Arterial blood gases

Internal medicine department
Khalid Yusuf El-zohryBy

The Goal :
To provide simple bedside approach to
interpretation of ABG ….
Not to:
To teach physiology .
To teach theories on acid-base regulation
To look for alternative approaches to interpretation
In detail

What is an ABG
 Arterial Blood Gas
 Drawn from artery- radial, brachial, femoral
 It is an invasive procedure.
 Caution must be taken with patient on
anticoagulants.
 Helps differentiate oxygen deficiencies from
primary ventilatory deficiencies from primary
metabolic acid-base abnormalities

…A respiratory component
…A respiratory acid
…Moves opposite to the direction of pH.
…A metabolic component
…It is a base (Metabolic)
…Moves in the same direction of pH.
…Moves in same direction
...Primary disorder
…Moves in opposite direction
…Mixed Disorder
CO2
HCO3
CO2
HCO3

H a 1
pH
H+ nmoles /L. pH
20 7.60
30 7.50
40 7.40
50 7.30
60 7.200
14
H+ = 80- last two digits of pH
OH
ion
H+
ion
Alkaline
Acidic

Acid/Base Relationship
 This relationship is critical for homeostasis
 Significant deviations from normal pH ranges are
poorly tolerated and may be life threatening
 Achieved by Respiratory and Renal systems

Acid Base Balance
1 7 14
Acidic Neutral Alkalotic
pH

Normal PH
 The normal blood pH range is
7.40 + 0.05
(7.35 - 7.45)
NB.
PH is – log of the hydrogen ion concentration , [ H ]

Henderson-Hasselbalch equation
181 X PaCO2
[ H ] =
HCO3
 ( 181 ) is the dissociation coefficient of carbonic
acid in the presence of carbonic anhydrase .

Components of the Arterial
Blood Gas
 pH:
 The normal range is 7.35 to 7.45
 PaO2
 The partial pressure of oxygen that is
dissolved in arterial blood.
 The normal range is 80 to 100 mm
Hg.
 SaO2
 The arterial oxygen saturation.
 The normal range is 95% to 100%.

 PaCO2
 The normal range is 35 to 45 mm Hg.
 HCO3
 The normal range is 22 to 26 mEq/liter
 B.E.
 The base excess indicates the amount of excess
or insufficient level of bicarbonate in the system.
 The normal range is –2 to +2 mEq/liter.
 (A negative base excess indicates a base deficit
in the blood.)

CO 2 CHANGES pH in opposite direction
Primary lesion
compensation
pH
HCO3
CO2
METABOLIC ACIDOSIS
HYPER VENTILATION
BICARB CHANGES
pH in same direction
HCO3
pH
pCO2
Low
Alkali

Anion Gap
Phosphate
Sulphate
Proteins
Calcium
Magnesium
gamma globulins
potassium
Anion gap = Na – [Cl- + HCO3
-]

Elevated AG
Metabolic Acidosis
 Causes
 Ketoacidosis - diabetic, alcoholic, starvation
 Lactic acidosis - hypoxia, shock, sepsis,
seizures
 Toxic ingestion - methanol, ethylene glycol,
ethanol, isopropyl alcohol, paraldehyde,
toluene
 Renal failure - uremia

Normal AG Metabolic Acidosis
 Causes
 Renal tubular
acidosis
 Post respiratory
alkalosis
 Hypoaldosteronism
 Potassium sparing
diuretics
 Pancreatic loss of
bicarbonate
 Diarrhea
 Carbonic anhydrase
inhibitors
 Acid administration (HCl,
NH4Cl, arginine HCl)
 Cholestyramine
 Ureteral diversions

CO 2 CHANGES
pH in opposite direction
Primary lesion
compensation
pH
HCO3
CO2
METABOLIC ALKALOSIS
HYPO VENTILATION
BICARB CHANGES
pH in same direction
HIGH HCO3
HIGH pH
HIGH CO2
High
Alkali

 Cushing’s syndrome – Conn’s
Syndrome

CO 2 CHANGES
Primary lesion
compensation
pH
CO 2
BICARB
Respiratory acidosis
HIGH pCO2
LOW pH
HIGH HCO3
High
CO2

Acute Respiratory Acidosis
 Bicarbonate and base excess will be
in the normal range because the
kidneys have not had adequate time
to establish effective compensatory
mechanisms

