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Evaluation of Postoperative Warming Care Protocol for Thermal Comfort and Temperature Management Immediately After Surgery: Nonrandomized Controlled Trial

Open AccessPublished:January 04, 2023DOI:https://doi.org/10.1016/j.jopan.2022.07.001

      Abstract

      Purpose

      This study aimed to determine the effects of a warming care protocol (WCM) on temperature control and thermal comfort perception in hypothermia following major abdominal surgery.

      Design

      A prospective nonrandomized controlled trial.

      Methods

      A total of 54 patients undergoing major abdominal surgery were assigned to receive routine care (control group, 27 patients) or the WCM (intervention group, 27 patients). The body temperature (core and peripheral) was measured, and physical symptoms were monitored every hour for 4 hours after arriving at the ward and then every 4 hours for up to 12 hours.

      Findings

      The temperature gap, calculated as the difference between the core and skin temperatures, was similar between the control and intervention groups at the end of surgery. However, the temperature gap in the intervention group decreased within 3 hours after arrival at the ward and remained lower than that in the control group. The visual analog scale score for postoperative thermal discomfort was significantly lower in the intervention group than in the control group, indicating achievement of higher comfort with the warming intervention.

      Conclusions

      Patients were warmed using active warming methods under the WCM, which in turn increased the thermal comfort perception with the body temperature. Postoperative patients often require warming care for thermal comfort, which may be improved by proper observation and management within 1 to 2 hours postoperatively. Our results indicate that nurses could effectively warm the patient to maintain normal body temperature following surgery not only to improve thermal comfort, but also to prevent shivering and possibly various postoperative complications.

      Keywords

      Hypothermia related to anesthesia and surgery is an important cause of postoperative complications, such as surgical site infections (SSI), postoperative myocardial ischemia, and prolonged hospital stay. The maintenance of body temperature with active warming prevents inadvertent hypothermia and reduces such complications through intraoperative active warming with forced-air warming devices.
      • Balki I
      • Khan JS
      • Staibano P
      • et al.
      Effect of perioperative active body surface warming systems on analgesic and clinical outcomes: a systematic review and meta-analysis of randomized controlled trials.
      ,
      • Poveda VB
      • Oliveira RA
      • Galvão CM.
      Perioperative body temperature maintenance and occurrence of surgical site infection: a systematic review with meta-analysis.
      Several studies on the prevention of perioperative hypothermia from the preoperative to the intraoperative period have been reported, and the practice of perioperative body temperature management has been significantly improved.
      • Granum MN
      • Kaasby K
      • Skou ST
      • Grønkjær M.
      Preventing inadvertent hypothermia in patients undergoing major spinal surgery: a nonrandomized controlled study of two different methods of preoperative and intraoperative warming.
      ,
      • Lau A
      • Lowlaavar N
      • Cooke EM
      • et al.
      Effect of preoperative warming on intraoperative hypothermia: a randomized-controlled trial.
      In contrast, studies on temperature management following surgery are lacking. Frank et al.
      • Frank SM
      • Kluger MJ
      • Kunkel SL.
      Elevated thermostatic setpoint in postoperative patients.
      elucidated the postoperative increase in core temperature and its mechanisms by assessing thermoregulatory responses, such as vasoconstriction and shivering, and the plasma concentrations of inflammatory cytokines in patients undergoing various surgical procedures. After surgery, elevation of the set point of core temperature occurs due to inflammation induced by surgical invasion and thermoregulatory response, including vasoconstriction in the peripheral blood vessels to produce heat. This significantly decreases the peripheral temperature, which would already be reduced by surgery or anesthesia and may continue until the core temperature reaches the elevated set point. Consequently, patients following surgery feel chills or exhibit shivering. The reduction of peripheral circulation also affects the immune response and wound healing at the surgical site and increases the risk of SSI.
      • Reynolds L
      • Beckmann J
      • Kurz A.
      Perioperative complications of hypothermia.
      Therefore, postoperative management of body temperature is as much a crucial issue as an intraoperative body temperature management protocol for the prevention of postoperative complications.
      In our previous study, we measured both the central and peripheral temperature transitions of the patients until 12 hours postoperatively and found that a continuous postoperative decrease in the peripheral temperature increased the gap between the core and peripheral temperatures during postoperative body temperature transition, and that active warming reduced the gap between core and peripheral temperatures and improved peripheral circulation.
      • Kameda N
      • Isono S
      • Okada S.
      Effects of postoperative active warming and early exercise on postoperative body temperature distribution: non-blinded and randomized controlled trial.
      Uncomfortable symptoms, such as shivering induced by the thermoregulatory response to an increased set point of temperature, were prevented by active warming. Active warming could accelerate the core temperature to reach the elevated set point and minimize the vasoconstriction of the peripheral blood vessels. Based on these results, we considered that body temperature management based on monitoring of the gap between the central and peripheral temperatures is effective and subsequently created a postoperative warming care protocol that can be immediately implemented. In this protocol, both the central and peripheral temperatures are monitored, and the implementation of warming care is determined based on the gap between the central and peripheral temperatures.
      This study aimed to evaluate the effectiveness of our postoperative warming care protocol on temperature control and thermal discomfort in patients undergoing major abdominal surgery.

