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Reducing the Risk

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 Bair Paws Gown UBB

Improving patient outcomes through perioperative warming

Almost any patient undergoing anaesthesia is susceptible to inadvertent perioperative hypothermia. Inadvertent perioperative hypothermia has been called a frequent, preventable complication of surgery.1

Many publications have documented the adverse effects on patient outcomes, which include an increase in wound infections,2 increased length of stay3 and higher mortality rates.4 Some estimates say that more than 50% of all surgical patients are hypothermic on arrival to the recovery room.5

Research has shown that patients can lose up to 1.6°C during the first 60 minutes of anaesthesia6, due to anaesthesia induced vasodilatation. Under normal conditions the temperature gradient between the body’s core and periphery is approximately 2 to 4°C and is very tightly controlled. Anaesthesia induced vasodilatation allows the warmer blood in the core, to flow freely around the cooler periphery. As the blood circulates throughout the periphery, it cools before returning back to the heart, where it causes a drop in core body temperature. This process of reducing core body temperature is known as redistribution temperature drop (RTD) and is responsible for 81% of the heat loss during the first hour of anaesthesia.7 After the first hour of anaesthesia, the body continues to lose heat, but at a slower rate, with RTD contributing to only 43% of this further reduction.7 Therefore during the first hour of anaesthesia the main cause of hypothermia, is core-to-periphery redistribution.

One of the most important factors controlling the extent redistribution hypothermia affects the patient’s temperature is their initial body heat content.7 Core body temperature remains relatively constant, even in warm environments. However as the peripheral tissues warm, the body heat content increases reducing the core-to-periphery gradient. As heat requires a gradient to flow, the extent to which redistribution hypothermia affects body temperature decreases as body heat content increases.

Actively warming patients before induction of anaesthesia (prewarming) is an effective way to increase body heat content and help prevent perioperative hypothermia in many surgical procedures. Cotton blankets, especially warmed ones may be comforting, but these passive insulators do not provide any active warming. In fact heat from cotton blankets dissipates into the environment.8

Prewarming patients before surgery has been shown to reduce the effect of RTD, maintain normothermia,9 reduce postoperative shivering9 and aid in the reduction of postoperative wound infection.10 Prewarming has also been shown to reduce length of stay in the recovery room and reduce the cost of anaesthesia.11

The 3M™ Bair Paws™ Patient Warming System offers a way of reducing anaesthesia induced RTD and improving patient outcomes, through a reduction in the adverse effects of hypothermia. The Bair Paws system uses forced-air warming technology to provide both preoperative warming, that will contribute to increasing body heat content, as well as perioperative clinical warming for many surgical procedures.

There are two parts to the Bair Paws system: the warming gown and the warming unit. The Bair Paws gown is worn like a traditional gown, however, unlike a traditional gown, it has its own special features.  Inside the front of the gown is a Bair Hugger blanket, that has two independent air channels for delivering forced-air warming pre, intra and postoperatively. The Bair Paws warming unit is attached to the gown to circulate warm air around the patient via the gown. The temperature of the air flowing through the gown can be controlled by the patient, by the use of a handheld controller. This ensures the patient remains comfortable during the preoperative warming period.

For a number of surgical procedures, the Bair Paws gown can be used to deliver intraoperative clinical warming, by connecting the Bair Paws gown to a Bair Hugger warming unit in the theatre

With only a minimum of 10 to 20 minutes of prewarming required,12 the Bair Paws system offers an easy method of ensuring you provide patients with a high standard of care and assists in reducing the adverse effects of inadvertent perioperative hypothermia.

 For further information visit and

3M is a trademark of 3M Company.

Bair Paws & Bair Hugger are trademarks of Arizant Healthcare Inc, a 3M Company.



  1. Kurz, A. Thermal care in the perioperative period. Best Practice & Research Clinical Anaesthesiology, 22 (1):39-62, 2008
  2. Barie, PS. Surgical site infections: epidemiology and prevention, Surgical Infections, 3:9-21, Supplement, 2002
  3. Kurz et al. Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group. New England Journal of Medicine, 334(19):1209-15, 1996
  4. Tryba et al. Does active warming of severely injured trauma patients influence perioperative morbidity? Anesthesiology, 85:A283, 1996
  5. Young, V. Prevention of Perioperative Hypothermia in Plastic Surgery. Aesthetic Surgery Journal :551-571, 2006
  6. Sessler, DI. Current concepts: mild perioperative hypothermia. New England Journal of Medicine, 336: 1730-1737, 1997
  7. Sessler, DI. Perioperative Heat Balance. Anesthesiology, 92: 578-596, 2000
  8. Sessler et al. Heat Loss in Humans Covered with Cotton Hospital Blankets, Anesthesia & Analgesia, 77(1):73-77, 1993
  9. Bernard et al. Prevention of Intraoperative Hypothermia by Preoperative Skin-Surface Warming, Anesthesiology, 79:214-218, 1993
  10. Melling et al. Effects of preoperative warming on the incidence of wound infection after clean surgery: a randomised controlled trial, The Lancet, 358:876-880, 2001
  11. Bock et al. Effects of preinduction and intraoperative warming during major laparotomy, British Journal of Anaesthesia, 80:159-163, 1998
  12. Horn et al. The effect of short time periods of pre-operative warming in the prevention of peri-operative hypothermia, Anaesthesia, 67:612-617, 2012