Warm patients are happy patients, but the benefits of maintaining normothermia extend well beyond the "ahh" factor. Warming surface skin areas increases blood flow and oxygen levels at the subcutaneous space, which is where superficial surgical site infections commonly occur. Increasing the blood supply to incisions also leads to better wound healing. Here's why controlling a patient's core body temperature through active warming should be part of your efforts to ensure patients leave your facility with nothing more than a healthy, healing scar.
1. Hypothermia helps bacteria
Bacteria that enter surgical incisions are attacked by white blood cells and antibodies. Quality laboratory-based data show white blood cells kill bacteria much more effectively when higher concentrations of oxygen are present within the white cells. Studies have also correlated low amounts of oxygen in tissue next to incisions with increased risk of surgical site infection. In other words, incisions with higher oxygen concentrations have better resistance to harmful bacteria.
Patient warming comes into play because the higher the body's core temperature, the higher the level of oxygen concentration in the surgical wound and surrounding tissues. Why? Vasoconstriction occurs in hypothermic patients to limit the amount of blood and oxygen that reaches the incision.
The link between normothermia and lower surgical infection risk has not been definitively proven, but there's plenty of evidence that suggests actively warmed patients are less likely to develop post-op infections. For example, research has shown that employing total body warming to maintain normothermia (36 ?C) in patients who underwent colorectal surgery reduced SSI risk by 67% compared with patients whose core body temperatures dipped into the hypothermic range (osmag.net/b5pfgd).
2. Anesthesia's chilling effect
Shorter outpatient procedures have a lower risk of infection than longer operations, which are typically more complex and expose wounds for longer periods of time. A study currently in press that I reviewed included a series of patients who underwent complicated procedures and found that patients with lower intraoperative temperatures had a higher risk of SSI. That risk increased when lower intraoperative temperatures persisted for longer durations.
But that doesn't mean patient warming is any less important for seemingly less complex procedures because redistribution hypothermia can occur in any surgical patient. Here's why: The body maintains core temperature by keeping blood flow and heat loss away from the skin. But as soon as general anesthesia is administered, the body's vascular control is immediately lost, core heat moves to the periphery to compensate and the core body temperature drops. Pre-warming the skin and subcutaneous tissue before the patient goes into the operating room prevents the early anesthetic-induced temperature drop from occurring.
Start active warming in pre-op and make sure the methods remain applied even if patients claim they feel warm enough. Informing patients that warming helps protect them from infection will make them understand why you're continuing to warm them, even if they feel comfortable. Here's another tip: Restart active warming if it's paused as patients receive regional blocks before heading to the OR. (I've noticed that pre-op staff at my facility sometimes forget to reapply warming measures after blocks are placed.)
3. Forced-air warming is fine
Research has not definitively shown one active warming method to be more effective than another in maintaining normothermia. It's likely best to use passive (warmed cotton blankets) and active (radiant warming, fluid warming, forced-air warming or conductive-fiber warming) warming methods in combination.
Much has been made recently about the possibility of forced-air warming causing SSIs. More than 4,000 patients from across the country have filed lawsuits against 3M, the maker of Bair Hugger warming units, claiming the company's units caused their deep surgical site infections by blowing contaminants off of OR floors and into the open wounds during joint replacement procedures.
Lawyers for the plaintiffs argue the Bair Hugger's blowers disrupt downward laminar flow that's designed to push bacteria-containing particles onto the floor and away from the sterile field. Their argument is based on research conducted in simulated ORs and expert testimony, not rigorous studies involving real-world OR settings. Lawyers for 3M have countered with studies that back the safety of forced-air warming and argue that no surgical site infection has been definitely linked to their devices. The first federal lawsuit, which will set legal precedent for the other cases, is scheduled to begin in the coming months.
The upshot of the legal wrangling: There is currently no clear evidence of associated infection risks that should prevent you from using forced-air warmers. It's important, however, to always follow the manufacturer's instructions for use and proper cleaning.
4. Surgeons shouldn't sweat
The ambient temperature ?in the OR should be kept between 68 ?F and 75 ?F to help maintain normothermia in patients, according to AORN's patient warming guidelines. It might be helpful to maintain room temperatures within that range, but turning the thermostat up to 75 ?F might overheat members of the surgical team and would still set the room temperature 13 ? lower than the normothermic threshold in patients. In my experience, pre-warming in pre-op and active warming during surgery has more of an impact on a patient's core body temperature than raising the OR temperature. I've found that actively warmed patients will remain normothermic during surgery, regardless of the ambient room temperature.
5. Normothermia is the new normal
The Surgical Care Improvement Project (SCIP) Core Measure 10 requires you to actively warm patients who undergo procedures under general or neuraxial anesthesia that last an hour or longer. You must record at least 1 normothermic body temperature reading within 30 minutes immediately before or 15 minutes immediately after anesthesia end time. Address the patient's core temperature during the pre-op time out. When a patient is hypothermic, you'll be made aware of the situation and can apply active warming measures and monitor temperature readings more closely.
Anesthesiologists can slide a temperature probe down the pharynx and into the upper esophagus to measure core temperature in anesthetized patients. There are other non-invasive options for monitoring patients' temperatures in the OR and in the pre-op and PACU areas, including temporal infrared scanners and temperature indication stickers. OSM