Can pre-emptive and continued transcutaneous electrical nerve stimulation (TENS) improve the management of post-operative knee pain?

Pao Yue-kong Library Electronic Theses Database

Can pre-emptive and continued transcutaneous electrical nerve stimulation (TENS) improve the management of post-operative knee pain?

 

Author: Wang, Ninghua
Title: Can pre-emptive and continued transcutaneous electrical nerve stimulation (TENS) improve the management of post-operative knee pain?
Degree: Ph.D.
Year: 2001
Subject: Knee -- Diseases -- Patients -- Rehabilitation
Transcutaneous electrical nerve stimulation
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Rehabilitation Sciences
Pages: xvii, 210 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1599564
URI: http://theses.lib.polyu.edu.hk/handle/200/1538
Abstract: Introduction. Research in human studies showed that TENS applications, repeated for 60 min 5 times a week over a 2-week period, produced cumulative antinociceptive effects on acute experimental electrical pain (Liu and Hui-Chan 1994), chronic low back pain (Cheing and Hui-Chan 1996) and chronic osteoarthritic knee pain (Cheing and Hui-Chan 1998). It should be noted that no study to-date has investigated the possible cumulative analgesic effect of repeated TENS applications on acute thermal pain, or more importantly the use of pre-emptive and continued daily TENS on the postoperative pain after total knee replacement. This thesis set out to investigate this subject matter through 3 inter-related studies with the following objectives. Objectives. First, to determine if the inhibitory effect of TENS applied to the acupuncture points, was specific to pain as measured by the heat pain threshold, when compared with tactile sensibility as measured by the vibration threshold. In this thesis, we did not attempt to compare the effects of TENS to the acupuncture points and non-acupuncture points. Second, to examine whether TENS applications to the acupoints, repeated twice daily for 3 days, produced more cumulative analgesic effects on the heat pain threshold than placebo stimulation in older normal subjects who could be more susceptible to placebo effects. Third, to determine if repeated TENS applications to the acupoints before, during and after total knee replacement improved the post-operative pain management, in a manner similar to the use of pre-emptive and continuous opioid analgesia. Specifically, we attempted to delineate whether pre-emptive and repeated TENS applications could exert cumulative inhibitory effects on the post-operative pain intensity, improve the range of knee motion, reduce analgesic consumption, and shorten the length of hospital stay more than that of placebo stimulation. Methods. In study 1, 20 young normal subjects, aged 20 to 39, were examined. They were randomly allocated to a TENS or placebo group. High-frequency (100 Hz, 200us) TENS or placebo stimulation was applied to the acupuncture points (LI4) on each subject's left hand for 30 min. Heat pain and vibration thresholds were measured using the Medoc TSA-2001 and VSA-3000 respectively on the thenar eminence of each subject's left hand. In study 2, 19 older normal subjects, aged 60 to 85, were investigated. They were randomly allocated to a TENS or placebo group. Subjects received 60 minutes of TENS or placebo stimulation applied to the four acupuncture points (Extra36, Gb34, Sp9 and St35) around the knee joint twice daily over a 3-day period. The heat pain thresholds were measured before and after TENS or placebo stimulation. In study 3, 42 patients with osteoarthritic knee pain, aged 60 to 90, were examined. They were randomly allocated to a TENS or placebo group. Sixty minutes of TENS or placebo stimulation was applied to the same four acupuncture points around the knee joint 2 times daily, 3 days before, 1 day during and 6 days after total knee replacement. The post-operative pain intensity and range of knee flexion were measured before, during and after treatment. The analgesic consumption at 6, 12 and 24 hours after operation, and the length of hospital stay were recorded, the latter as the number of days needed by the patients to reach the discharge criteria. Results. The findings from study 1 showed a significant increase in heat pain threshold after 30 min of TENS application to the LI4 acupoint in the young normal subjects, when compared with that of placebo stimulation (p=0.002 to 0.004). In contrast, no significant difference in the vibration threshold was found between the TENS and placebo groups. In study 2, a significant increase in the heat pain threshold obtained before treatment in session 1 was found, when compared with that in session 6 in the TENS group (by 1.7 C, p=0.007), but not in the placebo group (by 0.7 C). In study 3, 3 main findings emerged. (1) Sixty minutes of TENS application in session 1 was found to produce a significant decrease of the knee pain intensity during and after TENS when compared with that of placebo stimulation (p=0.000 to 0.003). The baseline VAS score of TENS group dropped gradually from 100% to 83.3% (p=0.000) at 60 min during, and further to 85.7% (p=0.001) at 20 min after TENS, in contrast to the negligible changes shown during and after placebo stimulation. By the completion of the treatment period consisted of 12 sessions after the surgery, there was a further decrease to 31.5% before, 25.6% at 60 min during and 27.3% at 60 min after TENS application. These scores were significantly less than those recorded in the placebo group, which showed a decrease to 50.0% (p=0.003) before, 47.6% (p=0.000) at 60 min during and 47.5% (p=0.000) at 60 min after placebo stimulation. (2) A significant increase in knee flexion range was found between the TENS and placebo groups on each of the 6 days after operation (p=0.000 to 0.012). (3) A final finding was that patients receiving repeated TENS reached the hospital discharge criteria 2 days earlier than those receiving placebo stimulation, though the difference was not statistically significant. Discussion. In contrast to placebo stimulation, 30 min of TENS to the LI4 acupoint increased the heat pain but not the vibration threshold in the young normal subjects. This result demonstrated that, like acupuncture, the effect of TENS on acupoint is to reduce pain but not tactile (specifically vibration) sensibility. Interestingly, repeated high-frequency TENS applications to the acupoints, for 60 min twice daily over a 3-day period, produced a cumulative antinociceptive effect on the heat pain threshold in the older normal subjects belonging to the TENS group. The important finding from our main study was that repeated TENS applications 2 times a day, 3 days before, 1 day during and 6 days after surgery, produced a reduction of the post-operative knee pain and an increase in the knee flexion range after total knee replacement significantly more than placebo stimulation. In addition, patients receiving repeated TENS applications reached the hospital discharge criteria 2 days earlier than those receiving placebo application. Taken together, these findings unequivocally demonstrated that TENS application to the acupoints before, during and after total knee replacement produced significant beneficial effects to the patients with osteoarthritic knee pain after surgery, in terms of improvement in their sensori-motor functions and the possible saving garnered from a tendency towards shortened hospital stay.

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