I have a few queries related to thiopentene administration. Please share your views. For how many days the inj. thiopentone can be given in refractory seizure or the maximum dose used for status epilepticus? How can one differentiate between the barbiturate coma and brain dead?

What should be thiopentone level in a patient to declare brain dead? What is the pharmacokinetics and pharmacodynamics of thiopentone when given by infusion for a long time say 7 days? After how many days the pt is said to be free of thiopentone?