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Measuring blood lactate

Measuring blood lactate. Lactate . Lactate production is a normal physiologic process and occurs in all animals its presence does not indicate disease A key indicator of hypoxia Correlates with mortality Lactate can also be used to characterize fitness levels. SUGAR. CO 2 and WATER.

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Measuring blood lactate

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  1. Measuring blood lactate

  2. Lactate • Lactate production is a normal physiologic process and occurs in all animals • its presence does not indicate disease • A key indicator of hypoxia • Correlates with mortality • Lactate can also be used to characterize fitness levels

  3. SUGAR CO2 and WATER ENERGY OXYGEN

  4. LACTATE Anaerobic conditions: without oxygen SUGAR CO2 and WATER ENERGY OXYGEN

  5. Why do cells make lactate? • Cells consume oxygen in a process that produces energy • When the oxygen supply is insufficient (anaerobic conditions) cells produce energy by another pathway that results in the production of lactate • Lactate accumulation is the price to be paid for maintaining energy production under anaerobic conditions

  6. A clinical example • Dog with gastric dilatation-volvulus (GDV) • A relatively common abdominal catastrophe requiring aggressive stabilisation and surgery • A vet’s nightmare

  7. Gastric dilatation-volvulus • Rapid onset, profound vomiting • Stomach twists about its axis and ‘bloats up’ • Respiratory difficulty • Cardiovascular collapse

  8. +1 hour +3 hours +2 hours +4 hours Gastric dilatation-volvulus • Lactic acidosis from hypoperfusion • Initial rise after restoring circulation • If it fails to fall rapidly, then you have not fully restored oxygen delivery • With GDVs, it is a strong indicator of likely outcome

  9. Do not over interpret the result • Vets (and owners) want tests that tell them the likely outcome • Magnitude of elevation corresponds to the severity of the underlying problem • Generally, severe disease is associated with poor prognosis (likely outcome) • However, some severe diseases are easily treatable

  10. +1 hour +3 hours +2 hours +4 hours Lactate trends • High lactate levels: the patient’s condition warrants aggressive treatment • Serial evaluation is a must • A decreasing trend towards normal is a good sign • A rising trend in the face of aggressive treatment is a very poor sign

  11. BLOOD GLUCOSE BLOOD LACTATE MUSCLES LIVER

  12. Lactic acid Lactic anion Blood lactate terminology • Blood lactate • Lactic acid • Lactate anion • Lactic acidosis - a common type of metabolic acidosis Lactate-H+ ↔ Lactate- + H+

  13. Blood sampling • Arterial blood is best • Venous blood drawn from a central venous catheter is essentially equivalent • Restraint and prolonged venous occlusion can cause mild increases • Venous blood drawn from a peripheral site should be interpreted with caution

  14. Handling blood samples • Do NOT use serum • Separate plasma within 5 minutes • lactate values can increase if sample stay in contact with RBCs • Only useful if fast turn around

  15. Avoiding confused vets • Does not replace acid-base analysis • there are other types of metabolic acidosis • does not look at respiratory component • poor correlation between blood lactate concentration and magnitude of metabolic acidosis

  16. Avoiding confused vets • Hartmann’s fluid • a.k.a. Lactated Ringer’s Solution or Compound Sodium Lactate • a treatment for mild metabolic acidosis • lactate converted by the liver to bicarbonate

  17. Respiratory/blood gases cassette

  18. Respiratory/blood gases cassette • Na+, K+, Cl-, HCO3-, anion gap, pH, pCO2, TCO2, pO2 • Use this cassette for patients with respiratory and cardiovascular disorders, advanced anesthetic cases and all patients on ventilators to improve their chances of success in critical situations. • Assess respiratory and breathing abnormalities • Monitor cardiovascular and respiratory functions • Assess a critical patient’s need for supplemental oxygen immediately • Monitor oxygen and respiratory function

  19. Respiratory/blood gases cassette • Na+, K+, Cl-, HCO3-, anion gap, pH, pCO2, TCO2, pO2 • Electrolytes and acid-base (like the fluid therapy/acid-base cassette) but also gives pO2 • Use this one whenever you are questioning the content of oxygen in the patient’s arterial blood

  20. Why do we need to do blood gases? An arterial blood sample is useful for assessment of: 1. alveolar ventilation 2. oxygenation 3. acid-base balance

  21. Our first example… • Eight-year-old Labrador • Increased respiratory rate • Chest x-ray: no abnormality detected • Previously treated with oxygen

  22. FiO2: fraction (%) of inspired oxygen Partial pressure of oxygen • Eight-year-old Labrador • Increased respiratory rate • Chest x-ray: no abnormality detected • Previously treated with oxygen ‘a’ indicates an arterial sample Partial pressure of carbon dioxide

  23. Percentage of haemoglobin molecules carrying oxygen Oxygen-haemoglobin dissociation curve Partial pressure of oxygen dissolved in the arterial blood

  24. How did the blood gas help? • High pH and low PaCO2 are consistent with respiratory alkalosis • ?pain ?fear • Changed direction of the treatment

  25. Understanding oxygen content • PaO2 determines what percentage of the haemoglobin molecules carry oxygen • Think of oxygen as being in two “states”: • dissolved in the plasma • in association with haemoglobin • Anaemia does not affect PaO2

  26. PLASMA PLASMA + RBCS

  27. How much oxygen is in the blood?

  28. How much oxygen is in the blood?

  29. How much oxygen is in the blood?

  30. Adequate oxygenation • If the PaO2 is less than 70mmHg (further) oxygen therapy is required • Alternative methods of assessment are of limited use

  31. Pulse oximetry • Non-invasive, easy to attach • Movement artifacts • Few vets attempt to use this on conscious patients

  32. Mucous membranes • Pink is desirable! • A pale colour could be due to: • drug induced vasoconstriction • poor peripheral perfusion • Cyanosis: takes 5g/dL of unoxygenated haemoglobin to generate the blue colour

  33. Our second example • One-year-old Newfie • Very flat one day following surgery for a fractured femur

  34. Using a pulse oximeter to estimate the % of haemoglobin molecules in association with oxygen • One-year-old Newfie • Very flat one day following surgery for a fractured femur

  35. PAO2 PaO2

  36. PAO2 calculated by VetSTAT as 124mmHG • PAO2 - PaO2 = 32mmHg • 10 to 20mmHg considered normal

  37. Assessing alveolar ventilation • High PaCO2 = hypoventilation • Low PaCO2 = hyperventilation • Capnography can provide a non-invasive estimate of PaCO2 • only intubated patients

  38. Our third example • Two-year-old spaniel • Rescued from the river yesterday • Near-drowning episode • Give oxygen via a face-mask

  39. Acidaemia if blood pH <7.3 • Two-year-old spaniel • Rescued from the river yesterday • Near-drowning episode • Give oxygen via a face-mask As a rule-of-thumb, the PaO2 should be 4 to 5 times the percentage inspired oxygen Metabolic acidosis

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