General discussion about ABG

1. ARTERIAL BLOOD GASES
By
Nafees Ahmad
Residency From Mount Sinai School of Medicine, New York

2. 1) We started ICU in December 2014.
2) We have so far received 505 patient
3) Majority of patient are from Medical ward but we have received from
Surgery, Orthopedic, OBGYN as well.
4) I will like to thank all consultants who have sent patient to ICU but
especially
Medical consultants
5) I will also thank Dr Ghias and Dr Ishaq
6) Last but not the least Prof. Dr Najib Ul Haq

4. HE RECOVERED AFTER SPENDING
ONE MONTH ON VENTILATOR
MACHINE.

11. 1) SITE
2) COLLECTION
3) TRANSPORT
4) PRIMARY ACID BASE DISORDERS
5) COMPENSATION

12. DEFINATION
An arterial blood gas (ABG) is a test that measures
1) oxygen tension (PaO2)
2) carbon dioxide tension (PaCO2)
3) acidity (pH),
4) bicarbonate (HCO3) concentration

13. PH 7.35 – 7.45
PCO2 40
PO2 80-100
HCO3 24

14. INDICATIONS FOR ABG:
Indications for ABG sampling include the following :
1- Identification of respiratory, metabolic, and mixed acid-base disorders
2-Measurement of the partial pressures of respiratory gases involved in
oxygenation
3-Monitoring of acid-base status, as in patient with diabetic ketoacidosis
(DKA) on insulin infusion
4-Assessment of the response to therapeutic interventions such
as mechanical ventilation in a patient with respiratory failure
5-Determination of arterial respiratory gases during diagnostic evaluations
(e.g., assessment of the need for home oxygen therapy in patients with
advanced chronic pulmonary disease)

15. SITE ?

16. SITE:
Radial artery( ideal)
Brachial artery
Femoral Artery

17. MODIFIED ALLEN TEST

20. APPLY PRESSURE AT PUNCTURE SITE AFTER TAKING ABG

21. USE 3 ML SYRINGE AND FLUSH IT WITH 0.5
ML HEPARIN
DO NOT USE EXCESSIVE HEPARIN IN THE
SYRINGE BECAUSE IT CAUSE
DILUTIONAL EFFECT.
EXCESSIVE HEPARIN CAUSES DECREASE IN
PCO2 AND HCO3

22. WHY WE NEED HEPARIN ?

24. IF THERE ARE AIR BUBBLES IN THE
SYRINGE ????

25. AIR BUBBLES IN SYRINGE
Ensure that there are no AIR BUBBLES in the syringe
It is presumed that AIR BUBBLES contain PO2 150 and PCO2 0
AIR BUBBLES + BLOOD = PO2 GOES UP + PCO2 GOES DOWN
If air bubbles are present, then remove the air bubbles otherwise
discard the syringe

26. HOW ARTERIAL BLOOD SHOULD
BE TRANSPORTED TO ABG
MACHINE????

27. ABG Syringe should be transported to LAB via
cold chain at earliest
Changes in values
every 10 minutes
UNICED SAMPLE
AT 37 DEGREE
ICED SAMPLE AT
4 DEGREE
PH 0.01 0.001
PCO2 1 0.1
PO2 0.1% 0.01%

28. HOW MUCH BLOOD WE NEED FOR ABG ????

29. WHICH SYRINGE SHOULD BE USED ????
A)PLASTIC
B) GLASS

31. INTERPRETATION OF ABG

32. 1- METABOLIC ACIDOSIS
2- METABOLIC ALKALOSIS
3-RESPIRATORY ACIDOSIS
4-RESPIRATORY ALKALOSIS

33. METABOLIC ACIDOSIS
1) PH decreased
2) Body produces excessive quantities of acid
or
Kidney are not removing enough acid from the body
When there is metabolic acidosis, always calculate AG

34. 16
12
ANION GAP

35. Normal Anion Gap Metabolic acidosis:
Diarrhea,
RTA,
Anhydrase inhibitor
High Anion Gap Metabolic Acidosis:
M- methanol
U- Uremia
D- Dka
P- paraldehyde
I-Infection
E-Ethylene Glycol
S- salicyclates

36. DELTA GAP
1) Delta gap = ( Actual AG – 12) + HCO3-
2) If Delta gap is > 30, additional Metabolic alkalosis
3) If Delta gap is < 18, additional non AG Metabolic acidosis
4) If Delta gap is between 18-30, no additional metabolic problem

