INTRODUCTION

In vitro studies have shown that culturing cells involved in healing at temperatures lower than or equal to 32 °C impairs the function of those cells.1 Other studies that evaluated the effect of devices to heat the wound bed have found better healing and lower risk of infection compared with gauze dressings, demonstrating the impact on key outcomes.2,3 Accordingly, providers should strive to maintain the temperature of the wound bed during dressing changes.

Dressing change procedures can lower the temperature of the wound bed. One study found that, immediately after removing the dressing, the average temperature of the wound bed was 32.6 °C, and after cleaning the wound with saline solution at room temperature (29.9 °C), there was an average drop of 2 °C.4 The time required for the temperature to return to the level prior to the procedure was on average 25 minutes.4 However, this measurement was not performed directly on the wound bed, but on the dressing, which does not represent the temperature of the wound bed.

Variations in wound bed temperature are still little studied, as indicated in a scoping review on the subject that included only 13 studies between 2010 and 2020.5 Some protocols and guidelines recommend heating cleaning solutions in order to reduce the impact of heat loss during dressing changes.6,7 However, there is little evidence to support this recommendation; that is, the impact of this intervention on wound healing has not been evaluated, and a local drop in temperature might not actually impact healing.

In addition, wound cleaning has been little investigated in the literature.8 There are studies evaluating the types of solution and cleaning methods applied to wound dressings,9–11 but few studies have been conducted on the temperature of the cleaning solution and its effects on the temperature of the wound bed or patients’ pain and comfort. One crossover randomized clinical trial compared the effects of heated saline solution on pain and comfort in 38 patients with lacerations.12 The wounds were irrigated with solution at room temperature (21 °C) versus heated solution (32.2 °C to 37.8 °C), with a washout of 10 minutes between them. The heated solution was preferred by the patients, although there were no significant differences between the groups regarding pain intensity.

Studies of this nature have not yet been carried out in patients with chronic wounds; the microenvironment of chronic wounds is different from that of acute wounds given high levels of proteolytic enzymes, inflammatory mediators, microorganisms, biofilm, and pain.13–16 In addition, pain can cause or intensify psychological stress and anxiety—hence the importance of pain assessment in the care of patients with chronic wounds as well as the search for interventions to relieve pain.17,18 Finally, promoting comfort is understood as a goal of nursing care for people with wounds, especially chronic wounds.19

The aim of this study was to evaluate the use of heated saline solution during wound cleaning on the intensity of pain related to the procedure, the temperature of the wound bed, and the comfort of patients with chronic wounds. Further, the authors aimed to investigate patient preference in relation to the temperature of the solution used for cleaning.

METHODS

This was a randomized, single-blind crossover clinical trial with a 1:1 allocation. The authors registered the trial on Brazilian Clinical Trials Registry (ReBec- https://ensaiosclinicos.gov.br/) protocol (RBR-10kpkctx). Investigators used the CONSORT recommendations and their extensions for cross-studies.20

Ethics

The study was carried out in accordance with the Declaration of Helsinki. The clinical trial protocol was approved by the Research Ethics Committee of the Federal University of Goiás (CAAE: 30611520.9.0000.5083/2021). The research team approached patients and invited them to participate in the study; those who agreed to participate signed a consent form and were informed of the study procedures.

Setting

The study was carried out in a specialized wound treatment center that treats patients from the public health network in Brazil, located in the municipality of Aparecida de Goiânia, Goiás.

Sample

The sample size was estimated based on the primary outcome—pain intensity—measured by the Numerical Pain Scale. The authors used a previous cross-sectional study that analyzed pain intensity during dressing change in patients with venous ulcers as a reference.21 The minimum sample required to detect a minimum difference of 2.5 points in mean pain intensity compared with the control group given a CI of 95% (α = .05) and statistical power of 80% (β = 0.2) was estimated to be 30 participants.22

Participants

Participant recruitment took place between September and December 2021. In the study setting, care records were consulted to identify eligible patients. Study participants were patients 18 years or older with chronic wounds. The definition of wound chronicity used was those wounds that had failed to proceed through the normal phases of wound healing in an orderly and timely manner with a minimum duration of 8 weeks.13,15 This duration was verified using the date of medical diagnosis recorded in the patient’s medical record. Individuals who had used psychoactive drugs or who had neuropathic wounds were excluded from the study. After verifying the inclusion and exclusion criteria, the patients were approached in person by the research team responsible for data collection and invited to participate in the study. If they accepted, they were included in the study at their appointment that day.

