Predictors of the variability in neuromuscular block duration following succinylcholine: A prospective, observational study.

BACKGROUND

The duration of neuromuscular block (NMB) following succinylcholine administration is characterised by a high interindividual variability. However, this has not yet been quantified in a large sample of surgical patients. The significance of underlying clinical factors is unknown.

OBJECTIVE

The objective of this study was to profile the variability in NMB duration following a standard dose of succinylcholine and to investigate contributing clinical and genetic factors.

DESIGN

A prospective, observational study.

SETTING

Tertiary referral centre.

PATIENTS

In a total of 1630 surgical patients undergoing a rapid sequence induction and intubation, clinical risk factors for a prolongation in NMB duration following succinylcholine were assessed. In a subset of 202 patients, additional biochemical and molecular genetic investigations of butyrylcholinesterase were performed.

INTERVENTION

A standard 1 mg kg dose of succinylcholine after administration of an induction drug and an opioid.

MAIN OUTCOME

NMB duration measured as the time between administration of succinylcholine until reappearance of palpable muscular response to supramaximal transcutaneous ulnar nerve stimulation.

RESULTS

NMB varied from 80 s to 44 min with a median duration of 7.3 min. Sixteen percent of patients had NMB duration in excess of 10 min. A multivariable survival model identified physical status, sex, age, hepatic disease, pregnancy, history of cancer and use of etomidate or metoclopramide as independent risk factors for a prolonged NMB. Three novel butyrylcholinesterase variants were identified: p.Ile5Thr; p.Val178Ile; and p.Try231Ser.

CONCLUSION

Neuromuscular blockade duration in excess of 10 min occurred in 16% of a general surgical population following a single dose of succinylcholine. The multivariable model of clinical risk factors for prolonged NMB revealed a negative predictive value of 87%, thereby indicating that absence of such risk factors may reliably predict a shorter duration of NMB. In patients with clinical risk factors for a prolonged NMB or with butyrylcholinesterase mutations, an alternative to succinylcholine should be considered.