      Methods

      Study Design

      This prospective, nonrandomized controlled trial was conducted at a university hospital in Japan from November 2018 to September 2019. The study protocol was approved by the university ethics review board (Approval No. 30-23).

      Participants

      The patients who met the following inclusion criteria were asked to participate in the study: male, aged between 50 and 80 years, body mass index of between 18.5 and 25 kg/m2, and scheduled for laparotomy. The exclusion criteria were peripheral vascular disease, serious preoperative and intraoperative complications, and receiving continuous catecholamine infusion. Study participants included patients with ASA-PS 1-3 undergoing hepatobiliary and pancreatic surgeries. Patients with uncontrolled diabetes and hypertension were included, whereas those with chronic obstructive pulmonary disease, heart disease, and active hepatitis were excluded. Furthermore, participants with complications such as arrhythmia, hypotension, or difficulty in airway management during the operation were excluded.
      The chief investigator explained the purpose of the study, research methods, and other precautions to the patients before their participation and obtained their consent the day before the surgery. The participants’ rights and privacy were protected throughout the study. Each participant completed a written consent form and had the right to withdraw from the study at any given time for any given reason. Information pertaining to the patients’ privacy was kept confidential. The right to be informed of the research findings if requested was also secured.
      The eligibility of each participant for this study was confirmed at the end of surgery. The participants were assigned to the control group, which received routine care, or the intervention group, which received the postoperative warming care protocol according to the period of implementation.

      Perioperative Management

      The anesthesia techniques and surgical procedures were not standardized for this clinical study. During surgery, the room temperature in the operating theater was controlled between 24°C and 26°C, and all patients received warming with a forced-air warmer under a forced-air cover (Bair Hugger 775, 3M; Maplewood, MN, USA). The anesthesiologists actively managed to maintain the core temperature near 37°C intraoperatively. The patients were sent to the ward after a core temperature above 36°C, and alertness with stable cardiorespiratory status was confirmed. Intraoperative core temperatures for patients ranged from 35.4°C to 37.9°C.

      Interventions

      Immediately after arrival at the ward, the warming care protocol was initiated for patients in the intervention group. The patients in the control group received the routine postoperative care at the surgical ward, which involved covering the patient with cotton blankets immediately after arrival. A flow diagram of the care protocol is presented in Figure 1. It demonstrates the preparation of a medical treatment environment, body temperature measurement and observation, and implementation of warming care.
      Figure 1
      Figure 1Postoperative warming care protocol.

      Preparation of a Medical Treatment Environment

      The preparation of a medical treatment environment is outlined as follows:
      • Set the room temperature to 24°C–26°C: This room temperature criterion has been commonly employed for hypothermia prevention and a comfortable bed environment.
      • Keep the bed warm with an electric blanket: Warming the bed can ease the patient's feeling of coldness and prevent body temperature loss due to conduction. Electric blankets were selected as the warming equipment, as they are usually prepared in surgical wards and have been proven useful in preventing hypothermia.
        • Zhang R
        • Chen X
        • Xiao Y.
        The effects of a forced-air warming system plus electric blanket for elderly patients undergoing transurethral resection of the prostate: a randomized controlled trial.
      • Prevention of body temperature loss during transportation from the operation theater: Heat loss occurs during patient transfer; thus, sufficient blankets for patient transfer need to be secured to minimize skin exposure.
        • Burger L
        • Fitzpatrick J.
        Prevention of inadvertent perioperative hypothermia.

