PENDEKATAN ASAM BASA
METODA STEWART
Anang Achmadi
Department of Anesthesiology & Intensive Care
Santosa Hospital Bandung Central
?
•
pH : 7.42
•
pCO2 : 35
•
pO2 : 100
•
BE : -‐2
•
HCO3 : 21
BGA/ AGD
DISORDER pH PRIMER RESPON KOMPENSASI
ASIDOSIS
METABOLIK ↓ HCO3- ↓ pCO2 ↓
ALKALOSIS
METABOLIK ↑ HCO3- ↑ pCO2 ↑
ASIDOSIS
RESPIRATORI ↓ pCO2 ↑ HCO3- ↑
ALKALOSIS
RESPIRATORI ↑ pCO2 ↓ HCO3- ↓
GANGGUAN KESEIMBANGAN ASAM BASA
TRADISIONAL
7.42 / 35 / 100 / -2 / 21
(a) Free water
n
0.3 x (140-140) = 0
(b) Chloride effect
n102-(102 x 140/140) = 0
(c) Albumin effect
n(0.148 x 7.42 - 0.818) (42-[18]) = 6.7
nUA = - 2 – [(0) + (0) + (6.7)] mEq/L = - 8.7
Na 140; Cl 102; Alb 1.8
Menurut H-H à normal
HIDDEN METABOLIC ACIDOSISTraditional view
• Problems:
• 1. Which one is the independent variable?
• 2. What is the source of hydrogen ions?
• 3. Does not provide quantitative assessment
• 4. Does not explain dilutional acidosis or
contraction alkalosis
Subversive New Concepts
in Acid-base Physiology
• New paradigms are emerging (
Current Opinion
Crit Care 1999; 5: 427- 477
) in acid base physiology
• Based on the work of the late Peter
Stewart (
Can J Physiol Pharmacol 1983; 61: 1444-1461
)
• They are subversive because they
challenge traditional teaching
Stewart’s Approach
• The Henderson-Hesselbach equation
describes the relationship of 3 linked
variables but does not say which is
dependent and which independent
• The solvent (H
2
O) not the solutes is the
DUA VARIABEL
pH atau [H
+] DALAM PLASMA
DITENTUKAN OLEH
VARIABEL INDEPENDEN
Stewart PA. Can J Physiol Pharmacol 61:1444-1461, 1983.
DEPENDENT VARIABLES
VARIABEL INDEPENDEN
CO2 STRONG ION DIFFERENCE WEAK ACID
pCO2
SID
A
tot Controlled by the respiratory system The electrolyte composition of the blood (controlled by the kidney) The protein concentration(controlled by the liver and metabolic state)
CO
2Didalam plasma berada
dalam 4 bentuk
– sCO
2(terlarut)
– H
2CO
3asam karbonat
– HCO
3-ion bikarbonat
– CO
32-ion karbonat
• Rx dominan dari CO
2adalah rx
absorpsi OH
-hasil disosiasi air
dengan melepas H
+.
• Semakin tinggi pCO
2semakin
banyak H
+yang terbentuk.
• Ini yg menjadi dasar dari
terminologi “respiratory acidosis,”
yaitu pelepasan ion hidrogen
akibat ↑ pCO
2CO
2
OH
-+ CO
2
⇔
HCO
3-+ H
+ CASTRONG ION DIFFERENCE
Definisi:
Strong ion difference adalah ketidakseimbangan muatan
dari ion-ion kuat. Lebih rinci lagi,
SID adalah jumlah
konsentrasi basa kation kuat dikurangi jumlah dari
konsentrasi asam anion kuat.
Untuk definisi ini semua
konsentrasi ion-ion diekspresikan dalam ekuivalensi
(mEq/L).
Semua ion kuat akan terdisosiasi sempurna
jika berada didalam
larutan, misalnya ion natrium (Na
+), atau klorida (Cl
-). Karena
selalu berdisosiasi ini maka ion-ion kuat tersebut
tidak
berpartisipasi dalam reaksi-reaksi kimia.
Perannya dalam kimia
asam basa hanya pada hubungan
elektronetraliti.
Na+ 140 K+ 4 Ca++ Mg++ Cl- 102
KATION
ANION
SID
STRONG ION DIFFERENCE
[Na+] + [K+] + [kation divalen] - [Cl-] - [asam organik kuat-]
[Na+] + [K+] - [Cl-] = [SID]
2 3 4 5 6 7 8 9 100 80 70 60 50 40 30 20 10 % ter-ionisasi pH pK
MENGAPA DISEBUT ION KUAT DAN LEMAH ?
