Abg Dr Pkjain Ccef July 2008
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Transcript of Abg Dr Pkjain Ccef July 2008
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Self assessment A 19 yr pregnant insulin dependent diabetic admitted
with polyuria and thirst. h/o poor compliance withmedical therapy.
She was afebrile. Chest was clear. Circulation was
adequate. Peri-oral herpes +. Urinalysis: 2+ ketones,4+ glucose. Biochemistry: Na+136, K+4.8, Cl-101,glucose 19 mmol/L, urea 8.1 mmol/L and creatinine0.09 mmol/L.Arterial Blood Gases:
pH 7.26
pCO216 mmHg
pO2128 mmHg
HCO37.1 mmol/l
Examples in ABG Interpretation (Dr. P.K.Jain)
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Case 1
A 26 year old man with unknown past medical history
is brought in to the ER by ambulance, after friends
found him unresponsive in his apartment. He had last
been seen at a party four hours prior.
ABG: pH 7.25 Na+ 137
PCO2 60 K+ 4.5
HCO3- 26 Cl- 100
PO2 55
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Case 2
A 67 year old man with diabetes and early diabeticnephropathy (without overt renal failure) presents for aroutine clinic visit. He is currently asymptomatic.Because of some abnormalities on his routine blood
chemistries, you elect to send him for an ABG.
ABG: pH 7.35 Na+ 135
PCO2 34 K+ 5.1
HCO3- 18 Cl- 110
PO2 92
Cr 1.4
Urine pH: 5.0
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Case 3
A 68 year old woman with metastatic colon cancerpresents to the ER with 1 hour of chest pain andshortness of breath. She has no known previouscardiac or pulmonary problems.
ABG: pH 7.49 Na+ 133
PCO2 28 K+ 3.9
HCO3- 21 Cl- 102PO2 52
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Case 4
A 6 year old girl with severe gastroenteritis is admittedto the hospital for fluid rehydration, and is noted tohave a high [HCO3
-] on hospital day #2. An ABG isordered:
ABG: pH 7.47 Na+ 130
PCO2 46 K+ 3.2
HCO3- 32 Cl- 86PO2 96
Urine pH: 5.8
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Case 5
A 75 year old man with morbid obesity is sent to theER by his skilled nursing facility after he developed afever of 103 and rigors 2 hours ago. In the ER he islucid and states that he feels terrible, but offers nolocalizing symptoms. His ER vitals include a heart rateof 115, and a blood pressure of 84/46.
ABG: pH 7.12 Na+ 138
PCO2 50 K+ 4.2HCO3
- 13 Cl- 99
PO2 52
Urine pH: 5.0
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Case 6
A 25 year old man with type I diabetes presents to theER with 24 hours of severe nausea, vomiting, andabdominal pain.
ABG: pH 7.15 Na+ 138
PCO2 30 K+ 5.6
HCO3- 10 Cl- 88
PO2 88Cr 1.1
Urine pH: 5.0
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Case 7
A 62 year old woman with severe COPD comes tothe ER complaining of increased cough andshortness of breath for the past 12 hours. There areno baseline ABGs to compare to, however, her
HCO3-
measured during a routine clinic visit 3months ago was 34 mEq/L.
ABG: pH 7.21 Na+ 135
PCO2 85 K+ 4.0HCO3
- 33 Cl- 90
PO2 47
Urine pH 5.5
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Examples in ABG Interpretation (Dr. P.K.Jain)
The Painful Fact
The more you learn
the more you wonder how youmanaged so far.
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Examples in ABG Interpretation (Dr. P.K.Jain)
Poorly collected sample wrong ABG report
Practical things they dont teach you atcollege:
Where to collect blood from?
Heparin amount.
Preventing air contact.
Transportation. Clinical Information: FiO2
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Examples in ABG Interpretation (Dr. P.K.Jain)
Do not Cap or Bend the needle !!!
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Examples in ABG Interpretation (Dr. P.K.Jain)
Plug (airtight) the needle !!!
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Examples in ABG Interpretation (Dr. P.K.Jain)
ABG
ICE
ABG
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Examples in ABG Interpretation (Dr. P.K.Jain)
APPROACH TO INTERPRETATION OF ABG
You are on duty. A 54 yr male patient, known Diabetic onirregular treatment is admitted to the ICU. You start him
on 2L/min oxygen. Arterial Blood Gas study shows:
PO2= 108 mmHg
PCO2= 30 mmHg
pH =7.20
HCO3=15 mmHg
What is your interpretation?
What will be your next action?
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Examples in ABG Interpretation (Dr. P.K.Jain)
[H+] x [HCO3]
PCO2
= 24 Henderson equation
Step 1: Check consistency of the Report !
pH Subtract from [H+]
6.8 160
6.9 130
7.0 100 100
7.1 90 80
7.2
80
60
7.3 50
7.4 40
7.5 30
7.6 85 25
7.7 90 20
7.8 95 15
40 x 24
40
= 24
60 x 15
30
= 30
Eg. In this patient
pH =7.2, PCO2= 30, HCO3=15
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8
6.9
7.0
7.1
7.2
7.3
7.4 40
7.5
7.67.7
7.8
7.9
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8
6.9
7.0
7.1
7.2
7.3 50
7.4 40
7.5 30
7.67.7
7.8
7.9
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8 160
6.9
7.0
7.1 80
7.2
7.3 50
7.4 40
7.5 30
7.67.7 20
7.8
7.9
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8 160
6.9 120
7.0
7.1 80
7.2 60
7.3 50
7.4 40
7.5 30
7.67.7 20
7.8 15
7.9
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8 160
6.9 120
7.0 100
7.1 80
7.2 60
7.3 50
7.4 40
7.5 30
7.6 257.7 20
7.8 15
7.9 12
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8 160
6.9 120
7.0 100
7.1 80
7.2 60
7.3 50
7.4 40
7.5 30
7.6 257.7 20
7.8 15
7.9 12
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8
6.9
7.0
7.1
7.2
7.3
7.4
7.5
7.67.7
7.8
7.9
What is the corresponding
[H] value for following pH?
pH
7.7 ..
