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DR BINOD KUMAR SINGHDR BINOD KUMAR SINGH Associate Professor, PMCH, PatnaAssociate Professor, PMCH, Patna
CIAP Executive board member- 2015 CIAP Executive board member- 2015 NNF State president,Bihar- 2014NNF State president,Bihar- 2014
IAP State secretary,Bihar-2010-2011IAP State secretary,Bihar-2010-2011 NNF State secretary,Bihar-2008-2009NNF State secretary,Bihar-2008-2009
Web site : www.shivshishuhospital.comWeb site : www.shivshishuhospital.com
ABG ABG INTERPRETATIONINTERPRETATION
ABG InterpretationABG Interpretation
First, does the patient have an First, does the patient have an acidosis or an alkalosisacidosis or an alkalosis
Second, what is the primary problem Second, what is the primary problem – metabolic or respiratory– metabolic or respiratory
Third, is there any compensation by Third, is there any compensation by the patient – respiratory the patient – respiratory compensation is immediate while compensation is immediate while renal compensation takes timerenal compensation takes time
ABG InterpretationABG Interpretation
It would be extremely unusual for It would be extremely unusual for either the respiratory or renal system either the respiratory or renal system to overcompensateto overcompensate
The pH determines the primary The pH determines the primary problemproblem
After determining the primary After determining the primary problem and compensatory problem and compensatory acid/base balance, always evaluate acid/base balance, always evaluate the effectiveness of oxygenationthe effectiveness of oxygenation
Normal ValuesNormal Values
pH - 7.35 to 7.45pH - 7.35 to 7.45paCOpaCO2- 2- 36 to 44 mm Hg 36 to 44 mm Hg
Putting It Together - Putting It Together - RespiratoryRespiratory
SoSo
paCOpaCO22 > 44 with a pH < 7.35 represents a > 44 with a pH < 7.35 represents a respiratory acidosisrespiratory acidosis
paCOpaCO22 < 36 with a pH > 7.45 represents a < 36 with a pH > 7.45 represents a respiratory alkalosisrespiratory alkalosis
For a primary respiratory problem, pH and For a primary respiratory problem, pH and paCOpaCO22 move in the opposite direction move in the opposite direction For each deviation in paCOFor each deviation in paCO22 of 10 mm Hg in of 10 mm Hg in
either direction, 0. 08 pH units change in the either direction, 0. 08 pH units change in the opposite directionopposite direction
Putting It Together - Putting It Together - MetabolicMetabolic
AndAnd
HCOHCO33 < 22 with a pH < 7.35 < 22 with a pH < 7.35 represents a metabolic acidosis represents a metabolic acidosis
HCOHCO33 > 26 with a pH > 7.45 > 26 with a pH > 7.45 represents a metabolic alkalosisrepresents a metabolic alkalosis
For a primary metabolic problem, pH For a primary metabolic problem, pH and HCOand HCO33 are in the same direction, are in the same direction, and paCOand paCO22 is also in the same is also in the same directiondirection
CompensationCompensation
The body’s attempt to return the The body’s attempt to return the acid/base status to normal (i.e. pH acid/base status to normal (i.e. pH closer to 7.4)closer to 7.4)
Primary ProblemPrimary Problem CompensationCompensation
CO2 IS A RESPIRATORY ACIDCO2 IS A RESPIRATORY ACIDPh and HCO3- Move in same direction.Ph and HCO3- Move in same direction.pH and PCO2- Move in opposite pH and PCO2- Move in opposite
direction.direction.HCO3 and PCO2- Move in same HCO3 and PCO2- Move in same
direction-simple disorder.direction-simple disorder.HCO3 and PCO2- Move in opposite HCO3 and PCO2- Move in opposite
Respiratory acidosisRespiratory acidosisAcute – the pH decreases 0.08 units for Acute – the pH decreases 0.08 units for
every 10 mm Hg increase in paCOevery 10 mm Hg increase in paCO22; ; HCOHCO33 1 mEq/liter per 1 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22
Chronic – the pH decreases 0.03 units Chronic – the pH decreases 0.03 units for every 10 mm Hg increase in paCOfor every 10 mm Hg increase in paCO22; ; HCOHCO33 4 mEq/liter per 4 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22
