[Use of nociceptive flexion reflex in the evaluation of morphine analgesia]

A close correlation between the threshold of the nociceptive flexion reflex and pain threshold makes this reflex useful for the examination of pain and analgesia level. Earlier investigations showed that in sciatica the threshold of the nociceptive reflex was decreased in the extremity with pain, and that the degree of this decrease was proportional++ to pain intensity and intensity of radicular sings. In the presently reported study the nociceptive flexion reflex was investigated in 20 patients after epidural injection of 5 mg of morphine. After this blockade the degree of analgesia and the value of the reflex were determined. Improvement was obtained in 80% of patients, with complete disappearance of pain in 55%. In all improved patients the previously decreased threshold of the nociceptive flexion reflex increased again to normal values.