Procedure

Researchers used simple randomization to allocate participants into two groups that received the same treatment in alternating order (Figure 1). Group A/B was treated with heated saline solution (39.8 ± 0.6 °C) first followed by room temperature saline (27.1 ± 1.1 °C), and group B/A was treated with room temperature saline solution first and heated saline solution second. The washout period between interventions was 10 minutes.12

Figure 1.: CONSORT STUDY FLOW DIAGRAM 21

For the heated solution, a 1,000-watt home microwave appliance was used, following the protocol established by Meyer et al.23 The temperature of the solution was checked with an infrared thermometer (contactless digital clinical thermometer; g-tech-Brasil) before use by dispensing about 10 mL of the solution in a plastic falcon tube. For irrigation with saline solution at room temperature, the solution was stored in a non-air-conditioned room, and the temperature was checked before use, in the same way as the heated solution. The same researcher assessed the temperature of all solutions.

After randomization, patient wounds were irrigated using a 40 × 12-gauge needle (18G) attached to the saline solution bag with a jet emission perpendicular to the wound at an average distance of 5 cm from the wound bed. A trained nurse from the research team performed all irrigations and completed the dressings.

Data Collection

For data collection, an interview was conducted with the participants using a three-part questionnaire. The first part comprised the baseline sociodemographic questionnaire and was completed by the research assistant. The second part of the questionnaire was completed by the same researcher who carried out the intervention. It addressed the wound variables, pain intensity, and wound bed temperature measured before and immediately after both cleanings. The third part, filled in by a researcher who was blinded to the order of treatments, detailed the patient’s response regarding which solution he or she considered more comfortable and preferable.

Outcome Variables

The investigators collected sociodemographic data of the patients such as sex and age. The wounds were evaluated using the Pressure Ulcer Scale for Healing.24 Despite being developed for pressure injuries, this scale has been used for chronic wounds of other etiologies.25 In addition, the etiology, location, duration of the wound, and signs of infection26 (odor, color and increased amount of exudate, friable granulation, presence of abscess, and increased pain) were evaluated, as well as any use of pain medications in the last 24 hours before the dressing change.

Pain intensity

The assessment of pain intensity was the primary outcome and obtained via a numeric rating scale ranging from 0 (no pain) to 10 (the most intense pain).27–29 This instrument was applied before dressing change (pain before the experiment), after the first cleaning (pain after the first intervention), and after the second cleaning (pain after the second intervention/after the procedure).

Wound bed temperature

The room temperature was stabilized via air conditioning at approximately 24 °C, verified through a room temperature thermometer. The temperature of the wound bed was checked with an infrared thermometer, positioned as recommended in the device’s user manual. The measurement was carried at four time points: (1) immediately after removing the dressing before the interventions; (2) immediately after the first cleaning; (3) after the washout period; and (4) immediately after the second cleaning.

Comfort

A research assistant who was blinded to the order of treatment asked participants about comfort and preference for the “first” or “second” solution, using the following questions after both cleanings were complete: “Which cleaning solution left you more comfortable in the procedure, the first or second? Which solution would you prefer for your dressing, the first or second?”

Statistical Analysis

Data were analyzed using STATA software version 17.0 (StataCorp). Initially, a descriptive analysis of sociodemographic and clinical characteristics at baseline by group (A/B or B/A) was performed. Quantitative variables were examined for data normality using the Shapiro-Wilk test. Quantitative variables were presented as mean, SD, median, 25th percentile (P25), and 75th percentile (P75), and qualitative variables as absolute (n) and relative (%). Comparisons between groups were performed using the Fisher exact test (qualitative or categorical variables) or Mann-Whitney U/Student t test for independent samples (quantitative variables).

To assess the effect of interventions on outcomes, two analytical approaches were performed. In the first, an intragroup analysis comparing the repeated data at the baseline period (before the intervention) and after both interventions was conducted using the Wilcoxon test for paired samples.

Next, a generalized linear model (GLM) adjusted for period, carryover, and intervention effects was conducted to analyze the effect of interventions on primary and secondary outcomes. Statistical significance was established by the F test at a significance level of .05.

