1、A Practical Approach to Acid-Base DisordersBin DU, MDMedical Intensive Care UnitPeking Union Medical College Hospital2021/7/20 星期二1Primary Acid-Base DisordersVariablePrimary DisorderNormal Range, Arterial GasPrimary DisorderpHAcidemia7.35 7.45AlkalemiaPCO2, mmHgRespiratory alkalosis35 45Respiratory

2、acidosisHCO3, mmol/LMetabolic acidosis22 26Metabolic alkalosis2021/7/20 星期二2Rules of Thumb for Recognizing Primary Acid-Base Disorders Without Using a NomogramRule 1Look at the pH. Whichever side of 7.40 the pH is on, the process that caused it to shift to that side is the primary abnormality.Princi

3、ple: The body does not fully compensate for primary acid-base disorders2021/7/20 星期二3Simple Acid-Base Disorders2021/7/20 星期二4Acute Respiratory AlkalosisArterial Gas ValueInterpretationpHPCO2*HCO37.5029 mmHg22 mmol/LAlkalemiaRespiratory alkalosisNormal HCO3CausesAnxietyHypoxiaLung disease with or wit

4、hout hypoxiaCentral nervous system diseaseDrug use salicylates, catecholamins, progesteronePregnancySepsisHepatic encephalopathyMechanical ventilation*This is the primary abnormality2021/7/20 星期二5Acute Respiratory AcidosisArterial Gas ValueInterpretationpHPCO2*HCO37.2560 mmHg26 mmol/LAcidemiaRespira

5、tory acidosisNormal HCO3CausesCentral nervous system (CNS) depression drugs, CNS eventNeuromuscular disorders myopathies, neuropathiesAcute airway obstruction upper airway, laryngospasm, bronchospasmSevere pneumonia or pulmonary edemaImpaired lung motion hemothorax, pneumothoraxThoracic cage injury

6、flail chestVentilator dysfunction*This is the primary abnormality2021/7/20 星期二6Chronic Respiratory Acidosis With Metabolic CompensationArterial Gas ValueInterpretationpHPCO2*HCO37.3460 mmHg31 mmol/LRespiratory acidosisMetabolic compensationCausesChronic lung disease obstructive or restrictiveChronic

7、 neuromuscular disordersChronic respiratory center depression central hypoventilation*This is the primary abnormality2021/7/20 星期二7The Importance of Differentiating Acute From Chronic Respiratory AcidosisAcute respiratory acidosisMedical emergency requiring emergent intubation and mechanical ventila

8、tionChronic respiratory acidosisOften a clinically stable condition2021/7/20 星期二8Metabolic Acidosis With Respiratory CompensationArterial Gas ValueInterpretationpHPCO2HCO3*7.5048 mmHg36 mmol/LAlkalemiaRespiratory compensationMetabolic alkalosisCausesUrinary Chloride Level LowUrinary Chloride Level N

9、ormal or HighVomiting, nasogastric suctionDiuretic use in pastPosthypercapniaExcess mineralocorticoid activity Cushings syndrome, Conns syndrome, exogenous steroids, licorice ingestion, increased renin states, Bartters syndromeCurrent or recent diuretic useExcess alkali administrationRefeeding alkal

10、osis*This is the primary abnormality2021/7/20 星期二9Importance of Urinary Chloride Level in Metabolic AlkalosisLow urinary chloride levelDecreased ECFOr posthypercapnic stateNormal or high urinary chloride levelNormal or increased ECFOr recent diuretic useUrinary chloride level = preferred method for

11、assessing the renal response to circulating volume in patients with metabolic alkalosisUrinary sodium level = less reliable as a guide2021/7/20 星期二10Metabolic Acidosis With Respiratory CompensationArterial Gas ValueInterpretationpHPCO2HCO3*7.2021 mmHg8 mmol/LAcidemiaRespiratory compensationMetabolic

12、 acidosisAnion gap = sodium chloride bicarbonateNormal = 12 2 (SD) mmol/LCausesNonanion GapAnion GapGI bicarbonate loss Diarrhea Ureteral diversionsHydrochloric administrationPosthypocapniaGI = gastrointestinalRenal bicarbonate loss Renal tubular acidosis Early renal failure Carbonic anhydrase inhib

13、itors Aldosterone inhibitorsKetoacidosis Diabetic AlcoholicRenal failureLactic acidosisRhabdomyolysisToxins Methanol Ethylene glycol Paraldehyde Salicylates*This is the primary abnormality2021/7/20 星期二11Mixed Acid-Base Disorders2021/7/20 星期二12ABG InterpretationABGpH 7.49, PCO2 47 mmHg, HCO3 35 mmol/

14、L, Na 139 mmol/L, K 3 mmol/L, Cl 89 mmol/LInterpretationSimple metabolic alkalosis with compensatory respiratory acidosis ?orMixed metabolic alkalosis and respiratory acidosis ?2021/7/20 星期二13Summary of Expected Compensation for Simple Acid-Base DisordersPrimary disorderInitial chemical changeCompen

