A former nurse who stole intravenous drugs from at least 25 patients in St. Cloud Hospital and replaced the narcotics with saltwater was sentenced Wednesday in Minneapolis to two years in federal prison.

State investigators found that the nurse’s actions in 2010 and 2011 resulted in bacterial contaminations in six people. Three required additional surgery and one died.

Blake Zenner, 43, of Kimball, Minn., had worked at the hospital for 17 years when he was caught diverting hydromorphone hydrochloride, known as Dilaudid, from patients’ intravenous drip bags for himself and his wife. He pleaded guilty to obtaining a controlled substance by fraud.

Paul Engh, his attorney, asked for a lenient sentence, arguing that Zenner, an addict, meant no harm. Most of the patients who suffered showed symptoms of fever or flu, Engh wrote. He said the government’s assertion that one patient died “does not prove causation,” and he noted that Zenner has not been charged with manslaughter.

The Health Department stopped short of saying that the infection was to blame for the patient’s death, but said it was “highly unlikely” that it was just a coincidence. The hospital disagreed, saying that the patient who died had tested positive for a bloodstream infection when admitted, and quickly deteriorated.

Federal sentencing guidelines called for a sentence of six months to a year. Federal prosecutors, citing the harm Zenner cause, argued for four years — the maximum possible under the plea agreement.

U.S. District Judge Patrick Schiltz split the difference, sentencing Zenner to two years in prison, plus a year of supervised release and $340,000 in restitution.

Engh said at least four of Zenner’s victims have filed lawsuits against him, but he lacks the funds to defend himself. “The cascading cost of litigation, not to mention access to the courts, is about to financially bury Mr. Zenner,” he wrote.

Dan Henson, special agent in charge of the U.S. Food and Drug Administration’s Office of Criminal Investigations in Chicago, issued a statement saying Zenner “exhibited a blatant and heartless disregard for the patients he victimized.”