Cholinesterase (includes phenotyping)

Cholinesterase levels and phenotype studies can be used to predict the potential degree of post-operative paralysis following the use of the short reacting muscle relaxant suxamethonium or mivacurium. Cholinesterase can be used to monitor exposure to organic phosphorus compounds in the agricultural and chemical industries.
Clinical details: 
Cholinesterase is involved in the metabolism of succinylcholine, mivacurium, procaine, chlorprocaine, tetracaine, cocaine, heroin, and other drugs. Following the introduction of the de-polarising muscle relaxant succinylcholine (Scoline, Suxamethonium, Anectine) to facilitate tracheal intubation, a number of patients experience a prolonged period of paralysis (Suxamethonium apnoea) lasting several hours instead of a few minutes. Most of these sensitive individuals have been found to possess one or more genetic variants of cholinesterase. Succinylcholine sensitivity may also be acquired as the result of the decreased total cholinesterase activity that is a feature of a number of disease states, primarily liver disease, malignancy and malnutrition, as well as iatrogenic causes and the physiological decrease which is observed in some pregnancies.
Reference range: 

3.0 - 9.0
Warning cards will be issued to all patients regarded as being 'at risk',whether by virtue of an episode of suspected apnoea or by the possession of a genetic variant. Please contact the laboratory for more information.

Sample type and Volume required: 
1 mL of serum or heparinised plasma (400 uL absolute minimum). Please note that blood collected into EDTA, citrate or fluoride/oxalate is not suitable for analysis. Grossly haemolysed samples are not suitable.
Turnaround time: 
3 weeks
Special sample instructions: 

The collection of samples for the investigation of suxamethonium apnoea should be delayed until the post-operative period since anaesthetics may produce anomalous results.
Monitoring of workers exposed to organo-phosphorus pesticides should be in accordance with HSE Guidance note MS 17.

Storage and transport: 
Samples are stable for 1 month at 4°C and for at least 1 year at -20°C. Samples can be sent by first class post.
Reference Chemistry Laboratory at St Thomas'
0207 188 1264
4th floor, North Wing
St Thomas' Hospital
Westminster Bridge Road
London SE1 7EH
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 02/09/2016