RESULTS

Analyses were performed for the A/B (n = 15), B/A (n = 17), A (n = 32), and B (n = 32) groups. Groups A/B and B/A were homogeneous for all sociodemographic and clinical characteristics at baseline, with no significant differences (Table 1). Also at baseline, 71.7% of patients reported pain, and 65.6% had used some analgesic medication in the last 24 hours prior to the intervention, predominantly dipyrone sodium (42.3%), paracetamol (30.0%), and sodium diclofenac (15.7%).

Table 1. - SOCIODEMOGRAPHIC AND CLINICAL CHARACTERISTICS OF PARTICIPANTS BY GROUP Variable Total (N = 32), Mean ± SD or n (%) A/B (n = 15), Mean ± SD or n (%) B/A (n = 17), Mean ± SD or n (%) P Age, y 59.3 ± 13.3 60.3 ± 15.1 58.4 ± 11.9 .681a  Median (P25-P75) 63.0 (48.5-67.8) 66.0 (48.0-69.0) 62.0 (53.0-66.0) Sex .712b  Female 11 (34.4) 6 (40.0) 5 (29.4)  Male 21(65.6) 9 (60.0) 12 (70.6) Wound etiology 1.000b  Venous 24 (75) 10 (66.7) 14 (82.4)  Arterial 3 (9.4) 2 (13.3) 1 (5.9)  Pressure injury 5 (15.6) 3 (20.0) 2 (11.7) Presence of exudate 31 (96.9) 15 (100.0) 16 (94.1) 1.000b Signs of infection 3 (9.4) 2 (13.3) 1 (5.9) .589b Wound duration, mo 45 ± 62.9 54 ± 65.6 37.35 ± 59.6 .126c  Median (P25-P75) 24 (8-55) 25.0 (10.0-108.0) 15.0 (6.5-42.0) Wound area, cm2 143 ± 220.5 165 ± 256.7 123 ± 189 .485c  Median (P25-P75) 45 (11.6-150.0) 56.0 (25.0-156.0) 36.0 (6.0-167.5) Pressure Ulcer Scale for Healing score 13 ± 2.6 13 ± 2.7 13 ± 2.7 .728c  Median (P25-P75) 15 (12.3-15.0) 14.0 (13.0-15.0) 14.0 (11.0-15.0) Wound pain present 23 (71.9) 10 (66.7) 13 (76.5) .699b Use of pain medication 21 (65.5) 10 (66.7) 11 (64.7) 1.000b

aStudent t test for independent samples.

bFisher exact test.

cMann-Whitney U test.

Pain Intensity

The authors compared baseline and postintervention endpoint results in the within-group analysis. Compared with baseline values, mean pain intensity was not significantly different between groups A/B (P = .172) versus B/A (P = .444). In group A (heated solution) and B (room temperature solution), there was no statistical difference between pain intensity values at baseline and after interventions (P = .172 and P = .166, respectively; Table 2).

Table 2. - REPORTED PAIN INTENSITY Baseline Postintervention P a Group Mean (SD) 95% CI Mean (SD) 95% CI A/B (n = 15) 1.71 (2.36) 0.49, 2.92 2.13 (2.52) 0.82, 3.41 .172 B/A (n = 17) 2.13 (3.68) 0.09, 4.17 2.73 (3.39) 0.86, 4.61 .444 Treatment A (n = 32) 1.91 (3.61) 0.82, 2.99 2.03 (2.83) 1.01, 3.05 .197 B (n = 32) 1.67 (2.35) 0.82, 2.99 2.25 (3.02) 1.16, 3.34 .166

aWilcoxon test for paired samples.

Intergroup analysis showed that pain intensity did not differ statistically between groups (P = .791; Figure 2A). Similarly, the isolated effect of the interventions showed no statistically significant difference in mean pain intensity after cleaning with the solution heated or at room temperature (P = .483; Figure 2B). These data were confirmed by GLM (P = .917; Table 3).

Figure 2.:

PAIN INTENSITY AFTER CLEANING THE WOUNDSA, Level of pain after cleansing in the A/B (heated/room) versus B/A (room/heated) groups. B, Level of pain after cleansing with heated versus room temperature saline solution.Abbreviation: PSS, physiologic saline solution.*Mann-Whitney U test for independent samples.

