Final answer:
The nurse must have a manual resuscitator at the bedside of a ventilator-dependent patient being admitted to the medical surgical unit, as it is essential for providing ventilation in case of an emergency or ventilator failure.
Step-by-step explanation:
The essential piece of equipment that the nurse must have at a ventilator-dependent client's bedside when admitted to the medical surgical unit is a manual resuscitator. Given the scenario that the intensive care unit is full, and the patient requires mechanical assistance to breathe, as deduced from the term ventilator-dependent, the manual resuscitator is critical.
It serves as a backup device to provide ventilation in case of mechanical ventilator failure or during transportation or movement of the patient within the hospital setting. Emergency situations in the medical surgical environment could necessitate immediate manual ventilation, and having a manual resuscitator handy ensures the nurse can maintain the patient's breathing as part of the resuscitation process.