Pain, 8 (1980) 299-302 © E~.sevier/North-Holland Biomedical Press

299

PAIN RELIEF AFTER LOW BACK SURGERY: THE EFFICACY OF TRANSCUTANEOUS ELECTRICAL NERVE STI2,1ULATiON

G.D. SCHUSTER and M.C. INFANTE

A&eociated Pain Consultants, Inc., and Doctors" Hospital, Silver Spring, Md. 209 ~ 0 (U.S.A.)

(Received 22 November 1979, accepted 3i January 1980)

SUMMARY

Transcutaneous electrical nerve stimulation (TENS) was used for the relief of post-operative pain following low back surgery in a consecutive selies of over 157 patients. A comparative study of the use of post-operative narcotic analgesics by 52 of these patients (26 in each of two groups) was made to determine the effectiveness of TENS in relieving post-operative pain. Fifty per cent of the sample used analgesics only; 50% used TENS in addition to analgesics. The data collected included its frequency of post-operative anal- gesic use, a rank order of analgesic potency, and a post-operative ;'pain score" derived from the combination of analgesic potency and frequevcy of use. Data analysis revealed significant differences between the groups in the use of analgesics. TENS decreased the need for narcotics in the relief of post-operative pain following low back surgery, although it is not a replace- ment for post-operative medication.

INTRODUCTION

In 1975, Vanderark and McGrath [8] presented a study showing the benefits of transcutaneous electrical nerve stimulation (TENS) in relieving post-operative pain. Of the 100 patients selected on a random basi~ and involved with various operative precedures, TENS provided pain reLef in 77% of the test patients as opposed to 17% of the controlpatients who were using TENS without batteries. In Minnesota, Hymes et al. [3] showe~ that the application of transcutaneous stimulation of 20--40 mA directly to the skin as close to the surgical wound as possible dramatically reduced the incidence of post-operative atelectasis and ileus. They also concluded that its use improved post.operative cough by as much as 65--70%. Furthermore, they and also Rosenberg et al. [6 ] noted that there was a d~finite subjective

r . r

300 ~ . . . . . .

reduction in post-operative pain. Banerjee [1] used TENS in pain associated with spinal injuries. In his study of 5 patients with spinal cord injury, there was definite relief of the constant burning and distress!ng pain associated with these injuries. Roberts [5], working with patients'suffering from severe pancreatitis, reported similar effects the reduction o r elimination of abdominal pain in each case where TENS was utilized.

In 1974 we began working with TENS; the initial success in controlling pain of patients with acute and chronic orthopedic l~roblems led us to under- take a study using TENS for various major orthopedic operative procedures. We selected patients who were to have partial laminectomy either with or without discectom:, and those with or without spinal fusion or decompres- sive laminectomy.

METHODS

The study group wa~ comprised of 52 patients undergoing iow back surgery: 26 used TENS post-operatively with analgesic medication available, and 26 control patients were selected at random. Records were matched as closely as possible for age, sex and type of 1o-¢¢ back surgery. There were 28 males ~nd 24 females with no significant difference in the mean age of the groups. Patients in both groups were on the same medications or sedatives.

One machine was u s e d - the Miniceptor II, manufactured by the Med- general Company. It had 3 settings and delivered an amplitude equal to 0--90 V in each channel, a rate of 25--100 pulses/sec and a pulse width of 40--100 /~sec. For purposes of standardization, the machine was run at an arbitrary setting (see discussions under specific technique).

Immediately after skin closure the surgical wound was sprayed with a plastic sealer (Aeroplast) which was prevented from flowing further than 0.5 in. lateral to the suture holes. A thin strip of dressing and a thin fold of gauze were placed cver the wound. Conductive gel was applied I in. from the incision line on both sides along its whole length. The adhesive fasteners and disc-type electrode leads were then positioned using dressing pads and tape to hold the wires in place on the patient's back. The patient was then turned and taken to the recovery room where the "neuroceptor" was attached. The control settings on the machine were set at a rate of " 3 " and an amplitude of "3" . Thewid th control was left at "0" . In more recent cases newer types of strip electrode leads have been used that are less bu]!ky, more comfortable, self-adherent ~_n.d e~ier to apply. We have encountered no significant differ- ence in the effective modulation of pain.

