abg dr pkjain ccef july 2008

8/10/2019 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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The Painful Fact

The more you learn

the more you wonder how youmanaged so far.


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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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Do not Cap or Bend the needle !!!


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14/128


Plug (airtight) the needle !!!


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ABG

ICE

ABG


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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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[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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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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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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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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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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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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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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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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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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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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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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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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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).




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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.



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FiO2 0.5

PO2 150 mmHg

pH 7.32pCO2 42 mmHg

HCO3 21.3 mmol/L

SBE -5.8 mmol/L




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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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



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Step 3: Oxygenation Status:

a. -oxemia statusb. expected Vs observed PaO2.

c. oxygen cost of breathing

Step 4: Ventilatory Status.

Look at PaCO2



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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



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FiO2 0.5

PO2 150 mmHg

pH 7.32

pCO2 42 mmHg

HCO3 21.3 mmol/L

SBE -5.8 mmol/L




Comment on her ventilatory status.



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FiO2 0.5

PO2 150 mmHg

pH 7.32

pCO2 42 mmHg

HCO3 21.3 mmol/L

SBE -5.8 mmol/L




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)



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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.



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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 !!!



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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




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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)



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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



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International Consensus Secondary or compensatory responses

should NOT be designated as acidosis

or alkalosis



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p p ( )

Simple acid base disorders

Disorder pH HCO3- PaCO2

Acidosis

Metabolic acid.

Respiratory acid.

Alkalosis

Metabolic alk.

Respiratory alk.



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p p ( )



Acidosis

Metabolic acid.

Respiratory acid.

Alkalosis

Metabolic alk.

Respiratory alk.



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p p ( )



Acidosis

Metabolic acid.

Respiratory acid.

Alkalosis

Metabolic alk.

Respiratory alk.



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Acidosis

Metabolic acid.

Respiratory acid.

Alkalosis

Metabolic alk.

Respiratory alk.



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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



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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 ??? ???

???

???

???

???

???



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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)



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K

UCUA

Na Cl

HCO3


K


Do not forget the bigger

picture



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Lactic acidosis/

Ketoacidosis

Na

K

UC

Cl

HCO3

UA

Na+K+UC= Cl+HCO3+UA

High anion gap metabolic acidosis



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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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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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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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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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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


R. acidosis R. Alkalosis

Acute 1 2

Chronic 3 4


S id S


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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


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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Current HCO3 is 10.

32

10

24

CB

A

vomiting



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Current HCO3 is 10.

32

10

24

CB

A

vomiting

Lacticacidosis(hypovolemicshock)



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Current HCO3 is 10.

32

18

10

24

CB

A

DKA


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80/128


Current HCO3 is 10.

32

18

10

24

CB

A



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Current HCO3 is 10.

10

CB

A


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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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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

???? ???? ????


Step 5 Acid Base Stat s


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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


A h M b li lk l i


90/128

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) --


Y i DKA i ICU 10 h t d i i


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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


Y i DKA i ICU 10 h t d i i


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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.




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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


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


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


DD: ethanolpoisoning, methanolpoisoning, ethyleneglycol poisoning



98/128

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




99/128

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


DD: ethanol poisoning, methanol poisoning,ethylene glycol poisoning



100/128

Oxalate

crystalsin another case



101/128

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 ?



102/128

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 ??



103/128



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



104/128



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 ??


f l l l h h d d h


105/128


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.


A i f l i l l i h h i d i d i h


106/128



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 ??


A ti t f lti l l ith th i d itt d ith


107/128



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




108/128



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




109/128



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


111/128

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


113/128

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


115/128

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


117/128

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


118/128

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


Wh ABG i il d i ?


119/128

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.


Case scenario 1


120/128

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?


Case scenario 1


121/128

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?


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


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%?


H t di t th P O


124/128

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


Back to case 1


125/128

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?


How to adjust MV for PCO


126/128

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)


Back to the case


127/128

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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abg dr pkjain ccef july 2008

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