The cold temperature inside an operating room is a calculated environmental control designed to support two primary objectives: minimizing the risk of patient infection and optimizing the performance of the surgical team. This low ambient temperature is a deliberate part of a complex system of ventilation and climate regulation. While the cold environment may seem uncomfortable for a patient, it is a necessary condition that must be actively managed alongside specialized patient warming techniques. The temperature setting is a non-negotiable factor in maintaining the strict safety standards required for any invasive procedure.
Controlling Infection and Sterility
The primary rationale for a cool operating environment stems from the need to suppress microbial growth and maintain air quality. Bacteria and fungi thrive in warm, humid conditions, and temperature control is one layer of defense against contamination. Guidelines recommend that operating rooms be maintained within a temperature range, often between 68°F and 75°F (20°C and 24°C), though the lower end is frequently preferred by staff.
A heating, ventilation, and air conditioning (HVAC) system works in tandem with this low temperature setting. These systems enforce a high air change rate, typically exchanging the room’s entire volume of air 20 to 25 times per hour. This constant flow of air, filtered through High-Efficiency Particulate Air (HEPA) filters, dilutes and removes airborne contaminants shed by staff and equipment.
The OR is also maintained under positive pressure, meaning air flows out of the room when doors open rather than allowing potentially contaminated air from adjacent hallways to flow in. A lower temperature helps the HVAC system more effectively maintain the relative humidity within the required range of 20% to 60%. This controlled humidity is important because high moisture levels encourage the survival and transport of airborne pathogens, while excessively dry air increases the risk of electrostatic discharge that could damage equipment.
Maintaining Surgeon Comfort and Focus
A cooler environment is a direct necessity for the surgical team, who work under layers of heat-trapping attire. The sterile barrier worn by personnel includes long-sleeved, impermeable gowns over their standard scrubs, head coverings, and masks. These garments prevent the shedding of skin cells and microorganisms into the sterile field, but they are highly effective at insulating body heat.
Surgical procedures can last for many hours, and the environment must counteract the heat generated by the team’s exertion and the overhead surgical lights. If the temperature were higher, the staff would overheat, leading to discomfort, fatigue, and impaired concentration. The cold air helps maintain the alertness and fine motor skills necessary for precision work.
Preventing excessive sweating is another function of the cold temperature, as perspiration poses a direct contamination risk. Sweat can compromise the sterile gown barrier or drip from exposed skin areas, introducing moisture and microorganisms into the sterile surgical field. The cool setting supports the surgical team’s ability to maintain focus and sterility throughout the operation.
Mitigating Patient Hypothermia Risks
While the environment is intentionally cool for infection control and staff comfort, patients are vulnerable to hypothermia, defined as a core body temperature below 96.8°F (36°C). Hypothermia can impair blood coagulation, increase the risk of surgical site infection, and contribute to adverse cardiovascular events. The patient’s normal thermoregulation is often compromised by anesthesia, which causes peripheral vasodilation and redistribution of body heat.
To counteract the cold ambient air and maintain a core temperature of 98.6°F (37°C), active warming strategies are employed. The most common device is a forced-air warming system, which uses a warming unit to blow heated air through a specialized blanket draped over the patient. This convective heat transfer delivers warmth across the patient’s skin surface.
The patient is also kept warm through the administration of warmed intravenous fluids and blood products, which are heated to body temperature before infusion. For procedures where large internal cavities are irrigated, the fluids used are also warmed to prevent internal heat loss. These specialized warming measures ensure that the patient’s core temperature is maintained, balancing the operating environment with the patient’s physiological safety requirements.