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Acid-base disturbance

Acid-base disturbance

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Acid-base disturbance

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  1. Acid-base disturbance Zhao Mingyao BMC.ZZU

  2. Acid? ------- Base? pH in arterial blood 7.35~7.45 [H+]

  3. ECFH+ mol/L pH Arterial blood 4.0 × 10-8 7.40 ± 0.05 Venous blood 4.5 × 10-8 7.35 Interstitial fluid 4.5 × 10-8 7.35 Intracellular fluid 1.0 × 10-6 6.0 to 4.0 × 10-8 7.4 Gastric fluid 0.9~1.8 (3.0) Pancrea fluid 7.8 ~ 8.4 H+ concentration in body fluid

  4. Metabolic processes generate acids Cells H+ ~ 100 nmol/L (pH ~ 7) H+ H+ Artery H+ ~ 36 nmol/L pH~7.4 H+ H+ H+ ~ 44 nmol/L pH~7.36 Capillary Vein

  5. Section 1 Acid-base biochemistry

  6. 1. Generation of Acid-Base (1) Sources of acid 1)volatile acid CO2 + H2O  H2CO3  H+ + HCO3- (H+ 15 mol /d) 2)fixed acid (non-volatile acid) phosphoric, sulfuric, lactic, ketone bodies etc. H+ 0.05 – 0.10 mol /d

  7. Sources of acid in body

  8. (2) Sources of bases 1)products of metabolism (small amounts)Such as ammonia (NH3) 2)dietary intake(vegetables and fruits) sodium citrate *acids production >>bases, in commen *renal reabsorption

  9. renal reabsorption pH 7.35~7.45 in Arterial blood

  10. 20 =pKa+lg 1 2. Henderson-Hasselbalch Equation [HCO3-] pH=pKa+lg [H2CO3] = 6.1 + lg HCO3- / 0.03 × PCO2 = 6.1 + lg 24 / 1.2 = 7.4 = 6.1 +1.3 = 7.4 pH 7.35~7.45

  11. [HCO3-] pH∝ [H2CO3]

  12. [HCO3-] [H2CO3] Strong acid pulse pH ∝ Strong base pulse 20 = ( eg . 24/1.2 or 40/2 or 10/0.5) 1 20 ≠ ( <20/1 or >20/1 ) 1

  13. Henderson-Hasselbalch Equation Compensatory ~: pH normal, but ? change Decompensatory ~: pH, HCO3 -, H2CO3change [HCO3-] pH ∝ [H2CO3]

  14. fulcrum Relationship between Henderson-Hasselbalch Equation and pH

  15. Section 2Regulation of acid-base in body fluid

  16. What happens in its body [H+] iv lactic acid iv bicarbonate ? ? ? ? acidosis alkalosis death death 【H+】 7.8 pH 6.8 7.35 7.45

  17. Why does body keep acid-base balance of body fluid ? [H+] Cellular signal → Enzyme ATP cell Ion distribution→ electrical action

  18. body maintain humoral acid-base balance by 1. blood buffer system 2. lung 3. kidney 4. cell

  19. 1. Blood buffer system HCO3-/ H2CO3 Hb- /HHb Pro- / HPro HPO42- /H2PO4- A-/HA Buffer system can bind and release H+ Dissociated buffer + H+H undissociated buffer

  20. HCO3- / H2CO3determines the pH of blood pH = pK + lg HCO3- / H2CO3 •HCO3- / H2CO3 is the major extracellular buffer 53% • H2CO3 regulated by lung • HCO3- regulated by kidney

  21. 2. Pulmonary regulation [HCO3-] pH∝ [H2CO3]

  22. Pulmonary regulation Central control PaCO2 CNS chemoreceptor + + Peripheral chemoreceptor respiration PaO2、pH、PaCO2 in the carotid and aortic bodies peripheral regulation

  23. 3. Renal regulation excreting H+ & keeping base (1) bicarbonate reabsorption(NaHCO3) (2) phosphate acidification (3) ammonia excretion