      Body Temperature Measurement and Observation

      After arrival at the ward, measurement of both the central and peripheral body temperatures was performed. A tympanic thermometer and an axillary thermometer were used for the measurements of the core and peripheral temperatures, respectively, both of which are widely used in clinical practice.
      According to a previous study, warming care implemented immediately after surgery to 3 hours after surgery improved body temperature dynamics,
      • Özsaban A
      • Acaroğlu R.
      The effect of active warming on postoperative hypothermia on body temperature and thermal comfort: a randomized controlled trial.
      and frequent temperature monitoring was considered necessary during this period. Measurement of the body temperature and observation of physical symptoms were performed every hour until 4 hours after arriving at the ward and then every 4 hours for up to 12 hours.

      Criteria for Starting Warming Care

      The baseline for implementing the protocol was set at 36°C due to previous studies showing decreased postoperative complications, such as SSI, when the core temperature was maintained at >36°C.
      • Kurz A
      • Sessler DI
      • Lenhardt R.
      Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of wound Infection and Temperature Group.
      When starting warming care with an electric blanket, the temperature was set to not exceed 38°C to avoid “low temperature burn injuries,” which are accidents or injuries caused by long-term direct contact with a low temperature heat source that would not normally cause burns, such as hot water bottles, electric blankets, and pads, and disposable body warmers.
      If the core temperature was above 36°C, the difference between the core and peripheral temperatures was calculated. Warming with an electric blanket was implemented when the difference between the core and peripheral temperatures was 1°C or more. The temperature difference for warming care implementation was determined based on our previous study, which demonstrated that thermoregulatory symptoms, such as shivering, were likely to occur when the temperature gap exceeded 1°C.
      • Kameda N
      • Isono S
      • Okada S.
      Effects of postoperative active warming and early exercise on postoperative body temperature distribution: non-blinded and randomized controlled trial.
      Therefore, both the core and peripheral temperatures were monitored and evaluated for early postoperative body temperature management, and a temperature gap of 1°C or more was immediately treated. When the difference between the core and peripheral temperatures was less than 1°C, routine care was continued.
      Although clinical symptoms resulting from decreased peripheral circulation due to body temperature gap have been demonstrated,
      • van Genderen ME
      • Paauwe J
      • de Jonge J
      • et al.
      Clinical assessment of peripheral perfusion to predict postoperative complications after major abdominal surgery early: a prospective observational study in adults.
      judgment of the necessity of warming care only by measuring the body temperature is difficult. Moreover, the patient's complaints were also considered in warming care implementation. Warming was started when the patient complained of coldness during routine care and stopped when the patient complained of heat pain.

      Data Collection

      Body Temperature

      The core and peripheral temperatures of the participants were measured before the surgery, at the end of the surgery, upon arrival at the ward, and at 1, 2, 3, 4, 8, and 12 hours after arrival at the ward. The core temperature was measured using an infrared tympanic thermometer (MC-510; Omron, Kyoto, Japan). The peripheral temperature was measured using an axillary thermometer (MC-1600W-HP; Omron, Kyoto, Japan). All measurements were performed at the same site for each patient for every measurement in the supine position at bedside. All participants wore similar hospital gowns, and the room temperature of the ward was maintained at approximately 24°C.

      Assessment of Thermal Discomfort and Wound Pain

      Thermal discomfort and wound pain were assessed on the day after the surgery using new, unmarked 100 visual analog scale (VAS) sheets that scored for thermal discomfort, with 0 and 100 indicating “completely comfortable” and “worst imaginable cold,” respectively. For wound pain, 0 and 100 indicated “no pain at all” and “pain as bad as it could possibly be,” respectively.

      Occurrence of Postoperative Complications

      Shivering immediately upon arrival at the surgical ward to 12 hours after was assessed by a clinical nurse. The degree of shivering was graded using a four-point scale (0 = no shivering; 1 = intermittent, low-intensity shivering; 2 = moderate shivering; 3 = continuous, intense shivering). The incidence of SSI, the day SSI was detected, and the grade of SSI were collected from the chart reviews in the electronic medical records.

