KULIAH KESEIMBANGAN ASAM-BASAdr Muhammad Zulkarnain B M.Ked(An), SpAn

*pH ReviewpH = - log [H+]H+ is really a protonRange is from 0 - 14If [H+] is high, the solution is acidic; pH < 7If [H+] is low, the solution is basic or alkaline ; pH > 7

ACIDS AND BASESSvante Arrhenius in 1903 established the foundations of acid-base chemistry.In an aqueous solution, an Arrhenius acid is any substance that delivers a hydrogen ion into the solution. (HCl) A base is any substance that delivers a hydroxyl ion into the solution. (NaOH) Notasi pH diciptakan oleh seorang ahli kimia dari Denmark yaitu Soren Peter Sorensen pada thn 1909, yang berarti log negatif dari konsentrasi ion hidrogen. Dalam bahasa Jerman disebutWasserstoffionenexponent (eksponen ion hidrogen) dan diberi simbol pH yang berarti: potenz (power) of Hydrogen.In 1909, L.J. Henderson coined the term acid-base balance. Hasselbalch (1916)

The degree of dissociation of substances in water determines whether they are strong acids or strong bases.Similarly, ions such as sodium, potassium, and chloride, which do not easily bind other molecules, are considered strong ions; they exist free in solution. Strong cations (Na+ , K+ , Ca2+ , Mg2+ ) act as Arrhenius bases Strong anions (Cl- , LA- [lactate], ketones, sulfate, formate) act as Arrhenius acids.In 1923, Brnsted and Lowry They defined acids as proton donors and bases as proton acceptors.

NH3 + H2 O NH4 + + OH In this situation, water is the proton donor, the Brnsted-Lowry acid, and ammonia the proton acceptor, the Brnsted-Lowry base. HCl + H2 O H3 O+ + Cl In the previous reaction, hydrogen chloride acts as a Brnsted-Lowry acid and water as a Brnsted-Lowry base. CO2 + H2 O H2 CO3 H+ + HCO3 In this reaction, carbon dioxide is hydrated to carbonic acid, a Brnsted-Lowry acid, which subsequently dissociates to hydrogen (H+ ) and bicarbonate (HCO3 - ) ions.

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*Acids are H+ donors.Bases are H+ acceptors, or give up OH- in solution.Acids and bases can be:Strong dissociate completely in solution HCl, NaOHWeak dissociate only partially in solutionLactic acid, carbonic acid

*The Body and pHHomeostasis of pH is tightly controlledExtracellular fluid = 7.4Blood = 7.35 7.45< 6.8 or > 8.0 death occursAcidosis (acidemia) below 7.35Alkalosis (alkalemia) above 7.45

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Normal values for arterial blood gasesArterial Blood Gases (ABG)* Indicates measured parameterNormal values may differ slightly in exams

Blood Gas ParameterParameter Reported and Symbol UsedNormal ValueCarbon dioxide tension*PCO235 45 mm Hg (average, 40)Oxygen tension*PO280 100 mm HgOxygen percent saturationSO297Hydrogen ion concentration*pH7.35 7.45BicarbonateHCO3-22 26 mmol/L

GANGGUAN KESEIMBANGAN ASAM-BASA TRADISIONAL

DISORDERpHPRIMERRESPON KOMPENSASIASIDOSIS METABOLIKHCO3- pCO2 ALKALOSIS METABOLIKHCO3- pCO2 ASIDOSIS RESPIRATORIpCO2 HCO3- ALKALOSIS RESPIRATORIpCO2 HCO3-

Normal Compensatory ResponseAny 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.

Mixed Acid - Base DisorderMost 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 others effects on the pH.

