Presentasi berjudul: "Biochemistry Departement Medical Faculty Of Andalas University"— Transcript presentasi:
1 Biochemistry Departement Medical Faculty Of Andalas University ACID-BASE BALANCEBy:Husnil KadriBiochemistry DepartementMedical Faculty Of Andalas UniversityPadang
2 Hendersen-Hasselbalch (1909) CARA TRADISIONAL :Hendersen-Hasselbalch (1909)
3 BASA [HCO3-] GINJAL ASAM PARU NormalBASA[HCO3-]GINJALpH = logKompensasi pCO2CO2NormalASAMPARUCO2
4 Carbonic acid/bicarbonate buffer system pKa = 6.1H2CO3 H HCO3-ECF:Carbonic acidBicarbonate ionThe pKa of carbonic acid is 6.1Carbonic acid is the major buffer in ECFThe pH of blood can be determined using the Henderson-Hasselbalch equation
5 Henderson-Hasselbalch equation pH = pKa + log [HCO3-]/[H2CO3]pH = pKa + log [HCO3-]/0.03 x PCO27.4 = log / 17.4 =Plasma pH equals 7.4 when buffer ratio is 20/1The solubility constant of CO2 is 0.03
7 Normal Compensatory Response Any primary disturbance in acid-base homeostasis invokes a normal compensatory response.A primary metabolic disorder leads to respiratory compensation, and a primary respiratory disorder leads to an acute metabolic response due to the buffering capacity of body fluids.A more chronic compensation (1-2 days) due to alterations in renal function.
8 Mixed Acid - Base Disorder Most acid-base disorders result from a single primary disturbance with the normal physiologic compensatory response and are called simple acid-base disorders.In certain cases, however, particularly in seriously ill patients, two or more different primary disorders may occur simultaneously, resulting in a mixed acid-base disorder.The net effect of mixed disorders may be additive (eg, metabolic acidosis and respiratory acidosis) and result in extreme alteration of pH;or they may be opposite (eg, metabolic acidosis and respiratory alkalosis) and nullify each other’s effects on the pH.
9 pH atau [H+] DALAM PLASMA DITENTUKAN OLEH Cara Stewart ;pH atau [H+] DALAM PLASMA DITENTUKAN OLEHDUA VARIABELVARIABELINDEPENDENVARIABELDEPENDENStewart PA. Can J Physiol Pharmacol 61: , 1983.
13 CO2 CO2 Didalam plasma berada dalam 4 bentuk sCO2 (terlarut)H2CO3 asam karbonatHCO3- ion bikarbonatCO32- ion karbonatRx dominan dari CO2 adalah rx absorpsi OH- hasil disosiasi air dengan melepas H+.Semakin tinggi pCO2 semakin banyak H+ yang terbentuk.Ini yg menjadi dasar dari terminologi “respiratory acidosis,” yaitu pelepasan ion hidrogen akibat pCO2
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.
20 KLASIFIKASI GANGGUAN KESEIMBANGAN ASAM BASA BERDASARKAN PRINSIP STEWART Fencl V, Jabor A, Kazda A, Figge J. Diagnosis of metabolic acid-base disturbances in critically ill patients. Am J Respir Crit Care Med 2000 Dec;162(6):
21 KLASIFIKASI ASIDOSIS ALKALOSIS I. Respiratori PCO2 PCO2 ASIDOSISALKALOSISI. Respiratori PCO2 PCO2II. Nonrespiratori (metabolik)1. Gangguan pd SIDa. Kelebihan / kekurangan air [Na+], SID [Na+], SIDb. Ketidakseimbangan anion kuat:i. Kelebihan / kekurangan Cl- [Cl-], SID [Cl-], SIDii. Ada anion tak terukur [UA-], SID2. Gangguan pd asam lemahi. Kadar albumin [Alb] [Alb]ii. Kadar posphate [Pi] [Pi]Fencl V, Jabor A, Kazda A, Figge J. Diagnosis of metabolic acid-base disturbances in critically ill patients. Am J Respir Crit Care Med 2000 Dec;162(6):
22 Fencl V, Am J Respir Crit Care Med 2000 Dec;162(6):2246-51 RESPIRASIM E T A B O L I KAbnormalpCO2AbnormalSIDAbnormalWeak acidAlbPO4-AIR Anion kuatCl-UA-TurunAlkalosisTurunkekuranganHipoAsidosisMeningkatkelebihanHiperPositifmeningkatFencl V, Am J Respir Crit Care Med 2000 Dec;162(6):
