Acid-and-Base-Balance-and-Imbalance：酸堿平衡與不平衡-課件

1、1Acid and Base Balance and Imbalance1Acid and Base Balance and Imb2pH ReviewpH = - log H+H+ is really a protonRange is from 0 - 14If H+ is high, the solution is acidic; pH 72pH ReviewpH = - log H+3Acids are H+ donors.Bases are H+ acceptors, or give up OH- in solution.Acids and bases can be:Strong di

2、ssociate completely in solution HCl, NaOHWeak dissociate only partially in solutionLactic acid, carbonic acid3Acids are H+ donors.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) abov

3、e 7.454The Body and pHHomeostasis of556Small changes in pH can produce major disturbancesMost enzymes function only with narrow pH rangesAcid-base balance can also affect electrolytes (Na+, K+, Cl-)Can also affect hormones6Small changes in pH can produ7The body produces more acids than basesAcids ta

4、ke in with foodsAcids produced by metabolism of lipids and proteinsCellular metabolism produces CO2.CO2 + H20 H2CO3 H+ + HCO3-7The body produces more acids 8Control of AcidsBuffer systemsTake up H+ or release H+ as conditions changeBuffer pairs weak acid and a baseExchange a strong acid or base for

5、a weak oneResults in a much smaller pH change8Control of AcidsBuffer system9Bicarbonate bufferSodium Bicarbonate (NaHCO3) and carbonic acid (H2CO3)Maintain a 20:1 ratio : HCO3- : H2CO3HCl + NaHCO3 H2CO3 + NaClNaOH + H2CO3 NaHCO3 + H2O9Bicarbonate bufferSodium Bica10Phosphate bufferMajor intracellula

6、r bufferH+ + HPO42- H2PO4-OH- + H2PO4- H2O + H2PO42-10Phosphate bufferMajor intrac11Protein BuffersIncludes hemoglobin, work in blood and ISFCarboxyl group gives up H+ Amino Group accepts H+Side chains that can buffer H+ are present on 27 amino acids.11Protein BuffersIncludes hemo122. Respiratory me

7、chanismsExhalation 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 rate and depth of breathing122. Respiratory mechanismsExh133. Kidney excretionCan eliminate large amounts of acidCan

8、 also excrete baseCan conserve and produce bicarb ionsMost effective regulator of pHIf kidneys fail, pH balance fails133. Kidney excretionCan elimi14Rates of correctionBuffers function almost instantaneouslyRespiratory mechanisms take several minutes to hoursRenal mechanisms may take several hours t

9、o days14Rates of correctionBuffers f1515161617Acid-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 is still outside norms.17Acid-Base ImbalancespH 7.3518CompensationIf und

10、erlying problem is metabolic, hyperventilation or hypoventilation can help : respiratory compensation.If problem is respiratory, renal mechanisms can bring about metabolic compensation.18CompensationIf underlying pr19AcidosisPrincipal effect of acidosis is depression of the CNS through in synaptic t

11、ransmission.Generalized weaknessDeranged CNS function the greatest threatSevere acidosis causes Disorientationcoma death19AcidosisPrincipal effect of 20AlkalosisAlkalosis causes over excitability of the central and peripheral nervous systems.NumbnessLightheadednessIt can cause :Nervousnessmuscle spa

12、sms or tetany Convulsions Loss of consciousnessDeath20AlkalosisAlkalosis causes ov212122Respiratory 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 r

13、ate drugs or head traumaParalysis of respiratory or chest musclesEmphysema22Respiratory AcidosisCarbonic23Respiratory AcidosisAcute conditons:Adult Respiratory Distress SyndromePulmonary edemaPneumothorax23Respiratory AcidosisAcute co24Compensation for Respiratory AcidosisKidneys eliminate hydrogen

14、ion and retain bicarbonate ion24Compensation for Respiratory25Signs and Symptoms of Respiratory AcidosisBreathlessnessRestlessnessLethargy and disorientationTremors, convulsions, comaRespiratory rate rapid, then gradually depressedSkin warm and flushed due to vasodilation caused by excess CO225Signs

15、 and Symptoms of Respir26Treatment of Respiratory AcidosisRestore ventilationIV lactate solutionTreat underlying dysfunction or disease26Treatment of Respiratory Aci27Respiratory AlkalosisCarbonic acid deficitpCO2 less than 35 mm Hg (hypocapnea)Most common acid-base imbalancePrimary cause is hyperve

16、ntilation27Respiratory AlkalosisCarboni28Respiratory AlkalosisConditions that stimulate respiratory center:Oxygen deficiency at high altitudesPulmonary disease and Congestive heart failure caused by hypoxia Acute anxietyFever, anemiaEarly salicylate intoxicationCirrhosisGram-negative sepsis28Respira

17、tory AlkalosisConditi29Compensation of Respiratory AlkalosisKidneys conserve hydrogen ionExcrete bicarbonate ion29Compensation of Respiratory 30Treatment of Respiratory AlkalosisTreat underlying causeBreathe into a paper bagIV Chloride containing solution Cl- ions replace lost bicarbonate ions30Trea

