Lactate Article Notes

Measuring Blood Lactate Levels

• Lactate in blood indicates anaerobic metabolism due to insufficient oxygen for energy production.

• Elevated lactate often results from reduced blood flow.

• Lactate trends are crucial for prognosis.

• Monitoring includes blood pressure, pulse oximetry, arterial blood gases, and urine output.

• Lactate measurement is vital for diagnosing, monitoring, and predicting outcomes in critical care.

Lactate as Indicator of Tissue Hypoperfusion

• Lactate mirrors anaerobic metabolism, signaling hypoperfusion.

• Lactate rises before other indicators, making it a sensitive marker.

• Early detection prevents complications and reduces mortality.

• Lactate values guide therapy; successful treatment lowers lactate.

• Persistent high lactate indicates ongoing issues and poorer prognosis.

Physiology of Energy Production and Lactate

• Cells need ATP for metabolic functions, produced via:

  • Glycolysis

  • Citric acid cycle

  • Electron transport chain

• Latter two need oxygen; glycolysis doesn't but yields less ATP.

• Glycolysis produces pyruvate, converted to lactate, regenerating nicotinamide dinucleotide via lactate dehydrogenase.

• Lactate production generates hydrogen ions, potentially causing acidosis.

• Lactate can revert to pyruvate: oxidizes into carbon dioxide and water or enters gluconeogenesis.

• Most lactate oxidizes; some enters gluconeogenesis.

• Skin, red blood cells, brain, and muscle produce the most lactate; liver and kidneys use it.

• Normal lactate: below $2.5 \, mmol/L$ in adults but higher in young dogs.

Pathophysiology of Hyperlactatemia

• Hyperlactatemia results from excess lactate production over use.

• Causes: Type A (hypoxemia) or Type B (diseases, toxins).

• Common cause: hypoperfusion.

• Reduced perfusion leads to hypoxia and anaerobic glycolysis.

• Excess lactate and hydrogen ions enter blood; liver and kidneys extract and use lactate.

• Severe hypoperfusion: liver and kidneys produce lactate, increasing hyperlactatemia.

• Intracellular lactate changes quickly affect interstitial and blood levels.

Measurement of Lactate Levels

• Point-of-care analyzers have simplified lactate measurement.

• Mild increases can result from patient restraint.

• Pronounced increases may occur with muscle activity.

• Minimal differences exist between arterial, jugular, and cephalic samples.

• Hyperlactatemia severity:

  • Mild: $3$ to $5 \, mmol/L$

  • Moderate: $5$ to $7 \, mmol/L$

  • Severe: above $7 \, mmol/L$

• Rear leg samples can be higher in gastric dilatation-volvulus; use cranial vessel.

• Measure lactate in serum, plasma, or whole blood; separate ASAP to prevent false elevation.

• Cool whole blood to prevent increases.

Indications: Diagnosis

• Increased lactate implies increased anaerobic metabolism.

• Common cause: local or systemic hypoperfusion.

• Any elevation should prompt hypoperfusion investigation.

• Other causes: ventilation issues, arterial oxygen, hemoglobin, metabolic rate.

• Lactate in fluids can diagnose bacterial colonization.

• High fluid lactate suggests bacterial presence.

• Blood-to-fluid lactate difference helps diagnose septic effusions in dogs.

Monitoring and Prognosis

• Studies show surgical nonsurvivors had higher lactate levels post-surgery.

• Failure of lactate to normalize indicates poor prognosis.

• High lactate in gastric dilatation-volvulus nonsurvivors.

• Lactate $> 6.6 \, mmol/L$ indicates poor outcome in gastric dilatation-volvulus.

• Lactate changes with treatment are more important than a single value.

Treatment

• Elevated lactate indicates an underlying issue.

• Rule out handling errors, hypoxia, and anemia.

• Administer oxygen or blood products as needed.

• Assess perfusion; use fluid therapy or blood pressure support.

• Maintain packed cell volume of at least 20%.

• Avoid sodium bicarbonate unless severe acidosis is present.

The Role of the Technician

• Technicians should understand lactate's significance and monitor trends.

• They are vital in finding the cause and executing treatment.

• Responsibilities: blood draws, tests