Many temperature-regulating devices are available today and perioperative personnel must use these devices in a safe and effective manner. That includes following manufacturers' recommendations and monitoring the devices during the surgical procedure, according to AORN's 2006 recommended practices.[1] Read on to learn the safety considerations for various warming devices.

Warmed cotton blankets
The use of warmed cotton blankets is very common in most ORs. Blankets slow heat loss, but are not very effective in raising core temperature once the patient becomes hypothermic. The number of warmed blankets used often depends on the patient's request as well as his temperature. Warmed cotton blankets act as a radiant heat source and are useful if they are changed as soon as they cool to the ambient room temperature. However, applying blankets that are too warm can result in patient discomfort or even burns. The manufacturers' guidelines for the maximum temperature setting for blanket warming cabinets should always be followed in order to prevent patient harm.

Warm irrigation or intravenous solutions
Using intravenous and irrigation solutions at room temperature, as well as cold blood products, can often lead to hypothermia. AORN recommends that irrigation or infusion solutions be warmed or cooled to temperatures appropriate to the surgical need in devices intended for that purpose.1 Warming irrigation solution bottles or intravenous solutions in an autoclave or microwave is not recommended, as this could pose a danger to the surgical patient. This practice can lead to a thermal injury, since autoclaves and microwaves cannot be monitored, do not heat uniformly and are not designed for medical use.[1]

These fluids should be warmed in a designated fluid warming cabinet with temperature controls so that the fluid temperature does not exceed the safe limit.[2] Refer to the cabinet manufacturer's guidelines for the appropriate temperature range for the make and model of the specific cabinet; for information on the length of time a fluid can safely remain in a warming cabinet, the manufacturer of the solution should be consulted.2 When using multifunction warming cabinets, the different compartments should be clearly designated as to their intended use (blankets or fluids, for example). The most recent industry recommendations suggest limiting the temperature of both blanket and fluid warming cabinets to 43?C (110?F).[3]

Blood/solution warmers
Pertinent safety issues regarding the use of blood/solution warmers are: inadequate heating of fluids at high flow rates, inadequate temperatures at low flow rates due to heat loss from the infusion lines and overheating of red blood cells.[4] A safe temperature of 42?C (107.6?F) is recommended by the American Association of Blood Banks.5 These devices often offer safety features such as temperature backup thermostats and overheating alarms. Be sure to take advantage of that technology.

Circulating water blankets
Two methods exist for active cutaneous warming: circulating water blankets and convective (forced-air) warming units. The transfer of heat through active warming systems is proportional to the surface area treated.

Circulating water blanket units have been the standard in surface heating for many years. They warm through a conductive heating mechanism where the heat is absorbed by the patient's cooler skin. Since these blankets are placed underneath the patient, their effectiveness is diminished because of the limited surface area contact. In addition, burns or tissue necrosis may occur in patients in the supine position due to decreased tissue perfusion. Blanket temperature should be kept within the range specified by the manufacturer to prevent patient burns.

Convective warming units
Convective warming devices usually consist of an electrically powered heater or blower unit and a patient cover, which is comprised of some combination of fabric, plastic or paper that is inflated with the warm air from the heating unit. Small holes in the blanket on the patient side allow the warm air to be directed over the patient. The forced-air warming unit uses convective heating where the heat is absorbed from the air passing over the patient's skin. As with other warming methods, these units can also pose the threat of traumatic thermal injuries. Safety considerations include the following:

• Place properly. The blanket distributes the warmed air from the heater/blower unit uniformly across skin surfaces. Placement considerations include: choosing the correct size and design for the surgical procedure; placing the blanket over the patient with the perforated side next to the patient's skin; contouring the blanket closely to the patient with the tape or tucks provided; and following the manufacturer's instructions for blanket use.
• Avoid mismatched brands. Use the unit only with the specified blanket, since these devices vary between manufacturers.
• Use all components. Avoid the practice of free hosing; that is, using the unit without the blanket by simply inserting the hose under the OR bed sheet. This is often perceived as a cost-containment measure, but in free hosing, the heated air from the hose is blown directly onto the patient's skin. This can result in traumatic thermal injuries due to the concentration of hot air in a single area over an extended time period.

Take ownership
Patient safety is the primary responsibility of every member of the surgical team. It is imperative that all staff members be educated about inadvertent perioperative hypothermia. This education should include in-service programs on the proper operation of the specific warming devices used in the clinical area as well as education activities on the clinical implications of hypothermia and the importance of maintaining a normo-thermic state. Competency in thermoregulatory measures should also be documented. Through these efforts, you can prevent complications and promote optimal outcomes.

References
1. Association of periOperative Registered Nurses (AORN). Recommended practices for safe care through identification of potential hazards in the surgical environment. Standards, Recommended Practices, and Guidelines. Denver, CO: AORN, Inc; 2006: 547-553.
2. Giarrizzo-Wilson S. Clinical issues: Fluid warming; microfiber mops; medication practices; guayule latex; dual-return electrodes. AORN Journal. 2005;81(6):1324-1332.
3. Limiting temperature settings on blanket and solution warming cabinets can prevent patient burns. Health Devices. 2005; 34(5): 168-171.
4. ECRI. Warming units, blood/solution. Healthcare Product Comparison System. Plymouth Meeting, PA: ECRI; 2004:1-23.
5. American Association of Blood Banks (AABB). Standards for Blood Banks and Transfusion Services. 17th ed. Bethesda, MD: AABB; 1996.