A nurse is assessing a client following treatment for serotonin syndrome caused by an antidepressant medication. Which of the following findings indicates the treatment has been effective?

Choice A reason: Altered mental status, such as confusion or agitation, is a hallmark of serotonin syndrome due to excessive serotonin affecting the central nervous system. Persistent altered status indicates ineffective treatment, as resolution would show improved cognition, making this an incorrect indicator of recovery. Choice B reason: Muscle rigidity is a symptom of serotonin syndrome, resulting from serotonin-mediated neuromuscular hyperactivity. Effective treatment, such as with cyproheptadine, reduces rigidity. Persistent rigidity suggests ongoing serotonin toxicity, making this an incorrect sign of treatment success in managing the condition. Choice C reason: Serotonin syndrome causes hypertension due to autonomic dysregulation. A decrease in blood pressure indicates effective treatment, as interventions like serotonin antagonists stabilize autonomic function, normalizing blood pressure. This physiological improvement reflects resolution of the syndrome’s life-threatening effects, confirming treatment efficacy. Choice D reason: Hyperpyrexia, or elevated temperature, is a critical symptom of serotonin syndrome due to serotonin’s effect on thermoregulation. Effective treatment lowers temperature toward normal. Persistent hyperpyrexia indicates unresolved toxicity, making this an incorrect indicator of successful treatment for serotonin syndrome.