You’re Getting Warmer

Innovative Patient Warming Techniques Prevent Unplanned Hypothermia

For most people, the term “unintended hypothermia” conjures a number of images — such as people caught in snowstorms or falling through an ice-covered pond and into the freezing water below. But unintended hypothermia doesn’t just happen in these extreme situations; in fact, the battle to keep surgery patients at a normal body temperature is a daily struggle for those in the medical field and evolving patient warming methods are the solution of choice.

The Cold, Hard Truth

Currently, there are more than 40 million inpatient and 31 million outpatient surgeries performed each year in the United States — and unintended hypothermia (a core temperature of less than 36 degrees C/96.8 degrees F) can be a risk during each operation.

“In total, one out of every two surgical patients has been noted to have temperatures below 36 degrees C/96.8 degrees F, and one out of every three surgical patients incurs core body temperatures below 35 degrees C/95 degrees F,” says David Parks, general manager of global business management at Kimberly-Clark Healthcare. “Hypothermia is one of the most common patient risk factors for perioperative complications.”

Such perioperative complications can include surgical site infection (SSI), altered drug metabolism, impaired blood clotting, cardiovascular ischemia and prolonged recovery following surgery.

“Patients acquiring an SSI are five times more likely to be readmitted to the hospital and 60 percent more likely to spend time in the ICU,” says Troy Bergstrom, marketing communications manager for Arizant Healthcare, Inc. “But the most frightening statistic may be that patients acquiring an SSI are twice as likely to die compared to patients without infections.”

He adds that SSIs, which can be caused by endogenous sources (bacteria on the patient’s skin) have been called the most frequent, but most preventable surgical complication, accounting for 14 percent to 16 percent of all hospital-acquired infections (HAIs).

Hypothermia contributes to this frequency by reducing the levels of oxygen in tissues, decreasing the strength of the body’s ability to heal wounds and impairing immune function.

“Hypothermia can lead to an increase of bacterial growth by 33 percent to 56 percent, which promotes wound infections,” Parks says. “While studies have shown a correlation between hypothermia and increased infection rates in more complex and invasive surgeries, recent studies in ‘clean’ surgeries like breasts, varicose veins or hernia also supported a significantly lower rate of wound infection in actively warmed patients versus the nonwarmed control group.”

The increased infection rate and other common complications of unplanned hypothermia also have a direct effect on the length of recovery time required by a patient.

“One of the most significant implications of SSIs is the prolonged treatment of those patients, in terms of their general care as well as that which is specific to the treatment of infection,” Parks says.

He adds that, conversely, studies have shown that patients who successfully reach normothermia during surgery have fewer transfusions, experience less postoperative bleeding, spend less time on mechanical ventilators, require less time in intensive care and generally go home sooner.

The increased need for continued care commonly associated with unplanned hypothermia translates to increased amounts of money spent on paying for the extra treatment. This means that implementing active patient warming methods can have serious financial benefits for both the patient and the surgery center.

“In addition to the clinical benefits of reduced SSI rates, decreased likelihood of postoperative heart attack, shorter hospital stays and lowered mortality rates, financial benefits may be realized as well,” Bergstrom says. “Studies show that maintaining normothermia results in a savings of $2,500 to $7,000 per patient.”

And in an ambulatory surgery center (ASC) where time is money, this savings is even greater.

“Throughput is an important consideration for surgicenters,” Parks says. “As you optimize the number of OR suites and recovery rooms, you need to process a postoperative patient as quickly as possible, which means many will look to high-end warming systems to help them with that throughput.”

Healthy Heat

To achieve the goal of preventing unintended hypothermia, patient warming techniques are implemented in the surgical process. With proper execution of those methods, normothermia (normal body temperature) can be maintained and the complications, risks and financial losses of unplanned hypothermia can be circumvented.

Warming is especially important if the circumstances surrounding the surgery result in increased susceptibility to hypothermia. “Any patient undergoing anesthesia is susceptible to unintended hypothermia,” Bergstrom says. “Research has shown that core body temperature drops rapidly following induction of general anesthesia — up to 1.6 degrees C in the first hour — which is known as redistribution temperature drop (RTD). This often means that patients are losing ground to hypothermia even before the surgical procedure begins.”

Parks adds that surgeries that require a large exposed body area, involve intra-operative timeframes, have large incision sites or require significant fluid changes also are susceptible to unintended hypothermia.

