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ABG’s

ABG’s. Blood gas slip. Data. Blood gases Electrolytes Haemoglobin Calculations Glucose “Balance”. What am I thinking ?. Importance of gases and acid base balance. Need oxygen to live Need to get rid of CO 2 a waste product Enzymes need pH 7.35 to 7.45 for optimal working.

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ABG’s

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  1. ABG’s

  2. Blood gas slip

  3. Data • Blood gases • Electrolytes • Haemoglobin • Calculations • Glucose • “Balance”

  4. What am I thinking ?

  5. Importance of gases and acid base balance • Need oxygen to live • Need to get rid of CO2 a waste product • Enzymes need pH 7.35 to 7.45 for optimal working

  6. Gas exchange in the body Carbon dioxide Oxyygen Lungs Heart Body Tissues

  7. Chemistry • C6H12O6 + 6O2 > 6CO2 + 6H2O • Glucose + Oxygen > Carbon dioxide + water • CO2 + H2O > H2CO3 > H+ + HCO3- • Carbon dioxide + water > carbonic acid > acid + bicarbonate • pH depends on H+

  8. Energy use in the body Glucose Pyruvate TCA cycle Oxygen ATP Energy

  9. Ways to loose acid • Lungs • Kidney

  10. Glucose metabolism I Glucose Rest of body Muscle Liver Insulin

  11. Glucose metabolism II • Glucose uptake depends on • Serum glucose • Blood flow • Insulin availability • Glucose doesn’t always cause acidosis

  12. Lactic acid I Glucose No oxygen Lactic acid Pyruvate TCA cycle Oxygen ATP Energy

  13. Lactic acid II - Lactic acidosis • Increased production • Tissue Hypoxia • Circulatory shock • Decreased utilisation • Liver failure • Circulatory shock • Acidosis dangerous, Lactate harmless • BE as surrogate marker

  14. Calcium • Total calcium = free Ca2+ and Protein bound Ca2+ • Active form is free Ca2 • Myocardial contraction and vasoconstriction • NOT with radial artery • Calcium chloride and gluconate

  15. Hct and haemoglobin • Bleeding • revealed • concealed • Chest • GIT • Retro peritoneum (IABP, recent angio)

  16. Balance I • Most are 500mL to 2.0 L +Ve by am • Depend on • fluids/loses in theatre • pre op dehydration • An aid to diagnosing internal bleeding and excessive vasodilatation

  17. Balance II • Always think (especially if CVP low) • Cold & 1.5L+Ve > CXR • Warm & 2.0 to 2.5L+Ve > CXR • Intra thoracic bleeding can occur regardless of chest tube drainage

  18. Acid - Base balance • Metabolic “HCO3/other acid problem” • Produce / loose acid / alkali • Respiratory “CO2” problem • Produce / retain CO2

  19. Base excess (BE)orHow much extra alkali • Meaning • Observation • Treatment

  20. BE I - meaning • Normal ~ 0 • If –Ve acidosis of any cause is present • Circulatory insufficiency • Cardiac • Circulatory volume • Renal failure • Liver failure • Ischaemic limb eg IABP • Ischaemic bowel • Respiratory • If +Ve alkalosis • Chronic hypokalaemia

  21. BE II - observation • A guide that patient is ok • If increasing negative monitor continuously • Can change from hour to hour

  22. BE III - treatment • If BE < -6.0 to –8.0 negatively inotropic • Acknowledge there is a problem, give bicarb, monitor BE frequently to reassess

  23. Blood gases I acid base balance • Uncompensated • No respiratory compensation when fully ventilated • Compensated • Most extreme value is usually primary problem • pO2 “unimportant” • CO2 + H2O > H2CO3 > H+ + HCO3- • Carbon dioxide + water > carbonic acid > acid + bicarbonate

  24. Blood gases II acid base balance Uncompensated

  25. Blood gases III acid base balance Compensated

  26. Predicted response

  27. Anion gap • What you can’t measure • (Na+ + K +) - (Cl - + HCO3 -) • Causes “KUSMAL” • Ketones • Uraemia • Salicylates • Methyl alcohol • Acid poisoning • Lactate

  28. Frequency of blood gases? ½ Hr, 1 Hr, 2 Hr • Recent admission • Unstable • Bleeding • Oliguria/ renal failure • Liver failure • “just unwell” or “just not right” • Previously abnormal result • Change in ventilation • Good lungs 5 minutes poor lungs 20 to 25 minutes

  29. Juniors and Fio2

  30. ABG verses pulse oximetry • CO2 • Carbon monoxide

  31. Calculated verses Measured oxygen • Different types of Haemoglobin • Oxyhaemoglobin • Reduced (Normal, but no oxygen bound) • Carboxyhaemoglobin (CO poisoning) • Methemoglobin • DPG, blood transfusions • Haemoglobinopathies

  32. Thank you

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