It’s a well-known fact that maintaining normothermia in patients during surgical procedures goes a long way towards controlling costs.

A study that’s often referred to when talking about the costs of hypothermia is the 1999 "Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs" by Christine Brown Mahoney, RN, PhD, MS and Jan Odom, RN, MS, CPAN, FAAN1. The researchers estimate that hypothermia averaging just 1.5°C less than normal results in adverse outcomes that add between $2,500 and $7,000 per surgical patient.

Post-surgical hypothermic conditions can increase a patient’s need for blood products, increase ventilator and recovery stay, even contribute to mortality rates.

In addition to warming patients during the surgical procedure, numerous studies underscore the importance of pre-operative warming.

"The industry actually evolved backwards", suggests John Carroll, product manager, Arizant Healthcare. Arizant was founded by Dr. Scott Augustine, who the company says introduced the industry’s first forced air warming system with the Bair Hugger system in 1987. "First, forced air warming systems were designed to re-warm patients post-operatively. And then with the publication of research, the industry started moving into the O.R. to keep patients from ever getting cold in the first place. And a line of blankets were designed for use intra-operatively in the O.R.

"And then studies by people like Dr. Sessler2 determined that you can actively bank heat prior to surgery. You only need about 30 minutes in order to build up enough protection in the body to protect against hypothermia in the O.R. So then forced air warming started to be used pre-operatively. It evolved from treating hypothermia to preventing it."

Laura Grisanti, RN, CNOR, perioperative and temperature management advisor, Gaymar Industries, has 25 years of experience in the O.R. in specialties such as orthopedics, ophthalmology and neurosurgery. In her role with Gaymar, she helps direct Temperature Effectiveness Analyses for hospitals across the country. By tracking a hospital’s perioperative temperature management protocol, following patients from pre-op to PACU, Gaymar can help improve temperature management effectiveness. One of the more recent emerging trends that Grisanti said could be garnered from these studies, is that a large number of laparoscopic patients are experiencing hypothermic symptoms. "Most O.R.s typically don’t warm their patients unless the surgeries are 60 minutes or more. What they don’t realize is patients have a natural drop in temperature of one to three degrees C simply because of the anesthesia agent," she said.

A good reference for temperature management is the American Society of PeriAnesthesia Nurses (ASPAN) "Clinical Guideline for the Prevention of Unplanned Perioperative Hypothermia".

Arizant Healthcare's Cardiac Underbody Blanket 635

Convective warmers
Today, forced-air, or convective, warming is considered a tried-and-true technology that’s made its way into operating rooms everywhere. Study after study confirms the effectiveness, as well as cost-effectiveness of the systems as a tool for preventing hypothermia in patients. The study by Mahoney & Odom1 recommends forced air warming as an effective way to maintain normothermia.

Though the concept behind the various convective warming systems on the market is basically the same (warmed air is forced through a blanket that covers or lays under the patient), there are variations and specific features you’ll want to consider.

Arizant Healthcare offers its Bair Hugger Temperature Management Units with 23 different styles of blankets. "We’ve been listening to our customers’ feedback about what they need, and we’ve come up with different models to allow the technology to be used more often," said Carroll.

Arizant recently introduced a line of underbody blankets that Carroll explains allows you to place the blanket on the operating table prior to the patient arriving in the O.R. In addition, by warming from the underside of the patient, the surgeon has access to the entire surface of the patient.

Gaymar Industries offers a convective warming option, the Thermacare Patient Warming System, that’s designed to travel with the patient from pre-op to PACU. The system has three temperature settings for the OR/ICU and four for the PACU. Gaymar’s full body Thermacare quilt can be used pre-operatively as well as post-operatively for single patient use.