      Statistical Analyses

      To calculate the appropriate sample size for this study, we assumed a standard deviation of 1.0°C from the previous research on our study population and expected a difference of >0.8°C between the control and intervention groups as a clinically meaningful effect. Accordingly, the required total sample size was estimated to be 52 subjects (G-POWER version 3.1 software: [t tests; effect size = 0.8; α = 0.05, two-tailed; β = 0.8; allocation ratio = 1]). Considering possible exclusion during operation due to intraoperative complications and catecholamine use, a total of 56 patients (28 patients for each group) were predetermined as the optimal sample size for this study. All statistical analyses were conducted using IBM SPSS Statistics ver. 27. Continuous, normally distributed variables were analyzed via one-way analysis of variance or Student's t test. Pearson's χ2 test was used for categorical variables. All values are expressed as mean ± standard deviation. P < .05 was considered statistically significant.

      Ethical Approval

      Ethical Committee of the Graduate School of Nursing, Chiba University, Chiba, Japan (Approval No. 30–23).

      Results

      Patient Characteristics and Intervention Status

      Figure 2 presents the study flowchart and the number of participants enrolled and evaluated in the study. A total of 28 patients were initially enrolled in each group, but one patient in each group was excluded from the analysis due to postoperative continuous catecholamine infusion. The patient characteristics and features of anesthesia management and surgical procedures are presented in Table 1. All patients underwent hepatobiliary pancreatic surgeries. No significant differences were observed between the control and intervention groups. Although the core temperature significantly decreased in both groups during anesthesia and surgery, no differences between the groups were observed in all body temperatures before and during surgery (Table 2).
      Figure 2
      Figure 2The study flowchart and the number of the participants enrolled and analyzed in the study.
      Table 1Patient Characteristics
      ControlInterventionP
      (n = 27)(n = 27)
      Age of the patients (years)69.8 ± 8.072.1 ± 6.8.46
      Body mass index (kg/m2)21.8 ± 2.222.2 ± 2.1.87
      ASA-PS.17
       15 (18.5)1 (3.7)
       218 (66.7)19 (70.4)
       34 (14.8)7 (25.9)
      Surgical procedure.41
       Pancreaticoduodenectomy8 (29.6)12 (44.4)
       Hepatectomy9 (33.3)9 (33.3)
       Other hepatobiliary surgery10 (37.0)6 (22.2)
      Length of anesthesia (minute)421 ± 162487 ± 139.52
      Length of operation (minute)336 ± 156399 ± 134.44
      Intraoperative bleeding (mL)729 ± 6381120 ± 1120.06
      Intraoperative infusion volume (mL)2650 ± 15903020 ± 1170.06
      Intraoperative urine volume (mL)336 ± 357360 ± 268.33
      Hospital admission period (day)24.1 ± 18.627.8 ± 22.9.71
      ASA-PS, American Society of Anesthesiologists Physical Status Classification System.
      Values are expressed as mean ± SD or number (percentage).
      Table 2Intraoperative Core Temperature Parameters
      Control (n = 27)Intervention (n = 27)P
      Preanesthesia temperature (°C)36.9 ± 0.136.9 ± 0.1.38
      Average intraoperative temperature (°C)36.9 ± 0.236.8 ± 0.3.49
      Maximum intraoperative temperature (°C)37.5 ± 0.337.5 ± 0.3.93
      Minimum intraoperative temperature (°C)36.1 ± 0.336.1 ± 0.3.45
      Postoperative temperature (°C)37.4 ± 0.337.3 ± 0.4.06
      Temperature fluctuation range (°C)1.4 ± 0.41.5 ± 0.4.72
      Values are expressed as mean ± SD
      In the intervention group, 11 patients (40.7%) were warmed at approximately 77.1 ± 38.8 minutes immediately after arriving at the ward due to a temperature difference of >1°C (eight patients, 29.6%) or a feeling of coldness (three patients, 11.1%). Furthermore, eight patients (29.6%) were warmed for approximately 98.5 ± 42.6 minutes several hours after arriving at the ward due to a temperature difference of >1°C (two patients, 7.4%) or a feeling of coldness (six patients, 22.2%). Two patients were observed with a temperature difference of >1°C when measured 1 hour postoperatively, and six patients were observed with a feeling of coldness at measurement ranged from 60 to 170 min for approximately 105.8 ± 42.3 minutes postoperatively. The average warming start time for those who received warming care several hours after arriving at the ward was 94.3 ± 38.3 minutes. Warming was discontinued as the temperature difference decreased within 1°C (13 patients, 68.4% of those who received warming care) or patient complained of symptoms like heat pain (6 patients, 31.6% of those who received warming care). The warming time of the 19 cases who received warming ranged from 25 to 180 minutes, with an average of 85.8 ± 56.8 minutes.

