arterial blood gas analysis - anion gap - diabetic ketoacidosis

1. Dr. Ashutosh kumar
(ABG )
ARTERIALBLOOD GAS

2. What is ABG ?
Blood gas analysis, also called Arterial Blood Gas (ABG)
analysis, is an invasive test which measures the amount of
oxygen (O2 ) and carbon dioxide (CO2 ) in the blood, as well
as the acidity (pH) of the blood.

3. Contents & normal values

4. Purpose of doing ABG !!!
• Evaluates how effectively the lungs are delivering O2 to
the blood and how efficiently they are eliminating CO2
from it.
• Indicates how well the lungs and kidneys are interacting to
maintain normal blood pH (acid-base balance).
• Assess respiratory disease and other conditions that may
affect the lungs, and to manage patients receiving oxygen
therapy (respiratory therapy).

5. Cont..
• Determine the pH of the blood and the partial pressures
of carbon dioxide (PaCO2 ) and oxygen (PaO2 ) within it.
• Assess the effectiveness of gaseous exchange and
ventilation, be it spontaneous or mechanical.
• Assess metabolic status of the patient, giving an
indication of how they are coping with their illness

6. Complication of arterial puncture

7. Contraindications

8. Allen’s test

9. ABG Interpretation
ABG Basic interpretation can be done by 6 easy steps.

10. Basic terminology

11. Step1 - Analyze pH
Normal blood pH is 7.4 (range 7.35 to 7.45).
• pH < 7.35 acidic.
• pH > 7.45 alkaline.
• If it falls into the normal range, label what side of
7.4 it falls on. Lower than 7.4 is normal/acidic,
higher than 7.4 is normal / alkalotic.

12. Step 2 - Analyze pCO2
Normal pCO2 levels = 35-45mmHg
• Below 35 is alkaline,
• Above 45 is acidic.

13. Step 3 – Analyze HCO3
Normal HCO3 level is 22-26 mEq/L.
• If the HCO3 is below 22, the patient is acidotic.
• If the HCO3 is above 26, the patient is alkalotic

14. Step 4 – Match Co2 or HCO3 with pH
If the pH is acidotic, and the CO2 is acidotic, then the
acid-base disturbance is being caused by the
respiratory system.
Therefore, we call it a respiratory acidosis.
• However, if the pH is alkalotic and the HCO3 is
alkalotic, the acid-base disturbance is being caused by
the metabolic (or renal) system.
Therefore, it will be a metabolic alkalosis.

15. Step-5 Does Co2 & HCO3 going in
opposite direction of pH???
If so, there is compensation by that system.
• For example, the pH is acidotic, the CO2 is acidotic,
and the HCO3 is alkalotic: The CO2 matches the pH
making the primary acid-base disorder i.e. respiratory
acidosis.
The HCO3 is opposite of the pH and would be
evidence of compensation from the metabolic system.

16. Compensation

17. Cont…

18. Step-6 -Analyze PO2 & O2 saturation
If they are below normal there is evidence of
hypoxemia.

19. Interpretation of Values

20. Arterial Vs Venous sample

21. Anion Gap
The anion gap is the difference between primary
measured cations (sodium Na+ and potassium K+) and
the primary measured anions (chloride Cl- and
bicarbonate HCO3-) in serum.
Normal Anion Gap is 12 +/- 2

22. Anion Gap Metabolic acidosis

23. Non anion gap metabolic acidosis

24. Respiratory Failure
Type I Respiratory Failure:
( Diffusion defect; CO2 diffusion is better; Eg: Pneumonia, Pulmonary
edema)
•  pO2 , but normal pCO2
• Type II Respiratory Failure:
( Respiratory gases not reaching alveoli for proper gaseous exchange;
Eg: HMD , Respiratory paralysis in Polio )
•  pO2 and  pCO2

25. DIABETIC KETOACIDOSIS

26. What is DKA??
Diabetic ketoacidosis (DKA) is an acute, life-
threatening complication of diabetes mellitus.
DKA occurs predominantly in patients with type 1
(insulin-dependent) diabetes mellitus.

27. Pathophysiology

28. Pathophysiology

29. Causes of DKA

30. Types
Types pH Hco3 Anion Gap
Mild 7.25-7.3 15-18 mEq/L >10 mEq/L
Moderate 7.0-7.24 10-15 mEq/L >12mEq/L
Alert / Drowsy
Severe < 7.0 <10 mEq/L >12 mEq/L
Stuporous
Comatose

32. Symptoms

33. Physical examination findings

34. Classic triad of DKA

35. Diagnosis
• blood glucose level >250 milligrams/dL (13.9 mmol/L)
• anion gap >10 to 12 mEq/L (>10 mmol/L)
• a bicarbonate level <15 mEq/L (<15 mmol/L)
• pH <7.3 with moderate ketonuria or ketonemia

36. Differential diagnosis

37. Treatment

38. Fluids & electrolytes

39. Initial fluid resuscitation

40. Cont..

41. Insulin therapy

42. Once DKA resolved

43. Complications of DKA