The Evaluation of the Effect of TENS Therapy on Reducing Acute and Chronic Pain Following Varicocelectomy ()
1. Introduction
From October 2010 to 2011 was named as global year against acute pain. Acute postoperative pain by interaction with several physiologic functions of organ systems can impair their function and result in mortality; however, it is important to consider treating acute pain [1] . Pain related to varicocelectomy can become chronic due to surgery technique damaging neuronal fibers. It has some reasons such as outpatient surgery and inadequate pain treatment. It can entail limited movement, problems in working, patient dissatisfaction and unnecessary consumption of treatment resources and long stay in the hospital. Overall, history and prevalence of pain are unknown [2] . The prevalence of varicocele in normal population is 15% to 20% and in infertile men is 68% to 81% with 2% to 10% prevalence of pain. Its actual etiology is yet unknown [3] [4] . Subinguinal microscopic surgery technique has led to less pain and side effects compared to other techniques [4] [5] . Transcutaneous electrical stimulation (TENS) is a non- pharmacologic and non-invasive, safe, inexpensive and easily applicable approach to reduce pain that stimulates transcutaneous peripheral nerves and creates a painless situation [6] [7] . The measurement of pain is usually based on the Visual Analogue Scale (VAS) and the Numerical Verbal Rating Scale(NVRS), but recently, cortisol level can be a good indicator of pain measurement during postoperative TENS therapy [8] . Several studies demonstrated that in spinal anesthesia and incision site infiltration with local anesthetics, TENS was more efficient than general anesthesia, causing complete nociceptive block and preventing spinal stimulations [9] . Therefore, we decided to conduct two-blinded clinical trial to evaluate control rate of acute pain, chronicity rate of pain, chronic pain intensity and analgesic consumption rate during postoperative period after varicocelectomy.
2. Methods and Materials
In this clinical trial, we randomly selected 80 patients undergoing varicocelectomy from July 2012 to March 2013 by easy non-probable sampling and classified two groups. Inclusion criteria included all patients undergoing varicocelectomy by high-ligation technique, ASAI-II, and aged between 20 and 40 years old. Patients with previous history of analgesic consumption, addiction, depression, psychosis and overweight were excluded from the study. After obtaining informed consent, the patients were divided into Group A (intervention group) and Group B (placebo group). Premedication with 1 μg/kg fentanyl and 0.01 mg/kg midazolam, induction with 2 mg/kg propofol and 0.4 mg/kg atracurium were administered. For security of airway, laryngeal mask airway was inserted. Anesthesia was maintained with inhaler anesthetics (i.e. N2O 50% + O2 50% + isoflurane 1% - 1.5%). At the end of high ligation varicocelectomy, the patient was extubated and transported to post anesthesia care unit. In the recovery room, TENS pads were inserted at 4 cm distance and parallel with incision site. After complete recovery, both groups received TENS with high frequency (100 HZ). Group A received current intensity at sensory level for 30 minutes, whereas Group B received current intensity equal to zero (placebo). These steps were performed by different persons. The evaluation of pain method was preoperatively explained to the patient (i.e. determinate by a special ruler, zero = complete analgesia, 10 = most severe pain). TENS therapy was repeated at 2, 6, 12 and 24 hours. The pain severity at recovery 2, 6, 12 and 24 hours after TENS therapy and the amount of analgesic consumption (meperidine) or its equal (NSAIDs) were recorded. After discharge, pain severity (NVRS) and NSAIDs consumption (mg/1st week, 1st month, 2th and 3th month) were recorded. Parametric tests (independent T-test) and non-parametric tests (Mann-Whitney, chi-square and Fisher exact test) were used for statistical analysis. P-value < 0.05 was considered significant.
3. Results
Demographic information is shown in the Table 1. In weight, age, preoperative smoking, there were no significant relationship between the two groups. The results showed that in placebo group, 13 patients (32.5%) had pain score equal with 8 at 2 hours after operation and pain score of 10 patients (25%) was 6. At 6 hours after surgery, pain score 5 in 15 cases (37.5%) and pain score 6 and 7 in 9 patients (22.5%) were showed.
