A 48-yeаr-оld mаle with а histоry оf severe alcohol use disorder is brought to the emergency department displaying acute confusion, ophthalmoplegia, and an ataxic gait. Pathophysiologically, chronic ethanol consumption has severely impaired his active GI transport and hepatic storage of a vital coenzyme, disrupting cerebral glucose utilization. To prevent the irreversible cellular necrosis and amnesic confabulation associated with Korsakoff's psychosis, the clinician must immediately administer an intravenous bolus of which nutrient prior to any glucose infusion?