33 GANGGUAN PD ASAM LEMAH: Hipo/Hiperalbumin- atau P- HCO3NaHCO3NaHCO3KKKSIDSIDSIDAlb-/P-Alb-/P-Alb/P ClClClAsidosis hiperprotein/ hiperposfatemiAlkalosis hipoalbumin/hipoposfatemiNormalAcidosisAlkalosis
34 Anion Gap Described by Gamble in 1939 Electroneutrality Na+, Cl-, and HCO3 are measured ionsNa + UC = Cl + HCO3 + UAUC = Sum of unmeasured cationsUA = Sum of unmeasured anionsThe concept of an anion gap in blood was described in 1939 by Gamble.It was felt that the law of electroneutrality required that the number of positive charges contributed by serum cations should equal the number of negative charges contributed by serum anions.Sodium (Na), chloride (Cl), and bicarbonate (HCO3) are considered the measured ions.Potassium is ignored because its value changes so little. Thus, the concept of electroneutrality can be expressed by the simple equation:Na + UC = Cl + HCO3 + UAwhere UC (unmeasured cations) indicates the sum of the charges of the cations other than sodium and UA (unmeasured anions) equals the sum of the charges of all of the anions other than chloride and bicarbonate.
35 Anion Gap Unmeasured Cations: Unmeasured Anions: total 11 mEq/L Potassium 4Calcium 5Magnesium 2Unmeasured Anions:total 23 mEq/LSulfates 1Phosphates 2Albumin 16Lactic acid 1Org. acids 3The “unmeasured cations” usually total about 11 mEq/L andinclude potassium (4 mEq/L), calcium (5 mEq/L), and magnesium (2 mEq/L).The “unmeasured” serum anions include sulfates (1 mEq/L), phosphates (2 mEq/L), proteins (16 mEq/L), lactic acid (1 mEq/L), and other organic acids (3 mEq/L).Ordinarily, the sodium concentration is about 140 mEq/L, and the sum of the CO2 content and chloride anions is about 128 mEq/L. Thus, the difference (or anion gap) between the sodium concentration and the sum of these two anions averages about 12 mEq/L.In patients with excessive acid production, the anion gap tends to be increased. On the other hand, in patients with metabolic acidosis due to loss of bicarbonate, the anion gap usually stays relatively normal.
36 Anion Gap = Na - (Cl + HCO3) Na + UC = Cl + HCO3 + UA=151 = 151UA – UC = Na - (Cl + HCO3);Anion Gap = Na - (Cl + HCO3)The “unmeasured cations” usually total about 11 mEq/L andinclude potassium (4 mEq/L), calcium (5 mEq/L), and magnesium (2 mEq/L).The “unmeasured” serum anions include sulfates (1 mEq/L), phosphates (2 mEq/L), proteins (16 mEq/L), lactic acid (1 mEq/L), and other organic acids (3 mEq/L).Ordinarily, the sodium concentration is about 140 mEq/L, and the sum of the CO2 content and chloride anions is about 128 mEq/L. Thus, the difference (or anion gap) between the sodium concentration and the sum of these two anions averages about 12 mEq/L.In patients with excessive acid production, the anion gap tends to be increased. On the other hand, in patients with metabolic acidosis due to loss of bicarbonate, the anion gap usually stays relatively normal.
37 If the anion gap is elevated Then compare the changes from normal between the anion gap and [HCO3 -].If the change in the anion gap is greater than the change in the [HCO3 -] from normal, then a metabolic alkalosis is present in addition to a gap metabolic acidosis.If the change in the anion gap is less than the change in the [HCO3 -] from normal, then a non gap metabolic acidosis is present in addition to a gap metabolic acidosis.
38 Anion Gap Acidosis:Anion gap >12 mEq/L; caused by a decrease in [HCO3 -]balanced by an increase in an unmeasured acid ion from either endogenous production or exogenous ingestion (normochloremic acidosis).
