Secondly, the safety of convection devices such as the Bair Hugger® has been under intense scrutiny based on the evidence that it disrupts the laminar airflow in the operating theater.23-26 This disruption in laminar air flow has been shown to cause emission of significant levels of airborne contaminants of size >0.3 μm (germ size).27 Isolates of Staphylococcus aureus, coagulase-negative Staphylococcus species, and methicillin-resistant Staphylococcus aureus were detected in 13.5%, 3.9%, and 1.9% of forced-air blowers, respectively.28 However, the clinical effect on the rate of deep joint infection due to the disruption of laminar air flow has been examined in only 1 study. McGovern and colleagues29 reported a significant increase in deep joint infection during a period when forced air warming was used compared to a period when conductive fabric warming was used (odds ratio, 3.8; P = .024) and recommended air-free warming by a conduction device over forced-air warming for orthopedic procedures. Unfortunately, the prophylactic antibiotic regimen was not kept constant during their study period. During an overlapping time frame during which they shifted from the use of a convection device (Bair Hugger®) to a conduction device (Hot Dog®), they also changed their antibiotic regimen from gentamicin 4.5 mg/kg intravenous (IV) to gentamicin 3 mg/kg IV plus teicoplanin 400 mg IV. This change in antibiotic regimen is a major confounding factor that calls into question the validity of the conclusions drawn by the authors.
Finally, the cost effectiveness of conduction and convection devices has never been studied. Hence, based on the current evidence, it is not possible to recommend a particular type of active patient-warming device.
Orthopedic surgeons should be aware that inadvertent perioperative hypothermia is a common phenomenon in perioperative patients. It must be recognized that the maintenance of perioperative normothermia during all major orthopedic surgical procedures is desirable, as inadvertent perioperative hypothermia is shown to be associated with increased mortality and systemic morbidity, such as stroke and sepsis. Compliance with the current clinical guidelines for assessment, prevention, and treatment of inadvertent perioperative hypothermia will minimize, if not eliminate, such risk. We recommend the following essential clinical guidelines to prevent inadvertent perioperative hypothermia (Table 3). Identification of patient-, anesthesia-, and procedure-related risk factors is an integral component of assessment of the risk of inadvertent perioperative hypothermia. In order to achieve full compliance with implementation of active patient warming during surgery, it is prudent to make active warming information a part of the surgical timeout checklist. Irrespective of the presence of risk factors, passive heat retention methods should be part of perioperative management of patients undergoing elective orthopedic surgery to prevent inadvertent perioperative hypothermia. In addition, there should be a minimum threshold to utilize active patient-warming techniques, especially in patients with inherent risk factors and surgeries that take >30 minutes of operating time, either under regional or general anesthesia. As there are concerns about safety issues with the use of convection devices, we believe a multicenter randomized controlled trial is warranted.
Table 3. Recommended Essential Clinical Guidelines for Prevention of Inadvertent Perioperative Hypothermia