2.1.1. Ethical approval
All the procedures performed in this study involving human participants were in accordance with the ethical standards of the Institutional and/or National Research Committee and with the Declaration of Helsinki,1964, and its later amendments or comparable ethical standards. Approval from the Institutional Review Board of Van Training and Research Hospital, Van, Turkey, was obtained prior to the execution of the study (2018/16). Written informed consent was obtained from all the patients. The study was reported in accordance with the Consolidated Standards of Reporting Trials statement, and the trial was registered at clinicaltrials.gov (NCT03790514).
Results
A total of 103 patients (51 treated with a heat-patch and 52 sham) with renal colic were included in the study. The baseline characteristics between the two groups did not differ significantly (Table 1). The dropout rates for the two groups were n =8 (13.5%) and n =7 (11.9%) patients, respectively (Fig.1).
On admission, both groups had similar VAS scores. The changes in VAS scores over time for the two groups are presented in Fig.2. In the heat-patch group, 15, 30, 45, and 60min VAS scores were significantly lower than those in the sham group. In addition, according to the baseline VAS score, the decrease in pain level in the heat-patch group at 15, 30, 45, and 60min was statistically significantly higher than that in the sham group. For both groups, 15, 30, 45, and 60 min VAS scores and changes in pain severity are provided in Table 2. Fourteen and six patients in the sham and heat-patch groups, respectively, needed pain salvage treatment (p =0.01).
There was no statistically significant difference between the two groups in terms of 15, 30, 45, and 60min Btemp values (p = 0.17, =0.21, =23, =0.37, and =0.23, respectively). In addition, there was no statistical difference found at 0 and 15min Stemp values of the two groups (p = 0.39 and p =0.10, respectively). However, when Stemp was analyzed between the heat-patch and place groups at 30, 45, and 60 min, a statistically significant difference was found (Table 3).
Discussion
Nowadays, NSAIDs, paracetamol, and opioids are considered first-line treatments for renal colic; however, these drugs have many side effects. Besides, patients cannot directly access these medicines when the pain starts. Therefore, a simple and safe analgesic method during the prehospital phase could be useful for patients with renal colic. In this study, heat-patch treatment performed as a local warming method was shown to be superior to sham as an alternative treatment method for the treatment of renal colic. The changes in VAS scores were statistically significantly and clinically relevant.
Mechanosensitive receptors that are stimulated by mechanical induction, such as lithiasis, are the receptors that innervate the kidney and ureter mainly (16). However, unlike somatic pain, visceral pain is generally diffuse and poorly localized. It is also referred to as the body wall, where viscerosomatic convergence is the key in the central pain pathways. Visceral afferents are placed in only a few of the afferent inflows of the dorsal horn and viscerosomatic convergence in the dorsal horn, and supraspinal centers are very well documented. Therefore, visceral mechanosensitive receptors converge with heat afferents, raising from the body wall, and may change the central viscerosensory response in the dorsal column (16,17). This hypothesis may explain the pain-relieving impact of body heating in this study. Another hypothesis that plays a role in reducing pain with the effect of heat may involve increased intravascular prostaglandins, bradykinin, and histamine secretion as a result of the increased blood flow to the region led by heat-patch treatment (12-14,15).
In a preclinical trial, sympathetic blockading was found to be associated with attenuated visceral nociceptive responses. Pertovaara et al. demonstrated that following sympathectomy, visceral nociceptive responses decreased in rats (18). In addition, Kober et al. treated patients with renal colic by active warming of the lower back region and showed high sympathetic activity in patients with pain and urolithiasis (12). These findings highlight the role of the sympathetic nervous system in the perception of visceral pain.
Outside any situation of urolithiasis, local heat was recommended as a way of reducing the pain of trauma patients in the emergency department. In a study conducted by Bertalanffy et al. on patients with acute pelvic pain, where the other reasons for pelvic pain excluded gynecological causes, active heat treatment (electric blanket) was found to be a significantly effective method in reducing pelvic pain (19). Similarly, a study conducted by Nuhr et al. on patients with acute back pain, the pain was found to be reduced more in active heat treatment areas compared to passive heat treatment areas (15). In a randomized controlled study performed by Kober et al. on patients with renal colic, it was shown that VAS scores were statistically decreased in patients receiving active heat treatment compared to those receiving passive heat treatment 12. Similar to these studies, in our study, we also showed that in the heat-patch group, Stemp values increased statistically, and the decrease in VAS scores was higher in the heat-patch group than in the sham group.
There are some inherent limitations in this study. The major limitation is the absence of comparison of heat-patch treatment and an analgesic agent. In addition, the fact that the patients received their actual treatment late could be considered a limitation; however, we were able to protect them from the possible side effects of the medications to be given. Another limitation that must be noted is that although we used patches that waited at room temperature for at least 24 h before the application in the sham group, we were aware that these patches would never reach the Stemp values of the study groups. However, no patient reported any heat-related complaints during the study. Last but not least, we did not include distal ureter stones, as the pain referred from these stones is mediated by the ilioinguinal and genitofemoral nerves, which radiate the pain to the groin, testicle, or labia majora.
Conclusions
Heat-patch treatment appears to be an ideal candidate to reduce pain in patients with urolithiasis, especially during the prehospital phase. As it does not contain any drug and has no side effects, healthcare professionals are not required for the application. We recommend that heat-patches be used at least as the primary treatment option for patients with urolithiasis before the actual treatment (if needed).