PENDEKATAN ASAM BASA METODA STEWART. Anang Achmadi Department of Anesthesiology & Intensive Care Santosa Hospital Bandung Central

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1 PENDEKATAN ASAM BASA METODA STEWART Anang Achmadi Department of Anesthesiology & Intensive Care Santosa Hospital Bandung Central

2 BGA/ AGD ph : 7.42 pco2 : 35 po2 : 100 BE : - 2? HCO3 : 21

3 GANGGUAN KESEIMBANGAN ASAM BASA TRADISIONAL DISORDER ph PRIMER RESPON KOMPENSASI ASIDOSIS METABOLIK HCO 3 - pco 2 ALKALOSIS METABOLIK ASIDOSIS RESPIRATORI ALKALOSIS RESPIRATORI HCO 3 - pco 2 pco 2 HCO 3 - pco 2 HCO 3 -

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5 7.42 / 35 / 100 / -2 / 21 Menurut H-H à normal Na 140; Cl 102; Alb 1.8 (a) Free water n 0.3 x ( ) = 0 (b) Chloride effect n 102-(102 x 140/140) = 0 (c) Albumin effect n (0.148 x ) (42-[18]) = 6.7 n UA = - 2 [(0) + (0) + (6.7)] meq/l = HIDDEN METABOLIC ACIDOSIS

6 Am J Respir Crit Care Med Vol 162. pp ,2000

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8 Traditional 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 5. Does not explain hypoalbuminemic alkalosis

9 Subversive New Concepts in Acid-base Physiology New paradigms are emerging (Current Opinion Crit Care 1999; 5: ) in acid base physiology Based on the work of the late Peter Stewart (Can J Physiol Pharmacol 1983; 61: ) They are subversive because they challenge traditional teaching

10 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 (H2O) not the solutes is the largest source of hydrogen ions

11 Menurut Stewart ph atau [H + ] DALAM PLASMA DITENTUKAN OLEH DUA VARIABEL VARIABEL INDEPENDEN DEPENDENT VARIABLES Stewart PA. Can J Physiol Pharmacol 61: , 1983.

12 VARIABEL INDEPENDEN CO 2 STRONG ION DIFFERENCE WEAK ACID pco 2 Controlled by the respiratory system SID The electrolyte composition of the blood (controlled by the kidney) A tot The protein concentration (controlled by the liver and metabolic state)

13 CO 2 CO 2 Didalam plasma berada dalam 4 bentuk sco 2 (terlarut) H 2 CO 3 asam karbonat HCO 3 - ion bikarbonat CO 3 2- ion karbonat Rx dominan dari CO 2 adalah rx absorpsi OH - hasil disosiasi air dengan melepas H +. Semakin tinggi pco 2 semakin banyak H + yang terbentuk. Ini yg menjadi dasar dari terminologi respiratory acidosis, yaitu pelepasan ion hidrogen akibat pco 2 OH - + CO 2 HCO H + CA

14 STRONG 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.

15 STRONG ION DIFFERENCE Mg ++ Ca ++ K + 4 SID [Na + ] + [K + ] + [kation divalen] - [Cl - ] - [asam organik kuat - ] Na Cl [Na+] + [K+] - [Cl-] = [SID] 140 meq/l + 4 meq/l meq/l = 34 meq/l KATION ANION

16 MENGAPA DISEBUT ION KUAT DAN LEMAH? % ter-ionisasi pk ph 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 ). H 2 CO 3 dan Alb disebut asam lemah karena pada ph normal hanya 50% substansinya terdisosiasi.

17 Elektrolit = Ion-ion Ion-ion kuat (Strong ions) : Ion-ion lemah (Weak ions) : Substansi yang terdisosiasi sempurna di dalam suatu larutan : à Kation; Na +,K +,Mg +,Ca ++ à Anion; Cl -,SO 4-,PO 4=, laktat -, keto -. Substansi yang hanya sebagian terdisosiasi dalam suatu larutan : à Albumin -, Posfat -, H 2 CO 3

18 Hubungan SID dgn ph/h + Konsentrasi H + [H + ] [OH - ] SID Na Cl Asidosis Na Cl Alkalosis Na Cl ( ) SID (+) Dalam cairan biologis (plasma) dgn suhu 37 0 C, SID selalu positif, nilainya berkisar meq/liter

19 DEPENDENT VARIABLES H + HCO3- OH - AH CO3 - A -

20 PRINSIP UMUM 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: , 1983.

21 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 2 O akan berdisosiasi menjadi ion-ion H 3 O + dan OH -

22 WEAK ACID [Protein H] disosiasi [Protein-] + [H+] Kombinasi protein dan posfat disebut asam lemah total (total weak acid) à [Atot]. Reaksi disosiasinya adalah: [A tot ] (KA) = [A - ].[H + ]

23 INDEPENDENT VARIABLES DEPENDENT VARIABLES Strong Ions Difference pco 2 PHYSICOCHEMICAL Rx CONSERVATION of MASS ELECTRONEUTRALITY H + HCO 3 - OH - tco 2 A - CO 3 = Protein Concentration

24 BLOOD PLASMA H + Na + K + Mg ++ Ca ++ HCO 3 - OH - CO 2-3 Alb - Posfat - XA - A Tot SID Unmeasured Anion Cl - CATION ANION

25 Clasification (Fencl et al) ACIDOSIS ALKALOSIS I. Respiratory PCO 2 PCO 2 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]

26 WORKSHOP ACIDBASE STEWART PERDICI 2006

27 Advantages of Stewart s Method 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

28 STOMACH Cl - Na: Cl: SID (-) ph Alkaline tide SID (+) ph Alkalosis Kellum JA. Diagnosis and Treatment of Acid-Base Disorders. In: Textbook of Critical Care, W.B. Saunders Co, Philadelphia, PA, Grenvik A, Shoemaker PK, Ayers S, Holbrook (eds). pp Magder S. Pathophysiology of metabolic acid-base disturbances in patients with critical illness.in: Critical Care Nephrology. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp Ronco C, Bellomo R (eds).

