urinary ACR / Input- output chart.
D – Diabetes mellitus – This is the cause
P – Paraldehyde – No history
I – Infection,Ischaemia,Isoniazide – CBC,ECG required
L – S.lactate – to be estimated
E – Ethanol – No history
S – Starvation, – Present for 2 days
Salicylat – No history.
Causes of Normal AG metabolic acidosis
- Gastrointestinal loss of HCO3 in diarrhoea (which was presenting problem).
- Renal Tubular Acidosis -> to be excluded by normal AG with no evidence of gastrointestinal disturbance and urinary pH is inappropriately high >5.5 .
Dr. R. K. Das 