A 52-year-old male from Delhi with a 15-year history of alcohol use disorder presents with acute confusion, ataxia, and ophthalmoplegia (inability to abduct both eyes). His wife reports he has not eaten properly for 2 weeks. On examination, he is disoriented to time and place, has nystagmus, and shows impaired eye movements. Blood glucose is 110 mg/dL, and liver function tests show mild elevation of transaminases. What is the most appropriate immediate management?