  24. (1)Reabsorption of HCO3- in different segments of renal tubule

  25. Bicarbonate reabsorptionin proximal tubules Na+ CA

  26. (2) Phosphate acidificationin distal tubules ATP Cl-

  27. (3) Ammonia excretionin proximaltubular cells Glutamine Tubular lumen glutaminase NH3 NH3 -ketoglutaric acid NH4+NH4+ H2CO3 Na+ Na+ HCO3- H+ H+ ATP

  28. 4. cellular buffer H+-K+ exchange between intra- and extra- cell Cl--HCO-3 exchange between intra- and extra-RBC or/ gastric cell

  29. Section 3 Laboratory tests Parameters of acid-base representing pH PaCO2 HCO3- ( SB, BE, BB ) Annion gap

  30. 1. pH in normal level (1) true normal (2) compensatory ~ (3) mixed ~ with opposite effect

  31. Weak tolerance to alkalosis pH 6.8 7.35 7.45 7.8 death acidosis alkalosis death 【H+】 160 40 16 nmol/L

  32. 2. Partial pressure of CO2, PaCO2 tension produced by CO2 dissolved physically in plasma Normal: 40mmHg (35~45) [H2CO3]: 40 × 0.03 = 1.2mmol/L PaCO2↑— Res Acidosis or ?PaCO2↓—Res alkalosis or ?

  33. 3. HCO3- normal: 24 mmol/L (22~27) SB and AB BB BE Primary and secondary change ?

  34. 4. Anion gap (AG) AG = UA – UC UA: Undetermined anion UC: Undetermined cation

  35. AG = UA - UC Cl- (104) Na+ (140) Na++ UC = Cl- + HCO3- + UA AG = Na+ - Cl- - HCO3- = 140-104-24 = 12 (mmol/L) HCO3- (24) AG UA (23) UC (11) Normal 10~14mmol/L Distinguishing metabolic acidosis

  36. If AG is 20-30 then high chance (67%) of metabolic acidosis If AG is > 30 then a metabolic acidosis is definitely present An elevated Anion Gap always strongly suggests a Metabolic Acidosis

  37. Summary of indexes 1. pH 2. Metabolic factor: HCO3- SB, BB, BE, AG 3. Respiratory factor:PaCO2

  38. Section 4Simple acid-base disorders Concept Compensation

  39. pH acidosis alkalosis metabolic respiratory metabolic respiratory [HCO3-]↓ PaCO2↑ [HCO3-]↑ PaCO2↓ Classification of ~

  40. Analysis of simple acid-base disorder =7.4?

  41. Part 1 Metabolic acidosis Concept: [HCO3-]p ↓ primarily

  42. Changes of laboratory test Primary: pH ? HCO3- ↓ Secondary: PaCO2 ↓ [K+]b↑

  43. Classification • Met acidosis with High AG • Met acidosis with Normal AG

  44. Cl- Na+ Cl- Na+ Cl- Na+ HCO3- HCO3- HCO3- AG AG AG(-) UA UA UA UC UC UC Met acidosis with High AG normal Met acidosis with normal AG Comparison betweenMet acidosis with High AG and normal AG

  45. (1) fixed acid production↑: lactic acidosis, ketoacidosis, excess acetylsalicylic acid , drugs yielding hydrochloride acid (2) fixed acid removing↓: RTA, RF (3) HCO3- loss↑: diarrhea , intestinal suction (4) hyperkalemia (5) hyperchloremia 1. Cause and mechanisms

  46. 2. Compensation of body [HCO3-] pH∝ [H2CO3] (1) Blood buffer system (2) lung (3) kidney (4) cell

  47. 3.Effects on the body (1) Cardiovascular system • Inhibiting myocardial contraction • Arrythmia • Responsibility↓of vessel to catecholamine

  48. (2) Central nervous system • Cerebral energy production • GABA ~ decarboxylase (+) Glutamate GABA