Blood Gas Interpretation Review for Pandemic

1. Blood Gas Interpretation Review for Pandemic

2. Blood Gases • Important diagnostic tool • Reveals: 1. acid-base balance 2. oxygenation status **arterial gases only** 3. abnormalities of ventilation

3. Acid- base balance • The body is designed for optimum performance at a specific pH level • Cell division • Metabolism

4. Components of Acid- Base Balance • pH- measures the bloods acidity • Normal range 7.35- 7.45 • Overall H+ from both respiratory and metabolic factors • pCO2- partial pressure of carbon dioxide in the blood • Normal range 35-45 mmHg • Snapshot of adequacy of alveolar ventilation • HCO3- the amount of bicarbonate in the blood • Normal range 22- 26 mEq/L

5. Acid – Base Balance Bicarbonate – carbonic acid buffer equation (H+)(HCO3) (H2CO3) (CO2)(H2O) It’s not that complicated! pH 1 7 14 Acidic Neutral Alkaline

6. Acid – Base Balance • Lungs • Respiratory • CO2 (acid) • Kidneys • Metabolic • HCO3 ( base/alkaline)

7. Making sense of it… pH 7.35 – 7.45 Respiratory Metabolic CO2=Acidosis HCO3=Acidosis CO2=Alkalosis HCO3=Alkalosis

8. Interpretation: 4 steps • Normal Values • pH 7.35 – 7.45 • pCO2 35 – 45 mmHg • HCO3 22 - 26 mEq/L • Evaluate each component as Acid or Base

9. Step 1… • Evaluate pH and determine acidosis or alkalosis 7.35 7.40 7.45 Acid Normal Base AcidosisAlkalosis

10. Step 2… 35 40 45 Base Normal Acid • Evaluate pCO2 (respiratory)

11. Step 3… • Evaluate HCO3 (metabolic) 22 24 26 Acid Normal Base

12. Step 4… • Determine which regulatory system is responsible for the imbalance by checking to see which component matches the pH. • If pH and pCO2 match = respiratory • If pH and HCO3 match = metabolic

13. ABG Analysis

14. Let’s practice… Respiratory Acidosis A A N Metabolic Alkalosis B N B Normal N N N B B N Respiratory Alkalosis A N A Metabolic Acidosis A A A Mixed Acidosis

15. Compensation • When an acid – base imbalance exists, over time the body attempts to compensate.

16. Understanding Compensation • Uncompensated – the alternate system has not attempted to adjust (remains within normal range), and the pH remains abnormal • Example • pH 7.30 A • pCO2 60 A • HCO3 25 N Uncompensated Respiratory Acidosis

17. Understanding Compensation • Partial Compensation – the alternate system is trying to create a balanced environment and bring the pH back within normal limits, but hasn’t yet succeeded. • Example • pH 7.34 A • pCO2 59 A • HCO3 28 B Partially Compensated Respiratory Acidosis

18. Understanding Compensation • Fully Compensated – the alternate system has adjusted enough to restore balance and normalize the pH • Example • pH 7.36 N (but slightly A) • pCO2 58 A • HCO3 31 B Compensated Respiratory Acidosis

19. Let’s Practice Compensation… Metabolic Alkalosis partially compensated B A B A A N Respiratory Acidosis uncompensated Metabolic Acidosis fully compensated N B A N A B Respiratory Acidosis fully compensated Respiratory Alkalosis partially compensated B B A Respiratory Acidosis partially compensated A A B

20. A Final Step… • Determine level of oxygenation (arterial samples only) • Normal = 80 – 100 mmHg • Mild hypoxemia = 60 – 80 mmHg • Moderate hypoxemia = 40 – 60 mmHg • Severe hypoxemia = less than 40 mmHg

21. Respiratory Acidosis • Excessive CO2 retention • Causes • Airway obstruction • Depression of respiratory drive • Sedatives, analgesics • Head trauma • Respiratory muscle weakness resulting from muscle disease or chest wall abnormalities • Decreased lung surface area participating in gas exchange

22. Respiratory Acidosis • Clues • Confusion, restlessness • Headache, dizziness • Lethargy • Dyspnea • Tachycardia • Dysrhythmias • Coma leading to death

23. Respiratory Acidosis • Solutions • Improve ventilation • Ensure adequate airway; positioning, suctioning • Encourage deep breathing and coughing • Frequent repositioning • Chest physio/ postural drainage • Bronchodilators • Decrease sedation/analgesia • Oxygen therapy

24. Respiratory Alkalosis • Excessive CO2 loss due to hyperventilation • Causes • CNS injury: brainstem lesions, salicylate overdose, Reye’s Syndrome, hepatic encephalopathy • Aggressive mechanical ventilation • Anxiety, fear or pain • Hypoxia • Fever • Congestive heart failure

25. Respiratory Alkalosis • Clues • Light headedness • Confusion • Decreased concentration • Tingling fingers and toes • Syncope • Tetany

26. Respiratory Alkalosis • Solutions • Decrease respiratory rate and depth • Sedation/analgesia as appropriate • Rebreather mask • Paper bag • Emotional support/encourage patient to slow breathing • Calm, soothing environment

27. Metabolic Acidosis • Excessive HCO3 loss, or acid gain • Causes • Diabetic ketoacidosis • Sepsis/shock • Diarrhea (fluid losses below gastric sphincter) • Renal Failure • Poison ingestion • Starvation • Dehydration

28. Metabolic Acidosis • Clues • Stupor • Restlessness • Kussmaul’s respirations (air hunger) • Seizures • Coma leading to death

29. Metabolic Acidosis • Solutions • Replace HCO3 while treating underlying cause • Monitor intake and output • Monitor electrolytes, especially K+ • Seizure precautions

30. Metabolic Alkalosis • HCO3 retention, or loss of extracellular acid, • Causes • GI losses above gastric sphincter • Vomiting • Nasogastric suction • Antacids • Diuretic therapy causing electrolyte loss

31. Metabolic Alkalosis • Clues • Weakness, dizziness • Disorientation • Hypoventilation • Muscle twitching • Tetany

32. Metabolic Alkalosis • Solutions • Control vomiting • Replace GI losses • Eliminate overuse of antacids • Monitor intake and output • Monitor electrolytes