Signs of lidocaine toxicity and occurrence of clinical adverse events
All patients’ median and IQR plasma lidocaine levels (ng/ml) do not exceed toxic levels at each measured time point of 5, 10, 15 and 20 minutes. However outlying plasma lidocaine levels exceeding 5000ng/ml do exist at every time point. Nevertheless there were no incidences of clinical adverse events or symptoms of local anaesthetic toxicity. This suggests toxic levels may differ between intravenous and mucosal administration of local anaesthetic agents. Our median time to peak plasma lidocaine concentration was 10 minutes as demonstrated in Table 1.
Four patients in the study exceeded lidocaine plasma levels of 5000ng/ml. Summary of demographics, baseline and descriptive data for these patients are in Table 2. There was no relationship between exceeding toxic lidocaine levels and age, weight or surgical procedure. However, a sample size of 4 in one group does not provide enough power to detect a difference.