Acute Respiratory Acidosis
 Causes
 Airway obstruction, severe pneumonia,
chest trauma/pneumothorax
 Acute drug intoxication (narcotics,
sedatives)
 Residual neuromuscular blockade
 CNS disease (head trauma)

Chronic Respiratory Acidosis
 paCO2 is elevated with a pH in the
acceptable range
 Renal mechanisms increase the excretion
of H+ within 24 hours and may correct the
resulting acidosis caused by chronic
retention of CO2 to a certain extent

Chronic Respiratory Acidosis
 Causes
 Chronic lung disease (COPD)
 Neuromuscular disease
 Extreme obesity
 Chest wall deformity

CO 2 CHANGES
Primary lesion
compensation
pH
CO 2
BICARB
Respiratory alkalosis
LOW pCO2
HIGH pH
LOW HCO3
Low
CO2

Acute Respiratory Alkalosis
 Bicarbonate and base excess will be in
the normal range because the kidneys
have not had sufficient time to establish
effective compensatory mechanisms

Respiratory Alkalosis
 Causes
 Pain
 Anxiety
 Hypoxemia
 Restrictive lung disease
 Severe congestive heart
failure
 Pulmonary emboli
 Sepsis
 Fever
 Thyrotoxicosis
 Pregnancy
 Overaggressive mechanical
ventilation
 Hepatic failure

Body’s physiologic response to Primary disorder
in order to bring pH towards NORMAL limit
Full compensation
Partial compensation
No compensation…. (uncompensated)
BUT never overshoots,
If overcompensation is there,
Take it granted it is a MIXED disorder

Remember…….
Respiratory compensation is always
FAST…12-24 hrs
Metabolic compensation always
SLOW...5 -7 days

How to identify the type of
compensation…..?
pH HCO3 CO2
7.20 15 40
7.25 15 30
7.37 15 20
Un Compensated
Partially Compensated
Fully Compensated

• PCO2 up to 10
Metabolic
Acidosis
• PaCO2 up to 60
Metabolic
Alkalosis
• Bicarb up to 40
Respiratory
Acidosis
• Bicarb up to 10
Respiratory
Alkalosis

• There are two buffers that work in pairs
H2CO3 NaHCO3
Carbonic acid base bicarbonate
• These buffers are linked to the respiratory and
renal compensatory system
Buffers

Buffer system
CO2
HCO3
Co2 + H2o2 Carbonic acid So CO2 is An Acid
Respiratory
Metabolic
H =

Respiratory Component
 function of the lungs
 Carbonic acid H2CO3
Approximately 98% normal metabolites are in the form
of CO2
CO2 + H2O  H2CO3
 excess CO2 exhaled by the lungs

Metabolic Component
 Function of the kidneys
 base bicarbonate Na HCO3
 Process of kidneys excreting H+ into the urine and reabsorbing
HCO3
- into the blood from the renal tubules
1) active exchange Na+ for H+ between the tubular
cells and glomerular filtrate
2) carbonic anhydrase is an enzyme that accelerates
hydration/dehydration CO2 in renal epithelial cells

PaO2
SaO2
OXY (Sat) 98%
HAEMOGLOBIN
2 % Dissolved
Oxygen
O.
D.
C.
PAO2
A.C.I.
CaO2
Content of oxygen
Ml/100 of blood
Delivery
Of
Oxygen
To
Tissues
DaO2
O2
Cardiac output
A.C.I.( Alveolar capillary interface)
FiO2….21%....150 mm of Hg

Now that I have
this data, what
does it mean?
----- XXXX Diagnostics ------
Blood Gas Report
248 05:36 Jul 22 2000
Pt ID 2570 / 00
Measured 37.0
o
C
pH 7.463
pCO2 44.4 mm Hg
pO2 113.2 mm Hg
Corrected 38.6
o
C
pH 7.439
pCO2 47.6 mm Hg
pO2 123.5 mm Hg
Calculated Data
HCO3 act 31.1 mmol / L
HCO3 std 30.5 mmol / L
BE 6.6 mmol / L
O2 CT 14.7 mL / dl
O2 Sat 98.3 %
ct CO2 32.4 mmol / L
pO2 (A - a) 32.2 mm Hg
pO2 (a / A) 0.79
Entered Data
Temp 38.6 oC
ct Hb 10.5 g/dl
FiO2 30.0 %

