I found an editorial in BJA that describes an issue with succinylcholine I wasn’t really aware of. Butyrylcholinesterase (BCheE) hyperactivity. BCheE is the non-specific cholinesterase that rapidly hydrolyses succinylcholine in the blood so that only 10% of the injected drug eventually reaches the neuromuscular endplate.
If BCheE activity is increased then the amount of sux reaching the endplate is further diminished so that neur0muscular block lasts shorter than expected. Apparently, increased BCheE-activity is commonly seen in patients with asthma, alcoholism diabetes, hypertension and some other diseases. Most patients will recover from sux-block in 4-8 minutes. These patients may recover as early as 2 minutes after injection.
Then there is the rare gene variants. I was aware about BCheE-variants that cause prolonged neuromuscular block. Apparently there are also BCheE-gene variants that cause increased BCheE-activity. Clinically it will present as resistance to sux or, in worst case scenarios, sux won’t work at all.
While the gene variants that cause very high BCheE are extremely rare the authors note that 10% of all caucasians carry a gene that causes a 30% increase in BCheE -activity.
Find the BJA editorial here. It’s a nice, short, read summarising the various ways succinylcholine can fail (myasthenia gravis, inadequate dosing, storage and impatient anaesthetists…) focusing on BCheE variants.