Final answer:
In the case of an unconscious individual, a phlebotomist should call for help immediately to ensure their safety and well-being.
Step-by-step explanation:
In the case of an unconscious individual, a phlebotomist should call for help immediately. Time is of the essence in situations like this, as the brain requires a continuous supply of oxygen to function properly. As mentioned in the provided information, brain cells can start dying after about six minutes without oxygen. Therefore, it is crucial to act quickly and call for help as soon as someone becomes unconscious.