APracticalApproachtoAcid-BaseDisordersBinDU,MDMedicalIntensiveCareUnitPekingUnionMedicalCollegeHospitalPrimaryAcid-BaseDisordersVariablePrimaryDisorderNormalRange,ArterialGasPrimaryDisorderpHAcidemia7.35–7.45AlkalemiaPCO2,mmHgRespiratoryalkalosis35–45RespiratoryacidosisHCO3,mmol/LMetabolicacidosis22–26MetabolicalkalosisRulesofThumbforRecognizingPrimaryAcid-BaseDisordersWithoutUsingaNomogramRule1LookatthepH.Whicheversideof7.40thepHison,theprocessthatcausedittoshifttothatsideistheprimaryabnormality.Principle:Thebodydoesnotfullycompensateforprimaryacid-basedisordersSimpleAcid-BaseDisordersAcuteRespiratoryAlkalosisArterialGasValueInterpretationpHPCO2*HCO37.5029mmHg22mmol/LAlkalemiaRespiratoryalkalosisNormalHCO3CausesAnxietyHypoxiaLungdiseasewithorwithouthypoxiaCentralnervoussystemdiseaseDruguse–salicylates,catecholamins,progesteronePregnancySepsisHepaticencephalopathyMechanicalventilation*ThisistheprimaryabnormalityAcuteRespiratoryAcidosisArterialGasValueInterpretationpHPCO2*HCO37.2560mmHg26mmol/LAcidemiaRespiratoryacidosisNormalHCO3CausesCentralnervoussystem(CNS)depression–drugs,CNSeventNeuromusculardisorders–myopathies,neuropathiesAcuteairwayobstruction–upperairway,laryngospasm,bronchospasmSeverepneumoniaorpulmonaryedemaImpairedlungmotion–hemothorax,pneumothoraxThoraciccageinjury–flailchestVentilatordysfunction*ThisistheprimaryabnormalityChronicRespiratoryAcidosisWithMetabolicCompensationArterialGasValueInterpretationpHPCO2*HCO37.3460mmHg31mmol/LRespiratoryacidosisMetaboliccompensationCausesChroniclungdisease–obstructiveorrestrictiveChronicneuromusculardisordersChronicrespiratorycenterdepression–centralhypoventilation*ThisistheprimaryabnormalityTheImportanceofDifferentiatingAcuteFromChronicRespiratoryAcidosis•Acuterespiratoryacidosis–Medicalemergencyrequiringemergentintubationandmechanicalventilation•Chronicrespiratoryacidosis–OftenaclinicallystableconditionMetabolicAcidosisWithRespiratoryCompensationArterialGasValueInterpretationpHPCO2HCO3*7.5048mmH...
