Acid Base Stepwise Pradik

8/18/2019 Acid Base Stepwise Pradik

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Keseimbangan Asam Basa

Edward Kusuma, Bambang Pujo Semedi


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ARTERIAL BLOOD GAS NORMAL


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EVALUASI OKSIGENASI

Cek PaO2

Berapa angka normal?

Menentukan angka normal berdasarkan ratio PaO2 / FiO2

Normal P/F ratio = 400 - 500

Jadi PaO2 = 100

adalah NORMAL bila FiO2 21% (P/F ratio = 476)adalah TIDAK NORMAL bila FiO2 100% (P/F ratio = 100)


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Give information about :

- Oxygenation

- Ventilation

- Acid - base status

ARTERIAL BLOOD GASES


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•

Oxygenation

• Ventilation

•

Acid base status

pH

PaCO2

P

a

O

HCO3-

Base excess

Saturation

Interpretation of arterialblood gases


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H20 CO2 HCO3- H+H2CO3

Acid-base


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Normal [H+] = 40 nmol/l

pH = - log [H+] = 7.4


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H2

0 CO2 HCO

3

- H+H2

CO3

Normal PaCO2 = 5.3 kPa

= 40 mmHg


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ALVEOLAR VENTILATION

Normal PaCO2 = 5.3 kPa

= 40 mmHg


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Normal HCO3- = 22-26 mmol/l


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ALVEOLAR VENTILATION

RENAL HCO3- HANDLING


Normal HCO3- = 22-26 mmol/l


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• Oxygenation

• Ventilation

• Acid base status

pH

PaCO2P

a

O

HCO3-

Base excess

Saturation

Interpretation of arterial

blood gases


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•What is the PaO2?

•Is this is adequate for theamount of inspired oxygen?

•Does the ABG result agreewith the saturation probe?

pH

PaCO2

P

a

O

HCO3-

Base excess

Saturation

OXYGENATION


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• Normal PaO2 breathing air (FiO2 = 21%) is 90 -100 mmHg; smallreduction with age

• Lower values constitute hypoxemia• PaO2 < 60 mmHg on room air = respiratory failure

• PaO2 should go up with increasing FiO2

• A PaO2 of 100 mmHg breathing 60% O2 is not normal

• You need to know the FiO2 to interpret the ABG

OXYGENATION


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- Correlate the ABG result with the saturation proberesult

- If there is a discrepancy:

- Is there a problem with the probe (poor perfusion? etc)

- Is there a problem with the blood gas (is it a venous sample?)

OXYGENATION


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• Is the PO2 is lower than expected?

• Calculate the A-a gradient to assess if the low PO2 is due to:• Low alveolar PO2

• Structural lung problems causing failure of oxygen transfer

OXYGENATION


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In clinical setting........ SpO2 can represent SaO2 if there is not source error

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! Poor peripheral perfusion

! Dark skin

! False nails or nail varnish

! Lipaemia

! Bright ambient light

! Poorly adherent probe

! Excessive motion

! Carboxy-haemoglobin ormethaemoglobin

Pulse oxymeter :Source error

H Y P O X E M

IA


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• (A-a) PO2 gradient = {[FiO2 x (760-47)] - (PCO2/RQ)} - PaO2

• Normal value : A-a gradient = (Age/4) + 4

• Young person at sea level :

• A-a increases 5 to 7 mmHg for every 10 % increase FiO2

• Room Air : 10 to 20 mmHg

• 100% oxygen : 60 to 70 mmH

• Increased age affects A-a gradient (at sea level)

• Age 20 years: 4 to 17 mmHg




OXYGENATION


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OXYGEN CASCADETransport oxygen to the cells can be divided into SIX simple steps :

VENTILATION1. Convection of O2 from ambient air into the body

O2 UPTAKE2. Diffusion of oxygen into the blood

HAEMOGLOBIN3. Chemical bonds with the Hgb that is reversible

CARDIAC OUTPUT4. Convective transport of O2 to the tissues

DIFFUSION DISTANCE5. Diffusion into the cells and organelles

}

S a O 2

D O 2

V O 2

METABOLISM6. Reduction and oxidation in mitochondria

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C a

O 2


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EXTERNAL RESPIRATION PROCESS

PAO2 : 40PACO2 : 46

PAO2 : 102PACO2 : 40

PAO2 : 100PACO2 : 40

PAO2 : 102PACO2 : 40

Pulmonary Gas Exchange

Pulmonary Ventilation

PIO2= 159

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Acid Base Analysis

“Stepswise Conventional Analysis”

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Metode Analisa Gas Darah

• Hendersson Hasselbach Klasik • Stewart

•Stepwise Conventional Analysis

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“Stepswise Conventional Analysis”

Berdasar pada pengukuran dan kalkulasi:

" pH

" PaCO2

" bicarbonat

" anion gap

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Komponen utama pada pendekatan iniadalah penghitungan:

