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Warming Protocols: Why Are They Not Widely Used in the OR?
Hypothermia/Warming Protocols: Why Are They Not Widely Used in the OR? TARA LYNN WEIRICH, RN, BSN
T
hermal regulation is the physiological mechanism that the body uses to balance heat production and heat loss.1 Body temperature is regulated by the hypothalamus through a negativefeedback system in the central nervous system.1-4 In response to changes in the body’s temperature, the hypothalamus acts as a thermostat, increasing body temperature through vasoconstriction or decreasing body temperature through vasodilation.1,5 The body controls its temperature, an indicator of thermal regulation, within a very tight range.6 Normal thermoregulatory vasoconstriction causes the core body temperature to be 2° C to 4° C (35.6° F to 39.2° F) warmer than the peripheral body temperature, resulting in a baseline temperature gradient.6 Hypothermia, defined as a core body temperature less than 36° C (96.8° F), is a common problem in patients having surgery.1,3,5,7-10 Researchers estimate that 50% to 90% of surgical patients experience hypothermia during surgery.7-8,10 Hypothermia in patients can result in negative physiological and psychological outcomes and may ultimately result in longer hospital stays and decreased patient satisfaction.8 Keeping perioperative patients normothermic should be a high priority for nurses. Not only does this make the patient feel more comfortable and increase his or her satisfaction, but normothermia also decreases the patient’s time in the postanesthesia care unit (PACU).8 Additionally, a reduction in core temperature of 1.5° C (3.3° F) or more from the patient’s normal body temperature is associated with many postoperative complications.11 It is estimated that complications from hypothermia can lead to increased hospital
© AORN, Inc, 2008
costs of $2,500 to $7,500.12 This article discusses the causes and effects of hypothermia, the lack of consistent normothermia practices among institutions, and the obstacles to achieving normothermia in the OR and offers suggestions for improved hypothermia prevention procedures.
FACTORS AFFECTING HYPOTHERMIA Hypothermia is a common and major concern for most patients undergoing surgery, but until recently, it was thought to be unavoidable.4,10,11 Risks for developing hypothermia during surgery include both extrinsic and intrinsic factors. Extrinsic risks include • the direct contact between the body and the cold OR bed; • long, open surgical procedures; • the cold OR environment;
ABSTRACT HYPOTHERMIA, A COMMON PROBLEM for patients having surgery, adversely affects multiple organ systems and physiologic functions. Research indicates that maintaining normothermia can reduce infection rates, operative blood loss, and length of hospital stay. OFTEN, PREVENTING HYPOTHERMIA is not a high priority to surgical staff members because forced-air warming systems may cause field contamination and passive warming may increase the ambient OR temperature. In addition, inconsistent practices and lack of guidelines may affect team members’ efforts. SURGICAL TEAM AWARENESS, education, and understanding of the effects of hypothermia are necessary components to enhance the ways clinicians provide quality, cost-effective patient care. AORN J 87 (February 2008) 333-344. © AORN, Inc, 2008.
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large volumes of room temperature irrigation fluid used in body cavities; • evaporative heat loss from surgical exposure; • major fluid or blood loss; • the administration of room temperature IV fluids; • delayed basal metabolic rate from the anesthesia5,8; • vasodilation induced by pharmacological agents; and • administration of room temperature skin preparations.1,8,13 Intrinsic risks include age, body size, physical status, and comorbidities.13 The risk to infants and children is especially concerning because they have a high ratio of body surface area to weight. Older adults also are at increased risk for hypothermia because of decreased thermoregulatory efficiency. Individuals of thin or small stature are at increased risk for hypothermia because of decreased tissue mass. The physical characteristics and comorbidities that predispose a person to hypothermia include diseases of the endocrine system, such as hypothyroidism.13
ANESTHESIA
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HYPOTHERMIA
The induction of general anesthesia impairs the function of the hypothalamus, the body’s natural thermostat.1,3,4,7 General anesthesia causes vasodilation and limits the body’s ability to vasoconstrict, which is the body’s normal protection against hypothermia.6 Core temperature changes occur in three stages during anesthesia. After the induction of general anesthesia, redistribution hypothermia is the main cause of potential perioperative hypothermia. Redistribution hypothermia allows warmer blood from the core to mix with cooler peripheral blood. As the blood circulates, it cools, and the cooled blood returns to the heart, causing a decrease in temperature.6,8 Within 30 minutes of anesthesia induction, core body temperature can decrease approximately 1° C (1.8° F); within the first 60 minutes of anesthesia induction, core body temperature can decrease 1.6° C (3.4° F).6 Surgical patients lose the most heat within the first hour of anesthesia because of heat redistribution.8,13,14 The second stage is slower and occurs during
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the next two to three hours. This stage occurs because the body is subject to greater heat loss than it can compensate for by metabolic heat production. The third and final core temperature changes occur three to four hours after anesthesia induction. In this stage, the core temperature plateaus and is maintained.5,10
ADVERSE EFFECTS
OF
HYPOTHERMIA
Perioperative hypothermia affects multiple organ systems, including the • respiratory, • cardiovascular, • adrenergic, and • immune systems, and several physiologic functions, including • metabolism, • coagulation, • electrolytes, and • pharmacokinetics. It also can affect a patient’s psychological and emotional states.3 Perioperative hypothermia can result in or contribute to several negative outcomes associated with each organ system or function. These include • postoperative shivering, • blunted ventilatory response to carbon dioxide, • systemic and pulmonary vasoconstriction and increased arterial blood pressure, • sympathetic nervous system activation, • impaired platelet function and coagulation cascade, • variations in serum potassium levels, • impaired neutrophils and macrophages and decreased partial pressure of oxygen, • increased effects and prolonged duration of neuromuscular blockers, and • unpleasant and frightening surgical experiences for patients. POSTOPERATIVE SHIVERING. Shivering increases total body oxygen consumption. Shivering is especially detrimental to patients with cardiac disease because it increases their metabolic rate by 400% to 500%.7 This increase in oxygen consumption is comparable to the cardiac strain an Olympic athlete experiences during an event. The cardiac strain from shivering is stressful for young adults, but it is often fatal for older adults.7,14
