Bair Hugger Warming Blankets

Bair Hugger systems are forced-air warming devices designed to keep patients warm before, during and immediately after surgery. The device filters air and then forces warm air into disposable blankets used to cover patients. Its original developer now says the device can spread bacteria during surgery, causing infections. 3M is fighting lawsuits from patients who allege the systems were responsible for their deep-joint infections.

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Bair Hugger Warming Blanket

The Bair Hugger Normothermia System is a forced-air warming (FAW) system designed to prevent hypothermia and keep patients at a normal core body temperature during all three phases of orthopedic surgery — preoperative, intraoperative and postoperative phases. The blankets stabilize core temperature ahead of surgery, then maintain it during the procedure and immediately afterwards as the patient recovers.

Hospitals have used Bair Hugger devices on more than 200 million patients since 1987 and continue to do so today. More than 50,000 units are installed in the 80 percent of hospitals in the U.S. that use FAW therapy today.

The current Bair Hugger warming units include models 505, 750 and 775. Model 500 is no longer made. 3M also makes disposable Bair Hugger blankets and gowns.

How Bair Hugger Therapy Works

Bair Hugger warming units filter air and then force warm air through Bair Hugger disposable blankets, which cover patients before, during and after surgery. Bair Hugger blankets are designed to use pressure points on the patient’s body to prevent heat from reaching areas at risk for pressure sores or burns. The blankets also include drain holes where fluid passes through the surface of the blanket to linen underneath, which is supposed to reduce the risk of skin softening and reduce the risk of unintended cooling because of heat loss from evaporation.

Bair Hugger blankets are disposable to reduce the chance of infection transmission from one patient to another. They are not designed to enter sterile fields during surgery.

warming blanket pressure points help prevent heat from causing harm

Bair Hugger History

Dr. Scott D. Augustine invented Bair Hugger in 1987 to keep patients warm during surgery. Almost all patients become hypothermic – a condition causing the body to lose heat faster than it can produce heat – during surgery. Even mild hypothermia during surgery can lead to blood loss, infections and prolonged hospital stays. The Bair Hugger equipment includes blankets, warming units and accessories.

Augustine began selling Bair Huggers through his company, Augustine Medical, 30 years ago. The company reorganized under new owners in 2003 and was renamed Arizant. In 2010 3M paid about $810 million to buy Arizant, and it continues to market Bair Hugger products today.

“I am very proud of the old technology,” he said in a New York Times article in 2010. “But I am also proud to spread the word that there is a problem.”

– Dr. Scott Augustine, Bair Hugger inventor

In 2010 Augustine’s company began selling a warming device called HotDog that’s a direct competitor to Bair Hugger. Augustine now says the Bair Hugger blanket should not be used in patients undergoing surgery, especially joint replacements including knee and hip replacement, because the device can spread bacteria linked to infections. “I am very proud of the old technology,” he said in a New York Times article in 2010.

More than 50 orthopedic surgery patients have sued 3M, alleging Bair Hugger was responsible for infections they experienced during surgery. Bacterial joint infection can cause septic arthritis, which can cause sudden pain and swelling and can destroy a joint if not treated promptly with antibiotics.

FDA History

The U.S. Food and Drug Administration (FDA) cleared the first Bair Hugger warming system in 1987 through the 510(k) premarket clearance program as a substantially equivalent device. Under the 510(k) program, the FDA can clear a medical device without clinical proof that it is safe if it is similar enough to a previous device already on the market.

The FDA issued 12 additional clearances for Augustine Medical devices through the 510(k) premarket program from 1990 through 2002. After Arizant took over the Bair Hugger product line, the FDA issued two more clearances for medical devices through the 510(k) program from 2004 through 2006.

Over the course of its 30 years on the market, numerous adverse events have been reported to the FDA. The majority of early adverse event reports involved burns from prolonged exposure to heat during surgery or equipment malfunctions that resulting in cold air circulating under the blanket.

