Lactic acidosis laboratory findings: Difference between revisions
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==Laboratory Findings== | ==Laboratory Findings== | ||
*Blood tests are used to check electrolyte levels. Lactate levels in the blood are monitored. | *Blood tests are used to check electrolyte levels typically showing a low plasma bicarbonate (<22 mmol/L). Lactate levels in the blood are continuously monitored. | ||
*Arterial blood gases usually show a metabolic acidosis (pH <7.35 with low or normal pCO2). In the absence of obvious acidic toxins or ketone bodies, the situation points to lactic acidosis. The anion gap should be calculated as below: | |||
Anion gap | |||
The anion gap is the difference between the sum of the cations (sodium plus potassium) and the anions (chloride plus bicarbonate), ie ([Na mmol/L] + [K mmol/L]) − ([Cl mmol/L] + [HCO3 mmol/L]). | |||
The normal reference range for the anion gap varies between different laboratories but is 8-16 mmol/L when not including potassium in the equation and 10-20 mmol/L when including potassium. | |||
Hypoalbuminaemia lowers the normal anion gap by approximately 2.5 mmol/L for every 10 g/L reduction in serum albumin. | |||
The anion gap will be elevated in lactic acidosis. | |||
It is also elevated in chronic kidney disease and other organic acidoses, ketoacidosis, and some poisoning/drug-induced acidoses. | |||
Plasma lactate should be measured to confirm that this is the likely anion causing the acidosis, to help distinguish from these other causes. | |||
Values in the range of 2-5 mmol/L are significant. | |||
Clinically significant hyperlactataemia can occur in the absence of a raised anion gap. | |||
Samples for lactate estimation should be taken from arterial or mixed central venous sites. Peripheral values may reflect local rather than systemic concentrations. The sample should be transported to the laboratory on ice and may utilise a special reagent that inhibits glycolysis, giving a true spot reading. | |||
In shocked patients, particularly those with cardiogenic shock, lactate concentrations >2.5 mmol/L are associated with a poor prognosis and the lactate level can be measured as a semi-quantitative marker of deterioration or improvement. | |||
Further investigations aimed at detecting the underlying cause should be requested as thought necessary. Blood, urine and other cultures are useful for detecting occult septic causes. | |||
==References== | ==References== | ||
Revision as of 12:36, 15 December 2021
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Saud Khan M.D.
Laboratory Findings
- Blood tests are used to check electrolyte levels typically showing a low plasma bicarbonate (<22 mmol/L). Lactate levels in the blood are continuously monitored.
- Arterial blood gases usually show a metabolic acidosis (pH <7.35 with low or normal pCO2). In the absence of obvious acidic toxins or ketone bodies, the situation points to lactic acidosis. The anion gap should be calculated as below:
Anion gap The anion gap is the difference between the sum of the cations (sodium plus potassium) and the anions (chloride plus bicarbonate), ie ([Na mmol/L] + [K mmol/L]) − ([Cl mmol/L] + [HCO3 mmol/L]). The normal reference range for the anion gap varies between different laboratories but is 8-16 mmol/L when not including potassium in the equation and 10-20 mmol/L when including potassium. Hypoalbuminaemia lowers the normal anion gap by approximately 2.5 mmol/L for every 10 g/L reduction in serum albumin. The anion gap will be elevated in lactic acidosis. It is also elevated in chronic kidney disease and other organic acidoses, ketoacidosis, and some poisoning/drug-induced acidoses.
Plasma lactate should be measured to confirm that this is the likely anion causing the acidosis, to help distinguish from these other causes. Values in the range of 2-5 mmol/L are significant. Clinically significant hyperlactataemia can occur in the absence of a raised anion gap.
Samples for lactate estimation should be taken from arterial or mixed central venous sites. Peripheral values may reflect local rather than systemic concentrations. The sample should be transported to the laboratory on ice and may utilise a special reagent that inhibits glycolysis, giving a true spot reading.
In shocked patients, particularly those with cardiogenic shock, lactate concentrations >2.5 mmol/L are associated with a poor prognosis and the lactate level can be measured as a semi-quantitative marker of deterioration or improvement.
Further investigations aimed at detecting the underlying cause should be requested as thought necessary. Blood, urine and other cultures are useful for detecting occult septic causes.