quiz Arterial Blood Gas Analysis 28-3-2024.ppt

cases with ABG for interpretation as quizz

1. Arterial Blood Gas Analysis
Anwar Yusr
Critical Care Consultant
Egyptian Fellowship in ICU 2015
USTH
28/4/2024

2. Six step method
1)Identifyanyabnormality(isthereacidemiaor
alkalemia?)
2)Istheprimaryprocessmetabolicorrespiratory?
3)Iftheprimaryprocessisrespiratory,isitacuteor
chronic?
4)Isthecompensationadequate?
5)IsthereanAG?
6)Isthereamixeddisorder?

3. Case:A Man with CCF and Vomiting
A70yearoldmanwasadmittedwithseverecongestive
cardiacfailure.Hehasbeenunwellforaboutaweekand
hasbeenvomitingfortheprevious5days.Hewasonno
medication.Hewashyperventilatingandwasvery
distressed.Admissionbiochemistryislistedbelow.He
wasonhighconcentrationoxygenbymask.
Biochemistryresults:Na
+
127,K
+
5.2,Cl
-
79,HCO3
-
20,urea50.5,
creatinine0.38&glucose171mg/dl.
Arterial Blood Gases
pH 7.58
pCO2 21mmHg
pO2 154mmHg
HCO319mmol/l

4. Initial Assessment
The historysuggests the following possibilities:
Respiratoryalkalosisinresponsetothe
dyspneaassociatewiththecongestiveheart
failure.
Alacticacidosisispossibleifcardiacoutputis
lowandtissueperfusionispoor.
Vomitingsuggests metabolic alkalosis.

5. Six Steps for Acid-Base Analysis
Step 1.
Is there an acidemia or alkalemia?
PH 7.58
Alkalaemia

6. Six Steps for Acid-Base Analysis
Step 2.
Istheprimaryprocessmetabolicor
respiratory?
PCO
2= 21 should drive pH ↑
HCO
3
-
= 19 should drive pH ↓
The primary disorder is a
respiratory alkalosis.

7. Six Steps for Acid-Base Analysis
Step 3:
Iftheprimaryprocessisrespiratory,is
itacuteorchronic?
From history its chronic.

8. Six Steps for Acid-Base Analysis
Step 4:
Is there an anion gap?
AG= Na
+
-(Cl
-
+ HCO
3
-
)> 12?
127 –(79 + 19) = 29!!
Anion Gap Metabolic Acidosis

9. Six Steps for Acid-Base Analysis
Step 5:
Isthemetaboliccompensationadequate?
Expected Hco3range:
chronic respiratory alkalosis
(using rule -"the 5 for 10" rule)
TheexpectedHCO3is (24 -10) = 14.
TheactualHCO3ishigher(19)whichindicates
thepresenceofametabolicalkalosis.

10. Final Assessment
Thispatienthasatripleacid-basedisorder:
1.Acutemetabolicacidosisprobablydueto
renalfailure(?prerenalfailure)andpossiblyto
lacticacidosis(hypoperfusiondueheartfailure
andhypovolaemia).
2.Metabolicalkalosisduetoseverevomiting.
3.Respiratoryalkalosisduetodyspnoeafrom
congestiveheartfailure.

11. Triple acid-base disorder:
1.Respiratory alkalosis,
2.High anion gap metabolic acidosis
3.Metabolic alkalosis.
Lactate
VOMITING
Dyspnea
CHF

12. CASE 2
A57-year-oldmanwithahistoryoftype1diabetes
mellitusisevaluatedintheemergencydepartmentfor
severeabdominalpain,nausea,andvomiting.heis
admittedtotheICU,pulse120/min,BP80/60.
ABGwasdoneandrevealed:
PH 7.12
PaCO240 mmHg
PaO2 60 mmHg on room air
HCO315 mmHg
Na 145
K 3.1
Cl 95
RBS 220 mmHg
What is the acid base status of this patient?
What is most probable cause?

13. Six Steps for Acid-Base Analysis
Step 1.
Is there an acidemia or alkalemia?
Acidemia

14. Six Steps for Acid-Base Analysis
Step 2.
Istheprimaryprocessmetabolicor
respiratory?
PCO
2 = 40
HCO
3
-
= 15 should drive pH ↓

15. Six Steps for Acid-Base Analysis
Step 3:
Iftheprimaryprocessisrespiratory,is
itacuteorchronic?
Skip this step as primary process is
metabolic!

16. Six Steps for Acid-Base Analysis
Step 4:
Is there an anion gap?
AG= Na
+
-(Cl
-
+ HCO
3
-
)> 12?
145 -95 -15 = 35!!
Anion Gap Metabolic Acidosis

17. Six Steps for Acid-Base Analysis
Step 5:
Istherespiratorycompensationadequate?
Expected pCO
2 range = Winter formula:
[1.5 x Hco3 + 8 +/-2
[1.5 (15) +8] +/-2 = [30.5 –32.5]
PCO
2=40,thereforethereisconcomitant
respiratoryAcidosis.

18. Six Steps for Acid-Base Analysis
Step 6:
Are there any other metabolic disturbances?
decrease in plasma bicarbonate = increase in AG
Anion Gap= 35 –12 = 23
HCO
3 = 24 –15 = 9
SO
Change in AG >> Change in Bicarb
Sincethisovercorrectsbicarbonatethereis
ametabolicALKALOSIS!!
> 2

19. Final Assessment
Inthiscase,theaniongapis35soananiongap
metabolicacidosismustbepresent.DKA
Thebodyattemptstocompensateby
hyperventilatinginordertoremovecarbon
dioxide.butthePaco2doesnotdecreaseatall
from40mmHg.RespiratoryAcidosis.
Inthiscase,thepatientwasadmittedfornausea
andvomiting,whichcouldleadtoamixed
picture,includingametabolicalkalosis.

20. 1.Anion Gap Metabolic Acidosis.
2.Concurrent Respiratory Acidosis.
3.Metabolic Alkalosis.
DKA
VOMITING
Respfailure

21. MetabolicAcidosis—Bad??
Impairedcardiaccontractility.
DecreasedthresholdforVF.
DecreasedHepaticandRenalperfusion.
IncreasedPulmonaryVascresistance.
Inabilitytorespondtocatecholamines.
Vascularcollapse.

22. “UnderstandingABGisnot
Magicbutanartlearnedby
continuedpractice”