      Changes in Body Temperature

      Figure 3 presents the changes in the core and peripheral temperatures from before surgery to 12 hours after arrival at the ward in the control and intervention groups. During the postoperative period, changes in the core temperature did not differ between the two groups.
      Figure 3
      Figure 3Changes in core and peripheral temperatures in control group and intervention group before and after surgery.
      Temperature gaps were then calculated as the difference between the core and peripheral temperatures. Figure 4 presents a comparison of the temperature gap between the control and intervention groups.
      Figure 4
      Figure 4Changes in temperature gap in two groups before and after surgery.
      The temperature gaps before surgery were 0.45°C ± 0.16°C and 0.44°C ± 0.10°C in the control and intervention groups, respectively. In the intervention group, the temperature gap continuously decreased until 3 hours after arrival at the ward (0.66°C ± 0.24°C vs 0.50°C ± 0.18°C, P = .01). At 4 hours after arriving at the ward, the temperature gap returned to the preoperative value (0.43°C ± 0.15°C). The temperature gap in the intervention group returned to the preoperative value 4 hours after arriving at the ward, whereas the temperature gap in the control group did not, even at 12 hours postoperatively. The temperature gap in the intervention group remained lower than that in the control group at all measurement points after arrival at the ward. Significant differences between the groups were observed at 3 hours (P = .01), 4 hours (P < .01), 8 hours (P = .04), and 12 hours (P = .03) after arrival at the ward.

      Thermal Discomfort and Wound Pain

      Figure 5 presents the VAS scores for postoperative thermal discomfort and wound pain. The VAS score for postoperative thermal discomfort was significantly lower in the intervention group than in the control group (22.3 ± 14.8 vs 11.9 ± 11.2; P = .01), indicating the achievement of higher comfort with the intervention. The VAS score for wound pain (26.7 ± 14.5 vs 25.9 ± 10.8; P = .81) did not differ between the two groups.
      Figure 5
      Figure 5Box plots presenting comparisons of Visual Analogue Scales (VAS) for thermal discomfort and wound pain in two groups.

      Occurrence of Postoperative Complications

      Intermittent, low-intensity shivering (grade 1) was observed in six patients (22.2%) in the control group and two patients (7.4%) in the intervention group. Moderate shivering (grade 2) was observed in only one patient (3.7%) in the control group. The occurrence of shivering in the control group did not vary significantly from that in the intervention group (P = .17). SSI developed in four patients (14.8%) in the control group. Enterococcus faecalis was isolated from three patients and Escherichia coli from one patient. In the intervention group, SSI developed in two patients (7.4%). E. faecalis and Klebsiella pneumoniae were isolated, one from each of the two patients. No significant difference was observed in the incidence of SSI between the control and intervention groups (P = .67).

      Discussion

      This study demonstrated that the postoperative warming care protocol that we designed significantly reduced thermal discomfort and shivering postoperatively in patients by preparing a medical treatment environment and performing warming care based on the difference between the core and peripheral temperatures. Our findings proved the importance of warming care provided immediately after surgery.

