Pediatric Critical Care ChapterIndonesian Pediatric Society2012

IntroductionBlood gas: O2, CO2, CO, Nitrogen, Helium (

>> H+OH-

Normal ValuesTable 1. Normal value of blood gas analysis (at sea level, FiO2 21%)

ArterialMixed veinVeinpH7,47,367,36Range pH7,35 7,457,31 7,417,31 7,41pO2 mmHg80 100 35 40 30 50 pCO2 mmHg35 45 41 51 40 52 Sat O2 > 95%60 80% 60 85%HCO3- 22 26 22 26 22 28 Base Excess-2 +2 -2 +2-2 +2

PaCO2: Partial pressure of CO2 dissolved within the arterial bloodAssess the effectiveness of ventilation

VCO2: minute CO2 productionVa: minute ventilation = TV x RR

PaCO2 and Ventilation Status Table 2. Interpretation of PaCO2 and ventilation status

PaCO2BloodVentilation status> 45 mmHgHypercapniaHypoventilation35 45 mmHgEucapniaNormal< 35 mmHgHypocapniaHyperventilation

Indicators used to assess oxygenation : PaO2 (Partial pressure of oxygen dissolved within the arterial blood)SaO2 (Arterial blood oxygen saturation)P(A-a)O2 (Alveolar to arterial O2 tension difference)PaO2/FiO2 (Arterial to fraction of inspired O2 ratio

PaO2At sea level, the normal PaO2 :Newborn : 40-70 mmHg with increasing age PaO2 increases until adult value of 90-120 mmHg Hypoxemia :PaO2 lower than the acceptable range for age For a child PaO2 < 60 mmHg

P(A-a)O2 Normal (at sea level / 760 cm Hg): < 25 mm Hg (according to age)P(A-a)O2 > 25 mm Hg : oxygen diffusion disturbance (right to left shunt)P(A-a)O2 = (PB P H2O) FiO2 (PaCO2 : 0.8)

Henderson-HasselbalchStewarts ApproachTo Evaluate Acid-Base Disorder

Steps to analyze acid-base disorder(Grogono method 2005)Step 1 : Analyze the pHStep 2 : Analyze the PaCO2Step 3 : Analyze SBEStep 4 : analyze severity PaCO2 and SBE Step 5 : Compensation

Step 1 : Analyze the pH

Step 2 : Match the PaCO2 with the pH

Table 3. Interpretation of correlation between pH and pCO2

pHPaCO2Interpretation< 7.35(acid)> 45 mmHg(acid)Respiratory acidosis>7.45(alkali)< 35 mmHg(alkali)Respiratory alkalosis

Step 3 : Match the SBE with the pH

Table 4. Interpretation of correlation between pH and SBE

pHSBEInterpretation< 7.35(acid)(acid)Metabolic acidosis>7.45(alkali)(alkali)Metabolic alkalosis

Step 4 : Assess acid-base disorder severityTable 5. Acid base disorder severity

DisorderInterpretationPaCO2(mmHg)SBE(mEq/L)AlkalosisVery severeSeveremoderatemild< 1818 2525 3030 35 > 1313 99 66 2 NormalNormal 35 - 452 to -2Acidosis MildmoderateSevereVery severe45 5050 5555 62> 62-2 to -6-6 to -9-9 to -13< -13

Step 5 : Analyze the compensation Compensation level 3 SBE for 5 PaCO2 or using the formula

Table 6. Correlation among [HC03-, PaC02 and SBE in acid-bace disorders

Kellum, JA. Critical Care 2005; 9:500-7

DisordersHCO3 (mEq/L) PaC02 (mm Hg)SBE (mEq/L)

Metabolic Acidosis < 22(1,5 x HC03 )+ 8 40 + SBE- 5Metabolic Alkalosis>26(0,7 x HCO3 + 21 10+(0,6 x SBE)> +5Acute Respiratory Acidosis[(PaCO2 40)/10] +24 >450Chronic Respiratory Acidosis[(PaC02 - 40)/3]+24>450Acute Respiratory Alkalosis24 - [(40 PaCO25]< 350Chronic Respiratory alkalosis 24 - [(40 PaCO2/2] < 350,4 (PaC02 - 40)

Table 7. Acid-Base Disorder Interpretation

pHPaCO2SBEInterpretationCompensationAcid Acid Alkali Respiratory acidosiswith compensationPartial SBE,Normal metabolic compensationNormal Pure respiratory acidosisNormal SBE,No compensationAlkali Acid Metabolic acidosis with compensationPartial PaCO2,Normal respiratory compensationAlkali Alkali AcidRespiratory alkalosis with compensationPartial SBE,Normal metabolic compensationNormalPure respiratory alkalosisNormal SBE,No compensationAcid Alkali Metabolic alkalosis with compensationPartial PaCO2,Normal respiratory compensation

Table 8. Acid-Base Disorder Interpretation

pHPaCO2SBEInterpretationCompensationAcid Acid Acid Mixed acidosisunmeasurableNormal Acid Pure metabolic acidosisNormal PaCO2 , No respiratory compensationAlkali Alkali AlkaliMixed alkalosisunmeasurableNormalAlkali Pure metabolic alkalosisNormal PaCO2,No respiratory compensation

Example pH: 7,15PaCO2: 60 mmHgSBE: - 6 mEq/LInterpretation?pH: acidosisPaCO2 : respiratory acidosisSBE : metabolic acidosisCompensation : (-) (acidosis and acidosis) Severe respiratory acidosis and mild metabolic acidosis

Example pH: 7,3PaCO2: 60 mmHgSBE: 7 mEq/LInterpretation?pH: acidosisPaCO2 : respiratory acidosisSBE : metabolic alkalosisCompensation : (+) ?

Expected compensation : PaCO2 : 60 40 = 20 mmHgSBE = 20 x 3/5 = 12 mEq/LActual value :SBE = 7 mEq/L Partial compensation Severe respiratory acidosis with moderate metabolic alkalosis as compensation

pH : 7,45 (Normal)SBE : AcidPCO2 : AcidKesan : Awalnya Alkalosis respiratorik, terkompensasiSaran : BGA UlangAlternatif : Asidosis metabolik, yang terkompensasi respiratorik