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BLUNTED VENTILATORY RESPONSE TO CARBON DIOXIDE. Blunted ventilatory response causes a left shift in the hemoglobin-oxygen dissociation curve and an increased need for mechanical ventilation.1,3,8 Moderate hypothermia, defined as a core temperature from 28° C to 32.1° C (82.4° F to 89.8° F), impairs respiratory drive and is associated with hypoventilation and loss of protective airway reflexes. This can lead to aspiration pneumonia, atelectasis, acidosis, and hypoxia. Hypothermia also inhibits hypoxic pulmonary vasoconstriction.15 The benefit of hypoxic pulmonary vasoconstriction is that it decreases ventilatory-perfusion mismatching. SYSTEMIC AND PULMONARY VASOCONSTRICTION AND INCREASED ARTERIAL BLOOD PRESSURE. Hypothermia may result in systemic and pulmonary vasoconstriction and increased arterial blood pressure. Vasoconstriction and increased blood pressure can increase a patient’s risk for ventricular dysrhythmias, myocardial infarction, and cardiac morbidity in postoperative patients.10,12 SYMPATHETIC NERVOUS SYSTEM ACTIVATION. Activation of a patient’s sympathetic nervous system. increases norepinephrine by 100% to 500% over baseline.3 An increase in norepinephrine may lead to hypertension, which can result in cardiac irritability, facilitating the development of ventricular dysrhythmias. IMPAIRED PLATELET FUNCTION AND COAGULATION CASCADE. Impaired platelet function and coagulation cascade can cause an increase in viscosity of blood, which impairs perfusion.7,10 Decreased perfusion, in turn, causes cell hypoxia, which may lead to development of pressure ulcers.14 Hypothermia causes enhanced fibrinolysis and thrombocytopenia because of sequestration of platelets in the liver and spleen. It also can impair platelet function because of defective thromboxane B2 synthesis.10 Hypothermia slows enzymatic reactions needed for intrinsic and extrinsic pathways in the clotting process and causes prolonged prothrombin time and partial thromboplastin time.10 All of these changes contribute to increased blood loss and an increased need for blood transfusion during surgical procedures. VARIATIONS IN SERUM POTASSIUM LEVELS. Variations in serum potassium levels can cause potentially fatal arrhythmias and have negative inotropic effects on the heart.14 Depression of left
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ventricular contractility with moderate hypothermia is associated with atrial and ventricular arrhythmias.15 The initial electrocardiographic (ECG) change is sinus tachycardia, but as a patient’s core temperature decreases, progressive bradycardia can develop. Hypothermic ECG changes also can include prolonged PR and QT intervals.15 These changes arise because of the alterations in electrophysiologic properties of the Purkinje fibers or the decreased serum potassium caused by hypothermia. Core temperature below 30° C (86° F) can create ectopic atrial rhythms such as atrial flutter and atrial fibrillation. Core temperature below 28° C (82.4° F) can result in ventricular tachycardia and ventricular fibrillation, and core temperature below 15° C (50° F) often results in asystole.15 IMPAIRED NEUTROPHILS AND MACROPHAGES AND DECREASED PARTIAL PRESSURE OF OXYGEN. Hypothermia can impair function of neutrophils and macrophages and decrease partial pressure of oxygen. This can increase a patient’s risk for bacterial wound infection and may delay wound healing.4,10 INCREASED EFFECTS AND PROLONGED DURATION OF NEUROMUSCULAR BLOCKERS. Residual effects of anesthetic and sedative medications are the most common reasons for persistent sleepiness and labile vital signs during the postoperative period.10 When this occurs, it can increase a patient’s length of stay in the PACU and related costs.5 Cohen et al12 found that hypothermic patients have prolonged hospital stays of approximately two to six days and are less able to tolerate food for approximately one extra day. The removal of their sutures may be delayed by one day. UNPLEASANT AND FRIGHTENING SURGICAL EXPERIENCES. Hypothermia causes an increased length of stay in the PACU because the hypothermic patient needs rewarming.1,3 This, in addition to the experience of feeling cold, can be unpleasant or frightening for surgical patients.
PREVENTION
OF
HYPOTHERMIA
The incidence of hypothermia during surgery can be reduced by prevention, treatment, and increased clinician awareness of the problem.8 The surgical team (ie, surgeons, preoperative nurses, circulating nurses, scrub persons,
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Forced-air warming has been proven to be a cost-effective and efficient method for keeping patients normothermic.
and PACU nurses) can implement many interventions to reduce the threat of hypothermia.8 Forced-air warming has proven to be a cost-effective and efficient method for maintaining normothermia, defined as a core temperature with ranges of 36° C to 38° C (96.8° F to 100.4° F).2-4,7,8,11,13,14 External warming improves local blood flow and, as a result, increases oxygen availability at the cellular level. Warming also positively influences metabolism and cellular proliferation. Systemic and local warming are effective prophylaxis against infection.10 Studies indicate that maintaining normothermia should begin preoperatively.5,8 PREOPERATIVE WARMING. Although redistribution heat loss is well researched in the literature, there is limited data on the efficacy of prewarming and heat redistribution.8 The currently available data on the efficacy of prewarming, however, demonstrate its effectiveness in maintaining perioperative normothermia.9-10 Prewarming patients before a surgical procedure can increase peripheral tissue heat by decreasing the core-to-peripheral heat gradient, resulting in less redistribution heat loss.5,8 Prewarming involves the transfer of large amounts of heat to the patient and can only be achieved by using active warming techniques such as forced-air warming.5 Forced-air warming blankets have multiple small holes throughout the blanket that allow air to reach the patient. The temperature of the air flowing through the blanket is controlled by a warming unit connected to the blanket by a hose. Application of external heat results in a presurgical vasodilation. Post-induction vasodilation has no further effect on the patient’s
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core temperature.5 Prewarming is easier than intraoperative warming because the patient’s body can be completely covered by the forcedair warming blanket. It also may make the patient feel comfortable and more relaxed, decreasing preoperative anxiety.5 Obtaining IV access before surgery also is easier when the patient is prewarmed because the warming promotes vasodilation. INTRAOPERATIVE WARMING. Kurz et al16 conducted a study on the effect of systemic intraoperative warming on wound infection rates after colorectal surgery. The authors studied a population of 200 patients using a randomized controlled trial method with blinded outcome assessment. Final mean core temperatures were measured for the two groups of patients labeled “hypothermic” and “warmed.” Temperature measurements were 34.7° C (94.4° F) and 36.6° C (97.8° F) respectively.16 A follow-up wound culture was conducted at three weeks after surgery. Any wound with culture-positive pus was categorized as a wound infection. Wound infection rates for the hypothermic group were three times higher than for those in the warmed group, with the hypothermic group having a positive infection rate of 19% and the warmed group having a positive infection rate of 6%.16 Melling et al17 conducted a study of wound infection rates after clean surgical procedures (eg, hernia repairs, breast procedures, varicose vein repair). In a randomized control trial of 421 patients, researchers placed patients into one of three groups: local warming, systemic warming, or unwarmed. Follow-up was conducted at two and six weeks by an observer who was blinded to the patient’s warming method. Wounds were directly observed, and if purulent drainage was noted, wound cultures were obtained. The researchers concluded that infection rates doubled for the unwarmed group of patients compared to the two groups of warmed patients. Results indicated that patients had a 4% rate of infection with local warming, 6% with systemic warming, and 15% when unwarmed.17 Schmied et al18 conducted a study in the 1990s to evaluate the effectiveness of warming to reduce operative blood loss. The study was