      Preparing a Medical Treatment Environment

      Preparing a medical treatment environment is important to prevent heat loss in the patient during transfer to and arrival at the ward. After surgery, when general anesthesia is completed, active warming is interrupted. Additionally, patients in transit are often at risk of hypothermia if their beds and blankets are not warmed. Our care protocol ensures the adjustment of the patient's bed environment to prevent a decrease in the body temperature. No significant differences were observed in the peripheral temperature upon arrival to the ward, but surgical inflammation is suspected to elevate the body temperature set point, resulting in vasoconstriction and skin temperature decreases.
      • Frank SM
      • Kluger MJ
      • Kunkel SL.
      Elevated thermostatic setpoint in postoperative patients.
      The risk of vasoconstriction and decreases in skin temperature must be prevented, and preparing a medical treatment environment should be included in the postoperative body temperature management.

      Effect of the Warming Care Protocol on Clinical Symptoms and Complications

      Performing warming care by monitoring both the central and peripheral temperatures was considered the key implementation of our warming protocol. Recovery of thermoregulatory response immediately after the end of anesthesia and surgery encourages vasoconstriction to keep the central temperature constant. Although vasoconstriction is beneficial in the reduction of heat loss and maintenance of the core temperature, patients may feel coldness. If vasoconstriction is insufficient in maintaining the core temperature, shivering will occur to produce heat. Our care protocol is designed as an intervention in an increased gap between the core and peripheral temperatures, which is the major indicator.
      In the intervention group, warming care was implemented for 11 patients immediately after surgery and 8 during recovery on the postoperative ward according to the criteria for starting warming care. Among these 19 patients who received warming care, 10 patients received it due to a temperature difference of >1°C. Patients in the intervention group had a statistically lower thermal discomfort perception than the control group. This finding indicates the considerable effect of warming care practices using temperature gaps as indicators, and it showed that thermal discomfort perception decreased with the temperature gap. Similar findings were reported in previous studies. Benson et al.
      • Benson EE
      • McMillan DE
      • Ong B.
      The effects of active warming on patient temperature and pain after total knee arthroplasty.
      demonstrated that the thermal comfort level in patients subjected to active warming methods was significantly higher than in those undergoing passive warming methods. Wasfie and Barber
      • Wasfie TJ
      • Barber KR.
      Value of extended warming in patients undergoing elective surgery.
      also reported higher thermal comfort in patients actively warmed before, during, and after surgery, and recommended that patients are warmed at all perioperative stages. Unintentional hypothermia following surgery affects a patient's thermal comfort. A feeling of coldness seems to be the worst experience of patients who undergo unintentional hypothermia following surgery.
      • Leeth D
      • Mamaril M
      • Oman KS
      • Krumbach B.
      Normothermia and patient comfort: a comparative study in an outpatient surgery setting.
      The warming care provided based on the monitoring of the temperature gap in our protocol was found to be effective in improving thermal comfort postoperatively.
      More notably, only 7.4% of patients in the intervention group experienced grade 1 shivering compared with 25.9% in the control group in which shivering of grade 2 was also observed. Shivering tremendously increases the pain level and oxygen consumption, causing discomfort and threatening the patient recovery process.
      • Lopez MB.
      Postanesthetic shivering—from pathophysiology to prevention.
      Although no significant difference was observed, administering timely warming care can reduce shivering. Warttig et al.
      • Warttig S
      • Alderson P
      • Campbell G
      • Smith AF.
      Interventions for treating inadvertent postoperative hypothermia.
      reported that actively warmed patients were less likely to shiver than those warmed only with a cotton blanket. Özsaban and Acaroğlu
      • Özsaban A
      • Acaroğlu R.
      The effect of active warming on postoperative hypothermia on body temperature and thermal comfort: a randomized controlled trial.
      similarly reported that more patients warmed only with a cotton blanket experienced higher levels of shivering than actively warmed patients. Our results are consistent with those of previous studies. Warming care based on the temperature gap monitoring helped prevent postoperative shivering, thereby alleviating thermal discomfort.
      The novelty of our protocol is to set clear criteria for both starting and terminating warming care and to use not only subjective symptoms but also the temperature gap between the core and peripheral temperatures. In previous studies, the intervention group was provided with warming care regardless of their body temperature. However, unnecessary active warming might cause heat pain, although no description about the adverse effect was provided. In our study, warming care was terminated in six patients due to heat pain. Thus, the prevention of heat pain is also important. Heat pain may occur when the patient is warmed. Even the vasoconstriction of the peripheral blood vessels stops as the core temperature reaches the elevated set point. Therefore, a temperature gap of less than 1°C as a criterion for stopping warming in our protocol seems useful as an early indicator of an increase in the peripheral temperature caused by the termination of vasoconstriction of the peripheral blood vessels.
      The incidence of SSI in the control group was higher than that in the intervention group, although a statistically significant difference was not observed. The employment of an active warming method can effectively maintain normal body temperature, and a previous study on intraoperative patients has provided suggestions for SSI prevention.
      • Poveda VB
      • Oliveira RA
      • Galvão CM.
      Perioperative body temperature maintenance and occurrence of surgical site infection: a systematic review with meta-analysis.
      The results of our study indicate that temperature control in the postoperative ward is important for preventing SSI. The deterioration of peripheral circulation has been implicated in the development of SSI, and our previous study has demonstrated that postoperative warming improves peripheral circulation.
      • Kameda N
      • Isono S
      • Okada S.
      Effects of postoperative active warming and early exercise on postoperative body temperature distribution: non-blinded and randomized controlled trial.
      Appropriate warming care based on the care protocol may have affected the occurrence of SSI with the improvement of peripheral circulation. Body temperature variations during the perioperative period may also affect immune function in patients; thus, maintaining a body temperature as close to normal as possible constrains variations in immune function.
      • Shao L
      • Pang N
      • Yan P
      • et al.
      Control of body temperature and immune function in patients undergoing open surgery for gastric cancer.
      However, further studies with larger datasets are necessary to establish the usefulness of this intervention in SSI prevention.