18、tment of Respiratory Alk31Metabolic AcidosisBicarbonate deficit - blood concentrations of bicarb drop below 22mEq/LCauses:Loss of bicarbonate through diarrhea or renal dysfunctionAccumulation of acids (lactic acid or ketones)Failure of kidneys to excrete H+31Metabolic AcidosisBicarbonat32Symptoms of

19、 Metabolic AcidosisHeadache, lethargyNausea, vomiting, diarrheaComaDeath32Symptoms of Metabolic Acidos33Compensation for Metabolic AcidosisIncreased ventilationRenal excretion of hydrogen ions if possibleK+ exchanges with excess H+ in ECF( H+ into cells, K+ out of cells)33Compensation for Metabolic

20、A34Treatment of Metabolic AcidosisIV lactate solution 34Treatment of Metabolic Acido35Metabolic AlkalosisBicarbonate excess - concentration in blood is greater than 26 mEq/LCauses:Excess vomiting = loss of stomach acidExcessive use of alkaline drugsCertain diureticsEndocrine disordersHeavy ingestion

21、 of antacidsSevere dehydration35Metabolic AlkalosisBicarbona36Compensation for Metabolic AlkalosisAlkalosis most commonly occurs with renal dysfunction, so cant count on kidneysRespiratory compensation difficult hypoventilation limited by hypoxia36Compensation for Metabolic A37Symptoms of Metabolic

22、AlkalosisRespiration slow and shallowHyperactive reflexes ; tetanyOften related to depletion of electrolytesAtrial tachycardiaDysrhythmias37Symptoms of Metabolic Alkalo38Treatment of Metabolic AlkalosisElectrolytes to replace those lostIV chloride containing solutionTreat underlying disorder38Treatm

23、ent of Metabolic Alkal39Diagnosis of Acid-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-

24、 the problem is metabolic.39Diagnosis of Acid-Base Imbal403. 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.403. Look at th

25、e value that do41ExampleA patient is in intensive care because he suffered a severe 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)41ExampleA patient is in inten42DiagnosisMetabolic acid

26、osisWith compensation42DiagnosisMetabolic acidosis4343BloodSodium 135-145 mEq/LPotassium 3.5-5.0 mEqlLChloride 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

27、 mm Hg (declines with age)44Blood4445DisorderExpected CompensationMetabolic acidosisPCO2 = 1.5 HCO3- + 8 2Metabolic 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

28、 3.5 for each 10mmHg increase in the PCO2Respiratory alkalosisAcuteHCO3- falls by 2 for each 10mmHg decrease in the PCO2ChronicHCO3- falls by 4 for each 10mmHg decrease in the PCO245DisorderExpected Compensatio46FormulasWomen: Total body water (TBW) = .5 X Body weight (kg)Men: Total body water (TBW)

29、 = .6 X Body weight (kg)Osmolal gap = OSM,measured) - OSM,caculatcd)Anion gap (AG) = UA - UC = Na - (CI- + HCO,-)46FormulasOSM 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.47OSM GAP = OSM(measu

30、red) - OSM(48Common Causes of Metabolic AcidosisIncreased anion gapDiabetic ketoacidosisL-lactic acidosisD-lactic acidosisAlcoholic ketoacidosisUremic acidosis (advanced renal failure)Salicylate intoxicationEthylene glycol intoxicationMethanol intoxicationParaldehyde intoxicationNormal anion gapMild

31、 to moderate renal failureGastrointestinal loss of HCO3- (acute diarrhea)Type I (distal) renal tubular acidosisType I1 (proximal) renal tubular acidosisQpe IV renal tubular acidosisDilutional acidosisTreatment of diabetic ketoacidosis (ketones lost in urine)Increased Anion Gap LA MUD PIE (Mnemonic)L

32、actate (sepsis, ischemia, etc.)AspirinMethanolUremiaDiabetic ketoacidosis Paraldehyde, Propylene glycolIsopropyl alcohol, INHEthylene glycol (antifreeze, low calcium)48Common Causes of Metabolic A49Diabetic ketoacidosis (DKA)Patients with severe diabetic ketoacidosis typically present withHigh anion

33、 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.58Step 1: Identify the most ap59A patient presents with: pH 7.15, calculated HC03- 6 mEq/L, PCOZ1 8 mmHg, sodium 135 mEq/L, chloride 114 mEq/L, potass

34、ium 4.5 mEqL, serumHC03- 6 mEq/L.59A patient presents with: pH 60A patient presents with: pH 7.49, HC03- 35, PCO2- 4 8, AG 16.60A patient presents with: pH 61A patient presents with: pH 7.68, PCO2 35, HC03- 40, AG 18.61A patient presents with: pH 62A previously well patient presents with 30 minutes of respiratory distress andpH 7.26, Pc02 60, HC03- 26, AG 14.62A previously well patient pr63Apatient presents with: pH 7.45, PCOZ65 , HC03- 44, AG 14. Short of breathfor 3 days.63Apatient presents with: pH 764A patient presents with diabetic ketoacidosis: pH 6.95, PCOZ 28, HC03-