The patient presents with massive hematemesis, hypotension, and tachycardia indicating active upper gastrointestinal bleeding with hemodynamic instability. The priority is rapid resuscitation with blood transfusion to restore circulating volume and improve oxygen delivery. Following initial stabilization, urgent endoscopy is essential for diagnosis and therapeutic intervention, such as variceal band ligation or sclerotherapy. Immediate correction of coagulopathy or other measures without addressing volume loss delays life-saving treatment. Nasogastric tube insertion or beta-blockers are secondary considerations.

Reference: Harrison's Principles of Internal Medicine, J. Larry Jameson, 20th Edition.