ABG’s

1. ABG’s

2. Indications • Technique • Complications • Analysis • Summary

3. Indications • Respiratory illness • Critical illness • Unwell patients • Other circumstances

4. Technique • Right pt? • Any artery : commonly radial • Allens test • Preparation pre test • Monitoring • Caution • Don’t loose it • Arterial lines and monitoring of IABP

6. Complications • Bleeding • Bruising • Thrombosis • AV fistula • Complication of arterial lines

7. Analysis • pH • PaCO2 • PaO2 • HCO3 • O2 sats • Electrolytes • Lactate • Hb, Meth Hb, Carboxy Hb

8. Normal values • pH: 7.35 – 7.45 • PaCO2: 4.7 – 6 kPa • PaO2: 11 – 13 kPa • HCO3: 22 – 26 mEq/L • Lactate: <2 • O2 sats: >96%

9. Step wise analysis • What is the pH? • Normal: 7.35 – 7.45 • Acidosis: < 7.35( more acid ie H+) • Alkalosis: > 7.45( less acid ie H+)

10. What is the PaCO2 • Normal: 4.7 – 6.0 • Hypercapnoea: > 6 ( more CO2) • Hypocapnoea: < 4.7( less CO2)

11. What is PaO2 • Normal? • High: > 13 on room air • Low: < 11 on room air

12. What is the HCO3 • Normal: 22 – 26 • Low: < 22 • High: > 26

13. Is it metabolic or respiratory?

14. Is there compensation? • Respiratory pathology the compensation is renal • Renal pathology the compensation is respiratory

15. Is there compensation?

16. Anion gap • Na – ( Cl+HCO3) • Normal 12 • Metabolic acidosis with normal anion gap • Metabolic acidosis with increased anion gap

17. Respiratory acidosis • Airway obstruction
- Upper
- Lower: COPD, asthma • CNS depression • Sleep disordered breathing • Neuromuscular impairment • Ventilatory restriction • Increased CO2  production: shivering, rigors, seizures, malignant hyperthermia, hypermetabolism • Incorrect mechanical ventilation settings

18. Respiratory alkalosis • CNS stimulation: fever, pain, fear, anxiety, CVA, cerebral edema, CNS infection • Hypoxemia or hypoxia: lung disease, profound anemia, low FiO2 • Stimulation of chest receptors: pulmonary edema, pleural effusion, pneumonia, pneumothorax, pulmonary embolus • Drugs, hormones: salicylates, catecholamines, medroxyprogesterone, progestins • Pregnancy, liver disease, sepsis, hyperthyroidism • Incorrect mechanical ventilation settings

19. Metabolic alkalosis • Hypovolemia with Cl- depletion • GI loss of H+Vomiting, gastric suction, villous adenoma, diarrhea with chloride-rich fluid • Renal loss H+Loop and thiazide diuretics • Renal loss of H+:  edematous states (heart failure, cirrhosis, nephrotic syndrome), hyperaldosteronism, hypercortisolism, excess ACTH, exogenous steroids, severe hypokalemia bicarbonate administration

20. Metabolic acidosis with elevated anion gap • M • U • D • P • I • L • E • S

21. Metabolic acidosis with normal anion gap • GI loss of HCO3-Diarrhoea, ileostomy, proximal colostomy • Renal loss of HCO3-proximal RTA • carbonic anhydrase inhibitor (acetazolamide) • Renal tubular disease, ATN, Chronic renal disease, Distal RTA, NaCl infusion

22. Metabolic acidosis with elevated anion gap • Methanol intoxication • Uremia • Diabetic ketoacidosis, alcoholic ketoacidosis, starvation ketoacidosis • Paraldehyde toxicity • Isoniazid • Lactic acidosis • Ethanol • Salicylate intoxication

23. ABG’s

24. What is the abnormality? • What might this patient have?

25. ABG’s

26. What is the abnormality? • What might this patient have?

27. ABG’s

28. What is the abnormality? • What might this patient have?

29. ABG’s

30. What is the abnormality? • What might this patient have?

31. ABG’s

32. What is the abnormality? • What might this patient have? • What other blood tests may you want to do?

33. ABG’s

34. Summary • Systematic approach in analysis of ABG’s • Can help you in difficult situations • Always co relate clinically • Should not be abused • Get slick at it

35. Thanks