Cardiac or central nervous system toxicity may result when standard lidocaine doses are administered to patients with circulatory failure. This may be due to the following reason –
Lidocaine concentration are initially higher in relatively well perfused tissues such as brain and heart Histamine receptors in brain and heart gets suddenly activated in circulatroy failure There is a sudden out-burst of release of adreneline, noradreneline and dopamine in brain and heart Lidocaine is converted into a toxic metabolite due to its longer stay in liver