酸碱平衡紊乱酸碱平衡紊乱酸碱平衡紊乱酸碱平衡紊乱Internal environment and homeostasisBODY FLUID: Volume: ICF -40% wt ECF -20% wt Electrolyte ：Na+, K+, Cl-, HCO3- Osmotic pressure: 280-310 mmol/LAcidity & basicity：7.357.45General concept of acid and base Acid :A substance that can provide protons (H+ions) Base :A substance that can accept protons (H+ions) Acid = Proton donor (HA) Base = Proton acceptor (A-) Normal concentration of H+ in body fluid is 410-8mol/L. Range of pH is from 0 - 14 Normal pH of blood is 7.35-7.45Generation of acids and bases1. generation of acid(1). Volatile acid: (H2CO3) The acid which can turn into CO2and then eliminated out of the body via lung. The most acid in the body.CO2H2OH+HCO3-H2CO3+300L15molRespiratory regulation of acid-base balanceLung:(2). Fixed acid(nonvolatile acid): the acid that eliminated out through kidney with urine. H+produced from fixed acids per day is about 50-100mmol.Renal regulation of acid-base balanceKidney:2. Generation of base Vegetarian diet containing large amounts of organic anions. Metabolism of amino acid (e.g. aspartate, glutamate) and organic anions (e.g. citrate(柠檬酸盐柠檬酸盐), lactate(如酸盐如酸盐), acetate（醋酸盐）（醋酸盐）)Regulation of acid-base balance blood buffering Reacts very rapidly (less than a second) respiratory regulation Reacts rapidly (seconds to minutes) ion exchange between intracellular and extracellular compartment and intracellular buffering Reacts slowly (24 hours) renal regulation Reacts very slowly (1224 hours) Buffer system: A-/HA H+ + A-(weak base) HA (weak acid) OH-+ HA A-+ H2O Main buffer system Bicarbonate buffer system (HCO3-/H2CO3) Plasma protein buffer system (Pr-/HPr) Phosphate buffer system (HPO42-/H2PO4-) Hemoglobin (Hb-/HHb) and oxyhemoglobin buffer system (HbO2-/HHbO2)1. Blood bufferingHCl+ HCO3- H2CO3+Cl- OH-+H2CO3HCO3-+H2OHH2 2COCO3 3HCOHCO3 3 pH pH Regulated by kidneyRegulated by lungBlood bufferingCO2H2OH+ HCO3-H2CO3+lungkidneyventilationH+secretion HCO3- -reabsorption H2CO3 HCO3 pH = pKa + log= 6.1 + log24 1.2(mmol/L)= 6.1 + log20 1 = 6.1+1.3 = 7.4 H2CO3HCO3 pH 2. Respiratory regulation The lung regulates the ratio of HCO3- /H2CO3 to approach 20/1 by controlling the alveolar ventilation and further elimination of CO2, so as to maintain constant pH value.pH = pK+ lgHCO3- H2CO3= pK + lgHCO3- PaCO2Respiratory regulationSensitive to the H+ change in CSFPaCOPaCO2 2pHpHCentral chemoreceptor 中枢化学感受器中枢化学感受器Peripheral chmoreceptor 外周化学感受器外周化学感受器PaO2 PaCO2 pHRespiratory regulation3. Renal regulationacid excretionbicarbonate conservationso that the ratio of HCO3-/H2CO3 approach 20/1 and pH value is constant.Na+Reabsoption of HCO3-in proximal tubulescapillaryTubular cellTubular lumenH2O + CO2H+HCO3-H2CO3H2OCO2Na+H2CO3HCO3-H+CAH2O + CO2H+Cl-H2CO3HCO3-H+CAHPO42-H2PO4-酸 化酸 化Reabsoption of HCO3-or secretion of H+ in distal tubulescapillaryTubular cellTubular lumenH2O + CO2H+H2CO3HCO3-H+谷氨酰胺谷氨酰胺NH3NH4+ +NH3NH3Na+NH4+Na+CAcapillaryTubular cellTubular lumenAmmonia secretion in proximal and distal tubulesHH+ +KK+ +ClCl- -HCOHCO3 3- -4. ion exchange between intra4. ion exchange between intra- - and and extracellularextracellular compartmentcompartmenti.e. Extracellular H+ H+shift into cells and K+ shift out of cells acidosis hyperkalemia alkalosis hypokalemia1. Simple acid1. Simple acid- -base disturbancesbase disturbancesHH2 2COCO3 3 (1)(1)HCOHCO3 3 (20)(20) pH pH MetabolicMetabolic (base)(base)(base)(base)RespiratoryRespiratory (acid)(acid)causesPrimary changePrimary changeMetabolic Metabolic alkalosisalkalosisMetabolicMetabolic acidosisacidosisRespiratoryRespiratory acidosisacidosisRespiratoryRespiratory alkalosisalkalosis1.simple1.simple- -Metabolic alkalosisMetabolic alkalosisMetabolic acidosisMetabolic acidosisRespiratory acidosisRespiratory acidosisRespiratory alkalosisRespiratory alkalosisCompensatoryCompensatory- - DecompensatoryDecompensatory- -2.mixed2.mixed- - Types of acidTypes of acid- -base disturbancesbase disturbances Essential parameters for acid-base assessment:1. pH1. pH2. PaCO2. PaCO2 23. SB 3. SB 与与与与 ABAB4. buffer bases (BB)4. buffer bases (BB)5. base excess (BE)5. base excess (BE)6. anion gap (AG)6. anion gap (AG)1. pH1. pHNormal pH of blood isNormal pH of blood is7.357.357.457.457.45 7.45 alkalosisalkalosisnormal?normal? normalnormalCompensatoryCompensatory- -MixedMixed- -2. PaCO2. PaCO2 2The pressure formed by dissolved CO2in arterial bloodnormalnormal3346 mmHg (40 mmHg)46 mmHg: hypoventilationhypoventilationPrimaryPrimary- -Respiratory Respiratory acidosisacidosis SecondarySecondary- - Compensatory ofCompensatory of Metabolic alkalosisMetabolic alkalosisSBABSBPaCOPaCOPaCOPaCO2 2 2 2ABSBABSBPaCOPaCOPaCOPaCO2 2 2 2HH2 2COCO3 3HCOHCO3 3 pH pH 4. BB 4. BB (缓冲碱缓冲碱 buffer base)Normal: 45Normal: 45- -52mmol/L52mmol/L