What should be the nurse's priority intervention for a client who injected an unknown substance?

In the context of a client who has injected an unknown substance, the priority intervention for the nurse is to maintain the airway. Ensuring that the airway is open and clear takes precedence because airway compromise can lead to life-threatening conditions. Regardless of the unknown substance injected, a compromised airway can quickly result in inadequate oxygenation and potential respiratory arrest.

It is critical to assess the client's breathing and responsiveness immediately. If the client is unconscious or has altered mental status due to the substance, they may be unable to protect their own airway, increasing the risk for aspiration and respiratory failure. Therefore, securing the airway should be the first step in addressing the emergency.

Other interventions, such as administering activated charcoal or IV fluids, may be necessary after the airway is secured, but they do not take priority over ensuring that the patient can breathe adequately. Similarly, performing CPR is only indicated if there is no pulse or if the patient is in cardiac arrest, which is not necessarily the case after substance injection without further assessment. Thus, airway management is the foundational step in emergency care for this situation.