The Anatomy
of a Blood Gas Report
-----XXXX Diagnostics-----
Blood Gas Report
328 03:44 Feb 5 2006
Pt ID 3245 / 00
Measured 37.0 0C
pH 7.452
pCO2 45.1 mm Hg
pO2 112.3 mm Hg
Corrected 38.6 0C
pH 7.436
pCO2 47.6 mm Hg
pO2 122.4 mm Hg
Calculated Data
B E 6.6 mmol / L
O2 ct 15.8 mL / dl
O2 Sat 98.4 %
pO2 (A -a) 30.2 mm Hg 
pO2 (a/A) 0.78
Entered Data
Temp 38.6 0C
FiO2 30.0 %
ct Hb 10.5 gm/dl
Measured values…
most important
Temperature Correction :
Is there any value to it ?
Calculated Data :
Which are useful one?
Entered Data :
Important

Measured values should be
considered
Corrected values should be
discarded

Bicarbonate is calculated on the basis
of the
Henderson equation:
[H
+
] = 24 pCO2 / [HCO3
-
]
or
for the
Mathematically
inclined…
Blood Gas Report
328 03:44 Feb 5 2006
Pt ID 3245 / 00
Measured 37.0 0C
pH 7.452
pCO2 45.1 mm Hg
pO2 112.3 mm Hg
Corrected 38.6 0C
pH 7.436
pCO2 47.6 mm Hg
pO2 122.4 mm Hg
Calculated Data
B E 6.6 mmol / L
O2 ct 15.8 mL / dl
O2 Sat 98.4 %
pO2 (A -a) 30.2 mm Hg 
pO2 (a/A) 0.78
Entered Data
Temp 38.6 0C
FiO2 30.0 %
ct Hb 10.5 gm/dl

Blood Gas Report
328 03:44 Feb 5 2006
Pt ID 3245 / 00
Measured 37.0 0C
pH 7.452
pCO2 45.1 mm Hg
pO2 112.3 mm Hg
Corrected 38.6 0C
pH 7.436
pCO2 47.6 mm Hg
pO2 122.4 mm Hg
Calculated Data
B E 6.6 mmol / L
O2 ct 15.8 mL / dl
O2 Sat 98.4 %
pO2 (A -a) 30.2 mm Hg 
pO2 (a/A) 0.78
Entered Data
Temp 38.6 0C
FiO2 30.0 %
ct Hb 10.5 gm/dl
Standard Bicarbonate:
Plasma HCO3 after equilibration
to a PCO2 of 40 mm Hg
: reflects non-respiratory acid base change
: does not quantify the extent of the buffer base
abnormality
: does not consider actual buffering capacity of blood
Base Excess:
D base to normalise HCO3 (to 24) with
PCO2 at 40 mm Hg
(Sigaard-Andersen)
: reflects metabolic part of acid base D
: no info. over that derived from pH, pCO2 and
HCO3
: Misinterpreted in chronic or mixed disorders

O2 Content of blood:
(Hb x1.34x O2 Sat + 0.003x Dissolved O2 )
Remember Hemoglobin
Oxygen Saturation:
( remember this is calculated …error prone)
Alveolar / arterial gradient:
( classify respiratory failure)
Arterial / alveolar ratio:
Proposed to be less variable
Same limitations as A-a gradient
Blood Gas Report
328 03:44 Feb 5 2006
Pt ID 3245 / 00
Measured 37.0 0C
pH 7.452
pCO2 45.1 mm Hg
pO2 112.3 mm Hg
Corrected 38.6 0C
pH 7.436
pCO2 47.6 mm Hg
pO2 122.4 mm Hg
Calculated Data
B E 6.6 mmol / L
O2 ct 15.8 mL / dl
O2 Sat 98.4 %
pO2 (A -a) 30.2 mm Hg 
pO2 (a/A) 0.78
Entered Data
Temp 38.6 0C
FiO2 30.0 %
ct Hb 10.5 gm/dl

Alveolar-arterial O2 Difference
* When FiO2 = 21 % :
PiO2 = (760-45) x .21= 150 mmHg
O2
CO2
PAO2 = 150 – 1.2 (PCO2)
= 150 – 1.2  40
= 150 – 50 = 100 mm Hg
PaO2 = 90 mmHg
………..PAO2 – PaO2 = ?
PAO2 = PiO2* -(PCO2/0.8)
PAO2 – PaO2 = 10 mmHg
PaO2
PAO2