6.9 ..
7.1 ..
7.55 ..
Self Assessment..
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Examples in ABG Interpretation (Dr. P.K.Jain)
pH [H]
6.8 160
6.9 120
7.0 100
7.1 80
7.2 60
7.3 50
7.4 40
7.5 30
7.6 257.7 20
7.8 15
7.9 12
What is the corresponding
[H] value for following pH?
pH
7.7 ..
6.9 ..
7.1 ..
7.55 ..
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Examples in ABG Interpretation (Dr. P.K.Jain)
Step 2: Obtain relevant clinical history!
a. Metabolic acidosis:
DM/renal failure/muscle over activity/ hypotension/
diarrhea/ diamox, metformin/ alcoholism.
b. Metabolic alkalosis:Vomiting, RT aspiration/hypovolemia, diuretic/ NaHCO3
administration/ hypokalemia (paralytic ileus)
c. Respiratory acidosis:
COPD, muscular weakness, post-op.
d. Respiratory alkalosis:
Tachypnea, hepatic coma, sepsis
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Examples in ABG Interpretation (Dr. P.K.Jain)
Importance of the Clinical Details
Case 1:A previously healthy 37 yr man ishaving an elective open cholecystectomy.He is on no routine medication.Preoperative urea /electrolytes were normal.
Parameter Value
pH 7.10
PO2 75 mmHg
PCO2 70 mmHg
HCO3 27 mmol/L
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Examples in ABG Interpretation (Dr. P.K.Jain)
Importance of the Clinical Details
Case 2:A 75 yr man with severe COPD isadmitted with fever, confusion andsignificant respiratory distress. He livesalone and has been unwell for a week andhas deteriorated over the previous 4 days.There is a long history of heavy smoking.Biochemistry & hematology results are notyet available..
Parameter Value
pH 7.10
PO2 75 mmHg
PCO2 90 mmHg
HCO3 27 mmol/L
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l G ( )
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Examples in ABG Interpretation (Dr. P.K.Jain)
Step 3: Oxygenation Status:
a. -oxemia statusb. expected Vs observed PaO2.c. oxygen cost of breathing
Step 4: Ventilatory Status.Look at PaCO2
Step 5: Acid - Base Status..
E l i ABG I t t ti (D P K J i )
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Interpretation of oxygenation status On room air,
PO2of 80-100 Normal
PO2of 60-79 Mild hypoxemia PO2of 40-59 Moderate hypoxemia
PO2of < 40 Severe hypoxemia
If patient receiving O2then expected PO2is ~ 5 x
FiO2. (on 30 %O2 the expectedPO2 will be 5 x 30=150 mmHg)
PAO2= [(760-47) x FiO2](PaCO2/ 0.8).
PAO2= (713 x FiO2)(PaCO2x 1.25).
Examples in ABG Interpretation (Dr. P.K.Jain)
E l i ABG I t t ti (D P K J i )
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Examples in ABG Interpretation (Dr. P.K.Jain)
FiO2 0.5
PO2
150 mmHg
pH 7.32
pCO2 42 mmHg
HCO3 21.3 mmol/L
SBE -5.8 mmol/L
A 32 yr female with 32 week pregnancy meets with motor vehicle
accident. Rib fractures ++ and on NSAIDs. BP-Normal, Abdomen
not tender. ABG report is as follows:
Comment on her oxygenation status.
E l i ABG I t t ti (D P K J i )
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Examples in ABG Interpretation (Dr. P.K.Jain)
FiO2 0.5
PO2 150 mmHg
pH 7.32pCO2 42 mmHg
HCO3 21.3 mmol/L
SBE -5.8 mmol/L
A 32 yr female with 32 week pregnancy meets with motor vehicle
accident. Rib fractures ++ and on NSAIDs. BP-Normal, Abdomen
not tender. ABG report is as follows:
PO2 high.
PAO2 = (713x0.5)-(42 x 1.25)
= 35653 = 303
PA-aO2 = 303-150 = 153 !!
? Pulm contusion, ? Pneumothorax
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Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
A 45 yr female on mechanical ventilation post-laparotomy. ABG
shows
FiO2 0.45
PO2 240 mmHg
pH 7.27
pCO2 75 mmHg
HCO3 34 mmol/L
SBE 5.2 mmol/L
PO2 is high.
PAO2= (713 x 0.45)-(75x1.25)
= 32094 = 226
PA-aO2 = 226-240 = -14 !!!
Either PO2 is wrong or patient on higher
FiO2 than 45%!
O2
Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
Step 3: Oxygenation Status:
a. -oxemia statusb. expected Vs observed PaO2.
c. oxygen cost of breathing
Step 4: Ventilatory Status.
Look at PaCO2
Step 5: Acid - Base Status..
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Interpretation of Ventilation status Normal PCO2is 35-45 mmHg.