Suatu ion dikatakan kuat atau lemah tergantung dari pKnya (pH, dimana 50% dari substansi tsb terdisosiasi). Mis; pK Lactate 3.9 (berarti, pada pH normal, hampir 100% laktat terdisosiasi ). H2CO3 dan Alb disebut asam lemah karena pada pH normal hanya 50% substansinya terdisosiasi.
Elektrolit = Ion-ion
Substansi yang terdisosiasi
sempurna di dalam suatu larutan :
àKation; Na+,K+,Mg+,Ca++
àAnion; Cl-,SO
4-,PO4=,
laktat-, keto-.
Substansi yang hanya
sebagian terdisosiasi dalam
suatu larutan :
à Albumin
-, Posfat
-, H
2CO
3 Ion-ion kuat (Strong ions) : Ion-ion lemah (Weak ions) :Cl Na
Hubungan SID dgn pH/H
+
SID
(–)
(+)
[H
+] ↑↑ [OH
-]
↑↑
Dalam cairan biologis (plasma) dgn suhu 37
0C, SID selalu positif,
nilainya berkisar 30-40 mEq/Liter
Asidosis
Alkalosis
Konsentrasi H
+ Na SID↓ Cl Na Cl SID↑ SIDDEPENDENT VARIABLES
H+ OH -CO3- A-AH
HCO3-• Hukum kekekalan massa (Law of Mass):
– Jumlah dari suatu zat/substansi akan selalu konstan
kecuali ditambahkan atau dikurangi dari luar, atau
dibuat/dirusak oleh suatu reaksi kimia.
• Netralitas elektrik (Electroneutrality):
– Semua larutan sejati mempunyai muatan listrik yang
netral, dimana konsentrasi total kation harus sama
dengan konsentrasi anion
Σ iones (+) = Σ iones (-)
Stewart PA. Modern quantitative acid-base chemistry. Can J Physiol Pharmacol 61:1444-1461, 1983.
Konsep larutan encer
(Aqueous solution)
• Semua cairan dalam tubuh manusia
mengandung air, dan air merupakan sumber [H
+
] yang tidak habis-habisnya
• [H
+] ditentukan oleh disosiasi air (K
w
), dimana
molekul H
2O akan berdisosiasi menjadi ion-ion
H
3O
+dan OH
-Kombinasi protein dan posfat disebut asam
lemah total (total weak acid) à [Atot].
Reaksi disosiasinya adalah:
[A
tot
] (KA) = [A
-
].[H
+
]
[Protein H]
[Protein-] + [H+]
WEAK ACID
Strong Ions Difference pCO2 Protein Concentration PHYSICOCHEMICAL Rx CONSERVATION of MASS ELECTRONEUTRALITY
H
+HCO
3-OH
-tCO
2A
-CO
3=BLOOD PLASMA
Na
+ K+ Mg++ Ca++ Cl- XA- Posfat - Alb - HCO3- OH- CO 32-SID
H+ ATot Unmeasured AnionCATION
ANION
Clasification (Fencl et al)
ACIDOSIS ALKALOSIS
I. Respiratory ↑ PCO2 ↓ PCO2
II. Nonrespiratory (metabolic)
1. Abnormal SID
a. Water excess/deficit ↓ SID, ↓ [Na+] ↑ SID, ↑ [Na+]
b. Imbalance of strong anions
i. Chloride excess/deficit ↓ SID, ↑ [Cl-] ↑ SID, ↓ [Cl-]
ii. Unidentified anion excess ↓ SID, ↑ [XA-]
2. Non-volatile acids
i. Serum albumin ↑ [Alb] ↓ [Alb] ii. Inorganic phosphate ↑ [Pi] ↓ [Pi]
WORKSHOP ACIDBASE STEWART PERDICI 2006
• The effect of chloride is explicitly recognized
• The effect of plasma proteins and phosphate in
appreciated and quantified
• The pathogenesis of the acid-base disorder is
better understood
• More logical therapies can be implemented
• Misdiagnoses are decreased, especially if
lactate is not immediately available
STOMACH
Alkaline tide SID (+) pH ↑ AlkalosisCl
- Na: 20-80 Cl: 150-180SID (-)
pH ↓Kellum JA. Diagnosis and Treatment of Acid-Base Disorders. In: Textbook of Critical Care, W.B. Saunders Co, Philadelphia, PA , 1999. Grenvik A, Shoemaker PK, Ayers
S, Holbrook (eds). pp839-853
Magder S. Pathophysiology of metabolic acid-base disturbances in patients with critical illness.In: Critical Care Nephrology. Kluwer Academic Publishers, Dordrecht, The Netherlands, 1998. pp 279-296.Ronco C, Bellomo R (eds).
