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TRANSCUTANEOUS ELECTRICAL NERVE STIMULATION FOR THE R E L ~ F O F P O S T O P E R A T ~ E PAIN *

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MORTON ROSENBERG, LON CURTIS and DENIS L. BOURKE

Departments of Anesthesiology and Surgery, Tufts-New England Medical Center Hospital, Boston, Mass. (U.SiA.)

(Accepted January 23rd, 1978)

SUMMARY

.The pain-killing abilities of electricity were known as fsz back as ,~,hc ancient: Egyptians and:Hippocrates, b u t it was not until 1965 when Melzack and Wall [ i 0 ] proposed the "gate theory of pain" that clinical interest was re-awakened,:~This theory postulated that a "ga te" for pain existed in the substantia gelatinosa of the post~lior spinal horns and that modification, of the: perception of pain might b~ oo~s{ble by blocking "~^ "-~-:-~" "-"~ painful stimuli. They suggested that selective stimulation of large diameter myelinated cutaneous afferent nerve fibers could set a process in motion

gate to information coming over smaller pain- which would close the " " carrying fibers

The first clinical application of this "theory centered around the relief of chronic pain by surgical placement of dorsal column stimulators [1] and implantation of stimulating devices around large peripheral nerves to brock p ~ sensations, i .I~ Transcutaneous electrical nerve stimulation was fhst employed:in: an :a t t empt t o select patients ,for implantable devices and then as a therapeutic :device toalleviate: Chronic pain [ 2,4,6,9,11]. :~ : ~ e n e x t :logical : : step / w a s t o apply • this modali ty to patients i~ the immediate:: postoperative: period to decrease incisional pain. Hymen et al. [8] noted a decrease in atelectasis, ileus, postoperative pain and days spen~ in intensive care in patients using transcutaneous el.ectrical stimulation. Vanderank and McC, rath [9] reported that 77% of their patients treated with stimulators experienced some relief of postoperative pain.

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INTRODUCTION

In the study presented, narcotic usage, incidence of ileus, atelectasis, respirato~ pm'amef~rs, patient and ndrsing acceptance were exa~-~ined in an

* This work was funded by Charlton Fund, T~fts University Schooi of Medicine.

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attempt to evaluate the transcutaneous e]ectrical nerve stimulator during the immediate postoperative period.

METHODS

After the protocol had been approved by the Human Investigational Con- trol Committee, informed consent was obtained from 12 randomly selected patients scheduled for cholecystectomy. The patients were randomly assigned to either a control (N = 6) or a test (N = 6 ) g r o u p . During the preoperative visit, both groups were informed that pain medication would be available only at their request. A neuropak I (model 7401, Medical Devices, St. Paul, Minn.) was demonstrated to the test group. This device enables the patient to control both the amplitude and frequency of the current. The electrical transcutaneous nerve stimulating device used had an output with an amplitude of 0--80 mA + 10 mA into a 500 ~2 load (adjustable), a fre- quency of 50--100 puIses/sec (adjustable)~ and a pulse width of 20--100 psec which automatically varied with amplitude. The patients would have com- plete control over the use of this device as far as dosimetry, duration of use and electrode placement.

All patients were premedicated with either 100 mg Nembutal or 10 mg diazepam or 0.4 mg atropine. Thiopental and succinylcholine were used for induction and mtubation, and maintenance consisted of nitrous oxide-oxygen, Ethrane and Pancuronium bromide. At the end of the procedure, the muscle relaxant was rever'~ed and all patients were extubated and brought to the recovery room. A midline upper abdominal incision was employed in all cases. The test group had electrode paste and sterile skin electrodes (45 mm × 45 ram, carbonized medical-grade silicone rubber} placed on the upper and lower limit~ of this incision.

In addition to routine pre- and postoperative observations the following parameters were recorded during the day of surgery and the two days post- operatively: chest X-rays, arterial blood gases, bedside pulmonary function tests (Air Shields Vitalor Model V-23-1), including vit~! capacity, forced expiratory volume in 1 sec, and maximum expiratory flow rate. The amount of narcotics administered, presence ,ff ileus, patient and nursing ~cceptance of the device were also recorded.

RESULTS

All patients tolerated the procedure well and the mean time of surgery was 2 h and 30 min. The mean age and weight of the contrel group was 43.2 years and 71.2 kg respectively; the test group 42 years and 83.9 kg. The amount of narcotics (Demerol) admimstered to both groups is summarized in Fi~. i . The control group used more than 3 times the total amount of . ~ , . o ic~ tha~i the test. group; but the ranges were wide in both groups. Student's t test for two means was performed or~ the Winsorized data. The test~ group d(':.~.onstrat'ed a significan~ (P < 0.05) decrease in the amoant of

13 i

Oemerol (mg)

3O0

I00

~ N o u r o p o ¢ @

~Controi

Ooy of Surgery

I , _I++ Doy I Day I!