The disadvantage of men not knowing the past is that they do not know the present. G. K. ChestertonCARA TRADISIONALHendersen-Hasselbalch

pH = 6.1 + log[HCO3-] pCO2GINJALPARUBASA ASAMCO2HCO3HCO3CO2KompensasiNormalNormal

RANGKUMAN GANGGUAN KESEIMBANGAN ASAM BASA TRADISIONAL

DISORDERpHPRIMERRESPON KOMPENSASIASIDOSIS METABOLIKHCO3- pCO2 ALKALOSIS METABOLIKHCO3- pCO2 ASIDOSIS RESPIRATORIpCO2 HCO3- ALKALOSIS RESPIRATORIpCO2 HCO3-

KLASIFIKASI GANGGUAN KESEIMBANGAN ASAM BASA BERDASARKAN PRINSIP STEWARTFencl 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):2246-51

DUA VARIABELpH atau [H+] DALAM PLASMA DITENTUKAN OLEHVARIABELINDEPENDENDEPENDENT VARIABLESMenurut Stewart ;

VARIABEL INDEPENDENCO2STRONG ION DIFFERENCEWEAK ACIDpCO2SIDAtot

CO2 Didalam plasma berada dalam 4 bentuksCO2 (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 pCO2CO2OH- + CO2 HCO3- + H+CA

STRONG ION DIFFERENCEDefinisi: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.

GamblegramNa+140K+ 4Ca++Mg++Cl-102KATIONANIONSIDSTRONG ION DIFFERENCE[Na+] + [K+] + [kation divalen] - [Cl-] - [asam organik kuat-][Na+] + [K+] - [Cl-] = [SID] 140 mEq/L + 4 mEq/L - 102 mEq/L = 34 mEq/L

SKETSA HUBUNGAN ANTARA SID,H+ DAN OH-SID()(+)[H+][OH-]Dalam cairan biologis (plasma) dgn suhu 370C, SID hampir selalu positif, biasanya berkisar 30-40 mEq/LiterAsidosisAlkalosisKonsentrasi [H+]

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

GamblegramNa+140K+ 4Ca++Mg++Cl-102HCO3-24KATIONANIONSIDWeak acid(Alb-,P-)

DEPENDENT VARIABLESH+OH-CO3-

A-AHHCO3-

Strong IonsDifferencepCO2ProteinConcentrationpHINDEPENDENT VARIABLESDEPENDENT VARIABLES

KLASIFIKASIFencl 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):2246-51

RESPIRASIM E T A B O L I KAbnormal pCO2AbnormalSIDAbnormalWeak acidAlbPO4-AlkalosisAsidosisTurunMeningkatTurunkelebihankekuranganPositifmeningkatFencl V, Am J Respir Crit Care Med 2000 Dec;162(6):2246-51 AIR Anion kuatCl-UA-HipoHiper

Na+ = 140 mEq/LCl- = 102 mEq/LSID = 38 mEq/L140/1/2 = 280 mEq/L102/1/2 = 204 mEq/L SID = 76 mEq/L1 liter literKEKURANGAN AIR - WATER DEFICITDiureticDiabetes InsipidusEvaporasiSID : 38 76 = alkalosisALKALOSIS KONTRAKSIPlasmaPlasma

Na+ = 140 mEq/LCl- = 102 mEq/L SID = 38 mEq/L140/2 = 70 mEq/L102/2 = 51 mEq/L SID = 19 mEq/L1 liter2 literKELEBIHAN AIR - WATER EXCESS1 Liter H2OSID : 38 19 = AcidosisASIDOSIS DILUSIPlasma

Na+ = 140 mEq/L Cl- = 95 mEq/LSID = 45 mEq/L2 literALKALOSIS HIPOKLOREMIKSID ALKALOSISGANGGUAN PD SID: Pengurangan Cl-Plasma

Na+ = 140 mEq/L Cl- = 120 mEq/LSID = 20 mEq/L2 literASIDOSIS HIPERKLOREMIKSID ASIDOSISGANGGUAN PD SID: Penambahan/akumulasi Cl-Plasma

Na+ = 140 mEq/LCl- = 102 mEq/LSID = 38 mEq/LNa+ = 154 mEq/LCl- = 154 mEq/LSID = 0 mEq/L1 liter1 literPLASMA + NaCl 0.9%SID : 38 PlasmaNaCl 0.9%