PCO2< 35 mmHg hyper ventilation
PCO2> 45 mmHg hypo ventilation
One exception
Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
FiO2 0.5
PO2 150 mmHg
pH 7.32
pCO2 42 mmHg
HCO3 21.3 mmol/L
SBE -5.8 mmol/L
A 32 yr female with 32 week pregnancy meets with motor vehicle
accident. Rib fractures ++ and on NSAIDs. BP-Normal, Abdomen
not tender. ABG report is as follows:
Comment on her ventilatory status.
Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
FiO2 0.5
PO2 150 mmHg
pH 7.32
pCO2 42 mmHg
HCO3 21.3 mmol/L
SBE -5.8 mmol/L
A 32 yr female with 32 week pregnancy meets with motor vehicle
accident. Rib fractures ++ and on NSAIDs. BP-Normal, Abdomen
not tender. ABG report is as follows:
Initial impression PCO2 is normal.
But at 32 wk pregnancy normally PCO2
is 30 with compensatory fall in HCO3 (10x .5 =5) i. e. HCO3 was 19 to start with!
The increase in CO2 is therefore not by 2
but by 12 and has therefore caused partial
compensation by increasing HCO3 by
less than (12 x .3 = 3.6)
Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
FiO2 0.21
PO2 60 mmHg
pH 7.34
pCO2 60 mmHg
HCO3 32 mmol/L
SBE 4.3 mmol/L
SaO2 90 %
You are called to casualty to opine on ABG of this 65 yr male
with mild pain in abdomen. The medical officer is concerned
about his barrel chest and low saturation on pulse oximetry. ABGreport is as follows:
Comment on his ventilatory status.
Explain the hypoxemia.
Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
FiO2 0.21
PO2 60 mmHgpH 7.34
pCO2 60 mmHg
HCO3 32 mmol/L
SBE 4.3 mmol/L
SaO2 90 %
You are called to casualty to opine on ABG of this 65 yr male
with mild pain in abdomen. The medical officer is concerned
about his barrel chest and low saturation on pulse oximetry.ABG report is as follows:
Patient is hypoventilating.PAO2 = (713 x .21)-(60 x 1.25)
= 150-75= 75
PA-aO2 = 75-60 = 15 (normal)
no lung pathology
Low PO2 is due to hypoventilation !!!
Examples in ABG Interpretation (Dr P K Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
APPROACH TO INTERPRETATION OF ABG
Step 3: Oxygenation Status:a. -oxemia statusb. expected Vs observed PaO2.
c. oxygen cost of breathing
Step 4: Ventilatory Status.Look at PaCO2
Step 5: Acid - Base Status..
Examples in ABG Interpretation (Dr. P.K.Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
Primary Acid-Base Disorders
Alterations in pH can result from:
1. Respiratory component (pCO2) or
2. Metabolic component (HCO3
-).
Metabolic Acidosis
(Too little HCO3-
)
Metabolic Alkalosis
(Too much HCO3-
)
Respiratory Acidosis
(Too much CO2)
Respiratory Alkalosis
(Too little CO2)
Examples in ABG Interpretation (Dr. P.K.Jain)
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Examples in ABG Interpretation (Dr. P.K.Jain)
CompensationWhen a primary acid-base disorder exists, thebody attempts to return the pH to normal viathe other half of acid base metabolism.
Primary metabolic disorder Respiratory compensation
Primary respiratory disorder Metabolic compensation
Examples in ABG Interpretation (Dr. P.K.Jain)
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International Consensus Secondary or compensatory responses
should NOT be designated as acidosis
or alkalosis
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Examples in ABG Interpretation (Dr. P.K.Jain)
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p p ( )
Simple acid base disorders
Disorder pH HCO3- PaCO2
Acidosis
Metabolic acid.
Respiratory acid.
Alkalosis
Metabolic alk.
Respiratory alk.
Examples in ABG Interpretation (Dr. P.K.Jain)
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p p ( )
Simple acid base disorders
Disorder pH HCO3- PaCO2
Acidosis
Metabolic acid.
Respiratory acid.
Alkalosis
Metabolic alk.
Respiratory alk.
Examples in ABG Interpretation (Dr. P.K.Jain)
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p p ( )
Simple acid base disorders
Disorder pH HCO3- PaCO2
Acidosis
Metabolic acid.
Respiratory acid.
Alkalosis
Metabolic alk.
Respiratory alk.
Examples in ABG Interpretation (Dr. P.K.Jain)
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Simple acid base disorders
Disorder pH HCO3- PaCO2
Acidosis
Metabolic acid.
Respiratory acid.
Alkalosis
Metabolic alk.
Respiratory alk.
Examples in ABG Interpretation (Dr. P.K.Jain)
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Practical Approach
Determine primary disorder:
pH < 7.35 acidemia
HCO3< 24 metabolic acidosispCO2> 40 respiratory acidosis
pH > 7.45 alkalemia
HCO3> 24 metabolic alkalosis
pCO2< 40 respiratory alkalosis
Examples in ABG Interpretation (Dr. P.K.Jain)
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Step 5: Acid - Base Status..b. Identify primary/dominant acid-base disorder.
A patient presents with breathlessness since 1 day. He isgiven oxygen. Arterial blood gas is analysed and shows
FiO2 0.40 Patient has diabetes with blood
sugar of 450 mg%.
pH acidemia
PCO2 low alkalosis
HCO3 low acidosis
ThereforeMetabolic Acidosis
PO2 165
pH 7.26
PCO2 27
HCO3
12
Na 140
cl 99
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Metabolic acidosis
Metformintoxicity ??
??Convulsions
Lactic acidosis ??
??Starvation
Diabetes ?
Ethylene Glycolintoxication ??? ???
???
???
???
???
???
