Infection Control Today - 10/2003: Clinical Update

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Temperature Management in the Intraoperative Setting

By Tina Brooks

Surgical site infections (SSIs), the third most frequently reported nosocomical infection, account for 14 percent to 16 percent of all nosocomical infections among hospitalized patients.1 “Surgical site infections remain one of the most common and serious complications of surgery,” says Daniel Sessler, MD, director of the Outcomes Research Institute at the University of Louisville in Kentucky. “The overall incidence is about 2 percent, but in selected operations the risk approaches to 10 percent. The average infection increases the duration of hospitalization by a week, costs thousands of dollars, doubles the risk of ICU admission, doubles mortality.”

To find solutions to many of these problems resulting from SSIs, researchers turned to the perioperative setting for answers. Many studies have shown that the utilization of temperature management devices in the intraoperative setting help reduce SSIs, however, more recent research suggests that the optimal use of these devices should begin preoperatively.

SSI and Hypothermia

“Surgical infections are one of maybe six or seven serious consequences of hypothermia,” Sessler says. Hypothermia is a core body temperature of less than 36 degrees C, whereas normal core body temperature ranges between 36 degrees C and 37.5 degrees C. Intraoperative hypothermia results because patients are exposed to several factors that contribute to heat loss including cold ambient temperatures in the surgical suite, an opened exposed wound area and administration or irrigation with cool fluids.2

The most important factor, though, is internal redistribution of body heat that results from anestheticinduced inhibition of tonic thermoregulatory vasoconstriction.

“As a result, unwarmed surgical patients almost inevitably become hypothermic,” says Sessler. “Even patients having short, small operations will become hypothermic during surgery.”

It is well documented that low body temperature may increase patients’ susceptibility to SSIs by causing vasoconstriction and impaired immunity. Vasoconstriction decreases the partial pressure of oxygen in tissues, which lowers resistance to infection in humans.3

“Prewarming is an effective way of preventing intraoperative hypothermia,” Sessler says. “This has been demonstrated in at least four different studies and there’s no question that it works.” Forced-air warming devices have been established as the most effective method of preventing and treating heat loss in patients.

A randomized study of patients undergoing elective laparoscopic cholecystectomy showed that a single hour of preoperative skin-surface warming reduced the rate at which core hypothermia developed during the first hour of anesthesia.4 Prewarming did not alter preoperative core temperature, but it markedly reduced the rate at which intraoperative core hypothermia developed: 1.1 ± 0.1 degrees C/hour in the control group, versus only 0.6 ± 0.1 degrees C/hour in the prewarmed group (<0.05).

Sessler, who was one of the researchers of this study, says that even if patients are pre-warmed for just one half hour, their peripheral tissues temperature is nearly equal to core temperature and there is therefore no redistribution hypothermia after the induction of anesthesia. Core temperature thus remains nearly normal even during large operations in prewarmed patients.

This same study also revealed that the prewarmed patients cooled at half the rate of the control patients, and prewarmed patients and remained significantly warmer even after two hours of surgery.

Although the use of warming devices is becoming standard practice for most major surgeries, their utilization for procedures that last less than an hour is not. Melling et al. aimed to assess whether warming patients before short duration, clean surgery would reduce infection rates.5 Their findings suggested that a 30- minute period of prewarming patients reduces infection rates from 5 percent to 14 percent. The 421 patients underwent breast, varicose or hernia surgeries.

Beyond the known adverse outcomes of hypothermia, Mahoney and Odom concluded that cumulative adverse outcomes added between $2,500 and $7,000 per surgical patient to hospitalization costs across a variety of surgical procedures.2 Other studies corroborate that SSIs increase costs as well as length of hospital stay.6-7

Patient Comfort

Comfort can be an elusive concept, but patients know when it is absent. Comfort, or lack thereof, is often the most memorable experience noted on patient satisfaction questionnaires.

“Surgical patients may not remember much else, but they remember if they were comfortable or freezing to death,” says V. Doreen Wagner, RN, MSN, CNOR, assistant professor of clinical nursing at North Georgia College and State University in Dahlonega.