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a randomized controlled trial of 60 patients undergoing total hip arthroplasty. The warmed group had a mean blood loss of 1.7 L ± 0.3 L while the hypothermic group had a mean blood loss of 2.2L ± 0.5 L resulting in higher transfusion rates for the hypothermic group.18 Normothermia can reduce the postoperative length of hospital stay by up to 40% because it can reduce the possibility of wound infections by up to 64%. The preventative use of one or two active warming devices would cost the patient approximately $7 to $20. These costs, however, offset the costs of potential stay in the intensive care unit at $1,000 per day and may prevent a prolonged hospital stay at $465 per day.13
CLINICAL GUIDELINES FOR THE PREVENTION OF HYPOTHERMIA Perioperative nurses must make the assessment, prevention, and treatment of hypothermia a patient-care priority. Nurses should be aware of the recommended practice guidelines for the prevention and treatment of hypothermia. The American Society of PeriAnesthesia Nurses (ASPAN) established the first clinical guideline in the United States for the prevention of hypothermia. This guideline contains major recommendations for hypothermia prevention but does not include requirements for implementation.2 It states that every patient is at risk for developing perioperative hypothermia, and it lists contributing factors that may increase this risk.2,19 According to ASPAN, normothermia is a temperature between 36° C and 38° C (96.8° F to 100.4° F), and hypothermia is a temperature less than 36° C (96.8° F). The ASPAN guideline recommends that a patient’s temperature be measured accurately and consistently using the correct monitoring device and in the correct manner.2 It provides direction for preoperative, intraoperative, and postoperative management of patient temperature and instructs nurses in preoperative assessment and interventions for hypothermia. The intraoperative and postoperative recommendations detail guidelines for assessment and intervention, with resultant expected outcomes. Guidelines of the American Association of Nurse Anesthetists recommend patient body
temperature monitoring during local, regional, and general surgical procedures, as deemed necessary.20 Similarly, the American Society of Anesthesiologists (ASA) recommends that temperature be evaluated continually during the administration of all anesthetics when clinically significant changes in body temperature are intended, anticipated, or suspected.21 AORN also has developed recommended practices for the prevention of unplanned perioperative hypothermia that are intended to guide perioperative RNs in optimizing patient care and preventing unplanned hypothermia in various practice settings.22 AORN states that normothermic patients experience fewer adverse outcomes as evidenced through randomized clinical trials.22 The 10 recommended practices that guide the perioperative RN through assessment include • plan of care, • selection of equipment, • monitoring, • intervention, • appropriate use of a warming device, • education validation, • competency validation, • documentation, • collaboration with anesthesia personnel for policies and procedures, and • quality improvement. AORN’s recommended practices focus on prevention of the redistribution phase of unplanned hypothermia. Prevention and management of unplanned perioperative hypothermia is a high national priority as evidenced in the directives of the Surgical Care Improvement Project (SCIP).23,24 The ultimate goal of the project is to decrease the incidence of surgical complications by 25% by the year 2010.23,24 According to SCIP resources, a number of studies have demonstrated that hypothermic patients have increased infection rates, providing the rationale for the SCIP focus on normothermia.24,25
OBSTACLES TO ACHIEVING WIDELY USED NORMOTHERMIA PRACTICES IN THE OR Even though clinical guidelines have been established and many research studies have shown perioperative normothermia to be AORN JOURNAL •
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an institution, the project ends. beneficial to the patient and the surgical institution, keeping patients warm often is not a Even when temperatures are being monihigh priority for surgical staff members. One tored, the results may fail to reflect the patient’s reason staff members may fail to focus on core temperature value. The most accurate sites patient normothermia could be that forced-air for core temperature measurement are the pulwarming can contribute to field contamination monary artery, the distal esophagus, the nasobecause the warming units can be a source of pharynx, and the tympanic membrane using a microbial pathogens.3,9 In a study conducted by thermocouple.3 The thermocouple thermometer Avidan et al26 in the 1990s, 10 agar plates were consists of two different types of metals joined placed directly in the path of the air blowing together at one end. When the junction of metals out of two popular warming units. Four of the is heated or cooled, voltage is created and can be plates grew potentially pathogenic organisms. correlated to temperature.3 In some surgical procedures, such as those using regional anesthesia, Three of the four positive findings revealed the ideal measurement sites are not available. that the colonization site was inside the warmFor example, a patient who is undergoing reing hose.26 Further testing showed that no gional anesthesia most likely organisms were detected if a still will be aware of noxious microbial filter was attached stimuli, such as insertion of an to the end of the hose or if the esophageal catheter. Additionhose was attached to the comally, anesthesia care providers mercial blanket.26 Even when temperatures need to be aware that patients Aside from the potential receiving regional anesthesia field contamination, forced-air are being monitored, will have impaired thermoregwarming often causes the surulatory systems.10 These pageon to get hot, resulting in the results may fail to 3 sweating and discomfort. tients often report feelings of Often, cold ambient room comfort and warmth when reflect the patient’s temperatures are necessary they are, in fact, hypothermic. for the OR staff members It is necessary to monitor temcore temperature value. because they need to wear perature in patients receiving heavy surgical gowns, gloves, regional anesthesia, even if and face masks and work unthe patient reports a perceived der hot lights for extended level of comfort. periods of time. Passive Anesthesia care providers warming includes increasing ambient room and surgical staff members may not have a comtemperatures; however, for the same reasons plete understanding of hypothermia or the efficaas discussed above, this often is not the precy of different warming methods. For example, ferred option. the surgical team needs to recognize that the Body temperature maintenance practices largest amount of heat loss occurs from radiation often are inconsistent within an institution, and convection from exposed body surfaces. and practices may vary from one institution to These heat losses can be alleviated only by a another. It may be more common for patients warming device that covers more of the exposed in one institution to arrive in the PACU with body surface or by a mechanism that delivers hypothermia, whereas in another institution more heat than is being lost.3 The surgical team 3 this condition rarely occurs. Staff member also should be aware that adding more layers of turnover within an institution is another facwarmed cotton blankets to warm the patient is tor contributing to inconsistent warming prac- ineffective in increasing the patient’s body temtice procedures. Inconsistent temperature perature.3 The first blanket can reduce heat loss by monitoring often occurs because of people, 33%. The addition of more layers of blankets only not policies. Often, when the person in charge adds another 18% reduction of heat loss, no matof the temperature monitoring project leaves ter how many additional blankets are added.
