AcidandBaseBalanceandImbalance：酸碱平衡与不平衡课件

1、1Acid and Base Balance and Imbalance第1页，共67页。2pH ReviewpH = - log H+H+ is really a protonRange is from 0 - 14If H+ is high, the solution is acidic; pH 7第2页，共67页。3Acids are H+ donors.Bases are H+ acceptors, or give up OH- in solution.Acids and bases can be:Strong dissociate completely in solution HCl

2、, NaOHWeak dissociate only partially in solutionLactic acid, carbonic acid第3页，共67页。4The Body and pHHomeostasis of pH is tightly controlledExtracellular fluid = 7.4Blood = 7.35 7.45 8.0 death occursAcidosis (acidemia) below 7.35Alkalosis (alkalemia) above 7.45第4页，共67页。5第5页，共67页。6Small changes in pH c

3、an produce major disturbancesMost enzymes function only with narrow pH rangesAcid-base balance can also affect electrolytes (Na+, K+, Cl-)Can also affect hormones第6页，共67页。7The body produces more acids than basesAcids take in with foodsAcids produced by metabolism of lipids and proteinsCellular metab

4、olism produces CO2.CO2 + H20 H2CO3 H+ + HCO3-第7页，共67页。8Control of AcidsBuffer systemsTake up H+ or release H+ as conditions changeBuffer pairs weak acid and a baseExchange a strong acid or base for a weak oneResults in a much smaller pH change第8页，共67页。9Bicarbonate bufferSodium Bicarbonate (NaHCO3) a

5、nd carbonic acid (H2CO3)Maintain a 20:1 ratio : HCO3- : H2CO3HCl + NaHCO3 H2CO3 + NaClNaOH + H2CO3 NaHCO3 + H2O第9页，共67页。10Phosphate bufferMajor intracellular bufferH+ + HPO42- H2PO4-OH- + H2PO4- H2O + H2PO42-第10页，共67页。11Protein BuffersIncludes hemoglobin, work in blood and ISFCarboxyl group gives up

6、 H+ Amino Group accepts H+Side chains that can buffer H+ are present on 27 amino acids.第11页，共67页。122. Respiratory mechanismsExhalation of carbon dioxidePowerful, but only works with volatile acidsDoesnt affect fixed acids like lactic acidCO2 + H20 H2CO3 H+ + HCO3-Body pH can be adjusted by changing

7、rate and depth of breathing第12页，共67页。133. Kidney excretionCan eliminate large amounts of acidCan also excrete baseCan conserve and produce bicarb ionsMost effective regulator of pHIf kidneys fail, pH balance fails第13页，共67页。14Rates of correctionBuffers function almost instantaneouslyRespiratory mecha

8、nisms take several minutes to hoursRenal mechanisms may take several hours to days第14页，共67页。15第15页，共67页。16第16页，共67页。17Acid-Base ImbalancespH 7.45 alkalosisThe body response to acid-base imbalance is called compensationMay be complete if brought back within normal limitsPartial compensation if range

9、is still outside norms.第17页，共67页。18CompensationIf underlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation.If problem is respiratory, renal mechanisms can bring about metabolic compensation.第18页，共67页。19AcidosisPrincipal effect of acidosis is depression

10、 of the CNS through in synaptic transmission.Generalized weaknessDeranged CNS function the greatest threatSevere acidosis causes Disorientationcoma death第19页，共67页。20AlkalosisAlkalosis causes over excitability of the central and peripheral nervous systems.NumbnessLightheadednessIt can cause :Nervousn

11、essmuscle spasms or tetany Convulsions Loss of consciousnessDeath第20页，共67页。21第21页，共67页。22Respiratory AcidosisCarbonic acid excess caused by blood levels of CO2 above 45 mm Hg. Hypercapnia high levels of CO2 in bloodChronic conditions:Depression of respiratory center in brain that controls breathing