15、satory responseExpected range of compensationMetabolic acidosisHCO3 decreasePCO2 decreasePCO2 = 1.5 (HCO3) + 8 2PCO2 = last two digits of pHPCO2 = 1 1.3 (HCO3)Metabolic alkalosisHCO3 increasePCO2 increasePCO2: variable increasePCO2 = 0.9 (HCO3) + 9PCO2 = 0.6 (HCO3)2021/7/20 星期二14Summary of Expected

16、Compensation for Simple Acid-Base DisordersPrimary disorderInitial chemical changeCompensatory responseExpected range of compensationRespiratory acidosisPCO2 increaseHCO3 increaseAcute(H+) = 0.8 (PCO2)HCO3 = PCO2 /10Chronic(H+) = 0.3 (PCO2)HCO3 = 3.5 x PCO2 /10Respiratory alkalosisPCO2 decreaseHCO3

17、decreaseAcute(H+) = 0.8 (PCO2)HCO3 = 2 x PCO2 /10Chronic(H+) = 0.17 (PCO2)HCO3 = 5 x PCO2 /102021/7/20 星期二15ABG InterpretationABGpH 7.40, PCO2 40 mmHg, HCO3 24 mmol/L, Na 139 mmol/L, K 4 mmol/L, Cl 105 mmol/LCalculationAG = 139 105 24 = 10Interpretationnormal2021/7/20 星期二16ABG InterpretationABGpH 7.

18、49, PCO2 47 mmHg, HCO3 35 mmol/L, Na 139 mmol/L, K 3 mmol/L, Cl 89 mmol/LCalculationAG = 139 89 35 = 15PCO2 = 0.6 (HCO3) = 0.6 x 11 = 6.6 mmHgInterpretationSimple metabolic alkalosis2021/7/20 星期二17ABG InterpretationABGpH 7.45, PCO2 25 mmHg, HCO3 17 mmol/L, Na 139 mmol/L, K 3.5 mmol/L, Cl 107 mmol/LC

19、alculationAG = 139 107 17 = 15HCO3 = 2 (PCO2 / 10) = 2 x 15 / 10 = 3 mmHgInterpretationSimple respiratory alkalosis ?2021/7/20 星期二18ABG InterpretationABGpH 7.65, PCO2 30 mmHg, HCO3 32 mmol/L, Na 139 mmol/L, K 2.8 mmol/L, Cl 92 mmol/LCalculationAG = 139 92 32 = 15HCO3 = 2 (PCO2 / 10) = 2 x 10 / 10 =

20、2 mmHgInterpretationMixed metabolic and respiratory alkalosis2021/7/20 星期二19ABG InterpretationABGpH 7.67, PCO2 30 mmHg, HCO3 34 mmol/L, Na 140 mmol/L, K 3 mmol/L, Cl 94 mmol/LCalculationAG = 140 94 34 = 12HCO3 = 2 (PCO2 / 10) = 2 x 10 / 10 = 2 mmHgInterpretationMixed metabolic and respiratory alkalo

21、sis2021/7/20 星期二20ABG InterpretationABGpH 7.61, PCO2 30 mmHg, HCO3 29 mmol/L, Na 140 mmol/L, K 3 mmol/L, Cl 94 mmol/LCalculationAG = 140 94 29 = 17HCO3 = 2 (PCO2 / 10) = 2 x 10 / 10 = 2 mmHgInterpretationMixed metabolic and respiratory alkalosis and lactic acidosis2021/7/20 星期二21ABG InterpretationAB

22、GpH 7.33, PCO2 70 mmHg, HCO3 36 mmol/L, Na 140 mmol/L, K 4.0 mmol/L, Cl 94 mmol/LCalculationAG = 140 94 36 = 10HCO3 = 3.5 (PCO2 / 10) = 3.5 x 30 / 10 = 10.5 mmHgInterpretationSimple chronic respiratory acidosis2021/7/20 星期二22ABG InterpretationABGpH 7.40, PCO2 67 mmHg, HCO3 40 mmol/L, Na 140 mmol/L,

23、K 3.5 mmol/L, Cl 90 mmol/LCalculationAG = 140 90 40 = 10HCO3 = 3.5 (PCO2 / 10) = 3.5 x 27 / 10 = 9.5 mmHgInterpretationMixed respiratory acidosis and metabolic alkalosis2021/7/20 星期二23ABG InterpretationABGpH 7.11, PCO2 16 mmHg, HCO3 5 mmol/L, Na 140 mmol/L, K 4.5 mmol/L, Cl 125 mmol/LCalculationAG =

24、 140 125 5 = 10PCO2 = 11 mmHgInterpretationSimple hyperchloremic metabolic acidosis2021/7/20 星期二24ABG InterpretationABGpH 7.11, PCO2 16 mmHg, HCO3 5 mmol/L, Na 140 mmol/L, K 4.0 mmol/L, Cl 105 mmol/LCalculationAG = 140 105 5 = 30PCO2 = 11 mmHgInterpretationSimple high AG metabolic acidosis2021/7/20