Traditionally, cotton blankets have been used in the preoperative setting to keep patients warm, Wagner says. However, cotton blankets produce only a small reduction of heat loss.2 The sensation of warmth, even when blankets are heated, dissipates quickly.2

“Sometimes using both prevention and different kinds of warming devices will actually save money,” Wagner says. “Those old tried-and-true practices, like warmed cotton blankets, can be even more costly than one would believe. You use nine to 12 of those blankets during somebody’s whole surgical experience, then you’ve got to tie in the cost of staff time involved in going back and forth to get the blankets, and last but not least, how much patient satisfaction is worth when a patient has to wait for comfort measures.”

Vallire Hooper, RN, MSN, CPAN, clinical nurse specialist in surgical services at St. Joseph Hospital in Augusta, Ga., says, “The important thing to remember is that every patient should have preventive warming measures, even if they’re normothermic — those basic common sense nursing interventions. They do not require doctor’s orders. They should be standard practice.”

Hooper, who sat on the development panel of a guideline to prevent unplanned perioperative hypothermia held by the American Society of PeriAnesthesia Nurses (ASPAN), says that if a patient is complaining of being cold, even if they have a normal temperature, they are most likely losing heat.

“We should protect our patients from the start in the preoperative arena,” Wagner stresses. “Don’t let them get cold to begin with. I know that a lot of clinicians begin trying to warm patients in the operating room. Warming should start in the preoperative phase where patient’s chillines’s and discomfort begins.”

ASPAN GUIDELINES ON PERIOPERATIVE HYPOTHERMIA

Research has shown there is a chronic problem with perioperative hypothermia.

To address this concern, the American Society of PeriAnesthesia Nurses (ASPAN) developed practice guidelines for the prevention, care and management of the adult surgical patient with unplanned perioperative hypothermia. Here is a portion of the guidelines that discusses preoperative patient management:

Assessment

  • Identify patient’s risk factors for unplanned perioperative hypothermia.
  • Measure patient temperature on admission.
  • Determine patient’s thermal comfort level (ask the patient if they are cold).
  • Assess for other signs and symptoms of hypothermia (shivering, piloerection, and/or cold extremities).

Interventions

  • Institute preventive warming measures for patients who are normothermic. A variety of measures may be used, unless contraindicated. Passive insulation may include warmed cotton blankets, socks, head covering, limited skin exposure, circulating water mattresses and increase in ambient temperature (minimum 20 degrees C to 24 degrees C or 68 degrees F to 75 degrees F).
  • Institute active warming measures for patients who are hypothermic. Active warming is the application of a forced air convection warming system. Apply appropriate passive insulation and increase the ambient room temperature (minimum 20 degrees C to 24 degrees C or 68 degrees F to 75 degrees F.) Consider warmed IV fluids.

From Pre-op to Post-op: Today’s Temperature Management Technologies

By Tina Brooks

The concept of using external heat during, not after anesthesia to prevent inadvertent hypothermia, is more than 100 years old. Early intraoperative interventions included the use of hot water bags and hot water coil slippers for patients’ feet.

Today’s temperature management technologies not only assist in the intraoperative setting, but maximize patient comfort as well, beginning in pre-op.

Alternatives for the Warm, Fuzzy Blanket

John Carroll, product manager for Bair Hugger therapy at Arizant Healthcare, Inc., says the company recently introduced the Bair PAWS system. PAWS stands for patient adjustable warming system.

The Bair PAWS system is designed to comfort patients who are waiting for, or recovering from, surgery. The single-use Bair PAWS gowns are made of soft, opaque material and are cut generously to protect patients’ modesty. Patients use a hand-held temperature controller to adjust the temperature of the air flowing through the warming gown.

“The PAWS system is used for patient comfort and satisfaction only,” Carroll says. “It is not designed to be a clinical warming system the way Bair Hugger therapy is. “ Arizant’s Bair Hugger therapy product line includes forced-air warming units and 19 different blanket models for use throughout the perioperative period.

“We have one main blanket that we use for prewarming,” Carroll says. “It is a blanket that helps to retain the body heat of the patient and is designed so the patient can sit up comfortably.” booties also accompany the blanket to keep patients’ feet warm.

The Bair Hugger system has been shown to help reduce surgical site infections. A study published in the The Lancet1 showed that warming surgical patients prior to surgery reduced the incidence of infections.

While it has been known for some time that warming patients in longer procedures will assist in maintaining normothermia and increasing patient comfort, this finding shows added benefits to warming for clean, bloodless surgeries of less than an hour in duration. In addition, prewarming patients may have benefits beyond maintaining core body temperature.