Fig. 1. Gxaphic represen ta t ion o f mean values for a m o u n t of narcot ic (Demero l ) adminis- tered wi th s t andard error of the mean.

narcotics administered in the first and second postoperative days and over the entire test period.

Despite this difference in the two groups, respiratory parameters such as arterial blood gases, FEV~, MEFR and vital capacity were nearly identical though decreased as expected from the upper abdominal incision. By chest X-ray there was one case of atelectasis in each group° The presence of ileus in both groups las~d into the evening of the second postoperative day. No correlation was found between age, weight; or sex and the amount of narcotics requested.

Scored nursing evaluations noted an increase in subjective respiratory functions (coughing, deep breathing, ability t.o Lake IPPB treatments) in the

. ..es~ group all ~ ~ test grouo. It is of note that the patients interviewed in the ~" '- that the stimulator offered some pain relief and preferred it to medication.

All patients using transcutaneous electrical nerve stimulators felt that they derived some pain relief from the device. Several claimed that the tingling sensation lulled them to sleep, and two patients desired to purchase ~he device.

DISCUSSION

Although quantitating pain and pain relief on a clinical basis is an extremely difficult task, the pain relief from. transcutaneous electrical nerve stimulation {TENS) is real, although subiec'ive. Recent ev!dence suggests that electrical neurostirr, u!ation and perhaps acupuncture may induce the

, . . . . [ 5 ~ ~.. nervous system to release an endogenous morp~.ine-iike suos~ance , ~ decrease response to pin prick by stimulating large mye!ir~ated periphera! nerves by W~I and Sweet [14] had led to the. use of TENS to produce !oca!. anesthesia [ 3 , !2] .

Although as previously noted, Hymes eL al. [8] described sigr}ificant

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reduction in postoperative ileus, our results did not concur. The reduction in the use of narcotics by the test group was significant in the last two post- operative days and although this did not lead to a concurrent rise in puhno- nary function tests over the control, this decrease in narcotics is higly desir- able. Theoretically, TENS by increasing appetite, ambulation, coughing, reduction in sluggishness and decreasing possible drug addiction sh.ou!d shorten the hospital ~tay, but the durations of hospitalization in both groups were identical. Nursing surveys indicated that the test group was more alert and responsive and tolerated their respiratory care better.

The role of placebo effect cannot be ruled out, but the purpose of this study was to judge the effectiveness of neurostimulation whatever the mechanism, psychological, central, or peripheral. Linzen and Long [9], by demonstrating that electrode location and other parameters are important in the success er failure of TENS, provide evidence against a major placebo effect.

No complications were observed in this study from the use of TENS and the only morbidity reported has involved skin reactions at the electrode sites [7]. Contrair.dications for the use of TENS would include: (1} use in patients with demand cardiac pacemakers, (2 )p lacement of the electrodes over the carotid sinus, and (3) use in patients during the first trimester of pregnancy [ 2 ].

Over 20 companies in the United States now manufacture TENS devices for the relief of chronic and acute pain. As with all new modes of therapy, the cost of these devices is high and although we conclude the TENS is of some benefit in the reduction of postoperative pain, it is still only an adjunct to more classical methods. We are now attempting to develop a psychological profile preoperatively that will enable us to choose those patients ~:nost likely to bene~iL from TENS.

SUMMARY AND CONCI.USION

In a random assigrment study of 2 groups of 6 patients, relief of post- operative pain with narcotics was evaluated and compared with trans- cutaneous electrical nerve stimulation for 2 days following surgery. Respiratory parameters and presence of ileus were nearly identical in both groups. The group utilizing electrical stimulation demonstrated a significant decrease in the amount of narcotics administered. There was favorable nursing and patient acceptance to these devices. Further clinical evaluation is, therefore, being pel formed.

ACKNOWLEDGEMENTS

The author~ ~'e grateful to P.M. Roche, Chief Technician of Anesthesiol- ogy, for her clinical ~¢;sistance in this study and for facilitating the statistical analyses of the data.

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REFERENCES

1 Burton, C.N., Neurosurgical treatment of intractable pain, Penn. reed. J., 75 (1972) 53--55.

2 Burton, C., Transcutaneous electrical nerve stimulation to relieve pain, Postgrad. Med., 59 (1976) 105--108.

3 Campbell, J.N. and Tane, A., Local anesthesia from percutaneous electrical stimula- tion, Arch. Neurol. (Chic.), 28 (1973) 3347.

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5 Cerebral "morphine" peptides are synthesized, New Wld News, 26 (1976) 86. 6 External electrical stimulation, Minn. Med., 57 (1974) 195--198. 7 Food and Drug Administration, Drug Bull., July/August (1975). 8 Hymes, A.C., Rabb, D.E. and Yonehis, E.G., Electrical surface stimulation for control

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