SMALL INTESTINE INTESTINE
SID (↓) pH ↓Cl
- PANCREAS pH > 7.7 ↑ GALL BLADDER pH > 7.5 ↑ CATIONCl
-Kellum JA. Diagnosis and Treatment of Acid-Base Disorders. In: Textbook of Critical Care, W.B. Saunders Co, Philadelphia, PA , 1999. Grenvik A, Shoemaker PK, Ayers
S, Holbrook (eds). pp839-853
Magder S. Pathophysiology of metabolic acid-base disturbances in patients with critical illness.In: Critical Care Nephrology. Kluwer Academic Publishers, Dordrecht, The Netherlands, 1998. pp 279-296.Ronco C, Bellomo R (eds).
Volume dan komposisi elektrolit cairan gastrointestinal
From Miller, Anesthesia, 5th ed,2000.
- 40 30 60 - Colon 27.5 92.5 5 115 1000-2000 Ileum 22.5 115 7.5 130 2000-4000 Jejunum 37.5 110 7.5 140 300-600 Bile 67.5 80 7.5 140 300-800 Pancreas
-20
115
15
80
1000-2000
Stomach
18 13 25 6 500-2000 Saliva HCO3- SID Cl- (mEq/ L) K+ (mEq/L) Na+ (mEq/L) 24 h vol. (mL)Na+ = 140 mEq/L Cl- = 110 mEq/L SID = 30 mEq/L Na+ = 70 mEq/L Cl- = 55 mEq/L SID = 15 mEq/L
1 liter
2 liter
DILUTIONAL ACIDOSIS
NaCl + H
2O à Na
++ Cl
-+ H
++ OH
-+ H
2O
1 L H2ONa+ = 140 mEq/L
Cl- = 110 mEq/L
SID = 30 mEq/L NaCl-+ = 220 mEq/L = 280 mEq/L
SID = 60 mEq/L
1 liter
½ liter
CONTRACTION ALKALOSIS
33
Ringer Laktat
Na Cl K Ca Osms bicnat
Ringer Laktat 131 111 5 4 276 29
34
NaCl
Na Cl Osm
NaCl 0,9% 154 154 308
NaCl 0,45% 77 77
Plasma 135 108 290 +10
NaCl 3% 513 513 1026
35 Na+ = 140 mEq/L Cl- = 102 mEq/L SID = 38 mEq/L Na+ = 154 mEq/L Cl- = 154 mEq/L SID = 0 mEq/L
1 liter
1 liter
PLASMA + NaCl 0.9%
SID : 38 à
Plasma
NaCl 0.9%
36
2 liter
ASIDOSIS HIPERKLOREMIK AKIBAT
PEMBERIAN LARUTAN Na Cl 0.9%
=
SID : 19
à Asidosis
Na+ = (140+154)/2 mEq/L= 147 mEq/L Cl- = (102+ 154)/2 mEq/L= 128 mEq/L SID = 19 mEq/LPlasma
37 Na+ = 140 mEq/L Cl- = 102 mEq/L SID= 38 mEq/L Cation+ = 137 mEq/L Cl- = 109 mEq/L Laktat- = 28 mEq/L SID = 0 mEq/L
1 liter
1 liter
PLASMA + Larutan RINGER LACTATE
SID : 38
Plasma
Ringer laktat
Laktat cepat dimetabolisme
38
2 liter
=
Normal pH setelah pemberian
RINGER LACTATE
SID : 34 à lebih kecil perubahan SID dibanding jika
diberikan NaCl 0.9%
Na+ = (140+137)/2 mEq/L= 139 mEq/L
Cl- = (102+ 109)/2 mEq/L = 105 mEq/L
Laktat- (termetabolisme) = 0 mEq/L
SID = 34 mEq/L
Kesimpulan
0.9% saline = (Ab)normal Saline
Reid et al, Clin Sci, 2003
Na+ = 140 mEq/L Cl- = 130 mEq/L SID =10 mEq/L Na+ = 165 mEq/L Cl- = 130 mEq/L SID = 35 mEq/L
1 liter
1.025
liter
25 mEq NaHCO3SID ↑ : 10 à 35 : à Alkalosis, pH kembali normal à namun mekanismenya bukan karena pemberian HCO3- melainkan karena pemberian Na+ tanpa anion kuat yg
tidak dimetabolisme seperti Cl- sehingga SID ↑ à alkalosis
Plasma;
asidosis hiperkloremik
MEKANISME PEMBERIAN NA-BIKARBONAT
PADA ASIDOSIS
Plasma + NaHCO3
HCO3 cepat dimetabolisme