Examples in ABG Interpretation (Dr. P.K.Jain)
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Cations = Anions
Na
K
UC
Cl
HCO3
UA
Na+K+UC= Cl+HCO3+UA
Concept of Anion gap
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Na Cl
HCO3
Anion gap = Na ( Cl+HCO3)
Examples in ABG Interpretation (Dr. P.K.Jain)
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K
UCUA
Na Cl
HCO3
Anion gap = Na ( Cl+HCO3)
K
Anion gap = Na ( Cl+HCO3)
Do not forget the bigger
picture
Examples in ABG Interpretation (Dr. P.K.Jain)
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Lactic acidosis/
Ketoacidosis
Na
K
UC
Cl
HCO3
UA
Na+K+UC= Cl+HCO3+UA
High anion gap metabolic acidosis
Examples in ABG Interpretation (Dr. P.K.Jain)
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Lactic acidosis/
Ketoacidosis
Na Cl
HCO3
Na+K+UC= Cl+HCO3+UA
High anion gap metabolic acidosis
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Hyperchloremic
acidosis
Na
K
UC
Cl
HCO3
UA
Na+K+UC= Cl+HCO3+UA
Normal anion gap metabolic acidosis
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Hyperchloremic
acidosis
Na
K
UC
Cl
HCO3
UA
Na+K+UC= Cl+HCO3+UA
Normal anion gap metabolic acidosis
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Calculate anionic gap (AG)
Anionic Gap = Na(Cl + HCO3). Metabolic acidosis with increased AG.
Lactic acidosis
Diabetic ketoacidosis, starvation ketoacidosis. Renal failure
Toxicity: ethanol, ethylene glycol, salicylate
Metabolic Acidosis with normal AG
Renal: RTA, Diamox. GI causes: severe diarrhea, fistulas/ drains.
Recovery from ketoacidosis (DKA + saline).
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Step 5: Acid - Base Status..
f. In Normal AG Acidosis
Urinary Anionic Gap = [Na + K][Cl](Pre-requisites: no ketosis, carbenicillin, urine pH GI or iatrogenic
Positive UAG(>20-30 meq/L)=> RTA- (I, II, IV). Look at urine pH: >6.0 Distal (type I) RTA Look at urine pH:
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Step 5: Acid - Base Status..f In N-AG Metabolic Acidosis look at urinary electrolytes.Normal AG acidosis:
1. Urinary electrolytes: urinary Na, K BOTH LOW diarrhea, recent diuretics. urinary Na, K BOTH HIGH RTA (1/2), current diuretics. urinary Na HIGHbut urinary K LOW vomiting, (RTA type 4). urinary Na LOWbut urinary K HIGH lower GI loss.2. Urinary pH and ammonia estimation:
i) If urine pH 6.0 before normalization of S.HCO3 => proximalRTA
If urine pH remains acidic => diarrhoeaii) If urine pH >6.0, give IV NaHCO3 and check urine pH. If urine pH remains unchanged despite NaHCO3 => distal RTA
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Step 5: Acid - Base Status..
Normal anion gap is 12 but is influenced by
1. albumin levels and
2. pH of blood.
Both disturbances common in critically ill patients!
SO it is important to know what should be the EXPECTED
value in that patient at that time.
HOW??
Anion Gap: Expected AG & Actual AG
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Step 5: Acid - Base Status..
a. Calculate actual Anionic Gap: = Na(Cl + HCO3)
b. Correct expected Anionic gap (S. proteins / pH):
for every 1 gm%
of S. albumin the AG
by 2 mEq/L
(4 gm% for albumin)
e.g. In patient with nephrotic syndrome/cirrhosis:S. Albumin 2 gm%, so expected AG = 124 = 8 mEq/L.
e.g. In volume depleted patient with S. Albumin is 6 gm%,
Therefore expected AG = 12 + 4 = 16 mEq/L.
In acidemic states : normal AG
by 2meq/L
In alkalemic states: normal AG by 4 mEq/L
e.g. In patient with contraction metabolic alkalosis (pH 7.5,
Albumin 5 gm%): expected AG = 12 + 4 + 2 = 18 mEq/L.
Anion Gap: Expected AG & Actual AG
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Step 5: Acid - Base Status..b. Identify primary/dominant acid-base disorder.
A patient presents with breathlessness since 1 day. He is givenoxygen. Arterial blood gas is analyzed and shows
FiO2 0.40 Patient has diabetes with blood sugar of 450mg%.
pH =>Acidemia
PCO2 =>alkalosis
HCO3 =>acidosis
Therefore Metabolic Acidosis.
Anionic Gap = Na(Cl + HCO3)= 140- (99+12) = 29
(expected AG = 12-2= 10)
PO2
165
pH 7.26
PCO2 27
HCO3 12
Na 140
cl 99
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Step 5: Acid - Base Status..c. Identify compensatory disorder.
1. Metabolic acidosis:a. PCO2 = HCO3 (actually 1.01.5 times HCO3)
2. Metabolic alkalosis:a. PCO2 = 0.5 HCO3 (actually 0.5 -1.0)
3. Respiratory acidosis:
a. Acute: Change in PCO2 by 10 changes HCO3 by 1Change in PCO2 by 10 changes pH by 0.08
b. Chronic: Change in PCO2 by 10 changes HCO3 by 3.5
Change in PCO2 by 10 changes pH by 0.03
4. Respiratory alkalosis:
a. Acute: Change in PCO2 by 10 changes HCO3 by 2Change in PCO2 by 10 changes pH by 0.08
b. Chronic: Change in PCO2 by 10 changes HCO3 by 5
Change in PCO2 by 10 changes pH by 0.03
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Step 5: Acid - Base Status..c. Identify compensatory disorder.
