RESEARCH NEWS

Hypothermia Mary W. Stewart, PhD EVERY PACU NURSE KNOWS the feeling of appreciation when patients sigh and relax with the application of warmed blankets after spending time in a frigid operating room. Beyond comfort, previous evidence suggests that hypothermia may lead to body stress, higher risk of infection, prolonged hospital stay, increased duration of medication action, and greater chance of cardiac events. This is not new information; however, we continue to gain knowledge about best practices to maintain normothermia for patients of various ages and undergoing different types of surgical procedures. The two studies that follow contribute to that knowledge gap. One was authored by certified registered nurse anesthetists in Bridgeport, Connecticut, and the other by a team of German physicians who acknowledged contributions by two registered nurses. Both investigated women, and one focused on mother-infant dyads. The randomized controlled trial identified statistically significant results, whereas the quasi-experimental study found no difference between the study and the control groups. These findings are explicated with special attention to implications for perianesthesia nursing. Preoperative Forced-Air Warming Combined With Intraoperative Warming Versus Intraoperative Warming Alone in the Prevention of Hypothermia During Gynecologic Surgery by Adriani MB, Moriber N. American Association of Nurse Anesthetists; 2013, 81: 446-451.

Mary W. Stewart, PhD, Professor and Director of the PhD program, Special Assistant to the Dean, School of Nursing, University of Mississippi Medical Center, Jackson, MS. Conflict of interest: None to report. Address correspondence to Mary W. Stewart, School of Nursing, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505; e-mail address: [email protected]. Ó 2014 by American Society of PeriAnesthesia Nurses 1089-9472/$36.00 http://dx.doi.org/10.1016/j.jopan.2014.07.004

Journal of PeriAnesthesia Nursing, Vol 29, No 5 (October), 2014: pp 441-444

Background and Purpose Consensus exists among the Centers for Disease Control, the American Society of Anesthesiologist, the Joint Commission, and the American Association of Perianesthesia Nurses regarding the following: (1) hypothermia is a problem and (2) normothermia is the goal. Various modes of perioperative warming have been studied. This particular study looked at two methods of warming patients who were undergoing gynecologic surgery. The purpose was to determine if preoperative warming with the patient-adjustable Bair Paws, 3M, combined with intraoperative warming with the Bair Hugger blanket, 3M, was more effective than intraoperative warming with the Bair Hugger blanket, 3M, alone in preventing hypothermia. Researchers identified three questions:  Does body temperature differ over time between patients who receive Bair Paws warming preoperatively along with routine intraoperative warming and patients who only receive routine intraoperative warming?  Does the effect of temperature differ across preoperative, intraoperative, and PACU time periods?  Does body temperature differ over time between patients having laparoscopic gynecological procedures versus patients having open gynecological procedures? Method and Analysis Women undergoing gynecologic surgery at one hospital in Connecticut were targeted for this study. To be included, patients had to be identified as ASA classes 1 to 3, aged 18 to 85 years, having general anesthesia with endotracheal intubation, and receiving intraoperative forced-air warming with the Bair Hugger device. Gynecologic surgeries included hysterectomies, ovarian cystectomies, myomectomies, and oophorectomies. Purposive nonrandomized sampling was used to secure the study groups: treatment (received preoperative and intraoperative warming) and control

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(received intraoperative warming). Patients in the treatment group received a minimum of 30 minutes of forced-air warming before surgery. Once in surgery, these patients continued to receive forced-air warming. When patients in the control group entered the operating room, forced-air warming was initiated. Oral temperature readings were documented in the preoperative area. Intraoperatively, anesthesia providers documented demographic information, esophageal thermometer readings of core temperature, amount and any warming of intravenous fluids, loss/receipt of blood products, and the use of the Bair Hugger. Final oral temperature readings were recorded in the PACU. Analysis included comparison between the two groups on age, body mass index (BMI), preoperative temperature, first intraoperative temperature reading, amount of intravenous fluids, and blood loss. Temperature readings were analyzed across time (preoperative, intraoperative, and postoperative) for the two groups. Finally, body temperature across time was compared with ASA status and type of gynecologic procedure—open versus laparoscopic. Results Thirty patients were recruited to each of the two study groups for a total of 60 participants. The groups did not differ on age, BMI, intravenous fluids, or blood loss. The groups did differ in preoperative temperatures, with the prewarmed (treatment) group having a significantly higher reading than the control group. By the time the patients got to the operating room and the first intraoperative temperature reading was taken, no differences in body temperature existed. In other words, the prewarming did not last long enough to make a difference in body temperature readings at the onset of surgery. No statistically significant differences were found when comparing the Bair Paws versus the traditional Bair Hugger for perioperative temperature management over time. Type of procedure—laparoscopic versus open—did not make a difference in body temperature over time. Finally, ASA class did not affect body temperature over time. In summary, refer to the three research questions identified earlier. The response to each question is ‘‘No.’’