“Surgeries that can increase the possibility of unintended hypothermia include cardiothoracic, major abdominal, major plastics, trauma and some orthopedics,” he says. “In addition, patient factors such as age and weight can impact their rate of heat loss.”

This necessitates a consistent approach to patient warming; one that begins prior to surgery, then continues throughout the procedure and into the postoperative period.

“Hypothermia is easier to prevent than to treat, and prevention is most effective when warming begins preoperatively,” Bergstrom says. “Pre-warming before surgery increases the mean body temperature and allows patients to ‘bank’ heat, which significantly minimizes the decrease in core temperature caused by anesthesia induction. Patients should then be warmed during surgery and again in recovery to ensure normothermia is maintained throughout.”

Because there are a variety of circumstances and settings in which a patient requires warming, multiple methods can be used. Having both passive and active warming systems available allows for individualized treatment, which in turn raises the probability of successfully maintaining normothermia.

“The key to effectively managing hypothermia across a facility’s full range of surgical procedures is to use the right intervention for a given situation,” Parks says.

In passive warming systems, insulation measures like warming blankets, socks, head covering and other apparel, as well as an increase in ambient temperature are used to keep the peripheral tissue closer to target temperatures, which can significantly reduce the impact of vasodilation and redistribution hypothermia that occurs.

“The function of passive warming systems is to isolate the patient from additional heat loss, but they don’t necessarily warm a patient,” Parks says. “A warm blanket’s impact is comfort at best, and its heat dissipates after a minute or two; therefore, piling on blankets is relatively ineffective at impacting core body temperatures. However, for simple surgeries where patient exposure to cold is limited, these traditional warming modalities can be sufficient.”

Active warming systems include the application of direct-conduction warmers like a forced-air convection warming system, water-circulating blanket or warming IV fluids. These products utilize active heat sources to deliver energy back to the body to replenish what it is lost during the perioperative time period.

“Studies have found forced-air warming to be one of the most effective warming methods in the prevention of hypothermia,” Bergstrom says. “Which is why Arizant Healthcare created forced-air warming technology 20 years ago — our Bair Paws warming system provides forced-air warming in a single patient gown throughout the perioperative process. It’s a tremendous pre-warming tool that stays with the patient to warm during surgery and again in recovery.”

He adds that Arizant’s Bair Hugger therapy offers 24 models of forced-air warming blankets, including six Underbody Series models. These blankets warm from beneath the patient, allowing clinicians the full access they require without compromising patient warming.

Parks, on the other hand, says that the most effective method for achieving normothermia in surgical situations is total immersion in warm water.

“Unfortunately, immersion is not pragmatic for surgeries because of potential ties to nosocomial pathogens,” he adds. “Because of this, we feel that the Kimberly-Clark Patient Warming System offers the best alternative — it acts like a whirlpool in a pad, brining the effectiveness of water’s heat delivery into intimate contact with the body in a safe and efficient way.”

Ultimately, however, Parks says that the decision regarding what type of active warming system to use generally comes down to surface area and procedural complexity. “If you’re doing a surgery with a small surgical site and you can cover the patient with a forced-air warming blanket system, you’ll typically get acceptable results,” he says. “If your surgery is quite large, however, you’ll need a system with more capability.”

Global (Patient) Warming

In today’s ASCs, patient warming goes beyond the rationale of hypothermia prevention — modern methods also are seeking to alleviate the complications associated with unplanned hypothermia and increase patient comfort and satisfaction, while improving the economic aspect of surgery.

“With more attention given to the tie between hypothermia and SSI, we will continue to see more attention paid to tracking post-op temperatures,” Parks says. “Facilities will standardize to the best preventable solutions they have and mandate them; in fact, most hospitals adhering to best practices are already doing that.”

He adds that studies have found that surgical teams often achieve only 50 percent to 60 percent normothermia with conventional perioperative warming techniques because the methods often cannot deliver enough heat to the body to balance the losses experienced during the intraoperative period.

“The ability to warm any patient to a target is now doable,” Parks says. “In order to more consistently achieve normothermia in the full range of surgery experiences and avoid the shortfall of hypothermia and its negative consequences, more effective solutions must be employed.”

Ultimately, as patient warming proponents look to the future, the goal is to continue to increase awareness regarding unplanned hypothermia and to improve the effectiveness of the warming techniques and equipment used during surgery to maintain normothermia.

“Patient warming technology has made tremendous progress in recent years,” Bergstrom says. “We expect that trend to continue.” 

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