Expected CompensationExpected Compensation
Respiratory alkalosisRespiratory alkalosisAcute – the pH increases 0.08 units for Acute – the pH increases 0.08 units for
every 10 mm Hg decrease in paCOevery 10 mm Hg decrease in paCO22; ; HCOHCO33 2 mEq/liter per 2 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22
Chronic - the pH increases 0.03 units for Chronic - the pH increases 0.03 units for every 10 mm Hg decrease in paCOevery 10 mm Hg decrease in paCO22; ; HCOHCO33 4 mEq/liter per 4 mEq/liter per 10 mm Hg paCO10 mm Hg paCO22
paCOpaCO22 is elevated and pH is acidotic is elevated and pH is acidoticThe decrease in pH is accounted for The decrease in pH is accounted for
entirely by the increase in paCOentirely by the increase in paCO22
Bicarbonate and base excess will be Bicarbonate and base excess will be in the normal range because the in the normal range because the kidneys have not had adequate time kidneys have not had adequate time to establish effective compensatory to establish effective compensatory mechanismsmechanisms
paCOpaCO22 is elevated with a pH in the is elevated with a pH in the acceptable rangeacceptable range
Renal mechanisms increase the Renal mechanisms increase the excretion of Hexcretion of H++ within 24 hours and within 24 hours and may correct the resulting acidosis may correct the resulting acidosis caused by chronic retention of COcaused by chronic retention of CO2 2 to to a certain extenta certain extent
paCOpaCO22 is low and the pH is alkalotic is low and the pH is alkaloticThe increase in pH is accounted for The increase in pH is accounted for
entirely by the decrease in paCOentirely by the decrease in paCO22
Bicarbonate and base excess will be Bicarbonate and base excess will be in the normal range because the in the normal range because the kidneys have not had sufficient time kidneys have not had sufficient time to establish effective compensatory to establish effective compensatory mechanismsmechanisms
Normal paCONormal paCO22, low HCO, low HCO33, and a pH , and a pH less than 7.30less than 7.30
Occurs as a result of increased Occurs as a result of increased production of acids and/or failure to production of acids and/or failure to eliminate these acidseliminate these acids
Respiratory system is not Respiratory system is not compensating by increasing alveolar compensating by increasing alveolar ventilation (hyperventilation)ventilation (hyperventilation)
paCOpaCO22 less than 30, low HCO less than 30, low HCO33, with a , with a pH of 7.3-7.4pH of 7.3-7.4
Patients with chronic metabolic Patients with chronic metabolic acidosis are unable to hyperventilate acidosis are unable to hyperventilate sufficiently to lower paCOsufficiently to lower paCO22 for for complete compensation to 7.4complete compensation to 7.4
Effectiveness of OxygenationEffectiveness of Oxygenation
Further evaluation of the arterial blood gas Further evaluation of the arterial blood gas requires assessment of the effectiveness requires assessment of the effectiveness of oxygenation of the bloodof oxygenation of the blood
Hypoxemia – decreased oxygen content of Hypoxemia – decreased oxygen content of blood - paOblood - paO22 less than 60 mm Hg and the less than 60 mm Hg and the saturation is less than 90%saturation is less than 90%
Hypoxia – inadequate amount of oxygen Hypoxia – inadequate amount of oxygen available to or used by tissues for available to or used by tissues for metabolic needsmetabolic needs
Mechanisms of HypoxemiaMechanisms of Hypoxemia
Inadequate inspiratory partial Inadequate inspiratory partial pressure of oxygenpressure of oxygen
HypoventilationHypoventilationRight to left shuntRight to left shuntVentilation-perfusion mismatchVentilation-perfusion mismatch Incomplete diffusion equilibriumIncomplete diffusion equilibrium
Assessment of Gas ExchangeAssessment of Gas Exchange