29 SMALL INTESTINE INTESTINE GALL BLADDER ph > 7.5 Cl - Cl - CATION PANCREAS ph > 7.7 SID ( ) ph Kellum JA. Diagnosis and Treatment of Acid-Base Disorders. In: Textbook of Critical Care, W.B. Saunders Co, Philadelphia, PA, Grenvik A, Shoemaker PK, Ayers S, Holbrook (eds). pp Magder S. Pathophysiology of metabolic acid-base disturbances in patients with critical illness.in: Critical Care Nephrology. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp Ronco C, Bellomo R (eds).

30 Volume dan komposisi elektrolit cairan gastrointestinal From Miller, Anesthesia, 5 th ed, h vol. (ml) Na + (meq/l) K + (meq/l) Cl - (meq/ L) HCO 3 - SID Saliva Stomach Pancreas Bile Jejunum Ileum Colon

31 DILUTIONAL ACIDOSIS NaCl + H 2 O à Na + + Cl - + H + + OH - + H 2 O Na + = 140 meq/l Cl - = 110 meq/l SID = 30 meq/l 1 L H 2 O 1 liter Na + = 70 meq/l Cl - = 55 meq/l SID = 15 meq/l 2 liter

32 CONTRACTION ALKALOSIS 1 Liter Na + = 140 meq/l Cl - = 110 meq/l SID = 30 meq/l 1 liter ½ liter Na + = 280 meq/l Cl - = 220 meq/l SID = 60 meq/l

33 Ringer Laktat Na Cl K Ca Osms bicnat Ringer Laktat Plasma

34 NaCl Na Cl Osm NaCl 0,9% NaCl 0,45% NaCl 3% Plasma

35 PLASMA + NaCl 0.9% Plasma NaCl 0.9% 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 SID : 38 à 35

36 ASIDOSIS HIPERKLOREMIK AKIBAT PEMBERIAN LARUTAN Na Cl 0.9% Plasma = Na + = ( )/2 meq/l= 147 meq/l Cl - = ( )/2 meq/l= 128 meq/l SID = 19 meq/l 2 liter SID : 19 à Asidosis 36

37 PLASMA + Larutan RINGER LACTATE Plasma Ringer laktat Laktat cepat dimetabolisme 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 SID : 38 37

38 Normal ph setelah pemberian RINGER LACTATE Plasma = Na + = ( )/2 meq/l= 139 meq/l Cl - = ( )/2 meq/l = 105 meq/l Laktat - (termetabolisme) = 0 meq/l SID = 34 meq/l 2 liter SID : 34 à lebih kecil perubahan SID dibanding jika diberikan NaCl 0.9% 38

39 Kesimpulan 0.9% saline = (Ab)normal Saline Reid et al, Clin Sci,

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42 MEKANISME PEMBERIAN NA-BIKARBONAT PADA ASIDOSIS Plasma; asidosis hiperkloremik Plasma + NaHCO 3 Na + = 140 meq/l Cl - = 130 meq/l SID =10 meq/l 25 meq NaHCO3 1 liter liter Na + = 165 meq/l Cl - = 130 meq/l SID = 35 meq/l HCO 3 cepat dimetabolisme SID : 10 à 35 : à Alkalosis, ph kembali normal à namun mekanismenya bukan karena pemberian HCO 3 - melainkan karena pemberian Na + tanpa anion kuat yg tidak dimetabolisme seperti Cl - sehingga SID à alkalosis

43 Efek pemberian bikarbonat: CO 2 + H 2 O HCO H + [HCO 3 - ] [CO 3 2- ] + [H + ] Reaksi pembentukan karbonat Alkalosis à [H + ] à reaksi ke kanan à [CO 3 2- ] Jika [CO 3 2- ] maka calcium yang terionisasi akan diikat oleh [CO 3 2- ] 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 2 à hipoventilasi à CO 2 narkosis à apneu Asidosis à [H + ] à reaksi ke kiri à [CO 3 2- ] Pada asidosis kronik; [CO 3 2- ] à pembentukan CaCO 3 << à integritas tulang terganggu à osteoporosis

44 OTHER FINDINGS : 1. HCO 3 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 HCO 3 loss.

45 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

46 BE = ( Hgb) (HCO (1.43Hgb + 7.7) (ph - 7.4)` 50 PCO 2 = [HCO 3 - ] 30 Base Excess" Alkalosis Metabolik" 20 Base Excess/ Base Deficit 20 Base Defisit" Normal" 10 Asidosis Metabolik" ph

47 UNMEASURED ANION (UA) PADA ASIDOSIS METABOLIK UA = BE [(efek Na + efek Cl) + efek Alb]

48 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 ) (42-[alb]) Jika + à efek alkalinisasi Jika - à efek asidifikasi 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, pp Ronco C, Bellomo R (eds).

49 Clinical Investigations 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, 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)] Unmeasured ion effect (meq/l)= SBE (Na Cl) effect alb effect

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