Measurements of autonomic function before, during, and after transcutaneous stimulation in patients with chronic pain and in control subjects.

Transcutaneous stimulation (TCS) has been reported to modify peripheral blood flow, skin temperature, blood pressure, and heart rate, all of which are under the influence of the autonomic nervous system (ANS). In 20 patients with intractable pain and in 10 control subjects, TCS was not found to alter significantly any of the observed properties of ANS function of control subjects or patients, except to decrease skin impedance in the patient group after the stimulation. Patients reporting pain relief during TCS were found to have significantly higher systolic blood pressure under all test conditions than patients reporting no pain relief (p less than 0.05). No other significant differences were found between these two groups. Finally, in the patients, no significant localized autonomic changes were demonstrated in the painful area by comparison with the homologous body part.