Blood Gas AnalysisZulkifli. Dr., SpAn., MKesDepartment of Anesthesiology and ReanimationFK Unsri/ RSMHSKILL STATION

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Definitiona technique to know the states of respiration and metabolic through measuring of blood gas tensions and pH.Evaluation ofOxygenationVentilationAcid-base balanceNormally arterial bloodCVPMixed venous

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Measurement of Blood Gas Tensions & pH Measuring Normal ValuepH 7.35 7.45PO2 60 100 mm HgPCO2 35 45 mm HgHCO3 19 -23 mmol/LBEexcess 0 mmol/LSO2 > 90 %Hb

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Sample Source & Collection

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Measurement of Blood Gas Tensions & pH

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Acute Respiratory Acidosis compensatory response limited[HCO3] increases only about 1 mEq/L For each 10 mm Hg increase in PaCO2 above 40 mmHg

Chronic Respiratory Acidosis [HCO3] increases approximately 4 mEq/L for each 10 mm Hg increase in PaCO2

above 40 mm Hg

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Metabolic Acidosis primary decrease in [HCO3]

Respiratory Alkalosis primary decrease in PaCO2

Metabolic Alkalosis primary increase in plasma [HCO3]

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Interpretation of BGA ResultNormal pH or Acidosis or alkalosisNormally or Respiratory or metabolic disorder or both

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Diagnosis of simple acidbase disorders.

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Defining Acid-Based Disorders.Disorder Primary Change Compensatory Response

RespiratoryAcidosis PaCO2 HCO3-Alkalosis PaCO2 HCO3-

MetabolicAcidosis HCO3- PaCO2Alkalosis HCO3- PaCO2

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Base Excessamount of acid or base that must be added for blood pH to return to 7.40 and PaCO2 to return to 40 mm Hg at full O2 saturation and 37Cpositive value indicates metabolic alkalosis negative value reveals metabolic acidosis

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Correct a Base Deficit (BD) BD x 30 % x BW in LIn practice, only 50% of the calculated dose is usually given

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Case Study 1A 57 old man with post operative. craniotomy found to be tachypnea, somnolent. Initial blood gas analysis was :pH 7.556PCO2 31.3 mmHgPO2 142 mmHgHCO3 28.8 mmol/LBEecf 7 mmol/LSO2 100%

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What is the types of disorder ?How to manage this patients to improve BGA result?

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Case Study 2A 50 years old man, BGA post operative thoracotomi, founds :pH 7.31pCO2 50 mmHgpO2 72 mmHgHCO3- 25.2 mmol/LBEecf -1.1 mmol/LSO2 93%

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What is the types of disorder ?How to manage this patients to improve BGA result?

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How patients compensate?If there are respiratory disorder, body compensates with metabolic conditionsIf there are metabolic disorder, body compensates with respiratory conditions

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Normal Compensatory Responses in AcidBase DisturbancesDisturbance ResponseExpected ChangeRespiratory acidosis Acute [HCO3] 1 mEq/L/10 mm Hg increase in PaCO2 Chronic [HCO3] 4 mEq/L/10 mm Hg increase in PaCO2

Respiratory alkalosis Acute [HCO3] 2 mEq/L/10 mm Hg decrease in PaCO2Chronic [HCO3] 4 mEq/L/10 mm Hg decrease in PaCO2Metabolic acidosis PaCO2 1.2 x the decrease in [HCO3]Metabolic alkalosis PaCO2 0.7 x the increase in [HCO3]

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Case 3Calculate the amount of NaHCO3 necessary to correct a base deficit (BD) of 10 mEq/L for a 70-kg man with an estimated HCO3 space of 30%:

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50% of the calculated dose =105 mEq

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