Control of Post-thoracotomy Pain by Transcutaneous Electrical Nerve Stimulation: Effect on Serum Cytokine Levels, Visual Analogue Scale, Pulmonary Function and Medication

Objectives: Transcutaneous electrical nerve stimulation (TENS) has been used to control post-thoracotomy pain with contrasting results. We aimed to assess the efficacy of TENS on post-thoracotomy pain in relation of four criterion measurements as: (i) cytokines; (ii) pain; (iii) respiratory function and (iv) intake of narcotic medication.

Methods: Between January 2008 and October 2010, 58 patients underwent standard posterolateral thoracotomy for resectable lung cancer. Fifty patients were enrolled in the present study and randomized in two groups: TENS group (25 patients) who received postoperatively TENS for 5 days and placebo group (25 patients) without TENS. In both groups (i) serum cytokines (IL-6, IL-10, TNF-α) were measured by ELISA before surgery and at 6, 12, 24, 48, 72, 96 and 120 postoperative hours (POHs); (ii) at the same POHs, the pain score was measured using visual analogue scale (VAS) ranging from 0 to 10 levels; (iii) respiratory function (FEV 1% and FVC % of predicted value) were valuated on 72, 96 and 120 POHs; (iv) the total intake of narcotic medication given during postoperative period of 5 days was recorded. Repeated measures of analysis of variance assess the difference between two study groups. A value of P < 0.05 was considered statistically significant.

Results: Of the 50 patients enrolled, two patients of TENS group and two patients of the placebo group were lost to follow-up. (i) Serum IL-6 (P = 0.001), IL-10 (P = 0.001) and TNF-α (P = 0.001) levels in TENS group were significantly lower than in the control group; (ii) VAS score in TENS group was significantly lower than in the control group (P < 0.001); (iii) recovery of FEV 1 (P = 0.02) and of FVC (P = 0.02) was statistically better in the TENS group than in control group; (iv) morphine requirement was lower in the TENS group with respect to placebo TENS (P = 0.004). After 48 POHs, no patient required supplementary dose of morphine. TENS group compared with placebo-group presented a significant reduction of non-opioid consumption (P = 0.002).

Conclusions: TENS is a valuable strategy to alleviate post-thoracotomy pain with reduction of cytokine production and of analgesic consumption, and with positive effects on pulmonary ventilation function.