Venipuncture for intravenous injection occupy an important position among the invasive procedures performed by nurses [1]. Venipuncture is often described as difficult for nurses and painful for patients [2]. If the pain experience due to venipuncture is repeated, the patient may feel fear of injections, which increases anxiety about future treatment, and if the patient does not actively participate in treatment due to pain, recovery may be delayed [3]. Most patients experience pain when the needle pierces the skin. Some patients may notice more pain and experience vagal reflexes, or it may lead to low blood pressure and syncope [4]. Therefore, continued research is needed to reduce patients' pain and anxiety related to venipuncture pain.

Previous research has consistently sought to identify methods to reduce the pain and stress associated with IV procedures. Pharmacological interventions, such as the application of topical anesthetics like lidocaine ointment or patches, have shown effectiveness in reducing pain during venipuncture [5,6]. Similarly, the application of Eutectic Mixture of Local Anesthetics (EMLA cream), consisting of 2.5% lidocaine and 2.5% prilocaine, has demonstrated significant pain-reducing effects [7]. However, the use of topical anesthetics may result in side effects such as hypersensitivity, skin erythema, swelling, and itching, warranting cautious application [6]. Additionally, the costs associated with these medications can be a financial burden for patients.

Non-pharmacological interventions, including cryotherapy [8] and thermotherapy [9], have also been employed to alleviate pain during venipuncture. Other methods such as music therapy [10], aromatherapy [11], distraction techniques using tablet video [12], and virtual reality content [13,14] have also been explored. Among these, thermotherapy is particularly noteworthy for its effectiveness as a nursing intervention for pain management [15]. Thermotherapy functions by enhancing nerve conduction, stimulating nerve endings, or blocking pain transmission through the gate control theory, thereby providing anesthetic and sedative effects. The relaxation induced by thermotherapy offers comfort, and its vasodilatory effect is particularly useful in alleviating pain associated with muscle spasms due to ischemia [16]. Research on thermotherapy has shown its effectiveness in reducing subjective pain during arteriovenous fistula needle insertion in hemodialysis patients [17] and in decreasing the time required for injections, the number of attempts, and increasing the success rate of first attempts in pediatric emergency patients [18]. Cryotherapy is a representative non-pharmacological intervention that reduces pain and swelling following tissue damage and suppresses inflammatory responses [19]. Cryotherapy induces vasoconstriction, which decreases local cellular metabolism and inhibits inflammatory and purulent processes, thereby preventing the accumulation of excess fluid in the injured tissue that could exacerbate pain [16]. Previous studies have shown that cryotherapy using an ice pack for 5~10 minutes is effective in reducing pain during venipuncture [20]. Although thermotherapy and cryotherapy are well-established non-pharmacological interventions for pain relief, there is limited evidence supporting their efficacy specifically for needle insertion pain. Furthermore, the inconvenience associated with the application methods of these therapies has restricted their widespread use during intravenous procedures. To promote broader application, it is necessary to address and mitigate the inconveniences related to the application methods of cryotherapy and thermotherapy.

Thermoelectric devices, which convert thermal energy directly into electrical energy and vice versa, are employed in various fields such as household appliances (refrigerators, dehumidifiers and water purifiers), computer systems (CPU cooling), automotive climate control seats, and industrial applications (waste heat generators, remote power generation) due to their excellent heating and cooling properties [21]. A pioneering study in South Korea developed a thermoelectric element band (TEE Band), enabling the convenient application of cryotherapy and thermotherapy using a thermoelectric device, and demonstrated its effectiveness in reducing pain during venipuncture [22].

The TEE Band, designed as a wristband, facilitates cryotherapy or thermotherapy during venipuncture through a button-controlled mechanism. It was found to be effective in pain relief when applied to the wrist during venipuncture while a tourniquet was used on the upper arm. The study recommended extending the application time of the band to maintain its effect during IV procedures [22]. Subsequently, the TEE tourniquet was developed, integrating flexible TEEs with a tourniquet and a temperature control device. This device proved significantly effective in pain relief, especially with thermotherapy, and both patients and practitioners reported high satisfaction. Recommendations included increasing the temperature plate area for more effective therapy application [23].