3. Respiratory acidosis:a. Acute: Change in PCO2 by 10 changes HCO3 by 1b. Chronic: Change in PCO2 by 10 changes HCO3 by 3.5
4. Respiratory alkalosis:a. Acute: Change in PCO2 by 10 changes HCO3 by 2
b. Chronic: Change in PCO2 by 10 changes HCO3 by 5
R. acidosis R. Alkalosis
Acute 1 2
Chronic 3 4
Examples in ABG Interpretation (Dr. P.K.Jain)
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Step 5: Acid - Base Status..c. Identify compensatory disorder.
3. Respiratory acidosis:a. Acute: Change in PCO2 by 10 changes HCO3 by 1b. Chronic: Change in PCO2 by 10 changes HCO3 by 3.5
4. Respiratory alkalosis:a. Acute: Change in PCO2 by 10 changes HCO3 by 2
b. Chronic: Change in PCO2 by 10 changes HCO3 by 5
R. acidosis R. Alkalosis
Acute 1 2
Chronic 3 (3.5) 4 (5)
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A 45 yr female on mechanical ventilation post-laparotomy. ABG
shows
FiO2 0.45
PO2 240 mmHg
pH 7.27
pCO2 75 mmHg
HCO3 34 mmol/L
SBE 5.2 mmol/L
Acidemia.
Acute resp. acidosis(acute because on vent PCO2 = 75 will not be
missed!)
HCO3 = 24 + (35 x .1) = 27.5
But HCO3 >27primary Met. Alkalosis
? Hypovolemia, ? Hypokalemia
If resp. acidosis is chronic then HCO3 = 24 + 35 x .3 = 34.5.
However clinical data insufficient (diagnosis of acute and
chronic).
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
Current HCO3 is 10.
10
24
CB
A
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
Current HCO3 is 10.
32
10
24
CB
A
vomiting
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
Current HCO3 is 10.
32
10
24
CB
A
vomiting
Lacticacidosis(hypovolemicshock)
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
Current HCO3 is 10.
32
18
10
24
CB
A
DKA
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Examples in ABG Interpretation (Dr. P.K.Jain)
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
Current HCO3 is 10.
32
18
10
24
CB
A
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
Current HCO3 is 10.
10
CB
A
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Examples in ABG Interpretation (Dr. P.K.Jain)
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
ABG Normal
Met.Acidosis
(High AG)
Met acidosis(High AG)
+ Met alkalosis
Met acidosis(High AG) +(Normal AG)
pH 7.40 7.29 7.38 7.10
PCO2 40 30 35 20
HCO3 24 14 20 6
AG 12 20 26 20
AG 0 +10 + 14 +10
HCO3 + AG 24 24 34 16
Corrected HCO3 = actual HCO3 + AG
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
ABG NormalMet. Acidosis
(a)
Met acidosis(b)
Met acidosis(c)
pH 7.40 7.29 7.38 7.10PCO2 40 30 35 20
HCO3 24 14 20 6
AG 12 20 26 20
???? ???? ????
Examples in ABG Interpretation (Dr. P.K.Jain)
Step 5 Acid Base Stat s
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Step 5: Acid - Base Status..d. Identify simple from mixed acid-base disorder.
ABG NormalMet. Acidosis
(High AG)
Met acidosis (High AG)
+ Met alkalosis
Met acidosis(High AG)+Met acidosis(Normal AG)
pH 7.40 7.29 7.38 7.10
PCO2 40 30 35 20
HCO3 24 14 20 6
AG 12 20 26 20
AG 0 +10 + 14 +10
HCO3 0 -10 -4 -18
AG/
HCO3 1 >1-2 (3.5)
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Metabolic acidosis with low ionized Calcium
1. Pancreatitis
2. Renal failure
3. Rabdomyolyisis
4. Tumor cell lysis syndrome
5. Ethylene glycol toxicity
6. HF poisoning
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Metabolic acidosis with low Blood sugar
1. Liver cell failure
2.Convulsions
3. Metformin toxicity
4. Adrenal insufficiency
5. ? starvation
M t b li Alk l i
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Metabolic Alkalosis
Bartters syndrome ???
Gitelmann Syndrome
???
Primaryhyperaldosteronism ???
Villus adenoma ???
Cl
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Metabolic Alkalosis
Commonest cause are
Hypovolemia(Contraction alkalosis)
Hypokalemia
So assess volume status
Cannot use Urinary Na?? If volume OK then investigate hypokalemia!
Cl
Na
HCO3
Examples in ABG Interpretation (Dr. P.K.Jain)
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Approach to Metabolic alkalosis
Check Urinary Chlorides:UCl< 20 mEq/LHypovolemia (Vomiting/ RT, Diuretics).UCl> 20 mEq/L Then Check Urinary K
+:
UK< 20 mEq/day vomiting
UK> 30 mEq/day diuretics or mineralocorticoid excess
Then Check BP:
Normaldiuretic abuse, Bartters syndrome.
Hypertensivecheck S. Aldosterone/ Renin:
- Primary hyperaldosteronism.
- Secondary hyperaldosteronism.
- Cushings syndrome (increased cortisol).
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Oxygen in Metabolic alkalosis!
Hypoventilation (response to metabolic alkalosis) Pulmonary microatelectasis (from hypoventilation)
Increased V/Q mismatch (as alkalosis inhibits hypoxicpulmonary vasoconstriction)
Peripheral oxygen unloading may be impairedbecause of the alkalotic shift of the haemoglobinoxygen dissociation curve to the left.