At 12 hours after surgery, pain scores 4 and 5 were calculated in 27.5% and 30% of cases. After 24 hours, pain scores 3 and 5 were observed in 12 patients (30%), respectively. One week after surgery, pain score 2 (15 cases, 37.5%) and pain score 4 in 30% of cases were calculated.
After one month, pain score 1 was reported in 40% of cases. In this group, opioid consumption amount in the first 2 hours was 42.5% (Table 2).
In the intervention group, 10 patients who received TENS therapy, had pain score 5 at 6 hours, VAS score was 3 to 6 post-operative. At 12 hours, pain scores 2 and 3 were seen in 37.5% and in 24 hours, pain scores 1 and 2 was 25%. After
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Table 1. Demographic and basic data in two groups.
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Table 2. Data base on the frequency of pain score (VAS) in placebo and TENS group. Score; score of pain.
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Table 3. Data about consumption of opioid (meperidine) in placebo and TENS group.
one week, pain score in 82.5% was zero and only 15% had pain score 6 (Table 2).
In comparison with the placebo group, pain score was lower after surgery. The variables correlations regard to pain score after 2 hours after surgery based on VAS had P-Value = 0.003. In other intervals-Value < 0.0001 was considered significant. The comparison of pain score in the second month showed P-Value = 0.003 and the difference among, amount of used analgesics at 2, 6 and 12 hours were significant with p-value = 0.001, <0.0001 and =0.02, respectively (Table 3).
In all of these variables and comparisons, p-value was significant. Thus, these results demonstrated that TENS therapy in controlling acute and chronic pain after surgery had statistically significant correlation. Low opioid consumption was observed in the intervention group.
4. Discussion
Varicocele is one cause of male infertility with negative effects on the sperm parameters. Varicocelectomy is one of the effective approaches for the treatment of varicocele and is associated with significant implication on sperm parameters, but after surgery, pain is the most important concern due to somatic and emotional effects on human life [1] [2] . There are several pharmacologic and non-pharmacologic methods to control of postoperative pain. Ahmed et al. Concluded that using TENS acts as an index of important and efficient postoperative pain after inguinal hernia operation without side effects and continuation of pain reduction until one month [2] . Matthew et al. demonstrated that TENS may reduce postoperative phantom pain on movement and at rest [10] . Our results indicated TENS effects for 3 month after surgery [6] . Wang et al. showed that TENS with high frequency (100 Hz) effects was superior to low frequency (2 Hz). In this study, we used only high frequency. In this regard, some maintained that spinal anesthesia and infiltration of incision cite, as well as TENS application were more efficient than general anesthesia, probably due to complete block of nociceptive and prevention of spinal movement [9] . In one study, Lewis defined using TENS as an alternative approach for pain reduction in osteoarthritis [11] . After 3 weeks, a significant difference between case and control groups was observed, like as our study. The results obtained by Chen et al. were the same as of those of the present study, i.e. remarkable TENS therapy effect on acute pain reduction rate and postoperative analgesic consumption [12] . In a study De Sanata et al. demonstrated that TENS therapy could result in reducing pain score and total postoperative analgesic consumption [13] . This result was in parallel with our study. Our results showed that unpleasant sense due to pain in case group was lower than the control group. Using TENS with modulation of frequency and effect on nociceptive and neuropathic pain can decrease pain and increase endothelial growth factor from the vascular wall [14] [15] . It seems that TENS by its artificial stimulation can stimulate large myelinated nerves (e.g. Aβ fibers) to disconnect the non-myelinated C nerves in spinal pathway that contain pathologic impulses in dorsal horn of spinal cord [6] [15] .
5. Conclusion
In the present study, TENS plays a safe and non-invasive role in reducing acute and chronic pain as well as analgesics consumption.