In this study, the modified TEE (M-TEE) tourniquet was developed by enlarging the plate area of the TEE tourniquet. The objective was to assess the effects of the M-TEE tourniquet's thermotherapy and cryotherapy on pain and regional blood flow during IV injections in hospitalized patients. The study also aimed to measure changes in regional blood flow due to thermotherapy and cryotherapy. Thermotherapy dilates blood vessels and increases regional blood flow, increasing the visibility of veins and thus increasing the success rate of intravenous injections. Therefore, it was thought that it would help reduce the number of intravenous injection attempts and pain, and the intention was to check data related to the actual regional blood flow rate. This investigation seeks to evaluate the M-TEE tourniquet’s impact on pain and regional blood flow during IV procedures, providing foundational data for improving pain management techniques in hospitalized patients requiring an 18-gauge angiocatheter for surgery.

This study evaluated the efficacy of the M-TEE tourniquet, a device with a plate area twice that of the standard TEE tourniquet, for thermotherapy and cryotherapy during intravenous catheter insertion. In the experimental group, participants received thermotherapy or cryotherapy for 10 seconds prior to venipuncture, while the control group underwent the procedure without temperature treatment. The choice of a 10-second duration aligns with findings from a Cochrane systematic review on vapocoolants for pain management during IV cannulation, which indicated that cold spray applications of 5~10 seconds yield significant pain relief [35].

Key variables included historical reports of injection pain, current pain levels during the injection, oxygen saturation, pulse rate, and both regional arterial and venous blood flow. The thermoelectric technology used in the M-TEE tourniquet, designed to create rapid temperature changes through electrical stimulation, was previously adapted into a band format [22] before this tourniquet adaptation [23]. In this study, the M-TEE tourniquet, which features an expanded surface area, was utilized to apply cryotherapy and thermotherapy. The results demonstrated a significant difference in pain perception among the three groups, with the cryotherapy group experiencing notably less pain.

Earlier studies have explored diverse approaches to injection pain relief using both cryotherapy and thermotherapy For instance, ice massage on the palm during arteriovenous fistula puncture in hemodialysis patients significantly reduced pain [36]. Applying ice packs for 10 minutes at cannulation sites also reduced arteriovenous fistula pain [37], while an RCT using vibration and cold gel packs during IV catheterization reported reduced pain in the intervention group [24].

Additionally, when measuring injection pain in participants undergoing peripheral intravenous cannulation, no significant difference was found between the experimental group that received local warming and the control group that did not [35]. In contrast, a study that assessed pain, anxiety, and vein assessment after applying either a hot or cold application to the insertion site for one minute prior to peripheral venous catheter insertion found that the groups receiving local hot and cold applications reported lower pain and anxiety levels compared to the control group [3]. Specifically, while pain levels were reduced in both the hot and cold application groups compared to the control group, there was no significant difference between the two experimental groups. However, anxiety levels were significantly lower in both the hot application and cold application groups compared to the control group, with the hot application group exhibiting significantly lower anxiety levels than both the cold application group and the control group [3].

Previous studies have reported significant differences in pain relief associated with cryotherapy, ice massage [36] and utilizing ice packs [37], as well as with thermotherapy involving hot packs [18], hand warmers [19] and hot packs containing silicate gel [32]. Additionally, both cryotherapy and thermotherapy proved effective when using a TEE band [22] and TEE tourniquet [23]. In research where hot packs were applied for 10 minutes and 20 minutes [32], both experimental groups exhibited significantly lower pain levels compared to the control group, and due to the minimal differences between the two experimental groups, it was concluded that a 10-minute application of hot packs could be effectively utilized without adverse effects. Similarly, another study applying a hot pack for 15 minutes demonstrated a reduction in pain associated with needle cannulation [17]. The time required for intravenous injections was shorter in the experimental group receiving heat therapy, with this difference being statistically significant [18].

However, in a RCT comparing the application of a TEE band on the wrist that provided heat therapy, cold therapy, and thermo-grill illusion therapy against a control group that received no treatment [22], the post-intervention pain scores indicated no significant differences among the four groups. Although the pain levels for the cryotherapy group were notably lower compared to pre-treatment measurements, statistical significance was not established among the four groups. Conversely, a study that modified the TEE band into a TEE tourniquet [23] reported that thermotherapy using the TEE tourniquet significantly reduced injection pain and also resulted in lower stress levels.

