LID Study: Plasma lidocaine levels following airway topicalisation for
paediatric microlaryngobronchoscopy (MLB)
Abstract
Background A dose of 5mg/kg lidocaine is considered appropriate for
paediatric airway topicalisation. Existing literature suggests younger
children are susceptible to toxic lidocaine plasma levels and achieve
this at a faster rate. Aims The primary outcome of this 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. Methods
Data was collected prospectively over 18 months at Royal Manchester
Children’s Hospital. Children aged 0-8 years undergoing elective
diagnostic or therapeutic airway endoscopy were included within the
study. Standardised 2% lidocaine was used for airway topicalisation.
Dose varied depending upon practitioner usual practice. Venous blood
sampling occurred at 5, 10, 15 and 20 minutes post administration and
plasma lidocaine levels (ng/ml) analysed. Results A significant
relationship exists between higher peak plasma levels and ages
<18 months (p=0.00973). Strong linear correlation exists
between weight and age for our cohort (r=0.88). Higher peak plasma
lidocaine levels occur with total dose volumes between 2 and 3mls of 2%
lidocaine local anaesthetic (p=0.03) compared with <2ml total
dose volumes. Data suggests a potential relationship of lower weights
achieving higher peak plasma levels (p=0.0516). Reduced IQR variation of
peak plasma lidocaine levels exists when lidocaine dosing is
<5mg/kg. Conclusions Age and total dose volume of topicalised
lidocaine have a significant relationship with plasma lidocaine levels.
A dose of 5mg/kg topicalised lidocaine for paediatric airway endoscopy
is safe and provides good operating conditions. Lower patient weights
trend toward higher peak lidocaine plasma concentrations and require
further investigation.