EFFECT OF INTRAVENOUS-SODIUM AMYTAL ON CUTANEOUS LIMB TEMPERATURES AND SYMPATHETIC SKIN-RESPONSES IN NORMAL SUBJECTS AND PAIN PATIENTS WITHAND WITHOUT COMPLEX REGIONAL PAIN SYNDROMES (TYPE-I AND TYPE-II) .1.

This study examined the effects of intravenous administration of sodiu m amytal (SA), a medium action barbiturate, on cutaneous limb temperat ures and sympathetic skin responses (SSR) to electrical stimulation. E ight normal volunteers and 13 patients with musculoskeletal pain, soma toform pain disorders or nerve/root injury (with findings strictly lim ited to the distribution of the involved nerve) were compared to 15 pa tients with Complex Regional Pain Syndromes (one of whom had documente d nerve injury). The Complex Regional Pain Syndromes (CRPS) patients w ere characterized by the presence of severe diffuse limb pain and extr aterritorial sensory, sudomotor and vasomotor abnormalities (i.e., not confined to the site of injury or the distribution of the injured ner ve). The CRPS patients were different from the normal controls and the non-CRPS patients in their tendency to warm significantly many of the ir limbs (not just the symptomatic ones). SSR were reduced or lost in a few limbs only in all three groups, irrespective of the increase or decrease of limb temperature and the side of symptoms. We argue that t he enhanced thermogenic effect of SA in CRPS patients is due to genera lized central changes of thermoregulatory control specifically in this group. (C) 1997 International Association for the Study of Pain.