Eighth Circuit breathes new life into In Re Bair Hugger Products Liability MDL

ABSTRACT: Litigation over medical warming devices may heat up, as the Eighth Circuit reverses a District Court decision that struck multiple expert witnesses and granted summary judgment.

On August 16, 2021, the Eighth Circuit Court of Appeals reversed a District Court decision striking class action plaintiffs’ experts and granting summary judgment to 3M Company in the In re Bair Hugger Forced Air Warming Devices Products Liability Litigation. This case is part of Multi-district Litigation (MDL) proceedings, consisting of nearly 6,000 lawsuits, pending in the District of Minnesota. The MDL court, following similar rulings by the trial court in the first bellwether case, excluded Plaintiffs’ general-causation medical experts as well as one of their engineering experts, and granted 3M summary judgment as to all of plaintiffs’ claims.

Plaintiffs in the MDL have brought claims against 3M asserting that they contracted periprosthetic joint infections due to the use of 3M’s Bair Hugger. The Bair Hugger is a convective, or forced-air, patient-warming device intended to stave off hypothermia related complications that can arise during or after surgery. The device consists of a central heating unit, a hose, and a disposable perforated blanket that is placed over the patient. The central unit draws in air through a filter, warms the air, and blows it out through the hose into the perforated blanket.  

MDL plaintiffs proffer two theories of causation: first, waste heat from the device creates currents that carry bacteria from nonsterile areas of the operating room to the surgical site (“the airflow theory”); or second, the device is internally contaminated and projects bacteria through the blanket into the operating room (“the contaminated product theory”). 

The MDL court excluded plaintiffs’ engineering expert on the grounds his opinion relied upon modeling developed for litigation and was unproven and untested in real-world operating rooms.

Plaintiffs’ engineering expert created a computational-fluid-dynamics (“CFD”) model to support the airflow theory that was eventually published in a peer-reviewed journal, and which the MDL court found to be reliable based upon the underlying physics.  Nonetheless, the MDL court excluded plaintiffs’ engineer because his conclusion “relies on an unproven and untested premise” in actual practice, and the CFD model was developed for litigation, raising “concerns about its reliability and objectivity.” The Eighth Circuit disagreed, ruling that when a “hired gun” expert’s work has been peer reviewed and published, and the developed-for-litigation concern is the only basis for excluding an expert, lingering questions of reliability and objectivity go to the weight of the evidence, rather than its admissibility. DiCarlo v. Keller Ladders, Inc., 211 F.3d 465, 468 (8th Cir. 2000). The Eighth Circuit found it was an abuse of discretion to wholly exclude the engineer’s testimony.

Plaintiffs’ medical causation experts asserted causation based upon the CFD model and an observational epidemiological study, which disclaimed establishing a causal connection, finding that patients warmed by the Bair Hugger were four times more likely to contract an infection.

The MDL court excluded plaintiffs’ medical experts, finding their opinions unreliable because there was “too great an analytical gap between the literature and the experts’ general causation opinion.”   The MDL court deemed it unreliable for the medical experts to draw an inference of causation from a study that disclaimed proving causation. The Eighth Circuit rejected that it is per se unreliable for an expert to draw an inference of causation from a study disclaiming having proved causation, if the expert does the work to bridge the gap between association and causation. The Eighth Circuit found that plaintiffs’ experts also relied on studies and reports showing plausible mechanisms for forced-air warming to cause infections. As such, the District Court should not have wholly excluded the experts as the disclaimer of causation from the epidemiological study went to the weight of the opinions rather than render them unreliable and inadmissible.

The MDL court’s grant of summary judgment to 3M was derivative of its order excluding Plaintiffs’ experts, and thus was reversed by the Eighth Circuit.

What does this mean for your company?

While the Eighth Circuit’s decision seems to be a boon to plaintiffs, who have the burden of proving their case, companies defending products liability cases can create a strategic advantage by retaining the right counsel and experts. If you, like 3M, are defending products liability litigation, you want to retain experts who can effectively bridge the gap between theory and the real world.