- Open Access
The Bair Hugger patient warming system in prolonged vascular surgery: an infection risk?
© Huang et al., licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. 2003
- Received: 20 January 2003
- Accepted: 22 January 2003
- Published: 4 March 2003
Use of the Bair Hugger forced-air patient warming system during prolonged abdominal vascular surgery may lead to increased bacterial contamination of the surgical field by mobilization of the patient's skin flora.
This possibility was studied by analyzing bacterial content in air and wound specimens collected during surgery in 16 patients undergoing abdominal vascular prosthetic graft insertion procedure, using the Bair Hugger patient warming system. The bacterial colony counts from the beginning and the end of surgery were compared, and the data analyzed using the Wilcoxon matched pairs test.
The results showed not only that there was no increase in bacterial counts at the study sites, but also that there was a decrease (P < 0.01) in air bacterial content around the patient and in the operating theatre after prolonged use of the patient warmer. No wound or graft infections occurred.
The use of this warming system does not lead to increased bacterial contamination of the operating theatre atmosphere, and it is unlikely to affect the surgical field adversely.
- air microbiology
- intraoperative care
- operating rooms
- surgical wound infection
Forced-air patient warming systems, such as Bair Hugger (Augustine Medical Inc., Eden Prairie, MN, USA), were developed in the 1980s and are acknowledged as being the most clinically effective patient warming modality [1, 2]. The advantages of avoiding hypothermia for patients undergoing major surgical procedures are well established, and include decreased blood loss (with consequent reduction in blood product use) , wound infection , duration of intensive care and hospital stay [5, 6] and cardiac ischaemia [7, 8], and increased survival [6, 9, 10]. However, a potential disadvantage is the risk for bacterial contamination of the operating theatre environment. Prolonged exposure of the patient to the exhaust of the warming blanket could potentially mobilize their resident skin organisms into the theatre atmosphere, and thence into the surgical field, possibly increasing the risk for prosthetic material infection. This has not previously been investigated.
We studied whether use of the Bair Hugger patient warming system increased bacterial contamination of the operating theatre and the surgical wound during prolonged surgery.
The duration of the operation was recorded. There were nine staff circulating in the operating theatre: three surgeons, two anaesthetists, one operating department assistant and three nurses. All patients had three doses of intravenous antibiotics perioperatively. The data were analyzed using the Wilcoxon matched pairs test .
Twelve male and four female patients were included in the present study. Their mean age was 72.5 years (range 60–86 years). The mean duration of use of the warming blanket was 234 min (range 180–270 min). From each site, the number of bacterial colonies at the start of surgery was compared with that at the end of the operation.
Comparison of the mean number of colonies
Mean number of colonies
Site (see Fig. 1)
Start of operation
End of operation
Operating room air (A1–A3)
Exhaust (B1 and B2)
Comparison of colony numbers
Number of bacterial colonies at different sites (see Fig. 1)
Room air (A1–A3)
Exhaust (B1 and B2)
None of the patients developed postoperative wound or prosthetic infections during a 6-month follow-up period.
In the present study bacteria were not typed; only the absolute numbers of colonies cultured were counted. Typing was to be done only if there was an increase in colony counts at the end of surgery, and this did not occur in any of the patients studied.
As indicated above, the benefits of maintaining normothermia in surgical patients is well documented. It has been shown that the warming equipment itself does not cause bacterial dispersal  but the role of patient flora was not investigated and the study was not conducted in a true surgical setting. This remained a concern in our unit, especially because some bacteria in wound infections originated from the patients' skin . The present study did not show any increase in the mobilization and dispersal of patient resident skin organisms. The exhaust air from beneath the surgical drapes, which had passed over the patient's skin, showed a decrease in the number of bacterial counts at the end of surgery, and this demonstrated that there was no increase in air contamination associated with the Bair Hugger patient warming system. Furthermore, it indicated that the warm air stream did not force circulation of the patients' skin organisms. If the Bair Hugger were affecting the atmosphere adversely, then the room air counts would also be expected to increase rather than decrease. In fact, the colony numbers in room air and system exhaust were reduced and this was consistent.
Although the study was not designed to evaluate other causes of bacterial presence in the operating theatre, we feel that the higher count at the beginning of surgery in room air may be due to the unrestricted movement of personnel in and out of the operating room, with opening and closing of doors, leading to increased air flow and turbulence. Toward the end of surgery, movement of staff is much less and this may explain the fall in bacterial counts seen as the air turbulence decreases [14, 15].
We conclude that the use of the Bair Hugger patient warming system during prolonged abdominal surgery does not lead to increased bacterial contamination of the operating theatre atmosphere, and it is therefore unlikely to cause contamination of the surgical field.
Forced-air warming does not force patient's resident skin organisms into and contaminate the operating theatre atmosphere
Such systems are unlikely to increase the incidence of wound and prosthetic infections
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