Bair Hugger lawsuit reinstated

Things are looking up for plaintiffs in the massive multi-district litigation against 3M over its patient warming device, the Bair Hugger, since the 8th U.S. Circuit Court of Appeals earlier this month cried foul and reversed a summary judgment for the defendant in Amador v. 3M.

The Bair Hugger is a machine that uses forced air in warming blankets used during surgery. The device allegedly causes infection by distributing bacteria.  It is the subject of a multi-district litigation venued in District Court in Minnesota.

The MDL collapsed in 2019 when U.S. District Court Judge Joan Ericksen excluded the plaintiffs’ general causation medical experts and one of its engineering experts. The defense prevailed in the first bellwether trial, Gareis v. 3M Co., which included expert testimony.  Ericksen then granted summary judgments to the defendants, dismissing in the neighborhood of 6,000 claims.

The 8th Circuit reversed. It acknowledged a deferential standard of review but said that the court committed a “clear error of judgment” based on the record before it by excluding expert testimony.

3M came back swinging. It released the following statement: “We are pleased by the Court of Appeals decision, which upheld a jury verdict that the 3M Bair Hugger system was not defective and did not cause a surgical site infection. In Monday’s procedural decision, the Court of Appeals ruled that the lower court should not have excluded the plaintiffs’ experts from testifying before a jury in other Bair Hugger cases. In the case addressed by this latest decision, those very experts testified to a jury. The jury unanimously rejected their testimony and reached a verdict for 3M. At 3M, we rely on science, and the science supports the clinical efficacy and safety of the Bair Hugger system.”

Minneapolis attorney Genevieve Zimmerman, co-lead counsel for plaintiffs, welcomed the ruling. She wrote to Minnesota Lawyer:

“Plaintiffs are gratified with the Amador decision, where the Eighth Circuit unanimously agreed that there is scientific evidence that shows 3M’s Bair Hugger is capable of causing deep-joint infections following joint replacement surgery. No challenge was ever lodged regarding the qualifications or methodology employed by the world-class experts offered by plaintiffs, who detailed precisely how it was they reached each of their respective opinions. Indeed, plaintiffs’ engineering expert, Dr. Said Elghobashi, submitted the very report he prepared regarding this case to the preeminent international journal on biomedical engineering, where it was subject to rigorous peer-review and ultimately published. The Eighth Circuit properly concluded it was clear error to exclude these experts, effectively reinstating nearly 6,000 cases.

“Many people understand after the past 18 months with COVID that pathogens — like bacteria and viruses — can be transmitted through the air, but these well- established and long understood principles of both engineering and medicine have been long known and understood by scientists at 3M. It is unfathomable that a company like 3M would simultaneously manufacture and sell N95 masks and also deny the risk of airborne contamination presented by the Bair Hugger.

“It is our sincere hope that 3M takes another close look at both the science here and the potential risks moving forward, and makes different choices with patient safety in mind moving forward. We are committed to representing those people injured by what we believe is a dangerous device, and look forward to presenting evidence supporting those claims in court.”

Experts excluded

Plaintiffs allege that they contracted joint infections because the device was used during orthopedic-implant surgery. The plaintiffs’ theorized that the movement of the air allows bacteria into the surgical site. Their cases are based on state-law claims of negligence and strict liability.

As the litigation progressed, 3M moved to exclude plaintiffs’ general causation medical experts (Dr. Jonathan M. Samet, an epidemiologist; Dr. William Jarvis, an infectious-disease specialist; and Dr. Michael J. Stonnington, an orthopedic surgeon) as well as plaintiffs’ engineering experts (including Dr. Said Elghobashi and Michael Buck).

After the Gareis trial, the court excluded the general-causation medical experts and Dr. Elghobashi, and entered an MDL-wide summary judgment.

‘Analytical gap’

Federal Rule of Evidence 702 requires that expert testimony be relevant and thus useful to the trier of fact. It also requires that the expert is qualified and the evidence is reliable or trustworthy.

The Court of Appeals said that the District Court excluded medical experts as unreliable because it concluded there was “too great an analytical gap between the literature and the experts’ general causation opinions” and “the causal inferences made by the experts have not been generally accepted by the scientific community.”

The judge also excluded an engineer’s testimony, which included a computational-fluid-dynamics model to support the plaintiffs. The judge said the witness’s conclusion about the Bair Hugger’s effects in real-world operating rooms relied on an unproven and untested premise. Ericksen also found that there was too great an analytical gap between the results of the witness’s model and his conclusion about the Bair Hugger’s actual effects, and also that the model was developed for litigation.

Evidence as a whole

The third part of the Rule 702 tests, reliability, is at issue. Reliability factors include testing of the expert’s theory, peer review or publication, known or potential rate of error, and general acceptance. Other factors include whether the research or opinion has been developed solely for the purpose of testifying.

But another line of case law states that the factual basis of an expert opinion goes to weight, not admissibility. Doubts should generally be resolved in favor of admissibility.

The trial court admitted a 2011 study that patients warmed with convective devices, such as Bair Huggers, were nearly four times more likely to contract a joint infection. But the court said that the experts’ reliance on it created the “analytical gap.”

The 8th Circuit said that one problem for the trial court was that the study did not claim to establish causation but the experts drew an inference of causation from it. This was not necessarily unreliable because the expert witnesses did the work to “bridge the gap between association and causation,” the 8^th Circuit said.

And although the experts did not adequately address the problems with the study, they relied on other evidence to support their inference, and the evidence should be viewed as a whole, the 8th Circuit said. That evidence included a model developed by Elghobahi as well as studies and reports that “ostensibly” supported plaintiffs’ theories about the Bair Hugger.

The 8th Circuit affirmed the trial court’s exclusion of the evidence of the “real world” effect of the Bair Hugger but not the “categorial exclusion” of the witness and his model. Again, the court said because the export’s conclusion had been published the “developed for litigation” questions go to weight and not admissibility.

It also said that “a few” of the other studies used by the medial experts “ameliorate the problematic gap” found by the trial court.

There was sufficient support for the experts’ opinions that the Bair Hugger can cause airflow disruption that transmits bacteria. Therefore, the court committed a clear error of judgment on the basis of the record before it.

“[T]his was an instance in which our ‘general rule’ that deficiencies in an expert’s factual basis go to weight and not admissibility should have been followed,” said the 8th Circuit.

‘Dirty machine theory’

In addition to the air-flow theory, the plaintiffs also argued a “dirty machine” theory, or that the Bair Hugger can emit bacteria harbored in the machine to the surgical site, relying on studies that the trial court found deficient, creating another analytical gap, the 8th Circuit said.

“Certainly there are weaknesses in the dirty machine theory. Again, however, redress for such weaknesses lies in cross-examination and contrary evidence rather than exclusion,” the court said.

The court then emphasized that its conclusion is a narrow one and that the standard for admissibility is lower than the merits standard of correctness.

It noted, “In several places in its order excluding the medical experts, the MDL court suggested that the weaknesses in the experts’ general-causation evidence, particularly in the evidence regarding the mechanisms of causation, would present significant hurdles for the specific-causation showing these Plaintiffs must make to prevail — that is, that they would not have contracted a [joint injury] but for use of the Bair Hugger during their surgeries. Whether this is so is not at issue in this appeal, and we express no view on it here. We hold only that the MDL court abused its discretion in excluding these experts’ general-causation opinions on the basis of excessive analytical gaps.”