Normal compensatory response is to increase cardiac
output but this ability is impaired if hypovolaemia anddecreased myocardial contractility are present.
Hypokalemia + Metabolic disorder
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Hypokalemia+ Metabolic disorder
? Metabolic acidosis ? Metabolic alkalosis Check Urinary K
Urinary K < 20 mEq/L + metabolic acidosis:
GI loss: diarrhea, laxative abuse, fistula, villusadenoma.
Urinary K > 20 mEq/L + metabolic acidosis: RTA (type 1 &2), acetazolamide therapy,DKA,
Ureterosigmoidostomy. Urinary K > 20 mEq/L + metabolic alkalosis:(see urinary chlorides) --
Examples in ABG Interpretation (Dr. P.K.Jain)
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FiO2 0.21
PO2 103 mmHg
pH 7.25
pCO2 26 mmHg
HCO3 11.2 mmol/L
SBE -16.2 mmol/L
Na 141 mEq/L
K 3.6 mEq/L
Cl 114 mEq/L
Glucose 180 mg %
You are managing a severe DKA in ICU. 10 hrs post admission,
there is persisting Acidemia despite aggressive treatment. ABG
and electrolytes of this 43 yr male at this time is as follows:
Comment on the acid base status
Examples in ABG Interpretation (Dr. P.K.Jain)
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FiO2 0.21
PO2 103 mmHg
pH 7.25
pCO2 26 mmHg
HCO3 11.2 mmol/L
SBE -16.2 mmol/L
Na 141 mEq/L
K 3.6 mEq/L
Cl 114 mEq/L
Glucose 180 mg %
You are managing a severe DKA in ICU. 10 hrs post admission,
there is persisting Acidemia despite aggressive treatment. ABG
and electrolytes of this 43 yr male at this time is as follows:
Acidemia. Met. Acidosis.
AG = 141- (114 + 11) = 16 (increased)
AG = 16 -10 = 6
Corrected HCO3 = 11.2 + 6 = 17.2
Therefore another acidosisnormal AG
metabolic acidosis (hyperchloremia due
to saline infusion in large quantity).
Final diagnosis:Met acidosis with
increased AG plus Met acidosis with
Normal AG.
Examples in ABG Interpretation (Dr. P.K.Jain)
Step 5: Acid - Base Status..
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Step 5: Acid Base Status..
e. In high AG acidosis: Calculate of Osmolal gap.
a. Osmolal gap = measured ~ calculated Osmolality< 10 mOsm/kg H20
b. Calculated Osmolality = 2[Na] + [glucose]/18 + [BUN]/2.8
Examples in ABG Interpretation (Dr. P.K.Jain)
A 24 yr male admitted in coma He has rapid deep breathing
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FiO2 0.21
PO2 112 mmHg
pH 7.10
pCO2 14 mmHg
HCO3 16 mmol/L
Na 131 mEq/L
K 3.0 mEq/L
Cl 94 mEq/L
Glucose 252 mg %
A 24 yr male admitted in coma. He has rapid deep breathing.
Clinical examination otherwise normal. His CSF and CT head are
normal. The ABG and biochemistry on admission is as follows:
Comment on the acid base status.
urea 10 mmol/L
creat 0.7 mg%
Posm 324 mosm/Kg
Ca ionized 1.2 mEq/L
Examples in ABG Interpretation (Dr. P.K.Jain)
A 24 yr male admitted in coma He has rapid deep breathing
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FiO2 0.21
PO2 112 mmHg
pH 7.10
pCO2 14 mmHg
HCO3 16 mmol/L
Na 131 mEq/L
K 3.0 mEq/L
Cl 94 mEq/L
Glucose 252 mg %
A 24 yr male admitted in coma. He has rapid deep breathing.
Clinical examination otherwise normal. His CSF and CT head are
normal. The ABG and biochemistry on admission is as follows:
Acidemia.
Metabolic acidosis with AG = 21.
Measured Posm = 324Calculated Posm = 2 x (131) + 252/18 = 276
Therefore osmolar gap = 324276 = 48
urea 10 mmol/L
creat 0.7 mg%
Posm 324 mosm/Kg
Ca ionized 1.2 mEq/L
DD: ethanolpoisoning, methanolpoisoning, ethyleneglycol poisoning
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FiO2 0.21
PO2 112 mmHg
pH 7.10
pCO2 14 mmHg
HCO3 16 mmol/L
Na 131 mEq/L
K 3.0 mEq/L
Cl 94 mEq/L
Glucose 252 mg %
This patient after 24 hrs develops fixed dilated pupils. Suggest a
likely diagnosis.
urea 10 mmol/L
creat 0.7 mg%
Posm 324 mosm/Kg
Ca ionized 1.2 mEq/L
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FiO2 0.21
PO2 112 mmHg
pH 7.10
pCO2 14 mmHg
HCO3 16 mmol/L
Na 131 mEq/L
K 3.0 mEq/L
Cl 94 mEq/L
Glucose 252 mg %
This patient after 24 hrs develops fixed dilated pupils. Suggest a
likely diagnosis.
Methanol toxicity manifests 1-7 hrs after
ingestion (CNS, visual, GI symptoms).
Visual symptoms due to formic acidNormal Ca ionized is against ethylene glycol.Urine examination showing calcium oxalate
crystals would favour ethylene glycol intoxication.
urea 10 mmol/L
creat 0.7 mg%
Posm 324 mosm/Kg
Ca ionized 1.2 mEq/L
DD: ethanol poisoning, methanol poisoning,ethylene glycol poisoning
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Oxalate
crystalsin another case
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A patient of multiple myeloma with asthma is admitted with status
asthma to the ICU and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:
FiO2 100%
PaO2 477
PaCO2 47
pH 7.23
HCO3 19
Hb 7.2
S. Albumin 2.0 gm%
You are the treating physician in the
ICU. How would you proceed on
seeing this report ?
