Which of the following is an undesirable effect of conscious sedation?

Nystagmus refers to a condition characterized by involuntary eye movement, which can occur as a result of certain sedatives used during conscious sedation. This is considered an undesirable effect because it may affect the patient's ability to remain focused and can indicate an underlying issue with the sedation level or the specific medication used.

In the context of conscious sedation, maintaining a balance between sedation and patient responsiveness is key. While cooperation and easy arousal from sleep are actually desired outcomes of effective conscious sedation, nystagmus serves as a potential complication that could necessitate further medical assessment or adjustment of the sedation plan. Diminished verbal communication might occur during conscious sedation as a result of the sedative effect, but it does not inherently indicate an undesirable or harmful reaction as nystagmus can.