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1356 Lactate Lactate Dehydrogenase (LDH)

Next Diagnostic Steps to Consider Specimen Collection and Handling before ketonuria during treatment of ketotic
if Levels Are High Perform with fresh urine. diabetes mellitus. See p. 254.
VetBooks.ir dosis (p. 251). Perform confirmatory Acetest®. Relative Cost: $ (reported as part of AUTHOR: Shannon D. Dehghanpir, DVM, MS, DACVP
Evaluate for diabetes mellitus/diabetic ketoaci-
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
urinalysis)
Lab Artifacts
Hematuria, hemoglobinuria, and highly con- Pearls
centrated, acidic urine may cause false-positive Serum or plasma can also be used to detect
results. ketonemia. Blood ketones typically resolve

Lactate

Definition • Nonhypoxemic (type B): gastric dilatation/ Specimen Collection and Handling
Metabolic end product of anaerobic glycolysis volvulus, diabetes mellitus, liver failure, Plasma collected in lithium heparin (green top
neoplasia, sepsis, renal failure, hypoglycemia, tube) or sodium fluoride (gray top tube); must
Synonym babesiosis, rare hereditary defects (mitochon- be centrifuged immediately and plasma removed
Lactic acid drial myopathy, pyruvate dehydrogenase from erythrocytes. Refrigerate immediately
deficiency) or freeze. Some blood gas and point-of-care
Physiology • Lactic acidosis should be suspected when analyzers use whole blood.
Lactate production increases with hypoxia there is an unexplained increase in the anion
(especially from skeletal muscle and GI gap. Relative Cost: $
tract) or abnormal carbohydrate metabolism
associated with some diseases. Liver, kidney, Next Diagnostic Steps to Consider Pearls
and heart consume lactate. Hyperlactemia if Levels Are High • Not measured as part of routine biochemical
(usually L-lactate) occurs when production Evaluate for underlying cause, depending on profile, but cage-side testing is increasingly
exceeds utilization, potentially causing lactic clinical signs and history. common in emergency/critical care settings.
acidosis. D-lactate is produced by bacteria; • Markedly elevated lactate concentrations
D-lactic acidosis is less common. Drug Effects have been associated with a poor prognosis
• Increase: ethylene glycol intoxication in critical care settings. For example, in dogs
Reference Interval • Decrease: bromide/potassium bromide with gastric dilatation/volvulus, an initial
< 2 mEq/L, < 2 mmol/L (experimental studies). plasma lactate > 7.4 mmol/L predicts a
Unit conversion: mg/dL × 0.112 = mEq/L; Lab Artifacts poor outcome with 88% accuracy.
1 mmol/L = 1 mEq/L. • Increase: delayed plasma harvest, venous • Most methods measure L-lactate but not
stasis (e.g., prolonged venous occlusion D-lactate.
Causes of Abnormally High Levels during venipuncture), struggling during
• Hypoxemic (type A): strenuous exercise, venipuncture AUTHOR & EDITOR: Lois Roth-Johnson, DVM, PhD,
DACVP
seizures, any cause of decreased oxygen • Decrease: free hemoglobin; metamizole
availability (shock, hypovolemia, cardiac (dipyrone) therapy
disease, pulmonary edema)

Lactate Dehydrogenase (LDH)

Definition reticuloendothelial system (LDH2); lung Next Diagnostic Steps to Consider
Cytosolic enzyme found in most cells in the (LDH3); kidney, placental, pancreas (LDH4); if Levels Are High
body and skeletal muscle and liver (LDH5). In veteri- Evaluate for muscle injury, hepatic disease, or
nary medicine, LDH isoenzyme measurement hemolytic anemia.
Physiology is usually restricted to research applications
LDH catalyzes the oxidation of L-lactate to because other markers of muscle and hepatic Lab Artifacts
pyruvate and the reverse reaction. LDH is injury exist that are more sensitive and specific. Hemolysis results in a false increase because
present in many tissues, notably heart, skeletal erythrocytes contain LDH.
muscle, liver, kidney, and erythrocytes. Leakage Reference Interval
into the blood and extracellular space occurs Dogs: 50-380 U/L; cats: 46-350 U/L Specimen Collection and Handling
with tissue injury. It also increases with Serum (red top tube), 1 mL. Store at 4°C.
even slight sample hemolysis. There are five Causes of Abnormally High Levels
site-specific LDH isoenzymes that can be Cardiac disease, skeletal muscle disease, renal Relative Cost: Single test $; included in
separated electrophoretically: heart (LDH1); injury, liver disease, and hemolysis many biochemistry profiles $$ - $$$

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