      Evaluation of Observation Intervals

      A temperature difference of 1°C or more occurred in 1 hour over the course of recovery in the postoperative ward, and the average time to start warming care was 94.3 ± 38.3 minutes. Both the body temperature and subjective symptoms tended to change from immediately to about 2 hours after surgery, indicating the usefulness of the observation interval of our care protocol. Furthermore, due to the practice of warming care, a significant difference was observed between the control and intervention groups in the temperature gap from 3 hours onwards after arrival at the ward. In addition, analysis of the body temperature gap changes revealed that the values had returned to the preoperative levels, confirming that body temperature distribution had recovered to an appropriate level.

      Improving the Quality of Nursing Practice

      Appropriate management of the patient's body temperature is a major task for nurses working in the surgical ward. We have designed a warming care protocol that can appropriately evaluate the body temperature distribution and thereby help maintain optimal peripheral circulation. More importantly, warming care improved the patient's thermal comfort immediately after surgery. We could not show a significant difference in the incidence of shivering; however, a tendency for improvement in moderate shivering was observed only in the control group and not in the intervention group. This approach adopts the practice of hypothermia prevention before, during, and after surgery. Our results indicate that nurses could effectively warm patients and help them maintain an optimal body temperature after surgery not only to improve thermal comfort, but also prevent shivering, and possibly, various postoperative complications.

      Limitations

      This study has several limitations. First, the study population was limited to male patients undergoing hepatobiliary pancreatic surgery under general anesthesia who were within certain age and body mass index ranges. These factors may have different effects on postoperative body temperature changes in the female gender. Thus, further research is warranted with a more diverse study population. Second, the rules for patient movement restriction were not strictly followed and might have affected our results. In particular, body movement just before measurement would have had different effects on body temperature. Third, the postoperative core temperature was relatively higher than those measured in previous studies. Different results may be obtained if the core temperature was lower.

      Conclusion

      The postoperative warming care protocol designed in this study improved thermal comfort perception with body temperature. The constant monitoring of body temperature as outlined in the care protocol is useful in correcting unstable body temperature dynamics following surgery. Furthermore, observing the patients’ subjective symptoms in addition to measuring body temperature also helped achieve thermoregulation and thermal comfort. Perioperative nurses should adopt a standardized approach to identify, prevent, and monitor the risk of unintentional hypothermia following surgery. Unintentional hypothermia following surgery is a threat to patient comfort and should be controlled with effective warming care. Further studies should be repeated in extensive sample groups with complication rates as the primary endpoint.

      Acknowledgments

      The authors thank the participants of this study and the hospital staff who co-operated in the research.

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