Study outcomes
The primary outcome of the study was to ascertain peak plasma lidocaine
levels after topicalisation for airway endoscopy. Secondary endpoints
included: time to peak lidocaine plasma levels, signs of lidocaine
toxicity (restricted to ECG changes or seizures when under anaesthesia)
and clinical adverse events of laryngospasm, coughing or desaturation
during the procedure.
Statistical analysis
Normally distributed variables were summarised by mean (standard
deviation, SD) and non-normally distributed variables by median
(interquartile, IQR) [range]. Categorical variables were summarised
by count (percentage). In comparison tests, ANOVA or equivalent
non-parametric tests were used for continuous variables. In assessing
the relationship between peak plasma and age, weight or volume
univariable regression models were used. As a result, multivariable
models were not followed due to the small sample size. Due to the
exploratory nature of the study, a nominal p-value of <0.05
indicates areas for further investigation.
Sample size
The sample size was derived from recruitment frequency at a specialist
institution and a quantity that allowed a clear relationship between the
primary outcome and defined variables to be explored. Fifty patients
undergoing airway endoscopy were recruited within the study and a total
of 198 samples were sent for analysis. A total of 198 human serum
samples were received frozen on dry ice and in good condition from the
[removed for blind peer review] on 26 Oct 2018 for preparation and
analysis at [removed for blind peer review]. Sample analysis was
performed between 17 Feb 2019 and 22 Feb 2019.