Normal A a gradient with hypoxemia- Normal A a gradient with hypoxemia- ventilation failure/hypoventilationventilation failure/hypoventilation
Assessment of Gas ExchangeAssessment of Gas ExchangeABGABG A-a gradA-a grad
PaOPaO22 PaCOPaCO22 RARA 100%100%
Low FIOLow FIO22 N*N* NN
Alveolar hypoventilationAlveolar hypoventilation NN NN
Altered gas exchangeAltered gas exchange
Regional V/Q mismatchRegional V/Q mismatch /N//N/ N/N/ Intrapulmonary R to L shuntIntrapulmonary R to L shunt N/N/ Impaired diffusionImpaired diffusion N/N/ NN
Anatomical R to L shuntAnatomical R to L shunt
(intrapulmonary or intracardiac)(intrapulmonary or intracardiac) N/N/ * N=normal* N=normal
INDICATION FOR ECMOINDICATION FOR ECMO
IF iNO VENTILATION INCLUDING HFO VENTILATION UNABLE TO SUSTAIN LIFE
IF AO2-aO2 GRADIENT OF MORE THAN 600 mmHg FOR 6 TO 12 hrs
VENTILATION INDEX= [ (RR * PIP * paCO2 ) / 1000 ] , of more than 90 for 4 hr
OXYGENATION INDEX= (MAP * FiO2) Post-ductal paO2
, of more than 40 in two ABGs at 1 hr apart
ABG REPORT - SHIV SHISHU HOSPITAL PATNAABG REPORT - SHIV SHISHU HOSPITAL PATNA DATE/TIME 27:07:2011 12:12DATE/TIME 27:07:2011 12:12 SAMPLE No- 5388SAMPLE No- 5388 Pat ID B N 5 Pat ID B N 5 Sample type arterial blood Sample type arterial blood BARO- 747.2mm HgBARO- 747.2mm Hg Temp- 37.0 CTemp- 37.0 C A/F FETALA/F FETAL PO2 82.5 mmHg(80.0-100.0PO2 82.5 mmHg(80.0-100.0 PCO2 36 mmHg(-)(35.0-45.0)PCO2 36 mmHg(-)(35.0-45.0) pH 7.393 (7.350-7.450)pH 7.393 (7.350-7.450) Na 143.1 mmol/L(135.0-148.0)Na 143.1 mmol/L(135.0-148.0) Cl 104.1 mmol/L(98.0-107.0)Cl 104.1 mmol/L(98.0-107.0) Ica 1.267 mmol/L(1.120-1.320)Ica 1.267 mmol/L(1.120-1.320) K 3.74 mmol/L(3.50-4.50) K 3.74 mmol/L(3.50-4.50) Hct 49.7 % (35.0-50.0)Hct 49.7 % (35.0-50.0) BE -3.6 mmol/LBE -3.6 mmol/L BEecf -4.5 mmol/LBEecf -4.5 mmol/L CHCO3st 23 mmol/LCHCO3st 23 mmol/L P50 21.5 mmHgP50 21.5 mmHg ctO2 20.7 vol%ctO2 20.7 vol%
First, does the patient have an acidosis or First, does the patient have an acidosis or an alkalosis an alkalosis Look at the pHLook at the pH
Second, what is the primary problem – Second, what is the primary problem – metabolic or respiratorymetabolic or respiratory Look at the pCOLook at the pCO22
If the pCOIf the pCO22 change is in the opposite direction change is in the opposite direction of the pH change, the primary problem is of the pH change, the primary problem is respiratoryrespiratory
SummarySummary
Third, is there any compensation by Third, is there any compensation by the patient - do the calculationsthe patient - do the calculationsFor a primary respiratory problem, is the For a primary respiratory problem, is the
pH change completely accounted for by pH change completely accounted for by the change in pCOthe change in pCO22if yes, then there is no metabolic if yes, then there is no metabolic
compensationcompensationif not, then there is either partial if not, then there is either partial
compensation or concomitant metabolic compensation or concomitant metabolic problemproblem
SummarySummary
For a metabolic problem, calculate the For a metabolic problem, calculate the expected pCOexpected pCO22if equal to calculated, then there is if equal to calculated, then there is
appropriate respiratory compensationappropriate respiratory compensationif higher than calculated, there is if higher than calculated, there is
concomitant respiratory acidosisconcomitant respiratory acidosisif lower than calculated, there is if lower than calculated, there is
Next, don’t forget to look at the Next, don’t forget to look at the effectiveness of oxygenation, (and effectiveness of oxygenation, (and look at the patient)look at the patient)your patient may have a significantly your patient may have a significantly
increased work of breathing in order to increased work of breathing in order to maintain a “normal” blood gasmaintain a “normal” blood gas
metabolic acidosis with a concomitant metabolic acidosis with a concomitant respiratory acidosis is concerningrespiratory acidosis is concerning