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:FiO2 100%
PaO2 477
PaCO2 47
pH 7.23
HCO3 19
Hb 7.2
S. Albumin 2.0 gm%
Oxygenation status:
Ventilatory Status:
Acid-base status:Acidemiaresp acidosis + metabolicacidosis
What next ??
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:FiO2 100%
PaO2 477
PaCo2 47
pH 7.23
HCO3 19
Hb 7.2
S. Albumin 2.0 gm%
Sr. Na 131
Sr. K 3.4
Sr. Cl 104
Resp acidosis + Metabolic acidosis
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:FiO2 100%
PaO2 477
PaCo2 47
pH 7.23HCO3 19
Hb 7.2
S. Albumin 2.0 gm%
Sr. Na 131
Sr. K 3.4
Sr. Cl 104
Resp acidosis + metabolic acidosis
Expected anionic gap = 1224 = 6 2
Actual AG = 131-(104+19) = 8
AG = 0
Therefore Met Acidosis with normal anionicgap
What next ??
Examples in ABG Interpretation (Dr. P.K.Jain)
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:What is your interpretation?FiO2 100%
PaO2 477
PaCo2 47
pH 7.23
HCO3 19
Hb 7.2
S. Albumin 2.0 gm%
Sr. Na 131
Sr. K 3.4
Sr. Cl 104
Ur. Na 146
Ur. K 27.6
Ur. Cl 146
Resp acidosis + metabolic acidosis with normalanionic gap.
Examples in ABG Interpretation (Dr. P.K.Jain)
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:What is your interpretation?FiO2 100%
PaO2 477
PaCo2 47
pH 7.23
HCO3 19
Hb 7.2
S. Albumin 2.0 gm%
Sr. Na 131
Sr. K 3.4
Sr. Cl 104
Ur. Na 146
Ur. K 27.6
Ur. Cl 146
Resp acidosis + normal AG metabolic acidosis
Urinary AG = 146 + 27.6146 =27.6
Positive UAGRTA
What next ??
Examples in ABG Interpretation (Dr. P.K.Jain)
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:What is your interpretation?FiO2 100%
PaO2 477
PaCo2 47
pH 7.23
HCO3 19
Hb 7.2
Sr. Na 131
Sr. K 3.4
Sr. Cl 104
Ur. Na 146
Ur. K 27.6
Ur. Cl 146
Ur. pH 6.1
Resp acidosis + normal AG metabolicacidosis due to RTA
Examples in ABG Interpretation (Dr. P.K.Jain)
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:What is your interpretation?FiO2 100%
PaO2 477
PaCo2 47
pH 7.23
HCO3 19
Hb 7.2
Sr. Na 131
Sr. K 3.4
Sr. Cl 104
Ur. Na 146
Ur. K 27.6
Ur. Cl 146
Ur. pH 6.1
Resp acidosis + normal AG metabolic acidosisdue to RTA
Urine pH > 5.5 and Serum K low
Therefore Distal (Type I) Renal TubularAcidosis
Examples in ABG Interpretation (Dr. P.K.Jain)
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A patient of multiple myeloma with asthma is admitted withstatus asthma and is put on ventilator. On 100% FiO2 the
arterial blood gas report is as follows:FiO2 100%
PaO2 477
PaCo2 47
pH 7.23
HCO3 19
Hb 7.2
Sr. Na 131
Sr. K 3.4
Sr. Cl 104Ur. Na 146
Ur. K 27.6
Ur. Cl 146
Ur. pH 6.1
Respiratory acidosis (related to severe airwaysresistance and permissive hypercapnia as
protective lung strategy)
+ normal AG metabolic acidosis (due to Type 1
RTA) from multiple myeloma.
Case 1
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A 26 year old man with unknown past medical historyis brought in to the ER by ambulance, after friends
found him unresponsive in his apartment. He had last
been seen at a party four hours prior.
ABG: pH 7.25 Na+ 137
PCO2 60 K+ 4.5
HCO3- 26 Cl- 100
PO2 55
Case 2
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A 67 year old man with diabetes and early diabetic
nephropathy (without overt renal failure) presents for aroutine clinic visit. He is currently asymptomatic.Because of some abnormalities on his routine bloodchemistries, you elect to send him for an ABG.
ABG: pH 7.35 Na+ 135
PCO2 34 K+ 5.1
HCO3-
18 Cl-
110PO2 92
Cr 1.4
Urine pH: 5.0
Case 3
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A 68 year old woman with metastatic colon cancerpresents to the ER with 1 hour of chest pain andshortness of breath. She has no known previouscardiac or pulmonary problems.
ABG: pH 7.49 Na+ 133
PCO2 28 K+ 3.9
HCO3
- 21 Cl- 102
PO2 52
Case 4
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A 6 year old girl with severe gastroenteritis is admittedto the hospital for fluid rehydration, and is noted tohave a high [HCO3
-] on hospital day #2. An ABG isordered:
ABG: pH 7.47 Na+ 130
PCO2 46 K+ 3.2
HCO3- 32 Cl- 86
PO2 96
Urine pH: 5.8
Case 5
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A 75 year old man with morbid obesity is sent to the
ER by his skilled nursing facility after he developed afever of 103 and rigors 2 hours ago. In the ER he islucid and states that he feels terrible, but offers nolocalizing symptoms. His ER vitals include a heart rate
of 115, and a blood pressure of 84/46.
