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.