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Patients may be at a greater risk for developing hypothermia during long surgical procedures; however, surgical staff members must pay close attention to potential signs of hypothermia during all procedures. Patients who have surgical procedures that last less than 30 minutes often develop hypothermia because active warming techniques typically are not used for these shorter procedures. Prewarming for this patient population is equally as important as prewarming patients whose procedures last longer than 30 minutes. Another barrier to hypothermia prevention is a lack of clear evidence-based guidelines on how best to warm patients. The ASA standards are general and vague. These standards allow clinicians maximum flexibility but offer little guidance as to the best method of warming patients. In many institutions, decisions about how to warm patients typically are based on tradition and convenience, making change very difficult. Practitioners often are reluctant to adopt new standards. Surgical team members appreciate and understand immediate outcomes following an intervention. Unfortunately, the positive outcomes of warming often are not immediately apparent. Increases in core temperature with active warming occur over hours, not minutes.3 If less-effective warming methods are used at an institution, it may lead the surgical team to conclude that warming practices are ineffective. The surgical team needs to be educated about the most effective methods of warming. Often, the negative outcomes of hypothermia are not realized until after the patient is in the PACU or is readmitted to the hospital, long after the surgical team has relinquished care of the patient.3 The decision about the ambient temperature in the surgical suite typically is made by the anesthesia care provider and the surgeon. Surgeons may not be aware that a delayed postoperative complication, such as a surgical wound infection, may be related to hypothermia in the OR. It is essential that the surgeon and anesthesia care provider work together to make patient temperature management a top priority.3 Surgeons typically only report surgical complications, whereas anesthesia care providers report surgical outcomes. Neither
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may be aware of the consequences of patient hypothermia. Many complications of hypothermia that are significant from the anesthesia care provider’s perspective are not linked to perioperative hypothermia in the minds of other clinicians.3 Anesthesia care providers must be vigilant in educating other surgical team members about the relationship between hypothermia and surgical complications. This lack of education about the connection of perioperative temperature regulation to negative patient outcomes most likely is the reason perioperative temperature regulation does not receive high priority treatment.3
SUMMARY Perioperative hypothermia is a condition that affects nearly all surgical patients.8 Hypothermia can increase a patient’s recovery time, increase patient and health care facility costs, and ultimately decreases patient satisfaction. Surgical team awareness, education, and understanding of the effects of hypothermia are necessary components to change how clinicians provide quality, cost-effective patient care. Further research studies into the benefits of prewarming and maintaining patient normothermia are needed to establish effective guidelines and standards for temperature monitoring and warming. It is possible that the concepts of prewarming and heat redistribution may be the key to the treatment of hypothermia. Acknowledgement: The author thanks Rosanne Griggs, PhD, FNP, APRN-BC, clinical assistant professor at Southern Illinois University in Edwardsville, IL, for her support and guidance.
REFERENCES 1. Good KK, Verble JA, Secrest J, Norwood BR. Postoperative hypothermia—the chilling consequences. AORN J. 2006;83(5):1054-1066. 2. Clinical Guideline for the Prevention of Unplanned Perioperative Hypothermia. American Society of PeriAnesthesia Nurses. http://www .aspan.org/hypothermia.htm. October 2001. Accessed December 21, 2007. 3. Roundtable summary: perioperative temperature management. Anesthesiology News. http:// www.anesthesiologynews.com. October 2005. Accessed December 21, 2007. AORN JOURNAL •
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4. Taguchi A, Ratnaraj J, Kabon B, et al. Effects of a circulating-water garment and forced-air warming on body heat content and core temperature. Anesthesiology. 2004;100(5):1058-1064. 5. Kiekkas P, Karga M. Prewarming: preventing intraoperative hypothermia. Br J Perioper Nurs. 2005;15(10):444-445. 6. Bair Hugger Therapy. The Bair Paws patient adjustable warming system. Arizant Healthcare. http://www.arizant.com/arizanthealthcare/bppreop.shtml. 2006. Accessed December 21, 2007. 7. Barone CP, Pablo CS, Barone GW. Postanesthetic care in the critical care unit. Crit Care Nurse. 2004; 24(1):38-45. http://ccn.aacnjournals.org/cgi/con tent/full/24/1/38?maxtoshow=&HITS=10&hits=10. Accessed December 21, 2007. 8. Cooper S. The effect of preoperative warming on patients’ postoperative temperatures. AORN J. 2006;83(5):1073-1084. 9. Kabbara A, Goldlust S, Smith C, Hagen J, Pinchak A. Randomized prospective comparison of forced air warming using hospital blankets versus commercial blankets in surgical patients. Anesthesiology. 2002;97:338-344. 10. Kumar S, Wong PF, Melling AC, Leaper DJ. Effects of perioperative hypothermia and warming in surgical practice. Int Wound J. 2005;2(3):193-204. 11. Hooper VD. Adoption of the ASPAN clinical guideline for the prevention of unplanned perioperative hypothermia: a data collection tool. J PeriAnesth Nurs. 2006;21:177-185. 12. Cohen S, Hayes JS, Tordella T, Puente I. Thermal efficiency of prewarmed cotton, reflective, and forced-warm-air inflatable blankets in trauma patients. Int J Trauma Nurs. March 2002;8(1):4-8. 13. Wagner VD. Unplanned perioperative hypothermia. AORN J. 2006;83(2):470-476. 14. Scott EM, Buckland R. A systematic review of intraoperative warming to prevent postoperative complications. AORN J. 2006;83(5):1090-1113. 15. Smith CE. Prevention and treatment of hypothermia in trauma patients. Spring 2004. http:// www.itaccs.com/traumacare/archive/-4_01_ Spring_2004/prevention.pdf. Accessed January 1, 2007. 16. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical wound infection and shorten hospitalization. N
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Engl J Med. 1996;334(19):1209-1215. 17. Melling AC, Ali B, Scott EM, Leaper DJ. Effects of preoperative warming on the incidence of wound infection after clean surgery: a randomized controlled trial. Lancet. 2001;358(9285):876-880. 18. Schmied H, Kurz A, Sessler DI, Kozek S, Reiter A. Mild hypothermia increases blood loss and transfusion requirements during hip arthroplasty. Lancet. 1996;347(8997):289-292. 19. National Guideline Clearinghouse. Clinical guideline for the prevention of unplanned perioperative hypothermia. http://www.guideline.gov /resources/summaryarchive.aspx#5527. September 23, 2004. Accessed July 19, 2007. 20. Scope and standards for nurse anesthesia practice. American Association of Nurse Anesthetists. http://www.aana.com/crna/prof/scope.asp. Accessed October 22, 2006. 21. American Society of Anesthesiologists. Standards for basic anesthetic monitoring. 2004. http://www .asahq.org/publicationsAndServices/standards/02 .pdf. Assessed December 21, 2007. 22. Recommended practices for the prevention of unplanned perioperative hypothermia. In: Perioperative Standards and Recommended Practices. Denver, CO: AORN, Inc; 2008:407-420. 23. SCIP. Making surgery safer: preliminary project overview. http://www.medqic.org/scip/pdf/SCIP projectoverview.pdf. Accessed January 27, 2007. 24. SCIP. Process and outcomes measures. http:// www.medqic.org/scip/pdf/scip_final_measures. pdf. Accessed January 1, 2007. 25. Premier. Surgical Care Improvement Project (SCIP)—A national quality partnership—Premier advisor live. http://www.premierinc.com/advisor live. October 26, 2005. Accessed December 21, 2007. 26. Avidan MS, Jones N, Ing R, Khoosal M, Lundgren C, Morrell DF. Convection warmers—not just hot air. Anaesthesia. 1997;52(11):1073-1076.
Tara Lynn Weirich, RN, BSN, is a graduate student in the Nurse Anesthesia Specialization program at Southern Illinois University, Edwardsville.
Submit Your Ideas for 2008 Patient Safety First Goals
T
he author of the “Patient Safety First” column, which appears each month in the AORN Journal, is seeking input for patient safety column topics in 2008. As nurses on the front lines of patient care,
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Journal readers are uniquely positioned to identify safety concerns. We welcome your suggestions for additions to the 2008 patient safety goals. Please submit your ideas by e-mail to [email protected].
