Acid-Base Balance Acid-Base Balance M. Rasjad Indra M. Rasjad Indra Laboratorium Ilmu Faal Laboratorium Ilmu Faal FK. UNIBRAW FK. UNIBRAW
Acid-Base BalanceAcid-Base Balance
M. Rasjad IndraM. Rasjad Indra
Laboratorium Ilmu FaalLaboratorium Ilmu Faal
FK. UNIBRAWFK. UNIBRAW
Seorang wanita 34 tahun hamil 32 minggu datang ke rumah sakit dengan keluhan muntah-muntah selama dua hari terakhir.
Penderita adalah peminum alkohol berat. Awal muntah terjadi setelah meneguk alkohol dalam jumlah besar, tetapi segera berhenti minum setelah mengalami muntah.
Hasil pemeriksaan darah:
pH : 7,17 (7,35 – 7,45)
PCO2 : 14 mm Hg (23 – 33)
HCO3 : 7 mmol/L (35 – 45)
What is Acid and Base ?What is Acid and Base ?
Acid is Acid is proton (Hproton (H++)) donordonor Base is Base is proton (Hproton (H++)) acceptoracceptor The most important acid in the blood is The most important acid in the blood is
HH22COCO33
The most important base is The most important base is HCOHCO33--
HH22COCO3 3 <=> HCO<=> HCO33--+H+H++
Henderson-Hasselbalch Henderson-Hasselbalch EquationEquation
pH=pK + log pH=pK + log kidneyskidneys lungslungs
pH=pK + log pH=pK + log [HCO[HCO33--]]
PCOPCO22
pH=6,1 + log pH=6,1 + log [HCO[HCO33--]]
0.03 * P CO0.03 * P CO22
pH 7.70 pH 7.70 [H+] = 20 nmol/L pH7.20 [H+] = 20 nmol/L pH7.20 [H+]=60 [H+]=60
nmol/Lnmol/L 7.60 25 7.10 807.60 25 7.10 80 7.50 30 7.00 1007.50 30 7.00 100 7.40 40 6.90 1257.40 40 6.90 125 7.30 50 6.80 1607.30 50 6.80 160
1.
2.
1
20
]32[
]3[
COH
HCO
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PCO
HCOpH
LmEqHCO
mmHgPCOxLnmolH
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ACIDACID Result of Result of metabolismmetabolism and and digestiondigestion Consist of: Consist of: volatilevolatile and and nonvolatilenonvolatile VolatileVolatile
– HCl, H2SO4, HNO3, H3PO4, NH4+, HCl, H2SO4, HNO3, H3PO4, NH4+, H2CO3H2CO3 HH22COCO3 3 ((primary)<=>Hprimary)<=>H220 + CO0 + CO22
Eliminated as COEliminated as CO22 gas via gas via lungslungs..
NonvolatileNonvolatile::– Small amount.Small amount.– Lactic acid, acetic acidLactic acid, acetic acid – Removed via the Removed via the kidneykidney
Base :•NaOH: Sodium hydroxide•KOH: Potasium hydroxide•NH3
+: Ammonia
•HCO3-: Bicarbonate
Amphoteric Substance: Can function as both an acid and a base.•Glycine( +H3N-CH2-COO-):
•NaOH++H3N-CH2-COO-=>H2N-CH2-COO-Na+ + H2O
•HCl + +H3N-CH2-COO- => Cl-+H3N-CH2-COOH
Buffer: Minimize the change & promote stability
1. Acid <=> Conjugate base : H2PO4
- <=> HPO42- + H+
H2CO3 <=> HCO3- + H+
NH4+ <=> NH3 + H+
2. Protein :Albumin; GlobulinHemoglobin
3. Lung and Kidney
[H[H22COCO33 ]~PaCO ]~PaCO22= = Respiratory Respiratory componentcomponent
[H[H22COCO33]<=>PaCO]<=>PaCO22 x (0.03) x (0.03)
PaCOPaCO22 : :
– Provides a measure of HProvides a measure of H22COCO33
– The respiratory component.The respiratory component. Normal:Normal:
– PaCOPaCO22 = 40 mm Hg. = 40 mm Hg.