ABG: pH 7.12 Na+ 138
PCO2 50 K+ 4.2
HCO3- 13 Cl- 99
PO2 52
Urine pH: 5.0
Case 6
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A 25 year old man with type I diabetes presents to theER with 24 hours of severe nausea, vomiting, andabdominal pain.
ABG: pH 7.15 Na+ 138PCO2 30 K
+ 5.6
HCO3- 10 Cl- 88
PO2 88 Cr 1.1
Urine pH: 5.0
Case 7
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A 62 year old woman with severe COPD comes to
the ER complaining of increased cough andshortness of breath for the past 12 hours. There areno baseline ABGs to compare to, however, herHCO3
-measured during a routine clinic visit 3
months ago was 34 mEq/L.
ABG: pH 7.21 Na+ 135
PCO
2 85 K
+
4.0HCO3- 33 Cl- 90
PO2 47
Urine pH 5.5
Case 8
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A 36 year old man with a history of alcoholism isbrought to the ER after being found on the floor of hisapartment unresponsive, soiled with vomit, and with anempty pill bottle nearby.
ABG: pH 7.03 Na+ 134
PCO2 75 K+ 5.2
HCO3- 19 Cl- 90
PO2 48 HCO3- 20
Urine pH 5.0
Additional case
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Additional case
65 yr male develops hypotension (90/56) intra-op withST depression. He is shifted to ICU where he has
Ventricular fibrillation that responds to DC shock. Arterial
Blood Gases are collected soon afterwards.
pH 7.27pCO2 55.4 mmHg
pO2 144 mmHg
HCO3 24.3 mmol/lBiochemistry (mmol/l): Na+138, K+4.7, Cl-103,
urea 6.4 & creatinine 0.07
Examples in ABG Interpretation (Dr. P.K.Jain)
Wh ABG i il d i ?
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Why ABG in a ventilated patient?
We take breathing for granted.
Mechanical ventilation shows us howcomplex it really is!
No substitute for measurement of PO2,PCO2, pH, HCO3in a ventilated patient.
Appropriateness of the ventilator setting.
As guide to corrections necessary.
Examples in ABG Interpretation (Dr. P.K.Jain)
Case scenario 1
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Case scenario 134 year male with GB syndromepresents with progressive weaknessinvolving muscles of breathing and isintubated and ventilated with Vt 600
ml, RR 20/min, FiO240%. ABG donesoon afterward shows:PO2 198, PCO2 28, pH 7.5, HCO322.
Is the ventilator settings appropriate forthis patient?
What is not right?
Examples in ABG Interpretation (Dr. P.K.Jain)
Case scenario 1
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Case scenario 1
34 year male with GB syndrome presentswith progressive weakness involvingmuscles of breathing and is intubated andventilated with Vt 600 ml, RR 20/min, FiO
2
40%. ABG done soon afterward shows:PO2 198, PCO2 28, pH 7.5, HCO322.
What are the adjustments to be made on the
ventilator to correct for PO2and PCO2?
Examples in ABG Interpretation (Dr. P.K.Jain)
How to adjust the FiO2 for the PaO2
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How to adjust the FiO2 for the PaO2
PaO2is directly proportional to FiO2.PaO2 FiO2
PaO2/ FiO2is a constant
PaO2/ FiO2(new) = PaO2/ FiO2(old)
In this patient: 100 / FiO2= 198 / 40FiO2 new = 100 x 40 = 20.2%198
Examples in ABG Interpretation (Dr. P.K.Jain)
Case Scenario 2
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Case Scenario 2
A patient being mechanically ventilatedon assist control mode with Vt 450 ml,RR 18, FiO270% has an ABG report asfollows:
PO2 170, PCO2 34, pH 7.5, HCO326.
What PO2can I expect if I reduce the FiO2to 40%?
Examples in ABG Interpretation (Dr. P.K.Jain)
H t di t th P O
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How to predict the PaO2
PaO2/FiO2is a constant at any giventime.
PaO2/FiO2(new) = PaO2/FiO2(old)
In this patient: PaO2/ 40 = 170/ 70
PaO2 expected = 170 x 40 = 97.1%70
Examples in ABG Interpretation (Dr. P.K.Jain)
Back to case 1
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Back to case 1
34 year male with GB syndromepresents with progressive weaknessinvolving muscles of breathing and is
intubated and ventilated with Vt 600ml, RR 20/min, FiO240%. ABG donesoon afterward shows:PO
2198, PCO
228,pH 7.5, HCO
322.
How to readjust ventilator for PCO2?
Examples in ABG Interpretation (Dr. P.K.Jain)
How to adjust MV for PCO
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How to adjust MV for PCO2
PCO2is inversely proportional to minuteventilation.
PCO2 1/ minute ventilation
PCO2x MV (old) = PCO2x MV (new)
PCO2x Vt (old) = PCO
2x Vt (new)
PCO2x RR (old) = PCO2x RR (new)
Examples in ABG Interpretation (Dr. P.K.Jain)
Back to the case
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Back to the case
Vt 600 ml, RR 20/min, FiO240%. ABG:PO2 198, PCO2 28, pH 7.5, HCO322.
PCO2x Vt (old) = PCO2x Vt (new)
28 x 600 = 35 x Vt (new)Correct Vt setting is 480 ml.
PCO2x RR (old) = PCO2x RR (new)
28 x 20 = 35 x RR (new)Correct RR = 16/min
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