Lethargy in a 65-yr-old Man

Essential Differential Diagnosis

Shortly after initial examination, the patient becomes extremely lethargic. He responds to deep pain by withdrawing, and he is able to protect his airway. He is noted to have the following:

• Heart rate 30 beats/min
• BP 74/52 mm Hg
• Respirations 10/min
• Pulse oximetry 94% on room air.
• His pupils remain equal and reactive.

At this time, essential differential diagnoses should include which of the following? (You may select more than one option.)