Cincinnati Sub-Zero (CSZ) has its WarmAir Warming System with WarmAir FilteredFlo Blankets. The unit is compact and lightweight and designed for cost-effective and convenient warming. According to Dave Frederick, sales director, Cincinnati Sub-Zero, the Warm Air FilteredFlo system is designed so that warmed air is immediately transferred to the patient in uniform quantity across the entire heating surface of the blanket. A unique WarmAir Warming Tube that Frederick says is primarily used in the Cath lab, PACU or ICU setting, inflates around the patient rather than on top of the patient providing full body access and distortion free radiographic imaging.

VitalHeat, Dyna- Therm Medical

Nellcor’s WarmTouch Convective Warming System includes the CareDrape Warming Blanket options for the operating room. These include the Upper Body, Lower Body, Pediatric OR and sterile Cardiac Blanket. In addition, the CareQuilt full body blankets are available in adult and pediatric sizes specifically designed for the PACU. The blankets are made from a non-woven Kimberly-Clark material that is soft and durable. If cut, the blankets continue to inflate and warm the patient. According to Amy Baker, temperature products manager, Nellcor, the blankets are versatile enough to accommodate all patient needs, eliminating the need to stock a variety of blanket designs. The WarmTouch comes with multiple mounting options which include mounting on an IV pole, bed rail or as a stand alone unit on the floor/bed.

Smiths Medical ASD offers the compact Equator Convective Warmer which incorporates temperature settings at the end of the air delivery hose rather than within the warming unit to ensure more accurate temperature delivery. The system works with the company’s Snuggle Warm Blankets which also incorporate a non-woven fabric material.

Whichever system you choose, you’ll want to look at safety features such as an audible alarm in the event of system failure and HEPA-filtered air flow.

Kimberly-Clark Thermal Pads

Conductive warmers
Another way to warm surgical patients is by conductive warming, or the transfer of heat from a warm mass to a cooler mass. Most conductive warming systems on the market today utilize circulating warmed water to keep patients at normothermia. Kimberly-Clark, Gaymar Industries, and Cincinnati Sub-Zero all offer variations of conductive warming systems.

While these systems tend to cost more than the convective warming systems, studies have proven that they are actually a more efficient, faster method of transferring heat energy.

Notes Tim Dye, general manager, critical care and temperature management, Kimberly-Clark, "water provides 1,500 times higher heat transfer rate than air. It also has a higher capacity to store heat."

Or, as Cincinnati Sub-Zero’s Frederick puts it, "Compare standing in 107°F water versus 107° air, or 50°F water versus 50°F air."

This becomes especially significant when rapid temperature changes are required, when there is limited patient surface area access, or during longer, more invasive surgeries, in particular cardiac surgeries. According to Dye, about 50% of patients coming out of cardiac surgery using traditional warming methods are hypothermic. "In the absence of any intervention, almost 100% will be hypothermic," he adds.

Another advantage of conductive water-based systems is that many of them can provide cooling options as well. Studies are pointing to the advantage of therapeutic cooling, or moderate hypothermia, for post cardiac arrest, stoke and head trauma patients. By rapidly cooling the body’s core temperature, significant neurological benefits have been realized.

The Kimberly-Clark Patient Warming System utilizes what the company calls "direct conduction". The company’s unique Thermal Pads contain an inner adhesive hydrogel layer of 50% water that clings to the skin and helps improve conduction. The company notes that optimal heat transfer can be obtained covering just 20% of the patient’s skin. The pads can be placed anywhere, but are normally used on the patient’s back, so they are out of the sterile field. A unique feature of the system is that it operates under negative pressure, which means if the pads are cut or punctured, air will be pulled into the system rather than water spilling out the O.R. and thereby causing an infection control risk.

Kimberly-Clark recently introduced its new model 1000 Control Unit that was designed using clinician feedback to be more flexible and user-friendly than the company’s previous control unit. For example, the M1000 has a temperature readout that can be detached and mounted on an IV pole to accommodate various O.R. configurations. It also offers more connectivity to other systems such as the anesthesia machine, which would prove useful in recording temperature readouts to a patient’s electronic health record (EHR). It also has the ability to self-diagnose technical problems.