Conclusions Both body warming methods were effective in preventing hypothermia; all patients were normothermic on arrival to the PACU. Preoperative temperatures did vary between the group that was prewarmed (higher body temperature) and the group that was not; however, the body temperature for the prewarmed group cooled to that of the non–prewarmed group by the time the first intraoperative body temperature was taken. Researchers did not control the amount of time from entry to the operative room and application of the Bair Hugger for any of the patients. Threats to the validity of this study include different methods of assessing body temperature in the preoperative and postoperative areas compared with the intraoperative measure. Ambient temperature and staff technique for temperature assessment were not controlled. Another limitation and threat to generalizability was the small convenience sample of only women experiencing gynecologic surgery. Patient satisfaction, particularly with the preoperative warming intervention, was not measured in this study, although previous research suggested a correlation between warming and reduced patient anxiety. The patient’s sense of control with the ability to self-regulate warming with the Bair Paws system would be a point of interest for future research. Of great relevance is the variance in cost of the Bair Paws warming gown ($15.57) versus the Bair Hugger warming blanket ($6.11). According to this one study, an investment in the more expensive option is not warranted in terms of preventing hypothermia is the population of patients. The Incidence and Prevention of Hypothermia in Newborn Bonding After Cesarean Delivery: A Randomized Controlled Trial by Horn E-P, Bein B, Steinfath M, Ramaker K, Buchloh B, Hocker J. Anesthesia & Analgesia. 2014;118:9971002. Background and Purpose Newborn hypothermia (less than 36.5 C or 97.7 F) is very common. Previous research supports even lower temperature values after cesarean section deliveries. As in adults, hypothermia

RESEARCH NEWS

in newborns poses risks. Neonates may experience increased risk for morbidity and mortality secondary to infection, prematurity, asphyxia, and intraventricular hemorrhage in the presence of hypothermia. Multiple actions are taken to prevent and treat hypothermia after delivery, including skin-to-skin contact with the mother. This bonding position is strongly encouraged by nurse midwives. Research is lacking in the area of newborn warming during the initial bonding time after cesarean delivery. Does the baby become hypothermic if placed on the mother’s chest immediately after birth by cesarean section? What are the effects of active skin warming of mothers and babies compared with passive insulation during this bonding time? These questions informed the purpose of this study to evaluate whether the newborn becomes hypothermic when bonding on the mother’s chest after cesarean delivery. Method and Analysis Women at one clinic and scheduled for cesarean delivery under spinal anesthesia were invited to participate in the research. Women aged less than 18 years , classified as ASA III or higher, and those who expected problems—preterm, post-term, placenta previa, placental abruption, meconiumstained amniotic fluid, fetal membrane inflammation, abnormalities with fetal heart rate, or maternal contractions—were excluded. During a 6-week period in 2013, 63 pregnant women were eligible for inclusion. Of those, 18 declined to participate, 1 received general anesthesia, and 4 did not deliver via cesarean section. The remaining 40 participants were randomized by flipping a coin to one of two groups: (1) receive active warming (treatment) or (2) receive passive insulation (control). Consequently, 19 women comprised the treatment group and 21 comprised the control group. On arrival to the hospital, all women received intravenous fluids at room temperature and 30 mL of sodium citrate. The intraoperative area was maintained at 23 C (73.4 F); all operations were done in the same operating room. Immediately before receiving spinal anesthesia, participants were assigned to a group. Those in the control group received no active warming (routine care), whereas those in the treatment group

