51 zyxwvutsrqp 0 zyxwvutsrqpon RESEARCH REPORT z TENS and Pain Control after Coronary Artery Bypass Surgery zy Melissa Domaille Barnaby Reeves Key Words TENS, cardiac surgery, post-operative pain, patient-controlled analgesia. Summary This paper describes a randomised controlled trial to evaluate the effectiveness of TENS in controlling pain following coronary artery bypass grafting (CABG). A total of 59 men undergoing CABG with internal mammary artery (IMA) at Bristol Royal infirmary were randomly allocated to receive TENS or placebo in conjunction with patient-controlled analgesia (PCA) for one hour on their first post- operative day. A visual analogue pain score and the hourly usage of the PCA were recorded before, during and after the application of TENS or placebo. The results show that although pain scores were significantly reduced in the hour in which TENS was applied, there was no significant difference in this reduction between the TENS and placebo groups. PCA use by patients during the study period was limited, with the majority making none or one successful request per hour. The results imply that the observed reductions in pain were due to a placebo effect and that the use of TENS in conjunction with PCA following CABG with IMA is unlikely to confer a clinically important reduction in post-operative pain. zyxwvuts Introduction zyxwvu Physiotherapy plays a critical role in the recovery of patients following coronary artery bypass grafts (CABG); it aims to prevent chest infections, facili- tate the normalisation of pulmonary function and allow for early mobilisation. Chest physiotherapy is particularly important because it has been reported that radiographically demonstrable atelectasis occurs in 51-90% of all CABG patients (Chulay zyxwvutsrq et al, 1982). Patients’ tolerance of chest physiotherapy and early mobilisation will undoubtedly be inhibited by pain caused by the sternotomy incision, retraction of the sternum and also surgical positioning (Jansen and McFadden, 1986; Pacificio et al, 1986; Kollef, 1990). Pain is an even greater problem for patients in whom the internal mammary artery (IMA) is used, due to additional left sternal retrac- tion and increased anterior chest wall trauma during harvesting (Jansen and McFadden, 1986). It is essential to control post-operative pain sufficiently to allow patients to carry out physio- therapy effectively, eg deep breathing, coughing and early mobilisation, in order to facilitate recovery (Jenkins et al, 1988). Intravenous narcotic analgesics are routinely used to control pain following CABG but unfortu- nately, despite their well-documented analgesic properties (Woolf and Thompson, 19941, their side-effects promote respiratory complications. Narcotics such as morphine have a sedative effect which induces sleep, reduces respiratory drive and impairs the cough mechanism (Rigg and Randi, 1981; Catley, 1984; Fairshter and Williams, 1987). The consequence of these side- effects of narcotic analgesics is retention of secretions and possible atelectasis leading to infection. As the aims of physiotherapy are to prevent and treat these potential problems, the beneficial effects of using morphine for effective pain control during physiotherapy are often outweighed by the detrimental side-effects. The search for effective pain relief without drawbacks of narcotics therefore needs to continue. The concept of using transcutaneous electrical nerve stimulation (TENS) for pain relief arose from the gate control theory of pain (Melzack and Wall, 1965). This theory has been amply confirmed electrophysiologically, behaviourally and clinically, the key aspect being the inhibitory effect of A afferent fibre input on C fibre evoked activity (Woolf and Thompson, 1994). Hymes et a2 (1974) were the first to investigate the use of TENS following surgery and reported significant reductions in pain in subjects receiving active TENS compared with a control group. TENS has since been found to reduce pain in patients after a variety of surgical procedures including ab- dominal and thoracic surgery (VanderArk and McGarth, 1975; Cooperman et al, 1977; Solomon et al, 1980; Ali et al, 1981).Results of some studies have also indicated a decreased requirement for narcotic analgesia in subjects receiving TENS (Pike, 1978; Rosenberg et al, 1978; Schuster and Infante, 1980; Soloman et al, 1980;Ali et al, 1981). Following cardiac surgery TENS has been reported to reduce pain and narcotic requirements (Bayindir et al, 1991; Navarathnam et al, 1984) and to improve lung function (Navarathnam et al, 1984). However, Forster et al (1994) found no significant benefit of TENS compared to placebo after CABG but concluded that the use of TENS over short time intervals should be investigated to minimise the possibility of accommodation to it. The aim of this study was to demonstrate whether TENS has an effect on reducing pain or narcotic requirements when used over a short time in patients having undergone CABG with IMA. The study was approved by the Ethics Committee to take place in the Cardiac Surgery Unit of Bristol Royal Infirmary. Physiotherapy, October 1997, vol83, no 10