A study by the Pensacola Heart Institute3 that compares the Kimberly-Clark Patient Warming System to conventional forced air warming systems during off-pump coronary artery bypass showed that the Kimberly-Clark version was 97% effective at maintaining normothermia in patients as compared to 42% of patients maintained at normothermia with conventional methods.

"Our experience has shown us that the longer the case, the bigger the operative field, the sicker the patient coming in, the bigger difference you’re going to have between the performance of our product and conventional methods," said Dye.

Cincinnati Sub-Zero Head Wrap with Patient Vest

He makes a point to note that "this product doesn’t really displace the utility of a lot of the other products on the market, it fills a gap that wasn’t being met on these high acuity patients."

In addition, a recent study from the Dept. of Anesthesiology, College of P&S of Columbia University, NY4, shows not only is the conductive system more effective than conventional warming methods at maintaining normothermia and preventing the afterdrop associated with cardiopulmonary bypass (CPB); it links that afterdrop to changes in oxygen saturation which can have a multitude of negative effects on the patient.

The system has even proven to be more effective at warming under cooler ambient room temperatures, which the O.R. staff will definitely find appealing, said Dye.

When comparing costs for warming systems, Dye urges purchasing managers to look at the global costs of maintaining hypothermia rather than the per unit basis. He notes that the company offers a money-back guarantee if their product is not able to maintain patients at normothermia.

"This is a classic cost in use story," he said. "If they make a direct comparison of the material costs of our system, it is more expensive. However, there’s definitely a significant benefit of utilizing our system in that it lowers the total costs via improved outcomes."

Cincinnati Sub-Zero offers several versions of a conductive warming system including the Blanketrol II and the Norm-O-Temp. Blanket/wrap options include the Maxi-Therm or Maxi-Therm Lite Blankets, PlastiPad Blankets, or the unique CSZ Head Wrap, Patient Vest, or Surgeon’s Vest. All the blankets incorporate a random flow design to maximize surface area.

The company says it pioneered the development of the compressor-driven hypo/hypothermia machine in 1964. It also contends that its Blanketrol II system offers the fastest heating and cooling of any hypo/hyperthermia system on the market due to its high flow rate.

The Blanketrol II along with any combination of CSZ blankets can be used for both heating and cooling.

The company’s whole body hypothermia system includes the Blanketrol II along with the newly introduced Head Wrap and Patient Vest. The system is used to actively cool the major blood supply to the brain and body cavity.

According to Frederick, preliminary studies show that use of the CSZ Head Wrap and the standard hypo/hyperthermia blanket for off-pump CABG (coronary artery bypass graft) procedures is resulting in normothermic patients.

The company also has a surgeon’s cooling vest that is designed similar to the patient vest.

Cincinnati Sub-Zero’s Norm-O-Temp is a heat-only conductive option that is compact and is priced at about half the cost of hypo/hyperthermia systems. "When the focus is keeping the patient warm, the Norm-O-Temp is an excellent substitute for convective air," said Frederick.

Cincinnati Sub-Zero also offers a cardiovascular heating/cooling unit that is used during by-pass procedures as well as an ECMO (extra corporeal membrane oxygenation) unit that is used in conjunction with a heat exchanger to warm blood in applications involving neonatal, pediatric or adult cases.

Gaymar offers the Medi-therm III conductive warming system which can be used with single-use or reusable blankets. Gaymar’s RaprRound blanket system includes a body wrap, torso and two separate leg wraps that can be used together or separately. It provides a good option for therapeutic cooling, Grisanti remarks.

She notes that several studies have confirmed the effectiveness of the Medi-therm for both pre-operative warming and for therapeutic cooling5,6.

Nellcor WarmFlo Fluid Warmer

Fluid/blood warmers
Fluid warming options include the more traditional water bath technology and dry heat technology that is becoming popular due to its low maintenance and reduced infection control risks. While fluid warmers alone are not effective at intra-operative therapeutic warming, they can be used in conjunction with other warming options.