2 literASIDOSIS HIPERKLOREMIK AKIBAT PEMBERIAN LARUTAN Na Cl 0.9% =SID : 19 AsidosisNa+ = (140+154)/2 mEq/L= 147 mEq/LCl- = (102+ 154)/2 mEq/L= 128 mEq/LSID = 19 mEq/LPlasma

Na+ = 140 mEq/L Cl- = 102 mEq/L SID= 38 mEq/L

Cation+ = 137 mEq/L Cl- = 109 mEq/LLaktat- = 28 mEq/L SID = 0 mEq/L 1 liter1 literPLASMA + Larutan RINGER LACTATESID : 38 PlasmaRinger laktatLaktat cepat dimetabolisme

2 liter=Normal pH setelah pemberian RINGER LACTATE SID : 34 lebih alkalosis 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/LPlasma

Na+ = 140 mEq/LCl- = 130 mEq/LSID =10 mEq/LNa+ = 165 mEq/LCl- = 130 mEq/LSID = 35 mEq/L1 liter1.025 liter25 mEq NaHCO3SID : 10 35 : Alkalosis, pH kembali normal namun mekanismenya bukan karena pemberian HCO3- melainkan karena pemberian Na+ tanpa anion kuat yg tidak dimetabolisme seperti Cl- sehingga SID alkalosisPlasma; asidosishiperkloremikMEKANISME PEMBERIAN NA-BIKARBONAT PADA ASIDOSISPlasma + NaHCO3 HCO3 cepat dimetabolisme

Na+Na+KHCO3-Cl-Cl-HCO3-SIDNormalKetosisUA = Unmeasured Anion:Laktat, acetoacetate, salisilat, metanol dll.A-A-Keto-SID KLactic/Keto asidosis

NaNaNaKKKHCO3ClClClHCO3HCO3SIDNormalAcidosisAlkalosisGANGGUAN PD ASAM LEMAH:Hipo/Hiperalbumin- atau P-Alb/P Alb-/P-Alb-/P-SIDSIDAlkalosis hipoalbumin/hipoposfatemiAsidosis hiperprotein/ hiperposfatemi

Calculate the anion gap. Anion gap = Na - (Cl + HCO3 ). Normal anion gap is 8 - 15 mEq/L.

If the anion gap is elevatedThen 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.

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).

Non anion Gap Acidosis:Anion gap = 8-12 mEq/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 The anion gap is helpful in identifying metabolic gap acidosis, non gap acidosis, mixed metabolic gap and non gap acidosis. If an elevated anion gap is present, a closer look at the anion gap and the bicarbonate helps differentiate among(a) a pure metabolic gap acidosis(b) a metabolic non gap acidosis(c) mixed metabolic gap and non gap acidosis, and (d) a metabolic gap acidosis and metabolic alkalosis.

Increased Anion GapNormal = 8-15May differ institutionallyAccumulation of organic acids (ketones, lactate)Toxic Ingestions methanol, ethylene glycol, salicylatesReduced inorganic acid excretionphosphates, sulfatesDecrease in unmeasured cations (unusual)

Increased AG Metabolic Acidosis: MethanolUremia/Renal FailureINH, Iron--lactateParaldehydeLactic AcidosisHas many etiologiesCyanide, CO, Toluene, HSPoor perfusion Ethylene glycolSalicylatesMethyl salicylate (Oil of wintergreen)Mg salicylate Levraut J et al. Int Care Med 23:417, 1997

Decreased or Negative Anion GapClin J Am Soc Nephrol 2: 162-174, 2007 Low protein most importantAlbumin has many unmeasured negative chargesNormal anion gap (12) in cachectic personIndicates anion gap metabolic acidosis2-2.5 mEq/liter drop in AG for every 1 g drop in albuminOther etiologies of low AG:Low K, Mg, Ca, increased globulins (Mult. Myeloma), Li, Br (bromism), I intoxicationNegative AGmore unmeasured cations than unmeasured anionsBromide, Iodide, Multiple Myeloma

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Lactate, Keto acids most common organic acids.AG> 35: M, EG, HHC, LA

Toxic ingestions: Cyanide, ASA, M, EG, Par, TolueneReduced Inorganic: Renal failure*