• Post-operative medication prescribed consisted of meprobamate, 400 rag, 3 times/day; ~md twc~ butabarbital (Fiorinal) tablets, every 4--6 h as neces- smT. Patients were also given a barbiturate or a tricyclic antidepressant at bedtime.

Patients ran the TENS unit continuously for the first 18--24 h and then used it as needed. The electrodes were removed, cleaned and re-applied twice a day according to routine skin care orders. All ol~her orders.such as position,

TABLE I

FREQUENCY OF ANALGESIC MEDICATION VS. PAIN SCORES

301

Frequency of analgesic medication

TENS Control

Pain scores

TENS Control

N Range X S.D.

Mean difference df t =

26 26 26 26 0--14 2--26 0--43.5 14.156 4.65 10.92 17.38 63.76 3.66 6.17 1.2.30 36.17

6.26 46.36 50 50

4.36 a 6.06 ~-

a p ~ 0.01.

meals, laxative or ambulation were the same as in the control group. Data were obtained as to the frequency of use of analgesics by ,each

patient. A scoring system was devised to account for the fact that different drugs were prescribed by different physicians. Analgesic drugs were rmlked on a scale from 1 to 8, using morphine as a number 8 prototype, and assign- ing rank of one to the least potent drug. Pain scores for the first 72 post- operative hours were calculated by multiplying the frequency of request for analgesic drugs by the rank order of ~he drug. The range, mean and standard deviation were computed for the frequency of medication use and the pain scores for both experimental and control groups. Mean scores for both groups were compared using the t-test for independent measures. The one- tailed test was used for both groups.

The data reveal a much higher use of analgesics in the control group for the first 72 post-operative hours. Table I shows the frequency of analgesic medication for both TENS and control groups. For df 50 the t-statistic 4.36 is significant at P <~ 0.01. This difference of means indicates that the TENS group had a significantly lower incidence of analgesic use in the first 72 ~)ost- operative hours. The difference in means of computed pain scores for df 50 is also Significant at P <: 0.01.

DISCUSSION

Post-operative pain is a most difficult phenomenon to analyze, due to its subjective nature. In this study, analgesic intake operationally defines [~ain. We demonstrated that TENS decreases the necessity for narcotic analgesic intake after major surgery. The complications frequer',ly associated with major spinal surgery - -notably , pulmonary function depression, atel.~cta- sis, gastrointestinal sluggishness, and urinary i n c o n t i n e n c e - were not encountered in the TENS group. Though we did not set out to measure these

302

phenomena, it would appear that the diminution of pain and muscle spasm prevented respiratory and gastrointestinal complications. In ad~t iom patients in the study group did not suffer any wound infections despite the proxim- ity of the electrodes to the incision.

REFERENCES

1 Banerjee,: T., Letter: Transcutaneous nerve stimulation for pain after spinal surgery, New Engl. J. Med., 291 (1974) 796.

2 Campbell, J.N. and Taub, A., Lr~cal analgesia from percutsneous electrical stimulation: a peripheral mechanism, Arch. Neurol. (Chic.), 28 (1973) 347--350.

3 Hymes, A.C., Raab, D.E. and Yonehiro, E.G., Electrical surface stimulation for con- trol of acute postoperative pain and prevention of ileus, Surg. Forum, 26 (1975) 474-- 476.

4 Melzack, R. and Wall, P.D., Pain mechanisms: a new tbeory, Science, 150 (1965) 971-979 .

5 Roberts, H.J., Transcutaneous electrical nerve stimulation in the management of pan- creatitis pain, Sth. reed. J. (Bgham, Ala.)', 71 (1978) 396--398.

6 Rc;senberg, M,, Curtis, L. and Bourke, D.L., Transcutaneous electrical nerve stimula- tion for the relief of post-operative pain, Pain, 5 (1978) 129--133.

7 Sternbach, R .A. , Ignelzi, R.J, , Deems, L.M. and Timmermans, G., Transcutaneous electrical analgesia: a follow-up analysis, Pain, 2 (1976) 35--41.

3 Vanderark, G.D. and McGrath, K.A., Transcutaneous electrical stimulation in treat- ment of postoperative pain; Amer. J. Surg., 13,n (1975) 338--340.