Previous studies have primarily focused on alleviating injection pain in pediatric patients or those with arteriovenous fistulas. However, this study broadens the scope by examining the effects of cryotherapy and thermotherapy on adult patients undergoing surgery. Most of the participants in the study were otolaryngology patients and obstetrics and gynecology patients, most of whom had no underlying diseases and were discharged about 2-3 days after surgery. They were subjects who could reduce differences in vascular conditions depending on disease and intravenous injection pain depending on vascular conditions. This expansion of the target population is a notable contribution of the study. Nevertheless, discrepancies were observed in the effectiveness of temperature therapies. In prior research applying thermotherapy or cryotherapy in the form of tourniquets, thermotherapy alone was found to be effective for pain relief [23].

In contrast, the current study, which utilized the M-TEE tourniquet with an expanded temperature application area, found that only cryotherapy was effective. This variation is likely influenced by factors such as application time, area size, and temperature. In this study, the application time ranged from 10 to 30 seconds, while previous studies reported application times from 10 to 60 seconds. The plate area in prior research was 19.3 cm², compared to 38.5 cm² in this study. There is limited data on the application area size for ice packs or heating pads. The variation in findings across studies suggests that while thermoelectric devices demonstrate potential for pain management during injections, the relative efficacy of thermotherapy versus cryotherapy remains inconclusive. These discrepancies may arise from differences in methodological approaches, including the duration of application, the surface area treated, specific temperature settings, and patient-specific factors. To ensure the effective integration of thermoelectric devices into clinical practice, further research is essential to develop standardized guidelines that optimize these variables for pain relief. One possible reason for the differences in study outcomes may be the presence of multiple confounding variables in intravenous catheter insertion. Previous studies have indicated that factors such as the nurse’s age, level of experience, specialty, and proficiency in intravenous skills, along with patient-related and IV-related variables, can all have diverse influences on the outcomes [35].

No significant differences in SpO₂ or pulse rates were observed among groups. A similar study on arteriovenous fistula patients found no significant changes in physiological stress indicators like blood pressure and pulse with ice application [37]. The absence of significant changes in this study suggests that the pain levels experienced by adult participants may not have been high enough to alter SpO₂ or pulse.

In this study, regional blood flow was selected as an outcome variable because hot application is generally known to promote vasodilation, and previous research [3] has shown that vein visibility increased in the hot application group during vein assessment. Therefore, this study measured both regional venous and arterial blood flow. While no significant differences were observed in regional arterial blood flow before and after the intervention, a significant difference was found among the three groups regarding regional venous blood flow, with the thermotherapy group showing a marked increase.

In studies measuring regional blood flow during the application of thermotherapy, it was found that regional venous blood flow significantly increased in subjects receiving thermotherapy. This aligns with the known effects of heat and cold, where increased temperature causes vasodilation, and decreased temperature causes vasoconstriction [16]. However, the absence of significant differences in regional arterial blood flow among the three groups suggests that the effects of temperature did not extend to the arteries. This effect is considered beneficial as it may enhance the ease of intravenous injection for nurses, thereby offering positive implications for clinical practice.

Regarding satisfaction, participants in the cryotherapy group reported higher satisfaction, likely due to effective pain relief. For nurses, satisfaction levels increased in both cryotherapy and thermotherapy groups, with thermotherapy showing a greater impact. The increased venous flow from thermotherapy likely contributed to easier venous cannulation, positively affecting nurse satisfaction.

This study faced limitations in participant blinding, as randomization did not prevent participants from identifying their group upon receiving the intervention. Additionally, nurses were likely aware of each participant’s group during device activation, limiting the study's double-blind nature—a core aspect of RCTs. Although it was not possible to completely blind the group to which participants were assigned, the nurse tried to remain neutral to ensure accurate research results, refrained from mentioning the intervention, and tried to focus on investigating the items felt by the participants.

The M-TEE tourniquet was effective in reducing injection pain and enhancing patient satisfaction in the cryotherapy group, with higher practitioner satisfaction noted in the thermotherapy group. Nonetheless, evidence regarding optimal application duration, surface area, and temperature remains insufficient, calling for further studies to establish standardized guidelines for effective clinical use of thermoelectric devices in pain relief. The M-TEE tourniquet demonstrates potential as an effective and convenient tool for managing injection pain. Although initial equipment costs may be incurred, the device's ease of use, simple training requirements, and effectiveness in alleviating patient pain make it a worthwhile investment. This study highlights its nursing significance, as the M-TEE tourniquet allows for easy implementation of pain-relief interventions. By expanding the temperature application area, this study contributes to optimizing pain management and improving patient and practitioner satisfaction during IV procedures.