Transcutaneous electrical nerve stimulation for the relief of postoperative pain.

The pain-killing abilities of electricity were known as far back as the ancient Egyptians and Hippocrates, but it was not until 1965 when Melzack and Wall [10] proposed the “gate theory of pain” that clinical interest was re-awakened. This theory postulated that a “gate” for pain existed in the substantia gelatinosa of the posterior spinal horns and that modification of the perception of pain might be possible by blocking the “gate” with non-painful stimuli. They suggested that selective stimulation of large diameter myelinated cutaneous afferent nerve fibers could set a process in motion which would close the “gate” to information coming over smaller pain-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 block pain sensations. Transcutaneous electrical nerve stimulation was first employed in an attempt to select patients for implantable devices and then as a therapeutic device to alleviate chronic pain [2,4,6,9,11].The next logical step was to apply this modality to patients in the immediate postoperative period to decrease incisional pain. Hymes et al. [8] noted a decrease in atelectasis, ileus, postoperative pain and days spent in intensive care in patients using transcutaneous electrical stimulation. Vanderank and McGrath [9] reported that 77% of their patients treated with stimulators experienced some relief of postoperative pain.