A Dallas anesthesiologist was arrested on charges alleging that he injected nerve-blocking agents and other drugs into bags of intravenous fluids at the surgical center where he works, which led to the death of a co-worker and caused cardiac emergencies for several patients, authorities announced Thursday.

Dr. Raynaldo Rivera Ortiz Jr. was arrested Wednesday on a criminal complaint alleging that he tampered with a consumer product causing death and intentional drug adulteration, according to a statement from the U.S. attorney’s office for the northern district of Texas. If convicted, he could be sentenced to life in prison.

Ortiz, 59, remained in the Dallas County jail without bond on Thursday. Records don’t list an attorney for him.

According to the criminal complaint, a 55-year-old female coworker of Ortiz experienced a medical emergency and died June 21 immediately after treating herself for dehydration with an IV bag of what she thought was saline taken from the surgical center. An autopsy found that she died from a lethal dose of bupivacaine, a nerve-blocking drug that is rarely abused but often is used when an anesthetic is given.

On Aug. 24, an 18-year-old male patient experienced a cardiac emergency during routine sinus surgery, was intubated and transferred to an intensive care unit. Chemical analysis of the fluid from a saline bag used during his surgery revealed the presence of bupivacaine, the stimulant epinephrine and the topical anesthetic lidocaine, drugs that could have caused the patient’s sudden symptoms, according to prosecutors.