37. WHICH BODY SYSTEMS ARE INVOLVED IN COMPENSATION ????
COMPENSATION MEANS RESTORING NORMAL PH

38. 1)
2)
COMPENSATION

39. Respiratory compensation is fast,
it occurs in seconds to minutes

40. Renal compensation is slow

41. WHY WE NEED PH TO BE WITHIN
NORMAL LIMITS ????

43. IN METABOLIC ACIDOSIS, COMPENSATION OCCUR THROUGH
LUNGS
METABOLIC ACIDOSIS

44. UNCOMPENSATED
METABOLIC ACIDOSIS
PARTIALLY
COMPENSATED
METABOLIC ACIDOSIS
COMPENSATED
METABOLIC ACIDOSIS
PH 7.20 PH 7.30 PH 7.35
PCO2 40 (ACID) PCO2 33 PCO2 30.5
HCO3 15 (BASE) HCO3 15 HCO3 15
PO2 90 PO2 90 PO2 90
METABOLIC ACIDOSIS

45. In Metabolic Acidosis, if PCO2 level is achieved as per Winter`s formula
Expected pCO2 = 1.5 * HCO3
- + 8 +/- 2
Expected PCO2: 1.5 X 15 +8 = 30.5 +/- 2
METABOLIC ACIDOSIS
compensation

47. 1) PH increases
1) Decreased hydrogen ion concentration, leading to increased
bicarbonate,
2) Alternatively a direct result of increased bicarbonate
concentrations.
METABOLIC ALKALOSIS

48. 1) Excess vomiting
2) Overuse of diuretics
3) Adrenal disease
4) Antacids
5) Accidental ingestion of bicarbonate, which can be found in baking
soda
6) Laxatives
METABOLIC ALKALOSIS CAUSES

49. IN METABOLIC ALKALOSIS, COMPENSATION OCCUR THROUGH LUNGS

50. UNCOMPENSATED
METABOLIC
ALKALOSIS
PARTIALLY
COMPENSATED
METABOLIC
ALKALOSIS
COMPENSATED METABOLIC
ALKALOSIS
PH 7.55 PH 7.50 PH 7.45
PCO2 40 (ACID) PCO2 47 PCO2 51.2
HCO3 40 (BASE) HCO 40 HCO3 40
PO2 90 PO2 90 PO2 90
METABOLIC ALKALOSIS
Hypoventilation

51. METABOLIC ALKALOSIS
Compensation
For every increase in HCO3- by 1 mEq/L, PCO2 increases by 0.7 mmHG
So For increase in HCO3- by 16 mEq/L, PCO2 increase by 11.2 mmHG

53. Respiratory acidosis, also called respiratory failure or ventilatory
failure,
1) PH is decreased
2) Lungs can not remove enough CO2 from the body
RESPIRATORY ACIDOSIS

54. Asthma
Chronic obstructive pulmonary disease (COPD)
Acute pulmonary edema
Severe obesity (which can interfere with expansion of the
lungs)
neuromuscular disorders
Scoliosis
RESPIRATORY ACIDOSIS

55. RESPIRATORY ACIDOSIS

56. UNCOMPENSATED
RESPIRATORY ACIDOSIS
PARTIALLY COMPENSATD
RESPIRATORY ACIDOSIS
COMPENSATED
RESPIRATORY
ACIDOSIS
PH 7.20 PH 7.30 PH 7.35
PCO2 70 (ACID) PCO2 7 0 PCO2 70
HCO3 24 (BASE) HCO3 28 HCO3 34.5
PO2 ….. PO2 …… PO2 …..
RESPIRATORY ACIDOSIS

57. RESPIRATORY ACIDOSIS
Acute: For every increase in PCO2 by 10 mmHg, HCO3- should increase by 1
mEq/l
Chronic: For every increase in PCO2 by 10 mmHg, HCO3- should increase by
3.5 mEq/l
COMPENSATION

59. RESPIRATORY ALKALOSIS
1) PH increases
2) Alveolar hyper ventilation leading to decreased PCO2

60. Heart attack
Pain
Drug use
Asthma
Fever
Chronic obstructive pulmonary disease (COPD)
Infection
Pulmonary embolism
Pregnancy
RESPIRATORY ALKALOSIS CAUSES

61. RESPIRATORY ALKALOSIS

62. UNCOMPENSATED
RESPIRATOTY
ALKALOSIS
PARTIALLY COMPENSATED
RESPIRATORY ALKALOSIS
COMPENSATED
RESPIRATORY
ALKALOSIS
PH 7.55 PH 7.50 PH 7.45
PCO2 20 ( ACID) PCO2 20 PCO2 20
HCO3 24 ( BASE) HCO3 20 HCO3 16
PO2 90 PO2 90 PO2 90
RESPIRATORY ALKALOSIS

63. RESPIRATORY ALKALOSIS
COMPENSATION
Acute: For every decreases in PCO2 by 10 mmHg, HCO3- should decrease by 2 mEq/L
Chronic: For every decrease in PCO2 by 10 mmHg, HCO3- should decrease by 4 mEq/L