“Where postoperative patients are concerned, this is as big a finding as penicillin. I think we’re going to find that this effect is going to save a lot of lives and a lot of cost,” says Dr. Thomas Hunt, a wound healing expert and professor emeritus at the University of California San Francisco who was not involved in the study.

According to the study, wound infection after clean surgery is an expensive and often underestimated cause of patient morbidity, and the benefits of using prophylactic antibiotics in clean surgery have not been proven. As wound infections remain one of the most common complications of surgery, warming patients may provide an alternative infection prevention method for surgical procedures. Based on these findings, warming has benefits that extend beyond maintaining normothermia for all patients, including short, clean and bloodless procedures.

Localized Warming

Gaymar Industries, Inc. offers the T/Pump Localized Heat Therapy System. “We use the T/Pump for a lot of inflammatory conditions, pain relief and muscle spasm, but it can also be used to warm the pre-surgical site,” says Teresa Wozniak, product manager for temperature management products at Gaymar.

The T/Pump is a localized heat therapy pump that circulates warm water through pads that are applied to specific areas of the patient’s body. The temperature settings on the pump range from 30 degrees C to 42 degrees C. Dual back-up thermostats provide over temperature protection. The random flow pattern in the pads allows them to be folded to fit specific areas of the body without occluding flow. Two pads may be used simultaneously with Clik-Tite hose connections.

Gaymar also offers the Thermacare Convective Warming System and the Medi-Therm III Hyper/Hypothermia System. The Thermacare convective warming system safely and effectively warms the patient in the perioperative environment. The warm-air blower unit offers three temperature settings ranging from low (32 degrees C) to high (43 degrees C) for the operating room, and four settings for the PACU, including a maximum setting (46 degrees C) for enhanced warming. Dual back-up thermostats provide over temperature protection. Thermacare quilts are designed to cover the upper body, torso, lower body and the full body. A pediatric quilt also is available.

The Medi-therm III Hyper/Hypothermia system employs water-circulating blankets to warm or cool the patient in the perioperative setting. Therapy may be provided manually by controlling the blanket temperature, or automatically by inserting a temperature probe in the patient. Blankets have a random flow pattern that allows them to be placed beneath the patient without occluding flow. Patients may be sandwiched between two blankets for enhanced therapy. For maximum body surface contact and optimal warming/cooling therapy, Rapr.Round blankets may be used that wrap the torso and the legs.

“It’s very important to warm the patient in order to minimize the insults of surgery,” Wozniak says. “Surgery has a big traumatic impact on the patient’s body. Clinicians really need to do something, as much as they can, to keep the patient’s condition at an optimal level.”

Before, During and After

“Some of our products can be taken right from pre-op into the surgical setting, so there’s no additional costs,” says Laurie Schechter, director of global marketing at Level 1, Inc., a part of the medical division of Smiths Group plc, London.

Level 1’s Equator Convective Warmer, a forced-air warming unit, is designed for use with a range of SnuggleWarm blankets for multiple pediatric and adult uses. The company also provides the Hotline Fluid and Blood Warmer, which incorporates a patented triple lumen tubing that eliminates patient-line cool down and assures infusion of warm blood and fluids at routine flow rates.

“The patient can begin to become hypothermic in the pre-operative setting,” Schechter says. “Clinicians can certainly use convective warming and fluid warming and should to prevent what we call redistribution (hypothermia). Patients get cold and tense, and then lose heat quite a bit of heat in the first half hour to hour of surgery. Using some of the warming devises in the preoperative setting can prevent that initial heat loss.”

Cincinnati-Sub Zero Products, Inc. offers the CSZ WarmAir 135 Convective Air Warming Unit and FilteredFlo air blankets for the intraoperative and postoperative settings. The WarmAir 135 unit is small and lightweight, easily attaching to operating room tables, stretchers, bed ends, side rails, or IV poles. All air is filtered before being distributed to the air blanket to prevent airborne bacterial contamination in critical areas.

FilteredFlo air blankets conform to the patient’s body to deliver evenly distributed warm air without a hint of blowing air or discomfort. For added performance, a reflective material is utilized to retain heat, eliminating the need for a top blanket or sheet, reducing laundry and processing costs. These blankets are easy to manage, will not “fly away,” and may be folded back to provide access to the patient. FilteredFlo blankets are available in upper body, lower body, full body adult and pediatric sizes.

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