T
hermal regulation is the physiological mechanism that the body uses to balance heat production and heat loss.1 Body temperature is regulated by the hypothalamus through a negativefeedback system in the central nervous system.1-4 In response to changes in the body’s temperature, the hypothalamus acts as a thermostat, increasing body temperature through vasoconstriction or decreasing body temperature through vasodilation.1,5 The body controls its temperature, an indicator of thermal regulation, within a very tight range.6 Normal thermoregulatory vasoconstriction causes the core body temperature to be 2° C to 4° C (35.6° F to 39.2° F) warmer than the peripheral body temperature, resulting in a baseline temperature gradient.6 Hypothermia, defined as a core body temperature less than 36° C (96.8° F), is a common problem in patients having surgery.1,3,5,7-10 Researchers estimate that 50% to 90% of surgical patients experience hypothermia during surgery.7-8,10 Hypothermia in patients can result in negative physiological and psychological outcomes and may ultimately result in longer hospital stays and decreased patient satisfaction.8 Keeping perioperative patients normothermic should be a high priority for nurses. Not only does this make the patient feel more comfortable and increase his or her satisfaction, but normothermia also decreases the patient’s time in the postanesthesia care unit (PACU).8 Additionally, a reduction in core temperature of 1.5° C (3.3° F) or more from the patient’s normal body temperature is associated with many postoperative complications.11 It is estimated that complications from hypothermia can lead to increased hospital
© AORN, Inc, 2008
costs of $2,500 to $7,500.12 This article discusses the causes and effects of hypothermia, the lack of consistent normothermia practices among institutions, and the obstacles to achieving normothermia in the OR and offers suggestions for improved hypothermia prevention procedures.
FACTORS AFFECTING HYPOTHERMIA Hypothermia is a common and major concern for most patients undergoing surgery, but until recently, it was thought to be unavoidable.4,10,11 Risks for developing hypothermia during surgery include both extrinsic and intrinsic factors. Extrinsic risks include • the direct contact between the body and the cold OR bed; • long, open surgical procedures; • the cold OR environment;
ABSTRACT HYPOTHERMIA, A COMMON PROBLEM for patients having surgery, adversely affects multiple organ systems and physiologic functions. Research indicates that maintaining normothermia can reduce infection rates, operative blood loss, and length of hospital stay. OFTEN, PREVENTING HYPOTHERMIA is not a high priority to surgical staff members because forced-air warming systems may cause field contamination and passive warming may increase the ambient OR temperature. In addition, inconsistent practices and lack of guidelines may affect team members’ efforts. SURGICAL TEAM AWARENESS, education, and understanding of the effects of hypothermia are necessary components to enhance the ways clinicians provide quality, cost-effective patient care. AORN J 87 (February 2008) 333-344. © AORN, Inc, 2008.
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large volumes of room temperature irrigation fluid used in body cavities; • evaporative heat loss from surgical exposure; • major fluid or blood loss; • the administration of room temperature IV fluids; • delayed basal metabolic rate from the anesthesia5,8; • vasodilation induced by pharmacological agents; and • administration of room temperature skin preparations.1,8,13 Intrinsic risks include age, body size, physical status, and comorbidities.13 The risk to infants and children is especially concerning because they have a high ratio of body surface area to weight. Older adults also are at increased risk for hypothermia because of decreased thermoregulatory efficiency. Individuals of thin or small stature are at increased risk for hypothermia because of decreased tissue mass. The physical characteristics and comorbidities that predispose a person to hypothermia include diseases of the endocrine system, such as hypothyroidism.13
ANESTHESIA
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HYPOTHERMIA
The induction of general anesthesia impairs the function of the hypothalamus, the body’s natural thermostat.1,3,4,7 General anesthesia causes vasodilation and limits the body’s ability to vasoconstrict, which is the body’s normal protection against hypothermia.6 Core temperature changes occur in three stages during anesthesia. After the induction of general anesthesia, redistribution hypothermia is the main cause of potential perioperative hypothermia. Redistribution hypothermia allows warmer blood from the core to mix with cooler peripheral blood. As the blood circulates, it cools, and the cooled blood returns to the heart, causing a decrease in temperature.6,8 Within 30 minutes of anesthesia induction, core body temperature can decrease approximately 1° C (1.8° F); within the first 60 minutes of anesthesia induction, core body temperature can decrease 1.6° C (3.4° F).6 Surgical patients lose the most heat within the first hour of anesthesia because of heat redistribution.8,13,14 The second stage is slower and occurs during
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the next two to three hours. This stage occurs because the body is subject to greater heat loss than it can compensate for by metabolic heat production. The third and final core temperature changes occur three to four hours after anesthesia induction. In this stage, the core temperature plateaus and is maintained.5,10
ADVERSE EFFECTS
OF
HYPOTHERMIA
Perioperative hypothermia affects multiple organ systems, including the • respiratory, • cardiovascular, • adrenergic, and • immune systems, and several physiologic functions, including • metabolism, • coagulation, • electrolytes, and • pharmacokinetics. It also can affect a patient’s psychological and emotional states.3 Perioperative hypothermia can result in or contribute to several negative outcomes associated with each organ system or function. These include • postoperative shivering, • blunted ventilatory response to carbon dioxide, • systemic and pulmonary vasoconstriction and increased arterial blood pressure, • sympathetic nervous system activation, • impaired platelet function and coagulation cascade, • variations in serum potassium levels, • impaired neutrophils and macrophages and decreased partial pressure of oxygen, • increased effects and prolonged duration of neuromuscular blockers, and • unpleasant and frightening surgical experiences for patients. POSTOPERATIVE SHIVERING. Shivering increases total body oxygen consumption. Shivering is especially detrimental to patients with cardiac disease because it increases their metabolic rate by 400% to 500%.7 This increase in oxygen consumption is comparable to the cardiac strain an Olympic athlete experiences during an event. The cardiac strain from shivering is stressful for young adults, but it is often fatal for older adults.7,14
