Final answer:
An EEG of a comatose 73-year-old post-cardiac arrest may show generalized slowing, a burst-suppression pattern, or even isoelectric activity, indicating various degrees of brain injury.
Step-by-step explanation:
Three days post-cardiac arrest and CPR, a 73-year-old man who is comatose would likely show specific findings on an EEG (electroencephalogram). Considering the patient's clinical presentation with being comatose, not fixing and following with his eyes, but having full horizontal eye movements on Doll's eye maneuver, and symmetrical spontaneous limb movements, the EEG may demonstrate generalized slowing or abnormal patterns such as a burst-suppression pattern or even isoelectric activity, depending on the extent of brain injury. Burst-suppression would indicate severe brain damage, which is consistent with hypoxic-ischemic encephalopathy after cardiac arrest. An isoelectric EEG, showing flat or nearly flat traces, indicates profound brain dysfunction, which is a serious condition. Given the patient's history and symptoms, it is imperative to consider these potential EEG findings and correlate them with his clinical status and further diagnostic information to guide prognosis and management.