A former nurse has been accused of trying to kill her sick husband by injecting faeces into his hospital drip.

Rose Vogel, 65, of Sun Lakes, Arizona, who used to work at Chandler Regional Medical Centre, was arrested on suspicion of attempted first-degree murder after a nurse at the hospital, in a suburb of Phoenix, found her handling her husband's drip.

The drip was found to contain a brown substance, which a hospital lab test identified as faecal matter. A trace amount of a brown substance also was found in the needle of an empty syringe found in Vogel's purse, police said.

Vogel's purse contained a total of three syringes, including two with a clear liquid. Police documents said Vogel was a retired registered nurse who formerly worked at the hospital.

Police do not have a possible motive and investigators will conduct forensic tests on all the materials involved over the next week or two, Sgt Joe Favazzo said

He said the hospital had to test the brown substance in the drip immediately for treatment purposes. "The lab came back with faecal matter," he said.

The incident occurred after Vogel's 66-year-old husband had undergone a heart procedure. He is expected to survive that, as well as the alleged attempt on his life.

Vogel, who declined to be interviewed by police and asked for a lawyer, appeared in court yesterday and bail was set at $100,000.