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BLUNTED VENTILATORY RESPONSE TO CARBON DIOXIDE. Blunted ventilatory response causes a left shift in the hemoglobin-oxygen dissociation curve and an increased need for mechanical ventilation.1,3,8 Moderate hypothermia, defined as a core temperature from 28° C to 32.1° C (82.4° F to 89.8° F), impairs respiratory drive and is associated with hypoventilation and loss of protective airway reflexes. This can lead to aspiration pneumonia, atelectasis, acidosis, and hypoxia. Hypothermia also inhibits hypoxic pulmonary vasoconstriction.15 The benefit of hypoxic pulmonary vasoconstriction is that it decreases ventilatory-perfusion mismatching. SYSTEMIC AND PULMONARY VASOCONSTRICTION AND INCREASED ARTERIAL BLOOD PRESSURE. Hypothermia may result in systemic and pulmonary vasoconstriction and increased arterial blood pressure. Vasoconstriction and increased blood pressure can increase a patient’s risk for ventricular dysrhythmias, myocardial infarction, and cardiac morbidity in postoperative patients.10,12 SYMPATHETIC NERVOUS SYSTEM ACTIVATION. Activation of a patient’s sympathetic nervous system. increases norepinephrine by 100% to 500% over baseline.3 An increase in norepinephrine may lead to hypertension, which can result in cardiac irritability, facilitating the development of ventricular dysrhythmias. IMPAIRED PLATELET FUNCTION AND COAGULATION CASCADE. Impaired platelet function and coagulation cascade can cause an increase in viscosity of blood, which impairs perfusion.7,10 Decreased perfusion, in turn, causes cell hypoxia, which may lead to development of pressure ulcers.14 Hypothermia causes enhanced fibrinolysis and thrombocytopenia because of sequestration of platelets in the liver and spleen. It also can impair platelet function because of defective thromboxane B2 synthesis.10 Hypothermia slows enzymatic reactions needed for intrinsic and extrinsic pathways in the clotting process and causes prolonged prothrombin time and partial thromboplastin time.10 All of these changes contribute to increased blood loss and an increased need for blood transfusion during surgical procedures. VARIATIONS IN SERUM POTASSIUM LEVELS. Variations in serum potassium levels can cause potentially fatal arrhythmias and have negative inotropic effects on the heart.14 Depression of left
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ventricular contractility with moderate hypothermia is associated with atrial and ventricular arrhythmias.15 The initial electrocardiographic (ECG) change is sinus tachycardia, but as a patient’s core temperature decreases, progressive bradycardia can develop. Hypothermic ECG changes also can include prolonged PR and QT intervals.15 These changes arise because of the alterations in electrophysiologic properties of the Purkinje fibers or the decreased serum potassium caused by hypothermia. Core temperature below 30° C (86° F) can create ectopic atrial rhythms such as atrial flutter and atrial fibrillation. Core temperature below 28° C (82.4° F) can result in ventricular tachycardia and ventricular fibrillation, and core temperature below 15° C (50° F) often results in asystole.15 IMPAIRED NEUTROPHILS AND MACROPHAGES AND DECREASED PARTIAL PRESSURE OF OXYGEN. Hypothermia can impair function of neutrophils and macrophages and decrease partial pressure of oxygen. This can increase a patient’s risk for bacterial wound infection and may delay wound healing.4,10 INCREASED EFFECTS AND PROLONGED DURATION OF NEUROMUSCULAR BLOCKERS. Residual effects of anesthetic and sedative medications are the most common reasons for persistent sleepiness and labile vital signs during the postoperative period.10 When this occurs, it can increase a patient’s length of stay in the PACU and related costs.5 Cohen et al12 found that hypothermic patients have prolonged hospital stays of approximately two to six days and are less able to tolerate food for approximately one extra day. The removal of their sutures may be delayed by one day. UNPLEASANT AND FRIGHTENING SURGICAL EXPERIENCES. Hypothermia causes an increased length of stay in the PACU because the hypothermic patient needs rewarming.1,3 This, in addition to the experience of feeling cold, can be unpleasant or frightening for surgical patients.
PREVENTION
OF
HYPOTHERMIA
The incidence of hypothermia during surgery can be reduced by prevention, treatment, and increased clinician awareness of the problem.8 The surgical team (ie, surgeons, preoperative nurses, circulating nurses, scrub persons,
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Forced-air warming has been proven to be a cost-effective and efficient method for keeping patients normothermic.
and PACU nurses) can implement many interventions to reduce the threat of hypothermia.8 Forced-air warming has proven to be a cost-effective and efficient method for maintaining normothermia, defined as a core temperature with ranges of 36° C to 38° C (96.8° F to 100.4° F).2-4,7,8,11,13,14 External warming improves local blood flow and, as a result, increases oxygen availability at the cellular level. Warming also positively influences metabolism and cellular proliferation. Systemic and local warming are effective prophylaxis against infection.10 Studies indicate that maintaining normothermia should begin preoperatively.5,8 PREOPERATIVE WARMING. Although redistribution heat loss is well researched in the literature, there is limited data on the efficacy of prewarming and heat redistribution.8 The currently available data on the efficacy of prewarming, however, demonstrate its effectiveness in maintaining perioperative normothermia.9-10 Prewarming patients before a surgical procedure can increase peripheral tissue heat by decreasing the core-to-peripheral heat gradient, resulting in less redistribution heat loss.5,8 Prewarming involves the transfer of large amounts of heat to the patient and can only be achieved by using active warming techniques such as forced-air warming.5 Forced-air warming blankets have multiple small holes throughout the blanket that allow air to reach the patient. The temperature of the air flowing through the blanket is controlled by a warming unit connected to the blanket by a hose. Application of external heat results in a presurgical vasodilation. Post-induction vasodilation has no further effect on the patient’s
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core temperature.5 Prewarming is easier than intraoperative warming because the patient’s body can be completely covered by the forcedair warming blanket. It also may make the patient feel comfortable and more relaxed, decreasing preoperative anxiety.5 Obtaining IV access before surgery also is easier when the patient is prewarmed because the warming promotes vasodilation. INTRAOPERATIVE WARMING. Kurz et al16 conducted a study on the effect of systemic intraoperative warming on wound infection rates after colorectal surgery. The authors studied a population of 200 patients using a randomized controlled trial method with blinded outcome assessment. Final mean core temperatures were measured for the two groups of patients labeled “hypothermic” and “warmed.” Temperature measurements were 34.7° C (94.4° F) and 36.6° C (97.8° F) respectively.16 A follow-up wound culture was conducted at three weeks after surgery. Any wound with culture-positive pus was categorized as a wound infection. Wound infection rates for the hypothermic group were three times higher than for those in the warmed group, with the hypothermic group having a positive infection rate of 19% and the warmed group having a positive infection rate of 6%.16 Melling et al17 conducted a study of wound infection rates after clean surgical procedures (eg, hernia repairs, breast procedures, varicose vein repair). In a randomized control trial of 421 patients, researchers placed patients into one of three groups: local warming, systemic warming, or unwarmed. Follow-up was conducted at two and six weeks by an observer who was blinded to the patient’s warming method. Wounds were directly observed, and if purulent drainage was noted, wound cultures were obtained. The researchers concluded that infection rates doubled for the unwarmed group of patients compared to the two groups of warmed patients. Results indicated that patients had a 4% rate of infection with local warming, 6% with systemic warming, and 15% when unwarmed.17 Schmied et al18 conducted a study in the 1990s to evaluate the effectiveness of warming to reduce operative blood loss. The study was
