A 27-year-old woman came to the dentist for the purpose of oral cavity sanation. After anesthesia, she started complaining of dizziness, ringing in her ears, dimming vision, and general weakness. Objectively, her skin is pale and covered in cold sweat. Her pulse is 94/min., of low volume and pressure. Her blood pressure is 96/60 mm Hg. She had a brief episode of unconsciousness that lasted 30 seconds. What urgent condition developed in this woman?