# ABG interpretation

Respiratory Care Student um UOD
24. Jun 2015
1 von 34

### ABG interpretation

• 2. INTRODUCTION: Interpreting an arterial blood gas (ABG) is a crucial skill for physicians, nurses, respiratory therapists, and other health care personnel. ABG interpretation is especially important in critically ill patients.
• 3. Arterial blood gasses provide information about : • Oxygenation • ventilation • acid-base balance.
• 4. 6 STEPS TO INTERPRET ABG RESULT: Step 1#: analyze the PaO2 and the SaO2 Step 2#: analyze the pH Step 3#: analyze the CO2 Step 4#: analyze the HCO3 Step 5#: match the CO2 or the HCO3 with the pH. Step 6#: does the CO2 or the HCO3 go opposite direction of the pH?
• 5. The PaO2 only tells you if you need to give a patient more oxygen or if you need to cut back on supplemental oxygen. These are normal values for arterial blood gases. opH= 7.35 – 7.45 oPaCO2= 35 – 45 mmHg oPaO2= 80 – 100 mmHg oHCO3= 23 – 26 MEq/L When interpreting ABGs, the most important values to look at are pH, PaCO2, and HCO3.
• 7. STEP 1#: ANALYZE THE PAO2 AND THE SAO2 PaO2 is depend upon : Age FiO2 Patm paO2 : Partial pressure of oxygen molecules dissolved in plasma.
• 8. PAO2: If the patient is hypoxemic, the low oxygen content in his blood will be reflected in low PaO2 and SaO2 values. Mild hypoxemia ,PaO2 of (60-79) mmHg. moderate hypoxemia, (40-59) mm Hg. severe hypoxemia, less than 40 mm Hg.
• 9. SAO2: Normal range (96% - 100%)
• 10. P/F RATIO: P:F ratio is the ratio of arterial oxygen concentration to the fraction of inspired oxygen. It reflects how well the lungs absorb oxygen from expired air. Based on Berlin definition: • mild (from 200 to 300), • moderate (from 100 to 200) • and severe (≤100  mmHg).
• 11. O2 CONTENT : Arterial oxygen content CaO2 is the amount of oxygen bound to hemoglobin plus the amount of oxygen dissolved in arterial blood. CaO2 = (Hgb x 1.36 x SaO2) + (0.0031 x PaO2) Normal CaO2 ranges from (16 – 22) ml O2/dl.
• 12. SCENARIO: A patient who presented to the ER with headache and dyspnea & h/o exposure to smoke in a closed room. His first blood gases showed Pao2 80 mmHg, PaCO2 38 mmHg, pH 7.43. and oxygenation was judged normal. He was sent out from the ER and returned a few hours later with mental confusion. This time both SaO2 and COHb were measured; paO2 79 mmHg,PaCO2 31 mmHg, pH7.36,SaO2 53%, carboxyhemoglobin 46%.  CO poisoning
• 13. CO POISONING: • SaO2 = NORMAL “false value on pulse oximetry” • PaO2 = NORMAL Symptoms: Cherry red color instead of cyanosis (even though there is Hypoxia), its because of the red pigment of CO, headache and dizzness . CARBOXYHEMOGLOB IN TEST CO-OXIMETRY
• 14. CARBOXYHEMOGLOBIN TEST:  Headache and nausea can begin when levels are 10 to 20%.  Levels > 20% commonly cause vague dizziness, generalized weakness, difficulty concentrating, and impaired judgment. Levels > 30% commonly cause dyspnea during exertion, chest pain (in patients with coronary artery disease), and confusion.  Higher levels can cause syncope, seizures, and obtundation.  Hypotension, coma, respiratory failure, and death may occur, usually when levels are > 60%.
• 16. 6 STEPS TO INTERPRET ABG RESULT: Step 1#: analyze the PaO2 and the SaO2 Step 2#: analyze the pH Step 3#: analyze the CO2 Step 4#: analyze the HCO3 Step 5#: match the CO2 or the HCO3 with the pH. Step 6#: does the CO2 or the HCO3 go opposite direction of the pH?
• 17. STEP 2#: ANALYZE THE pH: pH < 7.35 7.35-7.45 > 7.45 Acidosis Normal or Compensated Alkalosis •This is usually the primary disorder •Remember: an acidosis or alkalosis may be present even if the pH is in the normal range (7.35 – 7.45) HOW?? When it is fully compensated and that will be described later.