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received active forced-air warming from onset of anesthesia until the end of surgery. A Level I Snuggle Warm Upper Body Blanket heated to 44 C (111.2 F) was placed on the treatment group. Prewarmed cotton blankets from a heated cabinet (40 C; 104 F) were placed on the control group. After delivery and assessment of 1- and 5-minute healthy Apgar scores, the naked baby was placed on the mother’s chest—under either the cotton blanket or the forced-air cover, depending on group assignment. Rectal temperature probes were placed into the newborns and monitored throughout the 20 minutes the babies remained in this position. Afterward, babies were moved to the newborn table for skin temperature measurements. Active warming ceased for the treatment group. All babies were clothed and positioned again on the mother’s chest before departure from the surgical room. Maternal temperatures were measured by sublingual probe and skin temperature. Additionally, researchers evaluated shivering of the mother on a scale of 0 (no shivering) to 3 (intense continuous shivering) and maternal thermal comfort on a visual analog scale of 250 mm (worst imaginable cold) to 150 mm (insufferably hot). Analysis also included peripheral oxygen saturation, mean arterial blood pressure, and heart rate of the mothers. Results Both groups were similar at baseline. All newborns were stable at 5 minutes after birth and placed on the mother’s chest. Mothers reported being comfortable and feeling warm. Before the 20minute bonding period, maternal core temperatures were the same in both groups. In the control group (passive warming with cotton blankets), maternal skin temperatures at the start and end of the bonding period were similar to the skin temperature at baseline. Contrarily, in the treatment group (active warming with forced air), maternal skin temperature was significantly higher throughout bonding when compared with their baseline skin temperature and with the temperature of the mothers in the control group. After the bonding period, those who received active warming had significantly higher core and skin temperatures and reported greater thermal comfort. Only one of the 19 mothers in this group became hypothermic, whereas 10 of the 21

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mothers in the control group became hypothermic by the end of the bonding period. These differences reached statistical significance. Finally, 24% (5/21) of mothers who received passive warming only reported low-intensity shivering, whereas no mothers who received active warming complained of shivering.

delivery contributes positively to preventing hypothermia. Nevertheless, core body temperature declined in all babies during the bonding period, but significantly less in mothers and babies in the treatment group. More research is necessary to explore potential benefits of forced-air warming for mother-baby dyads in other birthing situations.

Babies did not differ on length, weight, and gestational age. Moreover, rectal (core) temperature of all the newborns was near 37.5 C (99.5 F). Soon after the bonding period began, core temperature in babies of both groups decreased. In the control group, however, the decrease was significantly more drastic than the decrease in the treatment group at four, 5-minute intervals. At the end of the 20 minutes, the mean temperature of the control group was 35.9 C (96.62 F) compared with 37.0 C (98.6 F) in the treatment group. There was also less deviation in the scores of the treatment group. Seventeen of the 21 (81%) of the control group babies were hypothermic at the end of the bonding period versus one of 10 (5%) of the treatment group babies. Mean skin temperature was also significantly lower in the control group at the same time point.

PeriAnesthesia Nursing Implications

Conclusions A large majority of the newborns whose mothers received the standard of care—passive warming with prewarmed cotton blankets—became hypothermic during the 20-minute bonding time after cesarean delivery. On the other hand, 95% of the newborns of mothers who received active warming remained normothermic during that time. More mothers in the treatment group remained normothermic, as well. These findings imply that the use of active warming of mothers and babies during and after cesarean

Beyond the boost to perianesthesia nurses’ selfesteem when our patients applaud our caring by applying warming blankets or devices to their cold bodies, research indicates patient benefits and reduced risks when normothermia is maintained. In addition to providing the optimal healing experience for patients, perianesthesia nurses are responsible for being knowledgeable about the advantages and costs of many interventions. These studies offer evidence that active warming is beneficial. However, we are also required to assess the cost. Routine practices—as a control group in research—is a smart way to evaluate the efficacy of what we are accustomed to doing and introduce options that may have higher potential. Like professional nurses in other areas of practice, perianesthesia nurses are on the frontline to identify what is working well, working inconsistently, or not working at all. We can question the usual care standards, we can develop potentially better practices, and we can compare the norm to the novel. As individuals, perianesthesia nurses may lack the knowledge, skills, or confidence to systematically test comparisons, but there are nurses who can partner with the clinical nurse to design, implement, evaluate, and disseminate sound research. These relationships are often the start to better standards, truly evidence-based practice, and healthier patient outcomes.

Hypothermia.

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