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.
(i) Gas Analysis
PaO2 – 139.0 mm of Hg –> High due to use of High Fio2
PAO2 – 139.0 mm of Hg –> Above normal alveolar oxygen content due to high Fio2 .
P(A-a)O2 = (139.0-139.0) mm of Hg
= 0 mm of Hg –> No Parenchymal
PaCo2 -> 11.3 mm of Hg –> Hyperventilation
No Hypoxemia/No respiratory failure.
P/F = 661.8 –> No ALI/ARDS –> gas exchange is very good.
SPO2– = 96.5 –> Probably due to increase H+ there is Rt shift of the Hb dissociation curve. So, PaO2 increase and SpO2 relatively Low.
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.
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+ 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.
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
pH = 7.029
H+ = 93.6 nmol/L
HCo3 = 2.9 mmol/L (< 24 mmol/L) so, metabolic acidosis.
PaCo2 = 11.3 mm of Hg (< 40 mm of Hg) so, respiratory alkalosis.
H+ & HCo3– moves in opposite direction.
so, metabolic cause.
So, PaCo2 & HCo3– moves in same direction.
so, simple cause.
So, the patient have metabolic acidosis (primary cause) with compensatory respiratory alkalosis.
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 .