Alveolar-arterial Difference
O2
CO2
Alveolar – arterial G.
100 - 45 = 55
……………….Wide A-a
Oxygenation Failure
Wide Gap
PCO2 = 40
PaO2 = 45
PAO2 = 150 – 1.2 (40)
= 150 - 50
= 100
Ventilation Failure
Normal Gap
PCO2 = 80
PaO2 = 45
PAO2 = 150-1.2(80)
= 150-100
= 50
Alveolar arterial G.
50 – 45 = 5
…………….Normal A-a

Always mention and see… FiO2
ct Hb
-----XXXX Diagnostics----
Blood Gas Report
Measured 37.0 0C
pH 7.452
pCO2 45.1 mm Hg
pO2 112.3 mm Hg
Calculated Data
O2 Sat 98.4 %
O2 ct 15.8
pO2 (A -a) 30.2 mm Hg 
pO2 (a/A) 0.78
Entered Data
FiO2 %
Ct Hb gm/dl
Blood Gas Report
328 03:44 Feb 5 2006
Pt ID 3245 / 00
Measured 37.0 0C
pH 7.452
pCO2 45.1 mm Hg
pO2 112.3 mm Hg
Corrected 38.6 0C
pH 7.436
pCO2 47.6 mm Hg
pO2 122.4 mm Hg
Calculated Data
B E 6.6 mmol / L
O2 ct 15.8 mL / dl
O2 Sat 98.4 %
pO2 (A -a) 30.2 mm Hg 
pO2 (a/A) 0.78
Entered Data
Temp 38.6 0C
FiO2 30.0 %
ct Hb 10.5 gm/dl
pH………..7.40 (7.35-7.45)
PCO2 …..40 (35-45) mm of Hg
HCO3 …..24 (22-26) mEq/L
PO2 ……. 80-100 mm of Hg
O2 Sat…. >95
O2 Ct…. >18
PCO2
pH
HCO3
PO2

Technical Errors
Glass vs. plastic syringe:
Changes in pO2 are not clinically important
No effect on pH or pCO2
Heparin (1000 u / ml):
Need <0.1 ml / ml of blood
pH of heparin is 7.0; pCO2 trends down
Avoided by heparin flushing & drawing 2-4 cc blood
Delay in measurement:
Rate of changes in pH, pCO2 and pO2 can be reduced to 1/10 by
cooling in ice slush(4
o
C)
Nomajordriftsupto1hour

1.
2. Look at pH?
3. Who is the culprit ?...Metabolic / Respiratory
4. If respiratory…… acute and /or chronic
5. If metabolic acidosis,
Anion gap ed and/or normal or both?
6. Is more than one disorder present?
7. Correlate clinically
Consider the clinical settings! Anticipate the disorder
7stepstoanalyzeABG

Step 2
Look at the pH
Is the patient acidemic pH < 7.35
or alkalemic pH > 7.45
If pH = 7.4 …… Normal
Mixed
or Fully compensated

Step 3 ……. CULPRIT?
HCO3…… METABOLIC
> 26 ….. Met. Alkalosis
< 22 ……Met. Acidosis
PCO2 ……RESPIRATORY
> 45 …… Resp. Acidosis
< 35 …… Resp. Alkalosis
HCO3 = Base
Normal…22-26
CO2 = ACID
Normal…35-45

Step 4
If there is a primary Respiratory disturbance,
is it acute ?
.08 change in pH ( Acute )
.03 change in pH (Chronic)
10 mm
Change
PaCO2
=
Remember………… relation of CO2 and pH

Step 5
If it is a primary Metabolic disturbance,
whether respiratory compensation appropriate?
For metabolic acidosis:
Expected PCO2 = (1.5 x [HCO3]) + 8 + 2
(Winter’s equation)
For metabolic alkalosis:
Expected PCO2 = 6 mm… for 10 mEq. rise in
Bicarb.
………UNCERTAIN COMPENSATION
CO2 is equal to
Last two digits
of pH
Remember If :
Suspect .............
actual PaCO2 is more than expected :
additional ...respiratory acidosis
actual PaCO2 is less than expected :
additional...respiratory alkalosis

Expected Compensation
Metabolic acidosis
 paCO2 = 1.5(HCO3) + 8 (2)
Metabolic alkalosis
 paCO2 = 0.7(HCO3) + 20
(1.5)

