Test Directory

Evaluate preoperative patients for succinylcholine (suxamethonium) anesthetic sensitivity, genetic or secondary to insecticide exposure, in appropriate circumstances. To prevent or evaluate prolonged anesthetic effect, prolonged apnea, after surgery. Very small amounts (0.04−0.06 mg/kg) of succinylcholine are needed to obtain 90% of neuromuscular blockade in patients with low levels of plasma cholinesterase activity.

Monitor organophosphorous or carbamate insecticide poisoning, in which level is decreased; establish patient's baseline value before exposure. Indications include such pesticide exposure, especially with miosis, blurred vision, muscle weakness, twitching, and fasciculation, bradycardia, nausea, diarrhea, vomiting, salivation, sweating, pulmonary edema, arrhythmias, and convulsions. The value of assessing risk status in persons exposed to organophosphate insecticides on the basis of plasma or serum cholinesterase levels alone has been called into question. Are normal levels indicative of no exposure or of a genetic variant with or without exposure? There are interpretive problems with low or high values.

Family studies may be done when an individual with a genetically abnormal type is documented by serum pseudocholinesterase deficiency and, ideally, confirmed by phenotyping.

Specimen Type: Serum

Collection Container: Gold Top, Serum Separator

Alternate Collection Container: Red Top, Plain

Desired Specimen Volume: 0.5 mL

1. Collect a gold top, serum separator tube via venipuncture.

1.  Allow specimen to clot for 30 minutes.
2. Separate serum from cells immediately after clotting.
3. Transfer 0.5 mL of serum to a clear aliquot tube (screw cap).

Transport to the laboratory refrigerated. 

• Whole blood specimen (a 20% to 25% increase can occur over a 24-hour period if serum is left on the clot)
• Hemolysis

 See patient report.

Serum cholinesterase may be decreased in patients on estrogens and oral contraceptives. Fluoride interferes.

Pseudocholinesterase is low also in some instances of liver disease, including decompensated cirrhosis, hepatitis, metastatic carcinoma, CHF, and in malnutrition, but not sufficiently consistently enough to be a useful clinical test for such disorders.

Genetic atypical enzyme does not explain every instance of prolonged postsurgical apnea. Red cell cholinesterase is more useful for chronic insecticide exposure. Carbamate-poisoned persons can appear to have near normal or normal levels of pseudocholinesterase.

•  Cholinesterase