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HelpTEST ID LID Lidocaine, Serum
Reporting Name
Lidocaine, SSpecimen Type
Serum RedSpecimen Required
Supplies: Sarstedt Aliquot Tube 5 mL (T914)
Collection Container/Tube: Red top (serum gel/SST are not acceptable)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.25 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum Red | Refrigerated (preferred) | 14 days |
| Ambient | 14 days | |
| Frozen | 14 days |
Method Name
Enzyme-Multiplied Immunoassay Technique (EMIT)
Reject Due To
| Gross hemolysis | Reject |
Reference Values
Therapeutic: 1.5-5.0 mcg/mL
Critical value: >6.0 mcg/mL
Day(s) Performed
Monday through Saturday
Report Available
Same day/1 to 2 daysSpecimen Retention Time
2 weeksPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
80176
Forms
If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
-Cardiovascular Test Request (T724)
-Therapeutics Test Request (T831)
Useful For
Assessing optimal lidocaine dosing during the acute management of ventricular arrhythmias following myocardial infarction or during cardiac manipulation such as surgery
Assessing potential lidocaine toxicity
Clinical Information
Lidocaine is commonly used as a local anesthetic, but it is also effective at controlling ventricular arrhythmia and ventricular fibrillation in children and adults. For cardiac therapy, optimal therapeutic response is seen when serum concentrations are between 1.5 and 5.0 mcg/mL. Lidocaine is protein-bound (60-80%), primarily to alpha-1-acid glycoprotein; concentrations of this protein increase after myocardial infarction, which may decrease the amount of free lidocaine and, thus, its efficacy.
Lidocaine undergoes extensive first-pass hepatic metabolism and, therefore, is not administered orally. It is eliminated via renal clearance, with a half-life of approximately 1.5 to 2 hours. Diseases that reduce hepatic or renal function reduce clearance and prolong elimination of lidocaine.
Toxicity occurs when the serum concentration of lidocaine is greater than 6.0 mcg/mL and is usually associated with symptoms of central nervous system excitation, light-headedness, confusion, dizziness, tinnitus, and blurred or double vision. This can be accompanied by bradycardia and hypotension leading to cardiovascular collapse.
Cautions
No significant cautionary statements
Method Description
The enzyme-multiplied immunoassay technique assay is a homogeneous enzyme immunoassay technique used for the analysis of specific compounds in biological fluids. The assay is based on competition between drug in the sample and drug labeled with the enzyme glucose-6-phosphate dehydrogenase (G6PD) for antibody binding sites. Enzyme activity decreases upon binding to the antibody, so the drug concentration in the sample can be measured in terms of enzyme activity. Active enzyme converts oxidized nicotinamide adenine dinucleotide (NAD) to NADH, resulting in an absorbance change, which is measured spectrophotometrically. Endogenous serum G6PD does not interfere because the coenzyme functions only with the bacterial (Leuconostoc mesenteroides) enzyme employed in the assay.(Package insert: Lidocaine reagent. Seimens Healthcare Diagnostics, Ltd; 04/2015)