Step 5 cont.
If metabolic acidosis is there
How is anion gap? Is it wide ...
Na - (Cl
-
+ HCO3
-
) = Anion Gap usually <12
If >12, Anion Gap Acidosis : M ethanol
U remia
D iabetic Ketoacidosis
P araldehyde
I nfection (lactic acid)
E thylene Glycol
S alicylate
Common pediatric causes
Lactic acidosis
Metabolic disorders
Renal failure

-- Clinical history
-- pH normal, abnormal PCO2 n HCO3
-- PCO2 & HCO3 moving opposite directions
-- Degree of compensation for primary
disorder is inappropriate
-- Rise of anion gap and Fall of HCO3…..
……..R/F equation

Validity of ABG report… a lab error
H= 24 x
PCO2
HCO3
e.g. pH = 7.30, PCO2 = 38.1, HCO3 = 30
By Henderson-Hasselbach
H+ = 24 x pCO2/HCO3
= 24 x (38/30) = 30
80 - last two digit pH = H+
80 - H+ = last two digit pH (after 7)
pH should be 7.50

Ready Chart………
Limitations…..

1. Not enough time lapsed for compensation
2. 5% out of confidence Bands
e.g. pH = 7.20, HCO3 = 18, PCO2 = 33
e.g. pH =7.24, PCO2 = 65, HCO3 = 26
Chronic Resp acidosis + Metabolic Acidosis
Chronic case …. History helps

 Pts. With severe asthma
 pH 7.22
 PaCO2 55
 HCO3 25
Steps:
 1. Assess the pH.
 It is low (normal 7.35-7.45);
 Acidosis.
 2. Assess the PaCO2.
 It is high (normal 35-45)
 Respiratory
 3. Assess the HCO3.
 It has remained within the normal range (22-26
Respiratory Acidosis

 Pts with intractable vomiting for the last several hours
 pH 7.50
 PaCO2 42
 HCO3 33
Steps
 1. Assess the pH.
 It is high (normal 7.35-7.45),
 Alkalosis.
 It is within the normal range (normal 35-45).
 It is high (normal 22-26) .
 Metabolic
Metabolic Alkalosis

 kidney dialysis patient who has missed his last two
appointments at the dialysis center
 pH 7.32
 PaCO2 32
 HCO3 18
Steps
 1- the pH.
 It is low (normal 7.35-7.45);
 Acidosis.
 It is low. (not resp acidosis)
 It is low (normal 22-26).
 Metabolic.
Metabolic Acidosis
with partial compensation

 patient with chronic COPD
 pH 7.35
 PaCO2 48
 HCO3 28
Steps:
 1.the pH.
 It is normal , but on the low side of neutral (<7.40).
 It is high. (moves opposite direction of pH)
 Respiratory
 It is also high (22-26).
 Normally, the pH and HCO3 should move in the same
direction. Because they are moving in opposite
directions, it confirms that the primary acid-base
disorder is respiratory and that the kidneys are
attempting to compensate by retaining HCO3.
fully compensated
respiratory acidosis

 trauma patient with an altered mental status.
 pH 7.33
 PaC02 62
 HC03 35
Steps:
 1. The pH.
 It is low
 Acidosis .
 2. The PaC02.
 It is high.
 Respiratory
 3. Assess the HC03.
 It is high .
 The kidneys are attempting to compensate by retaining
HCO3 in the blood in an order to return the pH back towards
its normal range.
partially compensated
respiratory acidosis

 Pt. with ileus. She had been experiencing nausea and
vomiting.
 pH 7.43
 PaC02 48
 HC03 36
Steps
 1. The pH.
 It is normal, but on the high side of neutral (>7.40).
 2. Assess the PaC02.
 It is high (normal 35-45).
 Not a primary respiratory problem
 3. Assess the HC03.
 It is high (normal 22-26).
 Metabolic
fully compensated
metabolic alkalosis.