• adekwasi kompensasi yang terjadi• kesesuaian anion gap dengan

perubahan konsentrasi serum

bikarbonat

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Metabolic and Respiratory Compensation

in Acid-Base Disorder

Metabolic acidosis Expected PaCO2 = (1.5 x [HCO3]) +8 +/-2

Metabolic alkalosis Expected PaCO2 = (0.7 x [HCO3]) + 21 +/- 1.5

Acute respiratory acidosis

Expected HCO3 = 24 + (PaCO2 - 40) / 10

Chronic Respiratory Acidosis Expected HCO3 = 24 + (PaCO2 - 40) / 3

Acute Respiratory Alkalosis

Expected HCO3 = 24 - (40 - PaCO2) / 5

Chronic respiratory alkalosis Expected HCO3 = 24 - (40 - PaCO2) / 2

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Metabolic acidosis ( HCO3 )

Expected PaCO2 = (1.5 x [HCO3]) +8 +/-2

Metabolic alkalosis ( HCO3 )

Expected PaCO2 = (0.7 x [HCO3]) + 21 +/- 1.5

Acute respiratory acidosis ( PaCO2 )


Chronic Respiratory Acidosis ( PaCO2 )


Acute Respiratory Alkalosis (PaCO2)


Chronic respiratory alkalosis ( PaCO2 )


Lower exp HCO3 ! superimposed metabolik

acidosis

Higher exp. HCO3 ! superimposed metabolikalkalosis

lower exp. pCO2 ! superimposed

respiratory alkalosis.

higher exp. pCO2 ! superimposedrespiratory acidosis

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Compensatory changes in acid base imbalances


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step 1

•Apakah data “internally

consistent”

• H+= 24 x [ PaCO2/HCO3-]

Internal Consistency

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step 2

• Apa gangguan primernya: acidosis ataualkalosis

• apakah pCO2, bicarbonate, anion gap dalambatas normal ?

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step 3

• apakah penyebabnya : respiratorik ataumetabolik ?

•lihat pCO2 dan HCO3

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step 4

• Bila kelainan metabolik yang ditemukan, apakahkompensasi respiratorik adekuat?

• Bila kelainan respiratorik yang ditemukan,apakah kompensasi metabolik adekuat?

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Metabolic acidosis ( HCO3 )


Metabolic alkalosis ( HCO3 )


Acute respiratory acidosis ( PaCO2 )


Chronic Respiratory Acidosis ( PaCO2 )


Acute Respiratory Alkalosis (PaCO2)


Chronic respiratory alkalosis ( PaCO2 )


lower exp. pCO2 !

superimposedrespiratory alkalosis.

higher exp. pCO2 ! superimposedrespiratory acidosis

Lower exp HCO3 ! superimposed metabolikacidosis

Higher exp. HCO3 !

superimposed metabolikalkalosis

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pH and HCO3

- changes

pH [HCO3-]

Acute respiratory

acidosis

Falls 0.06 Rises 0.8 mmol

(up to 30 mmol/l)

for every 1 kPa rise

in PaCO2

Acute respiratory

alkalosis

Rises 0.06 Falls 1.5 mmol

(down to 18 mmol/l)

for every 1 kPa fall in

PaCO2

Chronic respiratory

acidosis


(up to 36 mmol/l)


in PaCO2

Chronic respiratory

alkalosis


(down to 18 mmol/l)


PaCO2


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pH [HCO3-]

Acute respiratory

acidosis


(up to 30 mmol/l)


in PaCO2

Acute respiratory

alkalosis


(down to 18 mmol/l)


PaCO2

Chronic respiratory

acidosis


(up to 36 mmol/l)


in PaCO2

Chronic respiratory

alkalosis


(down to 18 mmol/l)


PaCO2

For acute respiratory

conditions

1 kPa = 7.5 mmHg


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pH [HCO3-]

Acute respiratory

acidosis


(up to 30 mmol/l)


in PaCO2

Acute respiratory

alkalosis


(down to 18 mmol/l)


PaCO2

Chronic respiratory

acidosis


(up to 36 mmol/l)


in PaCO2

Chronic respiratory

alkalosis


(down to 18 mmol/l)


PaCO2

Early renal compensation

for respiratory conditions

1 kPa = 7.5 mmHg


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pH [HCO3-]

Acute respiratory

acidosis


(up to 30 mmol/l)


in PaCO2

Acute respiratory

alkalosis


(down to 18 mmol/l)


PaCO2

Chronic respiratory

acidosis


(up to 36 mmol/l)


in PaCO2

Chronic respiratory

alkalosis


(down to 18 mmol/l)


PaCO2

Late renal compensationfor respiratory conditions

1 kPa = 7.5 mmHg


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step 5

• Apakah ada kenaikan anion gap?

• Anion gap = [Na+] - [Cl-] - [HCO3-] • Normal = 12 (+2) mEq/L

• apakah perubahan anion gap sebandingdengan perubahan bicarbonat

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Anion Gap

• The anion gap is an artificial

difference between the commonlymeasured anions and cations.

