Final answer:
Early symptoms of alcohol withdrawal syndrome include marked tachycardia, marked hypertension, diaphoresis, hallucinations, and hyperthermia, which appear due to the nervous system's hyperactivity after alcohol cessation.
Step-by-step explanation:
The early indications of alcohol withdrawal syndrome for which a nurse should monitor include marked tachycardia (rapid heart rate), marked hypertension (high blood pressure), diaphoresis (excessive sweating), delirium, hallucinations, and hyperthermia (high body temperature).
These symptoms can appear as early as a few hours after the last drink and are due to the central nervous system being hyperactive as a result of the lack of alcohol.
Additionally, since this person is in a critical care setting and has a history of significant alcohol use, withdrawal can progress to more serious conditions, such as seizures and delirium tremens (DTs), which require immediate medical attention.