A Minnesota Court of Appeals panel on Monday upheld the dismissal of dozens of state-court lawsuits that had claimed 3M Co.'s widely used Bair Hugger patient-warming system caused surgical infections.

Thousands of people who came down with infections after joint-replacement surgery have sued 3M after seeing commercials for the litigation on television or on the internet. 3M said there's no valid science behind the litigants' theory of infection, while the litigants said 3M has manipulated studies or ignored the science to protect sales of its popular medical device.

The Appeals Court ruling Monday pertains only to 61 Bair Hugger lawsuits filed against Maplewood-based 3M in state courts by residents of Minnesota. The vast majority of the Bair Hugger lawsuits — 5,000 or so — are pending in federal court, and are not affected by Monday's ruling.

Monday's ruling upholds a lower state court's decision to grant 3M pretrial summary judgment and dismiss the 61 lawsuits. The lower court ruled, and the Appeals Court agreed Monday, that the plaintiffs never offered strong enough general evidence from experts that the Bair Hugger can cause an infection in the way that the patients claim.

"We defer to the assessment of the relevant scientific community rejecting [the plaintiffs'] novel scientific theory and conclude there is no demonstrated causal relationship," between the use of forced-air warming systems like the Bair Hugger, and increased risk of surgical-site infections, Court of Appeals Judge Francis J. Connolly wrote on behalf of the undivided three-judge panel.

In an e-mailed statement, 3M reiterated that it stands by the science and will continue to defend the Bair Hugger from a "campaign of misinformation."

"The court's decision is yet another affirmation that there is no generally accepted science that the 3M Bair Hugger system causes infections," the 3M spokeswoman Fanna Haile-Selassie wrote.

The plaintiffs are likely to appeal Monday's ruling to the Minnesota Supreme Court, based on the belief that their experts' opinions are at least strong enough to prove a theory of "general causation" at trial. The plaintiffs would also have to prove specific-causation — that the device likely caused their specific infection — but they can't even have a trial without a showing of general causation under state law.

"We will digest and evaluate [Monday's ruling], but disagree with the ruling in light of evidentiary standards that govern admissibility of expert opinions in Minnesota courts. We anticipate filing a Petition for Review to the Minnesota Supreme Court," plaintiffs attorney Genevieve Zimmerman of Minneapolis' Meshbesher & Spence wrote by e-mail.

The 14-page decision from the Appeals Court describes in some depth the past actions of the Bair Hugger's inventor, Dr. Scott Augustine, who is not a party to the litigation (even though he's referred to erroneously as "appellant Scott Augustine" on page 2 of the decision).

Augustine invented the device in 1987, but he turned against it in the early 2000s and began selling a new device that warms patients without using forced-air. Augustine said the Bair Hugger's forced-air blower creates warm air under an operating-room table that rises, potentially carrying contaminated particles up from the floor to the region above a surgical wound.

Monday's ruling said Augustine hired a law firm to promote non-forced-air warming systems like his newer device, and soon after the same law firm began representing clients suing 3M over the Bair Hugger. It also said Augustine was warned by a court in Germany to stop making false claims the Bair Hugger increased bacterial contamination in operating rooms, and that Augustine "funded" the most critical study of the Bair Hugger to date, which is generally known as the "McGovern" study.

The ruling also sided with 3M in dismissing a request for punitive damages. The plaintiffs had asked the ability to sue for punitive damages against 3M, saying the company had disregarded patient safety by ignoring peer-reviewed articles that raised questions about the Bair Hugger's safety. The Appeals Court agreed that the plaintiffs had not offered enough evidence to support that claim.

"The Minnesota Court of Appeals got it right," 3M's outside counsel on the Bair Hugger litigation, Jerry Blackwell, said via e-mail. "Plaintiffs' lawyers working in cahoots with a motivated 3M competitor shouldn't be able to manufacture theories disparaging a lifesaving medical device, especially theories already rejected by good science and the FDA. The law should lag science and not lead it."

Zimmerman said it was "significant and troubling" that the Appeals Court labeled Augustine as a party to the case, when neither he nor Augustine Biomedical+Design has been a party. Asked about the statement that Augustine "funded" the most critical Bair Hugger study, Zimmerman said none of the authors benefited from the "minimal" funds Augustine Biomedical provided to buy equipment for McGovern.

The plaintiffs' attorney also took aim at a 2017 Safety Alert from the U.S. Food and Drug Administration referenced under the "Facts" section of Monday's ruling. The 2017 FDA alert said forced-air warming systems like the Bair Hugger have been shown to reduce bleeding, speed recovery and cut down on infection risk, and the FDA continued to recommend their use.

Zimmerman said that reassurance of safety from the federal regulator was not what it appeared to be.

"What was not part of the record before the Court of Appeals, but what we know to be true based on representations from counsel in public court, is that the FDA letter is the result of 3M lobbyist efforts rather than a result of review of published literature, much less any 3M internal documents," she wrote.

Joe Carlson • 612-673-4779