Bair Hugger Recall

In January 2018, Bair Hugger recalled 165,000 warming blankets due to a design defect. The recall was not related to infection risks. The company said a design change could prevent some blankets from fully inflating. This could lead to dangerous changes in body temperature during surgery.

“If blankets are only partially inflated during use in surgery, the potential exists for incomplete warming therapy to be given to a patient,” 3M said in a Field Safety Notice.

The FDA received a report in January 2018 of a blanket that failed to fully inflate. A patient suffered hypothermia as a result.

The patient’s body temperature dropped to 95 degrees during the surgery. Doctors moved the patient to the intensive care unit. The patient remained there until regaining normal body temperature.

3M later recalled the lot with the blanket used in the surgery.

The worldwide recall affected 33,108 cases of Bair Hugger blankets. Each case contains five blankets.

Distributors shipped the affected lots to hospitals around the U.S. and 17 other countries. The affected lots were all distributed after Oct. 26, 2017.

Bair Hugger Lot Numbers Recalled

  • R10359
  • R10360
  • R10361
  • R10362
  • R10363
  • R10364
  • R10365
  • R10366

Infection Risk

While some infections are easily treated, others are not. Patients can and have developed serious deep joint infections during surgery, including methicillin-resistant Staphylococcus aureus (MRSA), which can cause incurable problems ranging from skin infections and sepsis to pneumonia and bloodstream infections. Surgeries involving implants, including knee, hip and other joint implants, have a higher risk for contamination than other surgeries.

Beginning in 2011, some studies claimed to have found forced-air warming could increase the risk of infection during high-risk orthopedic surgeries. However, some researchers say these studies have flaws that make them inconclusive, unreliable and unable to prove that FAW increases infection risk. And Bair Hugger maker 3M maintains that the systems are safe and effective in all surgeries, including orthopedic surgeries.

Bair Hugger Infection Risk Studies

  • 2011: Deep Joint Infection

    A 2011 study published in The Journal of Bone and Joint Surgery simulated hip replacement and lumbar spinal procedures using both forced-air warming and conductive fabric warming, with a mannequin as a patient. The researchers released neutral-buoyancy detergent bubbles near the mannequin’s head and at floor level to assess the movement of non-sterile air into the clean airflow over the surgical site. They reported, “a significant increase in deep joint infection, as demonstrated by an elevated infection odds ratio … was identified during a period when forced-air warming was used compared to a period when conductive fabric warming was used.”

  • 2012: Convection

    Researchers in 2012 conducted a similar study, as reported in the journal Anesthesia & Analgesia. They released neutrally buoyant detergent bubbles on the head side of an anesthesia drape and tracked whether they moved to the surgical site. When forced-air warming was used, they found “a significant mean increase in the temperature … and number of particles … over the surgical site when compared with radiant warming, which raises concern as bacteria are known to require particles for transport.”

  • 2012: Visualizing Forced-Air Warming

    Another 2012 study, reported in Bone & Joint Journal, attempted to visualize “the airflow in theatre over a simulated total knee replacement using neutral-buoyancy helium bubbles.” Researchers used a smoke machine under an operating table to simulate potentially contaminating particles. They found that “waste heat from the poorly insulated forced-air warming blanket increased the air temperature on the surgical side of the drape,” creating convection currents that increased the number of particles found on the surgical side to more than a thousand times the number found without FAW.

  • 2013: Increased Air Temperature

    A 2013 study in the journal Anaesthesia put a mannequin on an operating table and covered it with three different kinds of lower-body warming devices: Bair Hugger forced-air warming blanket, HotDog conductive fabric blanket and Inditherm under-body resistive mattress. Researchers measured the temperatures at the mannequin’s shoulders, knees and abdomen and at five heights: floor, table, patient, head and overhead. They found “forced-air warming to generate increased ventilation field temperatures vs. both conductive warming devices.” Waste heat created convection currents that created turbulence over the patient that could draw damaging particles from below the operating table to the surgical site.