Partially compensated
Metabolic Acidosis
pH = 7.4
PaCO2 = 40
HCO3 = 24
1

Uncompensated
Metabolic Acidosis
pH = 7.4
PaCO2 = 40
HCO3 = 24
2

Metabolic Alkalosis
pH = 7.4
PaCO2 = 40
HCO3 = 24
3

pH = 7.4
PaCO2 = 40
HCO3 = 24
4

Uncompensated
Metabolic Alkalosis
pH = 7.4
PaCO2 = 40
HCO3 = 24
5

Normal A.B.G.
pH = 7.4
PaCO2 = 40
HCO3 = 24
6

Uncompensated
Respiratory Alkalosis
pH = 7.4
PaCO2 = 40
HCO3 = 24
7

Fully compensated
pH = 7.4
PaCO2 = 40
HCO3 = 24
8

Combined Alkalosis
pH = 7.4
PaCO2 = 40
HCO3 = 24
9

-----XXXX Diagnostics----
Blood Gas Report
Measured 37.0 0C
pH 7.301
pCO2 75.1 mm Hg
pO2 45.3 mm Hg
Calculated Data
O2 Sat 78.4 %
O2 ct 15.8
pO2 (A -a) 9.5 mm Hg 
pO2 (a/A) 0.83
Entered Data
FiO2 21 %
Ct Hb 12 gm/dl
D CO2 =75-40=35
Expected pH ( Acute ) = 7.11
Expected pH ( Chronic ) = 7.30
Chronic resp. acidosis
pH <7.30 …Acidosis
Normal A-a gradient
Hypoxia due to
Due to hypoventilation
Hypoxia….???
Case 1
6 year old male with progressive
respiratory distress due to
Muscular dystrophy .

Case 2
8-year-old male asthmatic;
3 days of cough, dyspnea
and orthopnea not
responding to usual
bronchodilators.
O/E: Respiratory distress;
suprasternal and
intercostal retraction;
tired looking; on 4 L NC.
Blood Gas Report
Measured 37.0
o
C
pH 7. 24
pCO2 49.1 mm Hg
pO2 66.3 mm Hg
Calculated Data
O2 Sat 92 %
pO2 (A - a) mm Hg D
pO2 (a / A)
Entered Data
FiO2 30 %
153-66= 87
pH <7.35 , acidosis
pCO2 >45; respiratory acidosis
Wide A / a gradient
Hypoxia
WITH INCREASE IN CO2 BICARB MUST RISE ?
Metabolic acidosis + respiratory acidosis
D CO2 = 49 - 40 = 9
Expected D pH ( Acute ) = 9/10 x 0.08 = 0.072
Expected pH ( Acute ) = 7.40 - 0.072 = 7.328
Acute resp. acidosis
30 × 5 = 150

Case 3
8 year old diabetic
with respi. distress
fatigue and loss of
appetite.
Blood Gas Report
Measured 37.0
o
C
pH 7.23
pCO2 23 mm Hg
pO2 110.5 mm Hg
Calculated Data
HCO3 act 14 mmol / L
O2 Sat %
pO2 (A - a) mm Hg D
pO2 (a / A)
Entered Data
FiO2 21.0 %
pH <7.35 , Acidosis
HCO3 <22; metabolic acidemia
Last two digits of pH
Correspond with co2
If Na = 130,
Cl = 90
Anion Gap = 130 - (90 + 14)
= 130 – 104 = 26

Blood Gas Report
Measured 37.0
o
C
pH 7.34
pCO2 38.1 mm Hg
pO2 90.3 mm Hg
Calculated Data
HCO3 act 30 mmol / L
O2 Sat 98.3 %
pO2 (A - a) 10 mm Hg
pO2 (a / A) 0.93
Entered Data
FiO2 21.0 %
Case 4
16 year old female with
sudden onset of dyspnea.
No Cough or Chest Pain
Vitals normal but RR 56,
anxious.
Acidosis
Low CO2..???
High HCO3…???
LAB ERROR!
By Henderson-Hasselbach
H+ = 24 x pCO2/HCO3
= 24 x (38/30) = 30
80 - last two digit pH = H+
80 - H+ = last two digit pH (after 7)
pH should be 7.50
  


3
2
24
HCO
PaCO
H

Case 5……
6 yrs old girl having type 1 Diabetic with H/O persistant vomiting
Lab: pH 7.37, pCO2 35 mm Hg, HCO3 22
Na 140, Cl 90,
Blood sugar : 300
Mild Metabolic acidosis ?
Should we send her Home?

NO !!
Anion gap = (140 - 112) = 28
Correlate Rise of Anion Gap with Fall of HCO3
Anion Gap ↑ed by 18, HCO3 should ↓ed by 18,
but ↓ed by 2 only
HCO3 retention (production) due to vomiting
Metabolic acidosis, metabolic alkalosis

Arterial blood gases

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Arterial blood gases