DALLAS (AP) — Federal agents have arrested a Dallas anesthesiologist on charges alleging that he injected nerve-blocking agents and other drugs into bags of intravenous fluids at the surgical center where he works, causing the death of a co-worker and cardiac emergencies for several patients. The U.S. attorney’s office for the northern district of Texas said Thursday that Dr. Raynaldo Rivera Ortiz Jr. was arrested Wednesday for allegedly tampering with a consumer product causing death and intentionally adulterating drugs. He could face life in prison if convicted. Prosecutors say a 55-year-old female co-worker died after treating herself with an IV bag of what she thought was saline. An autopsy found that she died from a lethal dose of a nerve-blocking drug.