Final answer:
The principle that guides the nurse in preventing harm when the client is excessively sedated is nonmaleficence.
Step-by-step explanation:
The principle that guides the nurse in preventing harm when the client is excessively sedated is nonmaleficence. The principle of nonmaleficence states that we should act in ways that do not cause harm to others. In the context of nursing, this means that the nurse should take measures to ensure that the client is not harmed by excessive sedation.