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Thousands of 3M Bair Hugger Warming System Suits Reinstated

Aug. 16, 2021, 7:30 PM

3M Co. faces nearly 6,000 reinstated lawsuits by patients alleging they developed severe infections from the Bair Hugger warming system used during joint replacement surgeries, following an Eighth Circuit ruling.

Testimony from the plaintiffs’ experts that the Bair Hugger can cause infection was incorrectly barred as unreliable, the U.S. Court of Appeals for the Eighth Circuit said on Monday.

The appeals court also reversed a district court’s grant of summary judgment to 3M and its Arizant Healthcare Inc. unit, which followed the order excluding the experts.

Plaintiffs allege the forced-air system, used to maintain patient temperature during procedures, caused infections in the affected joints. Their lawsuits were combined in multidistrict litigation in the U.S. District Court for the District of Minnesota, which dismissed them in 2019.

The system consists of a portable heater/blower connected by a flexible hose to a blanket. It warms patients by blowing heated air through the blanket onto their exposed skin.

Patients allege the system causes infections in one of two ways.

According to the “airflow disruption” theory, heat from the Bair Hugger creates currents that carry ambient bacteria to the surgical site. And under the “dirty machine” theory, plaintiffs say that the Bair Hugger is internally contaminated with bacteria, which become ambient and reach the surgical site.

The MDL court barred epidemiologist Jonathan M. Samet, infectious disease specialist William Jarvis, and orthopedic surgeon Michael J. Stonnington after finding too great an analytical gap between their opinions and the information on which they relied.

It also barred their engineering expert, Said Elghobashi, who developed a model showing how bacteria-tainted particles could reach a patient’s surgical site.

The appeals court acknowledged that there are weaknesses in the factual basis for the medical experts’ general-causation opinions.

For example, they have epidemiological evidence reporting an association between Bair Hugger use and joint infections, but they failed to grapple adequately with the shortcomings of that evidence, the court said.

And while the plaintiffs have identified two plausible mechanisms explaining this association, there are shortcomings in the supports for both theories, the appeals court said.

Nonetheless, the MDL court erred in finding that the experts’ general-causation opinions were so fundamentally unsupported that they had to be excluded, it said.

The appeals court upheld the exclusion of some of Elghobashi’s testimony but said his model may be considered as part of the factual basis for the airflow-disruption theory.

Judge Raymond W. Gruender wrote the opinion, joined by Judges Jane L. Kelly and L. Steven Grasz.

Ciresi Conlin LLP, Levin Papantonio Rafferty, and others represent the plaintiffs. Blackwell Burke P.A. and Faegre Drinker Biddle & Reath LLP represent 3M and Arizant.

The case is Amador v. 3M Co., 8th Cir., No. 19-02899, 8/16/21.

To contact the reporter on this story: Julie Steinberg in Washington at

To contact the editors responsible for this story: Rob Tricchinelli at; Patrick L. Gregory at