Table 3. - GLM OF THE EFFECT OF INTERVENTIONS ON PAIN INTENSITY AFTER CONTROLLING FOR PERIOD AND CARRYOVER EFFECTS Effect SS MS F P Intervention 0.10 0.10 0.01 .917 Period 0.27 0.27 0.03 .861 Carryover 2.10 2.10 0.24 .626 Residue 524.10 8.74

Abbreviations: GLM, generalized linear model; MS, mean of squares; SS, sum of squares.

Wound Bed Temperature

The average temperature in the procedure room was 24.7 °C. The average temperature of the unheated and heated solutions was 27.1 ± 1.1 and 39.8 ± 0.8 °C, respectively.

In the intragroup analysis, compared with baseline values, the mean wound bed temperature after intervention was higher in the B/A group (P = .025) and lower in the A/B group (P < .001), with an increase of 0.5 °C and a decrease of 0.7 °C, respectively. However, the authors did not find statistically significant differences between treatments A (heated solution) and B (solution at room temperature) when they compared the baseline and postintervention values (P = .133 and P = .487, respectively; Table 4).

Table 4. - TEMPERATURE OF THE WOUND BED AT BASELINE AND AFTER CLEANING Baseline, °C Postintervention, °C P a Group Mean (SD) 95% CI Mean (SD) 95% CI A/B (n = 15) 35.6 (0.58) 35.3-35.9 34.9 (0.59) 34.6-35.2 <.001 B/A (n = 17) 35.4 (0.44) 35.2-35.6 35.9 (0.60) 35.5-36.2 .025 Treatment A (n = 32) 35.5 (0.57) 35.3-35.7 35.7 (0.58) 35.5-35.9 .133 B (n = 32) 35.5 (0.44) 35.3-35.7 35.5 (0.56) 35.3-35.7 .486

aWilcoxon test for paired samples.

The intergroup analysis showed that the wound bed temperature differed significantly between groups A/B and B/A postintervention (P < .001; Figure 3A). The isolated effect of the interventions showed no statistically significant difference in the mean temperature of the wound bed with the heated solution and at room temperature in the unadjusted analysis (P = .356; Figure 3B). However, when controlling the effects of the analyzed control of period and of carryover and intervention in the GLM, a statistically significant difference was verified between the heated and ambient interventions (F = 47.0; P < .001; Table 5).

Figure 3.:

THE ORDER OF TREATMENTS INFLUENCED THE TEMPERATURE OF THE WOUND BED, BUT WITH NO STATISTICAL DIFFERENCE BETWEEN TREATMENTSA, Wound bed temperature at the end of the experiment in group A/B (heated/room) versus B/A (room/heated). B, Wound bed temperature after cleaning with heated saline versus room temperature saline.Abbreviation: PSS, physiologic saline solution.*Student t test for independent samples.

Table 5. - GLM OF THE EFFECT OF INTERVENTIONS ON WOUND BED TEMPERATURE AFTER CONTROL OF PERIOD AND CARRYOVER EFFECTS Effect SS MS F P Intervention 16.16 16.15 47.00 <.001 Period 1.55 1.55 4.51 .038 Carryover 0.79 0.79 2.29 .135 Residue 20.52 0.34

Abbreviations: GLM, generalized linear model; MS, mean of squares; SS, sum of squares.

Patient Preference

The comfort and solution temperature preferences are described in Table 6. The binomial test showed that the reported comfort was significantly higher with the heated solution compared with the solution at room temperature (P = .045), and participants preferred the heated solution over the solution at room temperature (P = .041).

Table 6. - DESCRIPTIVE MEASURES OF THE PARTICIPANTS’ COMFORT AND PREFERENCE REGARDING THE TEMPERATURE OF THE SOLUTION FOR CLEANING CHRONIC WOUNDS Variable Total, n (%) Group A/B, n (%) Group B/A, n (%) P a Most comfortable solution .045 Room temperature 15.9 (5) 13.3 (2) 17.6 (3) Heated 46.6 (15) 46.7 (7) 47.1 (8) No difference 37.5 (12) 40 (6) 35.3 (6) Preferred solution .041 Room temperature 28.1 (9) 33.3 (5) 23.5 (4) Heated 65.6 (21) 53.3 (8) 76.5 (13) No preference 6.3 (2) 13.3 (2) –
DISCUSSION

Venous ulcers were the most prevalent etiology of chronic wounds in this study, consistent with epidemiologic reports from different regions of the world;30 these wounds constitute a significant burden on health services.