– HH22COCO33 = 40 x 0.03 = 1.2 mEq/L = 40 x 0.03 = 1.2 mEq/L
HCOHCO33--=Metabolic component=Metabolic component
Regulated by the kidney.Regulated by the kidney. By modulating the rate of re-absorptionBy modulating the rate of re-absorption
Metabolic acid-base imbalance:Metabolic acid-base imbalance: Kidney-relatedKidney-related Non-kidney-relatedNon-kidney-related
Electrolite DisturbanceElectrolite Disturbance(Chloride depletion)(Chloride depletion)
Three Process in Urinary Acidification
1.Reabsorption of filtered bicarbonate
2.Formation of titrable acid
3.Excretion of ammonium
REABSORPTION OF FILTERED BICARBONATE
HCO3-
H2CO3
H+
H2O
CO2
Na+
HCO3- H+
H2CO3
HCO3-
+
CO2 CO2 H2O
Blood Plasma Tubular Epithelium Tubular Urine
+
CA
Na+
HCO3-
H2CO3
H+
H2O
CO2
Na+
HCO3- H+ HPO4
2-2Na
+
CO2
Blood Plasma Tubular Epithelium Tubular Urine
+
CA
Na+
H2PO4-2Na
FORMATION OF TITRATABLE ACID
HCO3-
2H2CO3
H+
2H2O
2CO2
2Na+
2HCO3-
H+
+
2CO2
Blood Plasma Tubular Epithelium Tubular Urine
CA
Na+
Glutamine
-ketoglutarate2- 2NH4+
NH3 NH3
NH4+
Na+
2H+Glucose or CO2
NH4+
+
EXCRETION OF AMMONIUM [NH4]
The acidity of bloodThe acidity of blood Depend on [HDepend on [H++]] Expressed by pHExpressed by pH
• The [HThe [H++] increase -> the pH decrease] increase -> the pH decrease• pH = -log[HpH = -log[H++]]
• pH = pK + log [HCOpH = pK + log [HCO33-- / H / H22COCO33]]
Henderson Hasselbalch equationHenderson Hasselbalch equation
Arterial Blood Gas (ABG):Arterial Blood Gas (ABG):• pH = measuredpH = measured - HCO- HCO33
-- = calculated = calculated
• PaCOPaCO22 = measured = measured
Normal Range
• PaCO2 = 38 to 42 mmHg
• HCO3- = 22 to 26 mEq/L
• pH = 7.38 to 7.42
• HCO3- / H2CO3 = 20 : 1
• Acid-base disturbance (blood):– Acidemia: pH< 7.38– Alkalemia: pH> 7.42
Acid-Base DisturbanceSimple :
• Respiratory acidosis: PaCO2 high / HCO3- normal or slightly high
• Respiratory alkalosis: PaCO2 low /HCO3- normal or low
• Metabolic acidosis: HCO3- low / PaCO2 normal or low
• Metabolic alkalosis: HCO3- high / PaCO2 normal or high
Mixed / Combination: • (Respiratory + Metabolic)
Physiologic compensation
Primary disorder Physiol. compensationRespiratory acidosis Kidney – retention of HCO3-
; excretion of H+Respiratory alkalosis Kidney – excretion of
HCO3-; retention of H+Metabolic acidosis Lung – excretion of H+
(CO2).Metabolic alkalosis Lung – possible retention of
H+ (CO2)
ExerciseExercise
► pH = 7.33pH = 7.33► PaCO2 = 50 mmHgPaCO2 = 50 mmHg► HCO3- =25.8 mEq/LHCO3- =25.8 mEq/L
Answer:Answer:► AcidemiaAcidemia► Primary respiratory Primary respiratory ► AcuteAcute
► pH = 7.55pH = 7.55► PaCO2 = 30 mmHgPaCO2 = 30 mmHg► HCO3- = 23.4 HCO3- = 23.4
mEq/LmEq/L
Answer:Answer:► AlkalemiaAlkalemia► Primary respiratoryPrimary respiratory► AcuteAcute
ExerciseExercise
pH = 7.31pH = 7.31
PaCO2 = 29.5 mmHgPaCO2 = 29.5 mmHg
HCO3- = 14.5 mEq/LHCO3- = 14.5 mEq/L
Answer:Answer:
AcidemiaAcidemia
Primary metabolicPrimary metabolic
Respiratory Respiratory compensationcompensation
pH = 7.59pH = 7.59
PaCO2 = 46.5 mmHgPaCO2 = 46.5 mmHg
HCO3- = 45 mEq/LHCO3- = 45 mEq/L
Answer:Answer:
AlkalemiaAlkalemia
Primary metabolicPrimary metabolic
Respiratory Respiratory compensationcompensation