12、rate drugs or head traumaParalysis of respiratory or chest musclesEmphysema第22页，共67页。23Respiratory AcidosisAcute conditons:Adult Respiratory Distress SyndromePulmonary edemaPneumothorax第23页，共67页。24Compensation for Respiratory AcidosisKidneys eliminate hydrogen ion and retain bicarbonate ion第24页，共67页

13、。25Signs and Symptoms of Respiratory AcidosisBreathlessnessRestlessnessLethargy and disorientationTremors, convulsions, comaRespiratory rate rapid, then gradually depressedSkin warm and flushed due to vasodilation caused by excess CO2第25页，共67页。26Treatment of Respiratory AcidosisRestore ventilationIV

14、 lactate solutionTreat underlying dysfunction or disease第26页，共67页。27Respiratory AlkalosisCarbonic acid deficitpCO2 less than 35 mm Hg (hypocapnea)Most common acid-base imbalancePrimary cause is hyperventilation第27页，共67页。28Respiratory AlkalosisConditions that stimulate respiratory center:Oxygen defic

15、iency at high altitudesPulmonary disease and Congestive heart failure caused by hypoxia Acute anxietyFever, anemiaEarly salicylate intoxicationCirrhosisGram-negative sepsis第28页，共67页。29Compensation of Respiratory AlkalosisKidneys conserve hydrogen ionExcrete bicarbonate ion第29页，共67页。30Treatment of Re

16、spiratory AlkalosisTreat underlying causeBreathe into a paper bagIV Chloride containing solution Cl- ions replace lost bicarbonate ions第30页，共67页。31Metabolic AcidosisBicarbonate deficit - blood concentrations of bicarb drop below 22mEq/LCauses:Loss of bicarbonate through diarrhea or renal dysfunction

17、Accumulation of acids (lactic acid or ketones)Failure of kidneys to excrete H+第31页，共67页。32Symptoms of Metabolic AcidosisHeadache, lethargyNausea, vomiting, diarrheaComaDeath第32页，共67页。33Compensation for Metabolic AcidosisIncreased ventilationRenal excretion of hydrogen ions if possibleK+ exchanges wi

18、th excess H+ in ECF( H+ into cells, K+ out of cells)第33页，共67页。34Treatment of Metabolic AcidosisIV lactate solution 第34页，共67页。35Metabolic AlkalosisBicarbonate excess - concentration in blood is greater than 26 mEq/LCauses:Excess vomiting = loss of stomach acidExcessive use of alkaline drugsCertain di

19、ureticsEndocrine disordersHeavy ingestion of antacidsSevere dehydration第35页，共67页。36Compensation for Metabolic AlkalosisAlkalosis most commonly occurs with renal dysfunction, so cant count on kidneysRespiratory compensation difficult hypoventilation limited by hypoxia第36页，共67页。37Symptoms of Metabolic

20、 AlkalosisRespiration slow and shallowHyperactive reflexes ; tetanyOften related to depletion of electrolytesAtrial tachycardiaDysrhythmias第37页，共67页。38Treatment of Metabolic AlkalosisElectrolytes to replace those lostIV chloride containing solutionTreat underlying disorder第38页，共67页。39Diagnosis of Ac

21、id-Base ImbalancesNote whether the pH is low (acidosis) or high (alkalosis)Decide which value, pCO2 or HCO3- , is outside the normal range and could be the cause of the problem. If the cause is a change in pCO2, the problem is respiratory. If the cause is HCO3- the problem is metabolic.第39页，共67页。403

22、. Look at the value that doesnt correspond to the observed pH change. If it is inside the normal range, there is no compensation occurring. If it is outside the normal range, the body is partially compensating for the problem.第40页，共67页。41ExampleA patient is in intensive care because he suffered a se

23、vere myocardial infarction 3 days ago. The lab reports the following values from an arterial blood sample:pH 7.3HCO3- = 20 mEq / L ( 22 - 26)pCO2 = 32 mm Hg (35 - 45)第41页，共67页。42DiagnosisMetabolic acidosisWith compensation第42页，共67页。43第43页，共67页。BloodSodium 135-145 mEq/LPotassium 3.5-5.0 mEqlLChloride

