Final answer:
In the case of aspirin poisoning in a child, the initial procedure to be implemented is gastric lavage and administration of activated charcoal.
Step-by-step explanation:
In the case of a 5-year-old boy ingesting a bottle of acetylsalicylic acid (aspirin), the initial procedure that should be implemented is Option 2: Institute a gastric lavage and administer activated charcoal. Gastric lavage involves the insertion of a tube into the stomach to remove the toxic substance, while activated charcoal helps to absorb and neutralize the aspirin in the gastrointestinal tract, preventing further absorption into the bloodstream.