Smiths Medical ASD offers its Level H-1200 Fast Flow which is a rapid infusion option used in trauma and other high blood loss cases. The system has a unique integrated air detection and automatic clamping ability. As a bolus of air displaces fluid, the system’s ultrasonic signal is broken and the clamp closes, stopping the air before it enters the patient line. When this happens, audible and visual alarms are activated, and the system can be cleared of the air without disconnecting the machine from the patient.

Gaymar’s Medi-Temp III Fluid Warmer includes adjustable default settings that allow the system to be pre-set prior to surgery and then turned off. When the system is turned back on again it will revert back to the previously set temperature.

Arizant is another company that has a fluid warmer that operates on dry heat technology, the Ranger. The system monitors temperature every four seconds for increased accuracy and safety. An optional pressure infusion system allows the Ranger to be used for rapid infusion.

Medical Solutions Inc. has fluid warmers in a variety of sizes that feature time/date stamp technology.

O.R. Solutions has a line of Irrigation Solution Warmers that can be used in the O.R. to maintain fluid temperature throughout the procedure, thus eliminating the need to retrieve irrigation bottles from a warming cabinet.

Warming cabinets
Traditional stainless steel warming cabinets can be used to warm fluids or blankets, and some units offer both in one.

Olympic Medical offers several versions of its Warmettes blanket and external solution warmers that can be used for nurseries, birthing rooms, emergency departments, operating rooms and recovery rooms.

Enthermics Medical Systems offers blanket warmers and fluid warmers in a variety of sizes and configurations, plus a combination unit. The company’s WarmRight Concept allows temperature stabilization for blankets, irrigation fluids and injection fluids at three different set-point temperatures in three different chambers to accommodate the varying temperature needs of the products. Blankets can be warmed up to 200°F, irrigation fluids up to 150°F, and injection fluids up to 110°F.

Blickman Inc. provides warming cabinets with either stainless steel or glass doors in a variety of configurations to warm both blankets and solutions.

Pedigo also offers a variety of blanket warming, fluid warming and stackable combination units that can include steel or glass doors.

Medical Solutions Inc. Temp 3

Localized warmers
These localized therapy units can be used for treating muscle and back pain, and can sometimes be used as a pre-warming option.

Microtek Medical’s ChillBuster is a portable unit that is designed for use from pre-op to surgery to recovery to the patient floor. It can be battery or AC operated and includes a blanket with disposable covers.

Gaymar’s T-Pump can go from hospital to home and Grisanti notes that it also can be used for pre-operative warming. She notes that studies show that pre-operative warming for the intended surgery site helps to decrease wound infection rates.

Cincinnati Sub-Zero’s Micro-Temp II heat therapy system works with a variety of localized pads such as their Maxi-Therm Lite and Temp-Pads for post-op care. The company also manufactures a localized cold therapy system for post-op care.

Specialty warmers
There are a few other new technologies in warming options that are worth mentioning.

VitalHeat from DynaTherm Medical Inc. uses technology patented at Stanford University to heat a patient’s core using just his/her hand. A combination of gentle vacuum and heat overcomes the patient’s vasoconstriction and opens a thermal pipeline to the patient’s core. "The VitalHeat is unique in that it heats the thermal core without heating the periphery," said Lawson Fisher, vice president, engineering, DynaTherm Medical. The VitalHeat will be available for sale early next year.

The Insuflow Filter Heater Hydrator from Lexion Medical is used during laparoscopic surgery to counteract the cold dry gas that is used to inflate the abdominal cavity. The Insuflow is used as an accessory to insufflators to heat and humidify laparoscopic gas to physiological conditions in order to reduce hypothermia and post-operative pain. This provides the added benefit to the surgeon of reduced lens fogging.

The Bair Paws Patient Adjustable Warming System from Arizant Healthcare provides gowning and warming in one system. With this comfort warming option, patients can control the temperature of air blowing through the gown simply by turning the knob on the hand-held controller.

