Value of the number of injured anatomical parts of the body and surgeries for pain chronicity in patients with gunshot wounds and blast injuries

. The outcome of pain treatment in patients with wounds at different stages of management is important, because chronic pain is diagnosed in 83.3 % of victims with blast injuries, and in 70 % of people with gunshot wounds. In civilian life, chronic pain occurs in 11–40 % of cases in a similar category of patients. The reasons for such a high frequency of chronicity have not been sufficiently studied. Thus, the study on the influence of the number of injured anatomical parts of the body on the results of pain treatment will play an important role and contribute to improving the latter in this category of patients. One of the factors that can influence pain chronicity is the number of injured anatomical parts of the body.


Introduction
It is reported that more than 70 % of patients experience wound-related pain [1,2]. Pain in a wound and its intensity vary a lot, so there are clinical assumptions that the type of injury and the number of injured anatomical parts of the body and operations, as well as the size of the wound, will determine the frequency of chronic pain. The intensity of pain can be stable for a long time, change from day to day and increase. Pain in the wound is an indicator of ineffective treatment. Ineffective pain management can lead to chronic pain, delayed healing, and patient noncompliance. Pain can be caused by damage to the skin, nerves, blood vessels, infection, and ischemia [1,3]. It also causes hypoxia, which impairs wound healing and increases the frequency of infectious complications [4,6]. Nerve damage is constantly occurring in a wound due to biochemical processes and external stimuli such as wound surgery, debridement, or dressing changes. Chronic pain can cause self-destructive behavior that leads to drug use, alcohol abuse, and social withdrawal [5].
The significance of the number of injured anatomical parts of the body for the results of pain treatment in this category of patients at different stages needs to be studied, because the subjective feelings and emotional experiences during the injury in combat conditions are special. Therefore, the data of our research will play an important role in their treatment.
The goal of the work is to investigate whether the number of injured anatomical parts of the body and operations affects the results of pain treatment in patients with gunshot wounds and blast injuries.

Materials and methods
The recruitment of patients was carried out in 2022, from February 24 to May 24, during the Russian invasion of Ukraine and the Kyiv offensive. It was performed at the National Military Medical Clinical Center "Main Military Clinical Hospital", where patients were evacuated from the battlefield. The assessment of anesthetic risk was carried out according to the scale of the American Society of Anesthesiologists. The basic tool for pain intensity assessment was the visual analog scale (VAS).
Pain treatment -scheduled analgesia: transdermal patch or injectable narcotic analgesic + nonsteroidal anti-inflammatory drugs (dexketoprofen (keydex)) + adjuvants + epidural catheter and/or regional blocks. Anesthetic support for Emergency Medicine (Ukraine), ISSN 2224-0586 (print), ISSN 2307-1230 (online) Оригінальні дослідження / Original Researches operative interventions was carried out in the form of general anesthesia or regional anesthesia. Some patients who underwent regional anesthesia received sedation. For sedation, a constant infusion of 1% propofol at a rate of 1-4 mg/kg/h was used. Analgesia was provided by 0.005% fentanyl: during induction -3-10 µg/kg or 0.05-0.2 µg/kg/min, and to maintain analgesia -2-10 µg/kg/h by periodic bolus administration for 25-100 µg or continuous infusion. Regional anesthesia was performed under ultrasound control. The needle was brought to the nerve roots and 10-20 ml of 7.5% ropivacaine solution (ropilong) was injected. Analgesia in the postope rative period was provided according to the local clinical protocol: paracetamol ± non-steroidal anti-inflammatory drugs (dexketoprofen (keydex)) ± opioids, repeated peripheral blocks or introduction into the catheter for prolonged regional anesthesia of 0.2% solution of ropivacaine (ropilong).
The analysis of the research results was carried out in the EZR v. 1.35 package (R statistical software version 3.4.3, R Foundation for Statistical Computing, Vienna, Austria). The Shapiro-Wilk test was used to check the distribution of quantitative indicators for normality. The law of distribution differed from the normal one, the median value (Me) and interquartile range (QI-QIII) were given to represent quantitative indicators, the comparison of indicators in two groups was carried out according to the Mann-Whitney test.
To analyze the dynamics of indicators, the Friedman test was used for related samples, the posterior comparison was performed using the Bonferroni correction. For qualitative indicators, the absolute frequency of symptom manifestation and relative frequency (%) are presented, and for the comparison of two groups, the chi-square test was used, taking into account the correction for continuity. When conducting the analysis in all cases, the critical level of significance was taken equal to 0.05.
The research was carried out within the framework of the biotic examination protocol -the Ministry of Health of Ukraine, Bogomolets National Medical University, Kyiv, Ukraine: protocol No. 158 dated May 23, 2022.

Results
The study presents own clinical experience of treating patients with gunshot wounds and blast injuries as a result of hostilities. The treatment outcomes were evaluated accor ding to VAS: if after 3 months the patient feels pain, then such pain is considered chronic. The results of treatment of 1,166 patients were analyzed: 786 with gunshot wounds and 380 with blast injuries. When after three months the VAS indicator was > 0, the positive effect was considered as not achieved (resulting variable Y = 1; 271 cases), and if it was equal to 0, the positive effect was considered to be achieved (the resulting variable Y = 0; 895 cases). The risk of chronic pain was 23.2 % (95% confidence interval (CI) 20.8-25.8 %). The following factors were used: patient's age, height, weight,   Table 1 presents the results of the analysis.
The area under the receiver operating characteristic (ROC) curve (AUC) was 0.56 (95% CI 0.53-0.59), which indicates the existence of a relationship between the risk of pain chronicity and the number of injured anatomical parts of the body and the type of wound. Table 2 shows the coefficients of the two-factor model.

Conclusions
1. When studying the value of the number of injured anatomical parts of the body and operations in terms of pain chronicity in patients with gunshot wounds and blast injuries, there was found a relationship (AUC = 0.54; 95% CI 0.51-0.57) between the risk of chronic pain and the number of wounded anatomical parts of the body. With the number of injured anatomical parts of the body > 2, the risk increases (risk ratio = 1.45; 95% CI 1.09-1.92; p = 0.010) compared to patients with 1 or 2 anatomical parts injured.
2. According to the results of the statistical analysis, two factors associated with the risk of pain chronicity were found: the number of injured anatomical parts of the body and the type of trauma (AUC = 0.56; 95% CI 0.53-0.59).