Cardiac or central nervous system toxicity may result when standard lignocaine doses are administered to patients with circulatory failure. This may be due to the following reason :
Lignocaine concentration is initially higher in relatively well perfused tissues such as brain and heart.
Histamine receptors in brain and heart get suddenly activated in circulatory failure
There is a sudden outburst of release of adrenaline, noradrenaline and dopamine in brain and heart
Lignocaine is converted to a toxic metabolite due to its longer stay in the liver.