• In reality there is electrochemicalneutrality

Anion Gap = [Na+] – [Cl-] - [HCO3-]

[Na+] + [unmeasured cations] = [Cl-] + [HCO3-] + [unmeasured anions]

[unmeasured anions] - [unmeasured cations] = [Na+] - ([Cl-] + [HCO3-])


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Untuk menentukan apakah px sudahmengalami acidosis/alkalosis metabolik

sebelumnya (kronis), hitung initial HCO3-

Initial HCO3- = anion gap measured - anion gap normal + HCO3- measured

hasil < 20 : px sudah mempunyai asidosis metabolik kronik (faktor

di luar anion gap)

hasil > 30 :px sudah mempunyai alkalosis metabolik kronik

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Normal Anion Gap

Asidosis Metabolik

HCO3 loss and replaced with Cl —> anion gap

normal

If hyponatraemia is present the plasma [Cl-] maybe normal despite the presence of a normalanion gap acidosis —> this could be considered

a ‘relative hyperchloraemia’

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step 6

Evaluasi ulang apakah analisa sesuaidengan situasi klinik pasien

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contoh kasus

• 36 tahun, laki - laki, Riwayat DM type 2,perokok kronis, alkoholik, ditemukan dalam

kondisi agitasi

• 1 jam kemudian px masuk ICU dalamkondisi penurunan kesadaran

•BGA: pH 7.18 PaCO2 23 PaO2 78

• Na 132 K 5.2 Cl 97 HCO3 21

• Glucose 23544

1 i l


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step 1 - internal

consistenc• H+= 24 x [ PaCO2/HCO3-]

•= 24 x 23 / 21

• = 26.3

Perkiraan H+ utk pH 7.18 adalah

sekitar 60 mmol/L

DATA TIDAK

KONSISTEN 45


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BGA diulang

Data baru:

pH 7.18 PaCO2 23 PaO2 78

Na 132 K 5.2 Cl 97

HCO3- 9

Glucose 235

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ulangi step 1

internal consistenc

• = 24 x (21/9)

• = 64 • sesuai dengan

perkiraan H+ utk

pH 7.18

DATA KONSISTEN

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2


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step 2

alkalosis atau acidosis?• pH 7.18 PaCO2 23 PaO2 78

• Na 132 K 5.2 Cl 97

• HCO3- 9

• Glucose 235

ACIDOSIS

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step 3

respiratorik atau metabolik?• pH 7.18 PaCO2 23 PaO2 78

•Na 132 K 5.2 Cl 97

• HCO3- 9

• Glucose 235

acidosis metabolik

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step 4 apakah kompensasi

adekuat ?

• expected PaCO2 =1.5 x 9 + 8 + 2 =

21.5 + 2

• pH 7.18 PaCO2 23 PaO2 78

• Na 132 K 5.2 Cl 97

• HCO3- 9• Glucose 235

Kesimpulan :

metabolik acidosis dengan

kompensasi respiratorik adekuat

Metabolic acidosis


Metabolic alkalosis


Acute respiratory acidosis


Chronic Respiratory Acidosis


Acute Respiratory Alkalosis


Chronic respiratory alkalosis


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step 5

anion gap

• Anion gap = [Na+

] - [Cl-

] - [HCO3-

]

• 132 - 97 - 9 = 26

• (Normal = 12 (+2) mEq/L)

kesimpulan: Ada kenaikan anion gap

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• pH 7.18 PaCO2 23 PaO2 78

• Na 132 K 5.2 Cl 97

• HCO3- 9• Glucose 235


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apakah ada faktor

asidosis / alkalosiskronis?

• ukur initial HCO3-

• Initial HCO3- = anion gap measured - anion gap normal+ HCO3 measured

•= 26 - 12 + 9 = 23

• pH 7.18 PaCO2 23 PaO2 78

• Na 132 K 5.2 Cl 97

• HCO3- 9

• Glucose 235

Kes: tak ada bukti kronis acidosis / alkalosis

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kesimpulan step 5

• anion gap meningkat • tak ada bukti kronis acidosis / alkalosis

metabolik

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kesimpulan kasus

• asidosis metabolik, kompensasi respiratorikadekuat, ada peningkatan anion gap,

• klinis DM, penurunan kesadaran • what next?

!adakah kemungkinan toxic ingestion?

!cek keton

!cek asam lactat

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Metabolic Acidosis

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Metabolic Alkalosis

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Respiratory Acidosis

• Pasien dengan acute hypercapnia selalumengalami acidosis

• Pasien dengan chronic hypercania jugamengalami acidosis. Bila terdapat

peningkatan pH yang signifikan, cari faktor

sebelumnya mis: diuretic, low sodium diet,atau post hypercapnic alkalosis

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Respiratory Alkalosis

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Take home message

• Evaluasi asam basa stepwise harusmemperhitungkan semua parameter yang adadalam AGD (PaO2, PCO2, HCO3, SaO2, Anion Gap)

• Tiap perubahan keasaman akan menimbulkankompensasi

• Cari apakah kompensasi adekuat / tidak • Jika kompesasi tidak adekuat / berlebihan: mungkin

terdapat kombinasi penyebab

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ARDAIR

BPS

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from the top of SEOUL tower62


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Gyeongbok Palace63


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Komapsumnida !

Thank You !

Documents

Acid Base Stepwise Pradik