Elec troencephalograph y and Clinical Neuroph ysiology , 1981, 52:157--162 157 Elsevier/North-Holland Scientific Publishers, Ltd. SOMATOSENSORY EVOKED POTENTIALS DURING WHOLE BODY HYPERTHERMIA IN HUMANS MICHEL DUBOIS a,1, RICHARD COPPOLA b, MONTE S. BUCHSBAUM b and DAVID E. LEES a a Anesthesiology Section, Clinical Center, National Institutes of Health, Bethesda, Md. 20205, and b Biological Psychiatry Branch, National Institute of Mental Health, Bethesda, Md. 20205 (U.S.A.) (Accepted for publication: March 9, 1981) Electroencephalographic changes during whole body hyperthermia in man have been previously reported (Dubois et al. 1980) and consisted mainly of a diffuse decrease of cor- tical activity which varied with the extent and duration of hyperthermia and was totally reversible within a few hours of cooling, with- out evidence of any EEG or neurological sequelae. In a follow-up study, we recorded somato- sensory evoked potentials (SEPs) in patients subjected to induced total body hyperthermia for the treatment of advanced neoplasms. Method Clinical protocol Four subjects (all male, 36--47 years old, without any chronic medication) eligible for the 'whole body hyperthermia treatment' protocol of the National Cancer Institute were selected and submitted (three of them on two separate occasions) to elevation of body temperature up to 42°C for 2 h, for treatment of metastatic carcinoma. Hyper- thermia was achieved using a computer<lriven external heating system. During the treat- ment, patients were sedated using a continu- I Correspondence and reprint requests should be addressed to: Michel Dubois, M.D., Anesthesiology Section, 3D42 Clinical Center, National Institutes of Health, Bethesda, Md. 20205, U.S.A. ous infusion of thiopental beginning 15 min from onset, and small 25--50 /~g increments of fentanyl were used to control spontaneous hyperventilation. In addition to accurate rectal and esophageal temperature monitor- ing, other recorded physiological parameters included heart rate, blood pressure, blood gases, respiratory rate and amplitude. Details concerning the hyperthermia set up, patient's selection, sedation and monitoring have been given elsewhere (Dubois et al. 1980; Lees et al. 1980). Recording technique Stimulus. Electrical stimulation was pro- vided via a digitally controlled constant cur- rent generator connected to spring wire ring electrodes placed over the middle finger of the left hand. A 1 msec biphasic pulse was presented between the proximal (base of the finger) and the distal (interphalangeal joint) electrode (as used by Lavine et al. 1980). Two stimulus levels (15 and 30 mA) were pre- sented 60 times each at 1 sec intervals in a random order an equal number of times. EEG was recorded from gold cup electrodes at ver- tex (Cz-right ear) and 2 cm posterior to C4- right ear, with left earground, amplified and filtered (flat bandpass 1--40 Hz; down 3 dB at 0.3 Hz and 42 dB at 60 Hz). The EEG follow- ing each stimulus was sampled at 250 Hz for 512 msec (128 samples). The averaging was done in real time, and the final 4 evoked po- tentials were displayed and written onto a floppy disc. Subjects were stimulated for 00134649/81/0000--0000/$02.50 © 1981 Elsevier/North-Holland Scientific Publishers, Ltd.