Pain associated with chronic wounds is very common and can significantly impair quality of life. This sensation is one of the most traumatic and stress-inducing aspects of living with a chronic wound.31 In this study, most patients reported mild pain throughout the investigation; most participants (65.6%) had used analgesic medication in the 24 hours prior to the investigation. Studies conducted worldwide have addressed pain during dressing changes in individuals with chronic wounds.21,29 Together, these data indicate that interventions aimed at reducing pain should be an important part of care for people with chronic wounds.

Because pain, anxiety, and stress are exacerbated by dressing changes,29,31 nonpharmacologic measures such as reflexology31 and cold water (5.74 °C)32 can help reduce these symptoms. The authors hypothesized that heated saline could reduce pain during dressing changes, as this measure was effective in other situations.33,34 However, there was no statistically significant difference in pain intensity before cleaning and after using solutions at different temperatures. The data obtained in the present investigation do not permit an extrapolation of the lack of effect of the heated solution to moderate and severe pain levels. Other studies carried out with patients with venous ulcers identified baseline mean pain intensity scores of 4.76 and 6.59.32 This demonstrates the need to evaluate the effect of the heated cleaning solution in individuals with moderate and severe pain.

Further, the type of dressing can influence the pain level during changes.16 However, in this study, all patients were using products that are changed daily, such as hydrogels or enzymatic debridants, and occluded with gauze and bandages or a compress as a secondary dressing. Therefore, in the patients in this study, the type of coverage did not influence the level of pain.

Few studies have evaluated the influence of the temperature of the cleaning solution on the level of pain that patients experience. To the best of the authors’ knowledge, only one study investigated this effect in acute wounds and also did not find a significant difference between the heated and ambient temperature solutions.12 Conversely, a study has shown that exposing the wound bed to cold water (5.74 °C) for 10 minutes before applying a vacuum dressing compared with water at room temperature (26.89 °C) significantly reduced pain intensity scores.32

There is growing interest in verifying wound bed temperature as a means of improving and objectively evaluating the wound bed.35–37 Variations in blood flow or tissue inflammation, together with the vaporization of the wound exudate, can influence wound bed temperature.37 The findings of a meta-analysis5 showed that the “normal” temperature of the wound bed is approximately 30.2 °C to 33.0 °C. The authors suggested that the critical level of 33 °C, previously established as compromising cellular functions based on in vitro studies, cannot be applied to in vivo conditions because temperatures below 33 °C in the wound bed are also considered physiologically plausible. In the present study, when using the heated solution, the temperature of the wound bed rose on average by only 0.5 °C. It has been demonstrated that there is a positive correlation between higher temperatures in the wound bed and better healing scores.35 However, this small increase detected after cleansing with heated saline may not be sufficient or sustained enough to affect healing.

Studies that evaluated the heating of wounds via devices2,3 showed beneficial effects on the healing outcome, but the devices promote a sustained effect of heat supply by maintaining higher temperatures for a longer time, promoting the vasodilation that is known to be beneficial for the healing process. However, when considering heating of the cleaning solution as a means of heating the wound bed, the results of this study demonstrated that increasing the temperature of the solution is not sufficient to achieve a sustained vasodilatory effect, although it may help to maintain a normothermic wound bed during dressing change. However, it is evident that cleaning with saline at room temperature did not significantly reduce the temperature of the wound bed.

Because patients with chronic wounds undergo daily and long-term dressings changes, and the dressing change can be painful and stressful,29 promoting comfort is fundamental. Although there is no scale for evaluating comfort for adults with chronic wounds, the authors evaluated comfort as an internal, subjective phenomenon. The heated solution was identified as the most comfortable and preferred by the study participants. These results are consistent with the data presented previously by Ernst et al,12 in which the heated solution was preferred by most patients.

Limitations

This study included different etiologies of wounds with variable characteristics (size, depth, locations). Further, the sample consisted only of patients with mild pain, which limits its generalization. The absence of a validated scale for assessing comfort in people with wounds and the lack of biometrics for the thermometer and microwave were other limitations of this research. Despite this, the study may contribute to clinical practice and the design of other research in the future.

CONCLUSIONS

Ultimately, the heated solution did not influence the patients’ pain intensity. However, the saline solution temperature significantly altered the wound bed temperature. Further, the heated solution was the most comfortable and preferred by patients. For providers seeking to offer greater comfort to people with wounds, heating the cleansing solution is recommended.

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