Thousands File Suit Over Bair Hugger Infections

The first lawsuit over an infection blamed on a Bair Hugger device was filed in 2013. By November 2013, more than 4,000 lawsuits had been filed. People who filed the lawsuits claim the device led to infections that required as many as 27 additional surgeries and even leg amputations.

Minneapolis Courthouse
Minneapolis U.S. Courthouse where the MDL was combined

The first 14 cases were combined in a multidistrict litigation (MDL) in a Minnesota federal court in 2015. Lawsuits filed around the country since then have been transferred to the MDL. MDLs allow several, similar cases to be combined in a single action to save time and money as they move through the legal system.

The judge in the MDL has chosen five bellwether cases, which will each be tried separately, beginning in early 2018. The outcome of these trials may determine if the other cases go forward and could factor into the amount of any settlement.

3M Defends Bair Huggers

In response to Augustine’s claims, these studies and increasing numbers of lawsuits, 3M launched a campaign to prove Bair Huggers were safe. 3M said Augustine’s claims are alarmist and based on faulty studies and offers as evidence the results of more than 170 studies and more than 60 randomized clinical trials that show the system’s benefits, efficacy and safety.

In 2016, 3M published a pamphlet entitled “Let’s spread good science” in which it maintained that an independent review of literature about FAW systems by ECRI Institute, an independent organization, found “insufficient evidence to establish that the use of FAW systems leads to an increase in SSIs (surgical site infections) compared to other warming methods,” and claimed that studies to the contrary used flawed methodologies.

“There is no evidence that forced-air warming increases the risk of infection,” 3M attorney Christiana Jacxsens told Outpatient Surgery Magazine in 2015. “In its entire history, not one hospital, doctor or medical provider has reported a single confirmed incidence of infection believed to be caused by the Bair Hugger device.”

Dr. Javad Parvizi, Professor of Orthopedic Surgery, Rothman Institute at Thomas Jefferson University, analyzed the evidence presented that FAW increased infections. He said, “There is no scientific proof that the use of forced-air warming blankets leads to an increase in surgical site infection regardless of the type of surgical procedure and the type of operating room.”

Alternative Treatment Options

For patients who want to avoid operating theatres where forced-air warming is used, there are alternatives. One alternative uses blankets with conductive fabric made with at least one layer of resistive polymers such as Augustine’s HotDog product. Another way of keeping patients warm uses a mattress or garments with circulating warm water. A third alternative is a mattress with a conductive heating surface, such as Inditherm.

Please seek the advice of a medical professional before making health care decisions.


Terry Turner is an Emmy-winning, former television journalist. He is an associate member of the American Bar Association, the ABA’s Health Law group and a member of the Alliance of Professional Health Advocates. He holds six certificates in Health Literacy for Healthcare Professionals from the Centers for Disease Control and Prevention. As a Washington-based investigative reporter, he routinely reported on health and medical policy issues before Congress, the FDA and other federal agencies. Terry received his B.A. in Media Arts from Lyon College.

