Comparison of High-and Low-frequency Transcutaneous Eletrical Nerve Stimulation Effect on Postthoracotomy Pain in Rats in Contralateral and Ipsilateral Side

Behavioral testing was alwaystested between 9 and 12 a.m. at the following time points in injured animals: 1 day before, the day of surgery, and 10, 11, 12, 13, 14, 15, 16, and 17 days after surgery (Fig 3). In addition, all animals were monitored at 0, 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 and 4.0 hours after TENS treatment.

Ting-Yun Chen

, M.S., Ching-Hsia Hung

, Ph.D., Yu-Wen Chen

, Ph.D.

1_{Department of Institute of Allied Health Sciences, College of Medicine, National Cheng Kung University, Tainan, Taiwan;} 2 _{Department of Physical Therapy, National Cheng Kung University, Tainan, Taiwan;}

3 _{Department of Physical Therapy, China Medical University, Taichung, Taiwan}

ABSTRACT

Background and Purpose: Post-thoracotomy pain is a clinically problem, pain may affect patients' coughing and deep breathing, and that may become more difficult for patients to carry out the rehabilitation program. Rib-retractor used in thoracotomy, which makes compression and damage intercostal nerves, may cause neuropathic pain. Transcutaneous electrical nerve stimulation (TENS) has been used in management of post-surgical pain for over 30 years. We try to supply more options to manage post-thoracotomy pain after our experiments. The aim of this study was to investigate the effect of high- and low-frequency TENS (either contralateral or ipsilateral side) on mechanical hypersensitivity in a rat model of postthoracotomy pain. Results: Among these interventions, high-frequency TENS on contralateral side showed the best effect to reduce postthoracotomy pain.

Conclusions: Application of TENS to the contralateral (mirror) side may be a good option for management of postthoracotomy pain.

INTRODUCTION

Postthoracotomy pain is a serious problem. Pain symptom usually in accordance with the allocation of around intercostal nerve, following along the surgical incision. (Benedetti et al 1997; Benedetti et al 1998). Resent studies showed that compression at the upper and lower intercostal nerves in surgery caused intercostal damage(Rogers et al 2002). In 2010, Shin and other scholars also believe that the action pull oppression rib

distraction induced the intercostal nerve functional disability and structural damage is the main reason to elicit postoperative pain (Shin et al 2010). Transcutaneous electrical nerve stimulation (TENS) is acceptable methods for the management of postthoracotomy pain clinically. In these years, contralateral antalgic effect have been proved in peripheral nerve stimulation in neuropathic pain(Somers & Clemente 2009; Buonocore et al. 2015). So it’s well worth looking forward to compare the effect in this study.

AIM

The purpose of this study was to evaluate the antiallodynic effect of TENS intervention on ipsilateral or contralateral side of incision with high- or low- frequency transcutaneous electrical nerve stimulation, using a thoracotomy rat model.

METHODS

Male Sprague-Dawley rats (300–350 g) were divided into 6 groups: postthoracotomy pain (PTP), postthoracotomy pain with ipslateral high-frequency TENS (PTP+IHFS), postthoracotomy pain with ipslateral low-frequency TENS (PTP+ILFS), postthoracotomy pain with contralateral high-frequency TENS (PTP+CHFS), postthoracotomy pain with contralateral low-frequency TENS (PTP+CFS), and sham postthoracotomy pain (SPTP) (Fig 1).

RESULTS

DISCUSSION

Fig.1 The groups of the experiment

To perform the postthoracotomy pain model, rib-retraction was placed as and lasting 1 hour described by Buvanendran et al. in 2004 (Buvanendran, Kroin et al., 2004). Treatment group (high-frequency in 100Hz; low high-(high-frequency in 20 Hz ) TENS were applied daily and started on the 11 days of surgery (Fig 2).

Fig.3 The time course of the experiment Fig.2 Rats after thoracotomy received TENS

Contralateral high-frequency TENS prevent the progression of allodynia in first-rate then other type of application

Rats receiving contralateral high-frequency (100Hz) TENS was experienced reduction from baseline in mean mechanical pain threshold of the same paw before surgery and sham operation group (Fig 4).

The main finding of this study is that contralateral high-frequency transcutaneous electrical nerve stimulators can reduce

mechanical allodynia in rats after thoracotomy.

REFERENCES

Benedetti, F., M. Amanzio, et al. (1997). "Control of postoperative pain by transcutaneous electrical nerve stimulation after thoracic operations." Ann Thorac Surg 63(3): 773-776. Benedetti, F., S. Vighetti, et al. (1998). "Neurophysiologic assessment of nerve impairment in posterolateral and muscle-sparing thoracotomy." J Thorac Cardiovasc Surg 115(4):

841-847.

Borgeat, A. and J. Aguirre (2010). "Update on local anesthetics." Curr Opin Anaesthesiol 23(4): 466-471.

Buonocore, M., N. Camuzzini, A. Dall'Angelo, S. Mandrini and E. Dalla Toffola (2015). "Contralateral antalgic effect of high-frequency transcutaneous peripheral nerve stimulation." PM R 7(1): 48-52.

Buvanendran, A., J. S. Kroin, et al. (2004). "Characterization of a new animal model for evaluation of persistent postthoracotomy pain." Anesth Analg 99(5): 1453-1460; table of contents.

Rogers, M. L., L. Henderson, et al. (2002). "Preliminary findings in the neurophysiological assessment of intercostal nerve injury during thoracotomy." Eur J Cardiothorac Surg 21(2). Somers, D. L. and F. R. Clemente (2009). "Contralateral high or a combination of high- and low-frequency transcutaneous electrical nerve stimulation reduces mechanical

allodynia and alters dorsal horn neurotransmitter content in neuropathic rats." J Pain 10(2): 221-229.

Fig.4 The time courses of mechanical withdrawal threshold by von Frey monofilaments (in grams) in SPTP, PTP, PTP+IHFS, PTP+ILFS, PTP+CHFS and PTP+CLFS rats (n=8 per group). Data represent as mean ± S.E.M The asterisk indicates p < 0.05 when compared with the PTP group