Pada asidosis kronik; [CO
32-]↓↓ à pembentukan CaCO
3
<< à integritas
tulang terganggu à osteoporosis
CO2 + H2O ⇔ HCO3- + H+
[HCO3- ] ⇔ [CO
32-] + [H+] Reaksi pembentukan karbonat Alkalosis à [H+]↓ à reaksi ke kanan à [CO
32-]↑ Efek pemberian bikarbonat:
• Jika [CO
32-] ↑ maka calcium yang terionisasi akan diikat oleh [CO
32-
] à
hipokalsemia akut; sensitifitas membran sel ↑ à tetany, hyperexcitability of
muscles, sustained contraction, dan gangguan kontraksi otot jantung.
•
Pe↑ natrium secara cepat à SID ↑ secara cepat à alkalosis berat à
kompensasi paru dengan cara menahan CO
2à hipoventilasi à CO
2narkosis à apneu
Asidosis à [H+]↑ à reaksi ke kiri à [CO
OTHER FINDINGS :
1. HCO3 doesn t improve hemodynamic in critically ill patients who have lactic acidosis (Cooper; Ann Inter Med. 1990)
2. HCO3 therapy in the treatment of lactic acidosis : Medicine or toxin?
(Sing Et Al, J Ann. Osteopath. Assoc. 1995) 3. The Routine use of sodium
bicarbonate is no longer recommended.
(In 1992, the American National Conference on Cardiopulmonary Resuscitation established current guidelines)
4. CONSENSUS CONFERENCE in FRANCE (June 2000) organized by The French Reanimation Society
recommend not to give sodium bicarbonate in any acidosis except in HCO3 loss.
PENILAIAN ANALISA GAS DARAH
MENGGUNAKAN KOMBINASI BASE EXCESS
DAN STEWART
Nilai2 yg diperlukan:
1. AGD (BE)
2. Natrium
3. Klorida
4. Albumin
Story DA, Bellomo R. Hendersen-Hasselbach vs Stewart: Another Acid-Base Controversy; Review Article, Crit Care & Shock (2002)2:59-63
[HC
O
3
-‐
]
P
CO2 = 8040
20
pH
7.0
7.2
7.4
7.6
7.8
10
20
30
40
50
Asidosis
Metabolik
"
Base Defisit"
Alkalosis
Metabolik
"
Base Excess"
Base Excess/
Base Deficit
BE = (1 - 0.014Hgb) (HCO
3– 24 + (1.43Hgb + 7.7) (pH - 7.4)`
Normal
"
UA = BE – [(efek Na + efek Cl) + efek Alb]
UNMEASURED ANION (UA)
PADA ASIDOSIS METABOLIK
BASE EXCESS DAN STEWART
(a) Free water
n
0.3 x (Na-140)
(b) Chloride effect
n
102-(Cl x 140/Na)
(c) Albumin effect
n
(0.148 x pH - 0.818) (42-[alb])
n
UA = BE/BD – [(a) + (b) + (c)] mEq/L
Magder S. Pathophysiology of metabolic acid-base disturbances in patients with critical illness. In: Critical Care Nephrology.Kluwer Academic Publishers, Dordrecht, The Netherlands, 1998. pp 279-296. Ronco C, Bellomo R (eds).
Jika + à efek alkalinisasi
Jika - à efek asidifikasi
Strong ions, weak acids and base excess:
a simplified Fencl–Stewart approach to
clinical acid–base disorders
D. A. Story, H. Morimatsu and R. Bellomo . British Journal of Anaesthesia, 2004, Vol. 92, Clinical Investigations
• SBE(mmol/l=meq/l);
– from a blood gas machine
• Na–Cl effect (meq/l)=
– [Na+]–[Cl–]–38
• Albumin effect (meq/l)=
– 0.25x[42–alb(g/l)]