39 Non anion Gap Acidosis: Anion gap = 8-12 mmol/L; caused by a decrease in [HCO3 -] balanced by an increase in chloride (hyperchloremic acidosis). Renal tubular acidosis is a type of non gap acidosis
41 Increased Anion Gap Normal = 8-15 May differ institutionally Accumulation of organic acids (ketones, lactate)Toxic Ingestionsmethanol, ethylene glycol, salicylatesReduced inorganic acid excretionphosphates, sulfatesDecrease in unmeasured cations (unusual)Lactate, Keto acids most common organic acids.AG> 35: M, EG, HHC, LAToxic ingestions: Cyanide, ASA, M, EG, Par, TolueneReduced Inorganic: Renal failure
42 Increased AG Metabolic Acidosis: Lactic AcidosisHas many etiologiesCyanide, CO, Toluene, HSPoor perfusionEthylene glycolSalicylatesMethyl salicylate(Oil of wintergreen)Mg salicylateMethanolUremia/Renal FailureINH, Iron--lactateParaldehydeLevraut J et al. Int Care Med 23:417, 1997
43 Increased Anion Gap Normal = 8-15 May differ institutionally “ion specific electrodes” Accumulation of organic acids (ketones, lactate)Toxic Ingestionsmethanol, ethylene glycol, salicylatesReduced inorganic acid excretionphosphates, sulfatesDecrease in unmeasured cations (unusual)Excessive exposure to air: Increase Na, Cl, and K with decrease in bicarb secondary to loss of CO2. AG after 2 hours can be increased by 6False elevation of CL: Hypertriglyceridemia, Bromide, IodideLactate, Keto acids most common organic acids.AG> 35: M, EG, HHC, LAToxic ingestions: Cyanide, ASA, M, EG, Par, TolueneReduced Inorganic: Renal failure
44 Decreased or Negative Anion Gap Clin J Am Soc Nephrol 2: 162-174, 2007 Low protein most importantAlbumin has many unmeasured negative charges“Normal” anion gap (12) in cachectic personIndicates anion gap metabolic acidosisOther etiologies of low AG:Low K, Mg, Ca, increased globulins (Mult. Myeloma), I intoxicationNegative AGmore unmeasured cations than unmeasured anionsBromide, Iodide, Multiple Myeloma
45 Change in Anion Gap vs HCO3 In simple AG Metabolic Acidosisdecrease in plasma bicarbonate = increase in AGAnion Gap = 1HCO3Helpful in identifying mixed disordersIn uncomplicated increased anion gap metabolic acidosis, the decrease (change) in plasma bicarbonate should be roughly equal to the increase (change) in the anion gap (that is, dAG/dHCO3 = 1.0).Whenever the anion gap changes much more or less than the bicarbonate, one should be suspicious of a coexisting or a mixed acid-base disorder.Ratios between 0.3 and 0.7 usually, but not always, indicate a mixed acid-base disorder or a preexisting low anion gap.Thus, the dAG/dHCO3 ratio is helpful in the diagnosis of mixed acid-base disorder because this ratio is usually close to 1.0 in typical organic acidoses. Values greater than 1.2 or less than 0.8 suggest the presence of a mixed acid-base disorder or an independent factor affecting the anion gap.
46 Respiratory Compensation for Metabolic Acidosis:Occurs rapidlyHyperventilation“Kussmaul Respirations”Deep > rapid (high tidal volume)Is not Respiratory AlkalosisMetabolic Alkalosis:Calculation not as accurateHypoventilationNot Respiratory AcidosisRestricted by hypoxemiaPCO2 seldom > 50-55Commonly, compensation for a Pure metabolic Alkalosis:pCO2= 0.9 x HCO3 + 9 (not 15)pCO2 cannot go below 10 experimentallyResp. Compensation never raises the pH above 7.35
47 ReferenceAchmadi, A., George, YWH., Mustafa, I. Pendekatan “Stewart” Dalam Fisiologi Keseimbangan Asam Basa. 2007Beaudoin, D. Electrolytes and ion sensitive electrodes. PPTIvkovic, A ., Dave, R. Renal review. PPTKersten. Fluid and electrolytes. PPT.Marieb, EN. Fluid, electrolyte, and acid-base balance. PPT. Pearson Education, Inc. 2004Rashid, FA. Respiratory mechanism in acid-base homeostasis. PPTSilverthorn, DU. Integrative Physiology II: Fluid and Electrolyte Balance. Chapter 20, part B. Pearson Education, Inc. 2004Smith, SW. Acid-Base Disorders.
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