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Fifth Example - ABG Report of the Patient
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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 Fio2.
Step: 2
PAo2 = 135.3 mm of Hg – Above normal, due
to high Fio2.
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