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a randomized controlled trial of 60 patients undergoing total hip arthroplasty. The warmed group had a mean blood loss of 1.7 L ± 0.3 L while the hypothermic group had a mean blood loss of 2.2L ± 0.5 L resulting in higher transfusion rates for the hypothermic group.18 Normothermia can reduce the postoperative length of hospital stay by up to 40% because it can reduce the possibility of wound infections by up to 64%. The preventative use of one or two active warming devices would cost the patient approximately $7 to $20. These costs, however, offset the costs of potential stay in the intensive care unit at $1,000 per day and may prevent a prolonged hospital stay at $465 per day.13
CLINICAL GUIDELINES FOR THE PREVENTION OF HYPOTHERMIA Perioperative nurses must make the assessment, prevention, and treatment of hypothermia a patient-care priority. Nurses should be aware of the recommended practice guidelines for the prevention and treatment of hypothermia. The American Society of PeriAnesthesia Nurses (ASPAN) established the first clinical guideline in the United States for the prevention of hypothermia. This guideline contains major recommendations for hypothermia prevention but does not include requirements for implementation.2 It states that every patient is at risk for developing perioperative hypothermia, and it lists contributing factors that may increase this risk.2,19 According to ASPAN, normothermia is a temperature between 36° C and 38° C (96.8° F to 100.4° F), and hypothermia is a temperature less than 36° C (96.8° F). The ASPAN guideline recommends that a patient’s temperature be measured accurately and consistently using the correct monitoring device and in the correct manner.2 It provides direction for preoperative, intraoperative, and postoperative management of patient temperature and instructs nurses in preoperative assessment and interventions for hypothermia. The intraoperative and postoperative recommendations detail guidelines for assessment and intervention, with resultant expected outcomes. Guidelines of the American Association of Nurse Anesthetists recommend patient body
temperature monitoring during local, regional, and general surgical procedures, as deemed necessary.20 Similarly, the American Society of Anesthesiologists (ASA) recommends that temperature be evaluated continually during the administration of all anesthetics when clinically significant changes in body temperature are intended, anticipated, or suspected.21 AORN also has developed recommended practices for the prevention of unplanned perioperative hypothermia that are intended to guide perioperative RNs in optimizing patient care and preventing unplanned hypothermia in various practice settings.22 AORN states that normothermic patients experience fewer adverse outcomes as evidenced through randomized clinical trials.22 The 10 recommended practices that guide the perioperative RN through assessment include • plan of care, • selection of equipment, • monitoring, • intervention, • appropriate use of a warming device, • education validation, • competency validation, • documentation, • collaboration with anesthesia personnel for policies and procedures, and • quality improvement. AORN’s recommended practices focus on prevention of the redistribution phase of unplanned hypothermia. Prevention and management of unplanned perioperative hypothermia is a high national priority as evidenced in the directives of the Surgical Care Improvement Project (SCIP).23,24 The ultimate goal of the project is to decrease the incidence of surgical complications by 25% by the year 2010.23,24 According to SCIP resources, a number of studies have demonstrated that hypothermic patients have increased infection rates, providing the rationale for the SCIP focus on normothermia.24,25
OBSTACLES TO ACHIEVING WIDELY USED NORMOTHERMIA PRACTICES IN THE OR Even though clinical guidelines have been established and many research studies have shown perioperative normothermia to be AORN JOURNAL •
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an institution, the project ends. beneficial to the patient and the surgical institution, keeping patients warm often is not a Even when temperatures are being monihigh priority for surgical staff members. One tored, the results may fail to reflect the patient’s reason staff members may fail to focus on core temperature value. The most accurate sites patient normothermia could be that forced-air for core temperature measurement are the pulwarming can contribute to field contamination monary artery, the distal esophagus, the nasobecause the warming units can be a source of pharynx, and the tympanic membrane using a microbial pathogens.3,9 In a study conducted by thermocouple.3 The thermocouple thermometer Avidan et al26 in the 1990s, 10 agar plates were consists of two different types of metals joined placed directly in the path of the air blowing together at one end. When the junction of metals out of two popular warming units. Four of the is heated or cooled, voltage is created and can be plates grew potentially pathogenic organisms. correlated to temperature.3 In some surgical procedures, such as those using regional anesthesia, Three of the four positive findings revealed the ideal measurement sites are not available. that the colonization site was inside the warmFor example, a patient who is undergoing reing hose.26 Further testing showed that no gional anesthesia most likely organisms were detected if a still will be aware of noxious microbial filter was attached stimuli, such as insertion of an to the end of the hose or if the esophageal catheter. Additionhose was attached to the comally, anesthesia care providers mercial blanket.26 Even when temperatures need to be aware that patients Aside from the potential receiving regional anesthesia field contamination, forced-air are being monitored, will have impaired thermoregwarming often causes the surulatory systems.10 These pageon to get hot, resulting in the results may fail to 3 sweating and discomfort. tients often report feelings of Often, cold ambient room comfort and warmth when reflect the patient’s temperatures are necessary they are, in fact, hypothermic. for the OR staff members It is necessary to monitor temcore temperature value. because they need to wear perature in patients receiving heavy surgical gowns, gloves, regional anesthesia, even if and face masks and work unthe patient reports a perceived der hot lights for extended level of comfort. periods of time. Passive Anesthesia care providers warming includes increasing ambient room and surgical staff members may not have a comtemperatures; however, for the same reasons plete understanding of hypothermia or the efficaas discussed above, this often is not the precy of different warming methods. For example, ferred option. the surgical team needs to recognize that the Body temperature maintenance practices largest amount of heat loss occurs from radiation often are inconsistent within an institution, and convection from exposed body surfaces. and practices may vary from one institution to These heat losses can be alleviated only by a another. It may be more common for patients warming device that covers more of the exposed in one institution to arrive in the PACU with body surface or by a mechanism that delivers hypothermia, whereas in another institution more heat than is being lost.3 The surgical team 3 this condition rarely occurs. Staff member also should be aware that adding more layers of turnover within an institution is another facwarmed cotton blankets to warm the patient is tor contributing to inconsistent warming prac- ineffective in increasing the patient’s body temtice procedures. Inconsistent temperature perature.3 The first blanket can reduce heat loss by monitoring often occurs because of people, 33%. The addition of more layers of blankets only not policies. Often, when the person in charge adds another 18% reduction of heat loss, no matof the temperature monitoring project leaves ter how many additional blankets are added.