Allen Medical Alto Surface

Positioning devices
In addition to maintaining patients’ temperature during surgery, pressure management is another critical factor. Positioning devices made of foam or gel are typically used to protect the patient’s skin during surgery.

Gaymar’s Grisanti recommends that positioning devices be used whenever a patient is at risk for developing pressure ulcers. She notes that pressure ulcers can occur in less than one hour, so all patients should be assessed for pressure ulcer occurrence. She explains that while a head "donut" is often used during surgery, clinicians should also consider protecting heels and elbows. "Whenever there’s a circulatory compromise, or when there’s a mobility issue, patients are at risk for pressure ulcers," said Grisanti. "Even if a patient is positioned for less than an hour in a certain position, a good pressure management positioning device should be used."

Gaymar’s PurGel line of O.R. positioning devices are latex-free reusable pads that utilize a patented XCelGel formula that conforms to the patient and helps distribute the patient’s weight, while preventing bottoming. The gel also moves with the patient to help prevent shear — another contributing factor to pressure sores.

With a unique purple color, the PurGel pads are easy to identify and less likely to get tossed with the laundry or left with the patient, notes Grisanti. These X-ray translucent pads are backed by a two-year warranty and a 30-day money back guarantee.

Action Products introduced its Action pads and positioners more than 15 years ago with a material it pioneered in 1970. Its soft Akton dry polymer looks and feels like a gel, with body-friendly characteristics. Akton polymer won’t leak, moves with the patient to reduce pressure and shear, is radiolucent and fire-rated. The company makes more than 100 different pads and petitioners. Action Products also offers two-year warranties.

Allen Medical, a division of Hill-Rom, offers its Cloud Series of pressure management surfaces. The line includes a variety of surfaces to accommodate various types of surgery. The pads incorporate multi-layered foam along with an Anti-Shear Cover to enhance pressure management. Pad sets come with integrated gel layers upon request.

For guidelines on pressure management, look at the Agency for Health Care Policy & Research (AHCPR) Clinical Practice Guidelines #3, Mechanical Loading and Support Services, and the Wound, Ostomy and Continence Nurses Society (WOCN) Guidelines for Prevention and Management of Pressure Ulcers. HPN

Resources
1."Maintaining intraoperative normothermia: A meta-analysis of outcomes with costs" by Christine Brown Mahoney, RN, PhD, MS and Jan Odom, RN, MS, CPAN, FAAN, AANA Journal, Vol. 67, No. 2, April 1999.
2."Optimal Duration and Temperature of Prewarming" by Daniel I. Sessler, M.D., Marc Schroeder, B.A., Benjamin Merrifield, B.A., Takashi Matsukawa, M.D. and Christi Cheng M.D., Anesthesiology, Vol. 82, No. 3, March 1995.
3.T.A. Vassiliades, MD, et al., Pensacola Heart Institute, Pensacola, FL, "Evaluation of the Arctic Sun During Off-Pump Coronary Artery Bypass," Presented at the Cardiothoracic Techniques and Technologies Conference, Miami, FL, Jan. 2002.
4."Amelioration of Thermal Stress by Intraoperative Surface Warming" by Playford HR, Frumento RJ, Mongero L, Lu J, Park H, Sladen RN, Dept. of Anesthesiology, College of P&S of Columbia University, NY. 2004.
5."Intraoperative Patient Warming: A Comparison of Air- and Water-Based Systems. Berry JM, Daoud R, Zahirul H, Coleman T and Coleman L. University of Mississippi Medical Center, Jackson MI.
6."Temperature Management in Patient Undergoing Endovascular Treatment for Cerebral Aneurysms. Deogaonkar A, Avitsian R, Andrews-Hinders D, Masaryk T, Rasmussen P, Schubert A. Departments of General Anesthesiology and Neurosurgery Cleveland Clinic Foundation, Cleveland, OH.