Hide Sources

  1. 3M Bair Hugger. Retrieved from
  2. Lee, Thomas. (2010, September 9). 3M to acquire patient-warming product maker Arizant for $810M. Retrieved from
  3. HotDog. Retrieved from
  4. Meier, Barry. (2010, December 24). Doctor Says a Device He Invented Poses Risks. Retrieved from
  5. Carlson, Joe. (2015, November 15). Lawsuits turn up heat on 3M's Bair Hugger warming blankets. Retrieved from
  6. Goldenberg, Don L., MD. (2015, June 10). Patient education: Joint infection (Beyond the Basics). UpToDate. Retrieved from
  7. Methicillin-resistant Staphylococcus aureus (MRSA). (2016, May 16). Centers for Disease Control and Prevention. Retrieved from
  8. McGovern, PD. (2011, November). Forced-air warming and ultra-clean ventilation do not mix: an investigation of theatre ventilation, patient warming and joint replacement infection in orthopaedics. The Journal of Bone and Joint Surgery. Retrieved from
  9. Belani, KG et al. (2012, July 19). Patient Warming Excess Heat: The Effects on Orthopedic Operating Room Ventilation Performance. Anesthesia & Analgesia. Retrieved from
  10. Legg, AJ. (2013). Forced-Air Patient Warming Blankets Disrupt Unidirectional Airflow. The Journal of Bone and Joint Surgery. Retrieved from
  11. Dasari, KB. (2012 March). Effect of forced-air warming on the performance of operating theatre laminar flow ventilation. Anaesthesia. Retrieved from
  12. FAWFACTS. 3M. Retrieved from
  13. Let’s spread good science. (2016). 3M. Retrieved from
  14. Wasfie, Tarik J. and Barber, Kimberly R. (2015, January). Value of Extended Warming in Patients Undergoing Elective Surgery. International Surgery. Retrieved from
  15. 3M Bair Hugger. Retrieved from
  16. Meier, Barry. (2010, December 24). Doctor Says a Device He Invented Poses Risks. Retrieved from
  17. Forced-air warming and ultra-clean ventilation do not mix: an investigation of theatre ventilation, patient warming and joint replacement infection in orthopaedics. (2011, November). Retrieved from
  18. Patient Warming Excess Heat: The Effects on Orthopedic Operating Room Ventilation Performance. (2012, July 19). Retrieved from
  19. Forced-Air Patient Warming Blankets Disrupt Unidirectional Airflow. (2013). Retrieved from
  20. Effect of forced-air warming on the performance of operating theatre laminar flow ventilation. (2012 March). Retrieved from
  21. FAWFACTS. 3M. Retrieved from
  22. Welbes, J. (2013, March 28). Texas patient suing 3M for Bair Hugger injury. Retrieved from:
  23. Gibb, Gordon. (2105, October 5). Bair Hugger: The Answer Is Blowing in the Wind. Retrieved from
  24. Gibb, Gordon. (2017, February 8). Federal Bair Hugger Lawsuits Climbing, Now Number 1105 in MDL. Retrieved from
  25. Johnson v. 3M Company and Arizant Healthcare. (2014, April 22). Retrieved from
  26. Torres, Louie. (2016, November 11). Woman blames Rush University Medical Center, others for alleged burn injuries from Bair Hugger. Retrieved from
  27. Kirk, Austin. (2015, August 24). Bair Hugger Warming Blanket Lawsuit Centralization Sought with JPML. Retrieved from
  28. Kirk, Austin. (2015, September 16). 3M Opposes Centralization of Bair Hugger Infection Lawsuits. Retrieved from
  29. Kirk, Austin. (2015, December 14). Bair Hugger Infection Lawsuits Centralized in MDL for Pretrial Proceedings. Retrieved from
  30. U.S. Dist, Court for the Dist. of Minnesota. (2017, October 20). In re: Bair Hugger Forced Air Warming Devices Products Liability Litigation, MDL No. 15-2666; Order. Retrieved from:
  31. U.S. Judicial Panel on Multidistrict Litigation. (2018, January 16). MDL Statistic Report. Retrieved from
  32. 3M Company. (2018, January 25, 2018). Field Safety Notice. Federal Institute for Drugs and Medical Devices (Germany). Retrieved from
  33. U.S. Food and Drug Administration. (2018, February 12). Class 2 Device Recall 3M Bair Hugger Normothermia System, Full Access Underbody Warming Blanket. Retrieved from
  34. Carlson, J. (2018, February 13). 3M Recalls Some Bair Hugger Underbody Warming Blankets. Minneapolis StarTribune. Retrieved from
  35. U.S. Food and Drug Administration. (2018, January 30). MAUDE Adverse Event Report: 3M Health Care 3M Bair Hugger Full Access Underbody Warming Blanket Disposable Thermal Blanket. Retrieved from
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