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Patients may be at a greater risk for developing hypothermia during long surgical procedures; however, surgical staff members must pay close attention to potential signs of hypothermia during all procedures. Patients who have surgical procedures that last less than 30 minutes often develop hypothermia because active warming techniques typically are not used for these shorter procedures. Prewarming for this patient population is equally as important as prewarming patients whose procedures last longer than 30 minutes. Another barrier to hypothermia prevention is a lack of clear evidence-based guidelines on how best to warm patients. The ASA standards are general and vague. These standards allow clinicians maximum flexibility but offer little guidance as to the best method of warming patients. In many institutions, decisions about how to warm patients typically are based on tradition and convenience, making change very difficult. Practitioners often are reluctant to adopt new standards. Surgical team members appreciate and understand immediate outcomes following an intervention. Unfortunately, the positive outcomes of warming often are not immediately apparent. Increases in core temperature with active warming occur over hours, not minutes.3 If less-effective warming methods are used at an institution, it may lead the surgical team to conclude that warming practices are ineffective. The surgical team needs to be educated about the most effective methods of warming. Often, the negative outcomes of hypothermia are not realized until after the patient is in the PACU or is readmitted to the hospital, long after the surgical team has relinquished care of the patient.3 The decision about the ambient temperature in the surgical suite typically is made by the anesthesia care provider and the surgeon. Surgeons may not be aware that a delayed postoperative complication, such as a surgical wound infection, may be related to hypothermia in the OR. It is essential that the surgeon and anesthesia care provider work together to make patient temperature management a top priority.3 Surgeons typically only report surgical complications, whereas anesthesia care providers report surgical outcomes. Neither
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may be aware of the consequences of patient hypothermia. Many complications of hypothermia that are significant from the anesthesia care provider’s perspective are not linked to perioperative hypothermia in the minds of other clinicians.3 Anesthesia care providers must be vigilant in educating other surgical team members about the relationship between hypothermia and surgical complications. This lack of education about the connection of perioperative temperature regulation to negative patient outcomes most likely is the reason perioperative temperature regulation does not receive high priority treatment.3
SUMMARY Perioperative hypothermia is a condition that affects nearly all surgical patients.8 Hypothermia can increase a patient’s recovery time, increase patient and health care facility costs, and ultimately decreases patient satisfaction. Surgical team awareness, education, and understanding of the effects of hypothermia are necessary components to change how clinicians provide quality, cost-effective patient care. Further research studies into the benefits of prewarming and maintaining patient normothermia are needed to establish effective guidelines and standards for temperature monitoring and warming. It is possible that the concepts of prewarming and heat redistribution may be the key to the treatment of hypothermia. Acknowledgement: The author thanks Rosanne Griggs, PhD, FNP, APRN-BC, clinical assistant professor at Southern Illinois University in Edwardsville, IL, for her support and guidance.
REFERENCES 1. Good KK, Verble JA, Secrest J, Norwood BR. Postoperative hypothermia—the chilling consequences. AORN J. 2006;83(5):1054-1066. 2. Clinical Guideline for the Prevention of Unplanned Perioperative Hypothermia. American Society of PeriAnesthesia Nurses. http://www .aspan.org/hypothermia.htm. October 2001. Accessed December 21, 2007. 3. Roundtable summary: perioperative temperature management. Anesthesiology News. http:// www.anesthesiologynews.com. October 2005. Accessed December 21, 2007. AORN JOURNAL •
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4. Taguchi A, Ratnaraj J, Kabon B, et al. Effects of a circulating-water garment and forced-air warming on body heat content and core temperature. Anesthesiology. 2004;100(5):1058-1064. 5. Kiekkas P, Karga M. Prewarming: preventing intraoperative hypothermia. Br J Perioper Nurs. 2005;15(10):444-445. 6. Bair Hugger Therapy. The Bair Paws patient adjustable warming system. Arizant Healthcare. http://www.arizant.com/arizanthealthcare/bppreop.shtml. 2006. Accessed December 21, 2007. 7. Barone CP, Pablo CS, Barone GW. Postanesthetic care in the critical care unit. Crit Care Nurse. 2004; 24(1):38-45. http://ccn.aacnjournals.org/cgi/con tent/full/24/1/38?maxtoshow=&HITS=10&hits=10. Accessed December 21, 2007. 8. Cooper S. The effect of preoperative warming on patients’ postoperative temperatures. AORN J. 2006;83(5):1073-1084. 9. Kabbara A, Goldlust S, Smith C, Hagen J, Pinchak A. Randomized prospective comparison of forced air warming using hospital blankets versus commercial blankets in surgical patients. Anesthesiology. 2002;97:338-344. 10. Kumar S, Wong PF, Melling AC, Leaper DJ. Effects of perioperative hypothermia and warming in surgical practice. Int Wound J. 2005;2(3):193-204. 11. Hooper VD. Adoption of the ASPAN clinical guideline for the prevention of unplanned perioperative hypothermia: a data collection tool. J PeriAnesth Nurs. 2006;21:177-185. 12. Cohen S, Hayes JS, Tordella T, Puente I. Thermal efficiency of prewarmed cotton, reflective, and forced-warm-air inflatable blankets in trauma patients. Int J Trauma Nurs. March 2002;8(1):4-8. 13. Wagner VD. Unplanned perioperative hypothermia. AORN J. 2006;83(2):470-476. 14. Scott EM, Buckland R. A systematic review of intraoperative warming to prevent postoperative complications. AORN J. 2006;83(5):1090-1113. 15. Smith CE. Prevention and treatment of hypothermia in trauma patients. Spring 2004. http:// www.itaccs.com/traumacare/archive/-4_01_ Spring_2004/prevention.pdf. Accessed January 1, 2007. 16. Kurz A, Sessler DI, Lenhardt R. Perioperative normothermia to reduce the incidence of surgical wound infection and shorten hospitalization. N
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Engl J Med. 1996;334(19):1209-1215. 17. Melling AC, Ali B, Scott EM, Leaper DJ. Effects of preoperative warming on the incidence of wound infection after clean surgery: a randomized controlled trial. Lancet. 2001;358(9285):876-880. 18. Schmied H, Kurz A, Sessler DI, Kozek S, Reiter A. Mild hypothermia increases blood loss and transfusion requirements during hip arthroplasty. Lancet. 1996;347(8997):289-292. 19. National Guideline Clearinghouse. Clinical guideline for the prevention of unplanned perioperative hypothermia. http://www.guideline.gov /resources/summaryarchive.aspx#5527. September 23, 2004. Accessed July 19, 2007. 20. Scope and standards for nurse anesthesia practice. American Association of Nurse Anesthetists. http://www.aana.com/crna/prof/scope.asp. Accessed October 22, 2006. 21. American Society of Anesthesiologists. Standards for basic anesthetic monitoring. 2004. http://www .asahq.org/publicationsAndServices/standards/02 .pdf. Assessed December 21, 2007. 22. Recommended practices for the prevention of unplanned perioperative hypothermia. In: Perioperative Standards and Recommended Practices. Denver, CO: AORN, Inc; 2008:407-420. 23. SCIP. Making surgery safer: preliminary project overview. http://www.medqic.org/scip/pdf/SCIP projectoverview.pdf. Accessed January 27, 2007. 24. SCIP. Process and outcomes measures. http:// www.medqic.org/scip/pdf/scip_final_measures. pdf. Accessed January 1, 2007. 25. Premier. Surgical Care Improvement Project (SCIP)—A national quality partnership—Premier advisor live. http://www.premierinc.com/advisor live. October 26, 2005. Accessed December 21, 2007. 26. Avidan MS, Jones N, Ing R, Khoosal M, Lundgren C, Morrell DF. Convection warmers—not just hot air. Anaesthesia. 1997;52(11):1073-1076.
Tara Lynn Weirich, RN, BSN, is a graduate student in the Nurse Anesthesia Specialization program at Southern Illinois University, Edwardsville.
Submit Your Ideas for 2008 Patient Safety First Goals
T
he author of the “Patient Safety First” column, which appears each month in the AORN Journal, is seeking input for patient safety column topics in 2008. As nurses on the front lines of patient care,
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Journal readers are uniquely positioned to identify safety concerns. We welcome your suggestions for additions to the 2008 patient safety goals. Please submit your ideas by e-mail to [email protected].