• 18. STEP 3#: ANALYZE THE CO2 PaCO2 < 35 35 -45 > 45 • Tends toward alkalosis •Causes high pH Normal or Compensated • Tends toward acidosis •Causes low pH
• 19. STEP 3#: ANALYZE THE HCO3: HCO3 < 22 22-26 > 26 •acidosis •Causes low pH Normal or Compensated •Alkalosis •Causes high pH
• 20. STEP 5+6#: MATCH THE CO2 OR THE HCO3 WITH THE pH. Acidosis Respiratory pH ↓ PaCO2 ↑ HCO3 N Acidosis Metabolic pH ↓ PaCO2 N HCO3 ↓ Alkalosis Respiratory pH ↑ PaCO2 ↓ HCO3 N Alkalosis Metabolic pH ↑ PaCO2 N HCO3 ↑ Acidosis mixed pH ↓ PaCO2 ↑ HCO3 ↓ What is the relationship between the direction of change in the pH and the direction of change in the PaCO2? In primary respiratory disorders, the pH and PaCO2 change inapposite directions; in metabolic disorders the pH and PaCO2 change in the same direction.
• 21. Metabolic Respirator y Acute chronicAnion gap Alkalosis Acidosis pH PaCO2
• 22. IF IT’S RESPIRATORY: ACUTE OR CHRONIC? Expected changes in pH for a 10-mmhg change PaCO2 resulting from either primary respiratory acidosis or respiratory alkalosis: • Respiratory acidosis pH↓ by 0.08 pH↓ BY 0.03 • Respiratory alkalosis pH↑by 0.08 pH↑by 0.03 Acute Chronic
• 23. COMPENSATED OR NOT: The body compensates for acid-base imbalance through either the lungs or the kidneys. If PaCO2 is abnormal and pH is normal, it indicates compensation.  pH > 7.4 would be a compensated alkalosis.  pH < 7.4 would be a compensated acidosis. Respiratory compensation  Complete within 24hrs Metabolic compensation  Complete within several days Both the respiratory or renal compensation almost never over compensates.
• 24. PARTIALLY COMPENSATED: With partially compensated ABGs, the body has begun to correct the acid-base problem via either the lungs or the kidneys. The pH has not returned to the normal range.
• 25. CASE #1 : A patient’s ABGs pH= 7.30; PaCO2=31 mmHg; PaO2=76 mmHG; HCO3=17 mEq/L. First, look at the pH. What does this pH value indicate? alkalosis acidosi s
• 26. CASE #1 : A patient’s ABGs pH= 7.30; PaCO2=31 mmHg; PaO2=76 mmHG; HCO3=17 mEq/L. The above ABG represents what kind of acidosis ? Respiratory acidosis Metabolic alkalosis Metabolic acidosis Respiratory alkalosis
• 27. CASE #1 : A patient’s ABGs pH= 7.30; PaCO2=31 mmHg; PaO2=76 mmHG; HCO3=17 mEq/L. Fully compensated patially Compensated Uncompensated
• 28. CASE #2 : A patient’s blood gases are pH= 7.35; PaCO2= 33; PaO2= 88; HCO3= 18. What does the pH indicate? alkalosis acidosi s
• 29. CASE #2 : A patient’s blood gases are pH= 7.35; PaCO2= 33; PaO2= 88; HCO3= 18. Based on this information, the above ABG represents what kind of acidosis? Respiratory acidosis Metabolic alkalosis Metabolic acidosis Respiratory alkalosis
• 30. CASE #2 : A patient’s blood gases are pH= 7.35; PaCO2= 33; PaO2= 88; HCO3= 18. patially Compensated Uncompensated Fully compensated
• 31. IF IT’S METABOLIC: ANION GAP Anion gap measures the difference between anions (-) and cations (+) present in blood. Normal value = 10 – 12 mmol/L AG = Na – (HCO3 + Cl)
• 32. CAUSES OF HIGH-ANION-GAP METABOLIC ACIDOSIS Elevated anion gap represents metabolic acidosis.
• 33. REFERENCES: • Interpreting Arterial Blood Gases :WILLIAM C. Pruitt CPFT, MBA, AND MICHAEL JACOBS, RN, CCRN, CEN,MSN. • Interpretation of Arterial Blood Gases (ABGs) David A. Kaufman, MD Chief, Section of Pulmonary, Critical Care & Sleep Medicine. • Clinical Blood Gases,2nd Edition, Assessment & Intervention: W.Malley,Imprint:Saunders. ISBN :9780721684222 • 6 Easy steps to ABG analysis,E-booklet, David W. Woodruff, MSN, RN-BC, CNS, CMSRN, CEN.
• 34. Presented by: Fay Ali Al-Buainain

### Hinweis der Redaktion

1. Anemic pt
2. Paco2 (below normal) – lack of acid would not cause the problem HCO3 (below normal) that will couse the imbalance.
3. Paco2 (below) HCO3 (below) it will couse the problem
4. to identify the cause of metabolic acidosis