24、 95-105 mEq/LBicarbonate 24-26 mEq/LOsmolality 280-295 mEqLOsmolal gap 10 mOsm/LAnion gap 9-16 mEqlLUrea nitrogen 10-20 mgldlArterial blood gas analysispH 7.35-7.45PCOZ35 -45 mm HgPoz 90-100 mm Hg (declines with age)44第44页，共67页。45DisorderExpected CompensationMetabolic acidosisPCO2 = 1.5 HCO3- + 8 2M

25、etabolic alkalosisPCO2 increases by 7mmHg for each 10mEq/L increase in the serum HCO3-Respiratory acidosisAcuteHCO3- increases by 1 for each 10mmHg increase in the PCO2ChronicHCO3- increases by 3.5 for each 10mmHg increase in the PCO2Respiratory alkalosisAcuteHCO3- falls by 2 for each 10mmHg decreas

26、e in the PCO2ChronicHCO3- falls by 4 for each 10mmHg decrease in the PCO2第45页，共67页。46FormulasWomen: Total body water (TBW) = .5 X Body weight (kg)Men: Total body water (TBW) = .6 X Body weight (kg)Osmolal gap = OSM,measured) - OSM,caculatcd)Anion gap (AG) = UA - UC = Na - (CI- + HCO,-)第46页，共67页。OSM

27、GAP = OSM(measured) - OSM(cal)Values of greater than 10 mOsm/L are abnormal and suggest the presence of an exogenous substanceAG is normally 9-16 mFq/L.47第47页，共67页。48Common Causes of Metabolic AcidosisIncreased anion gapDiabetic ketoacidosisL-lactic acidosisD-lactic acidosisAlcoholic ketoacidosisUre

28、mic acidosis (advanced renal failure)Salicylate intoxicationEthylene glycol intoxicationMethanol intoxicationParaldehyde intoxicationNormal anion gapMild to moderate renal failureGastrointestinal loss of HCO3- (acute diarrhea)Type I (distal) renal tubular acidosisType I1 (proximal) renal tubular aci

29、dosisQpe IV renal tubular acidosisDilutional acidosisTreatment of diabetic ketoacidosis (ketones lost in urine)Increased Anion Gap LA MUD PIE (Mnemonic)Lactate (sepsis, ischemia, etc.)AspirinMethanolUremiaDiabetic ketoacidosis Paraldehyde, Propylene glycolIsopropyl alcohol, INHEthylene glycol (antif

30、reeze, low calcium)第48页，共67页。49Diabetic ketoacidosis (DKA)Patients with severe diabetic ketoacidosis typically present withHigh anion gap metabolic acidosisSevere acidemia (pH 20 mEqn, high AG acidosis is probably present.If AG 30 mEq/L, high AG acidosis is almost certainly present.第58页，共67页。59A pat

31、ient presents with: pH 7.15, calculated HC03- 6 mEq/L, PCOZ1 8 mmHg, sodium 135 mEq/L, chloride 114 mEq/L, potassium 4.5 mEqL, serumHC03- 6 mEq/L.第59页，共67页。60A patient presents with: pH 7.49, HC03- 35, PCO2- 4 8, AG 16.第60页，共67页。61A patient presents with: pH 7.68, PCO2 35, HC03- 40, AG 18.第61页，共67页。

32、62A previously well patient presents with 30 minutes of respiratory distress andpH 7.26, Pc02 60, HC03- 26, AG 14.第62页，共67页。63Apatient presents with: pH 7.45, PCOZ65 , HC03- 44, AG 14. Short of breathfor 3 days.第63页，共67页。64A patient presents with diabetic ketoacidosis: pH 6.95, PCOZ 28, HC03- 6,AG 32.第64页，共67