25、星期二25ABG InterpretationABGpH 7.11, PCO2 16 mmHg, HCO3 5 mmol/L, Na 140 mmol/L, K 4.0 mmol/L, Cl 115 mmol/LCalculationAG = 140 115 5 = 20PCO2 = 11 mmHgInterpretationMixed hyperchloremic and high AG metabolic acidosis2021/7/20 星期二26Is There A Simple Way ?2021/7/20 星期二27Mixed Acid-Base DisordersABGpH 7

26、.32, PCO2 28 mmHg, HCO3 14 mmol/L, BUN 100 mmol/LInterpretationAcidemic with low PCO2 and low bicarbonate concentrationLow bicarbonate as a primary disorder metabolic acidosis (secondary to renal failure)PaCO2 30 in the presence of low HCO3 primary respiratory alkalosisPaCO2 30 in the presence of ac

27、utely elevated PCO2 primary metabolic alkalosisHCO3 45 in the presence of chronically elevated PCO2 primary metabolic alkalosisHCO3 30 in the presence of acutely elevated PCO2orHCO3 45 in the presence of chronically elevated PCO2 primary metabolic alkalosis2021/7/20 星期二29Mixed Acid-Base Disorders ?A

28、BGpH 7.50, PCO2 38 mmHg, HCO3 31 mmol/L, K 3.5 mmol/LInterpretationAlkalemic with low PCO2 and high bicarbonate concentrationHigh HCO3 as a primary disorder metabolic alkalosis PCO2 55 in the presence of elevated HCO3 primary respiratory alkalosisPCO2 55 in the presence of elevated HCO3 primary resp

29、iratory acidosis2021/7/20 星期二30Mixed Acid-Base Disorders ?ABGpH 7.48, PCO2 29 mmHg, HCO3 23 mmol/LInterpretationAlkalemic with low PCO2 and normal bicarbonate concentrationLow PCO2 as a primary disorder respiratory alkalosis (secondary to asthma)HCO3 20 in the presence of acutely decreased PCO2 prim

30、ary metabolic acidosisHCO3 15 in the presence of chronically decreased PCO2 primary metabolic acidosisHCO3 20 in the presence of acutely decreased PCO2orHCO3 30 mmol/L), there is an underlying metabolic alkalosis; if the sum is less than a normal serum bicarbonate ( 20 anion gap metabolic acidosisEx

31、cess AG = 22 12 = 10 mmol/LExcess AG + HCO3 = 25 mmol/L no further primary abnormalities2021/7/20 星期二36Respiratory Alkalosis And Metabolic AcidosisDiagnosisRespiratory Alkalosis And Metabolic AcidosisReasonIngestion of a large quantity of aspirinCentrally mediated respiratory alkalosisAnion gap meta

32、bolic acidosis associated with salicylate overdose2021/7/20 星期二37Metabolic Alkalosis And Metabolic AcidosisABGpH 7.40, PCO2 40 mmHg, HCO3 24 mmol/L, Na 145 mmol/L, Cl 100 mmol/LInterpretationNormal ABGAG = 145 (100 + 24) = 21 20 anion gap metabolic acidosisExcess AG = 21 12 = 9 mmol/LExcess AG + HCO

33、3 = 33 mmol/L metabolic alkalosis2021/7/20 星期二38Metabolic Alkalosis And Metabolic AcidosisDiagnosisMetabolic Alkalosis And Metabolic AcidosisReasonChronic renal failure (metabolic acidosis)Vomiting (metabolic alkalosis)2021/7/20 星期二39Respiratory Alkalosis, Metabolic Acidosis and Metabolic AlkalosisA

34、BGpH 7.50, PCO2 20 mmHg, HCO3 15 mmol/L, Na 145 mmol/L, Cl 100 mmol/LInterpretationAlkalemic with low PCO2 and low bicarbonate concentrationLow PCO2 as a primary disorder respiratory alkalosisAG = 145 (100 + 15) = 30 20 anion gap metabolic acidosisExcess AG = 30 12 = 18 mmol/LExcess AG + HCO3 = 33 m

35、mol/L metabolic alkalosis2021/7/20 星期二40Respiratory Alkalosis, Metabolic Acidosis and Metabolic AlkalosisDiagnosisRespiratory Alkalosis, Metabolic Acidosis and Metabolic AlkalosisReasonHistory of vomiting (metabolic alkalosis)Evidence of alcoholic ketoacidosis (metabolic acidosis)Bacterial pneumonia

36、 (respiratory alkalosis)2021/7/20 星期二41Respiratory Acidosis, Metabolic Acidosis and Metabolic AlkalosisABGpH 7.10, PCO2 50 mmHg, HCO3 15 mmol/L, Na 145 mmol/L, Cl 100 mmol/LInterpretationAcidemic with elevated PCO2 and low bicarbonate concentrationIncreased PCO2 and decreased bicarbonate both as primary disorders respir