Fig. 19. Changes in tympanic membrane (TM) temperatures and thermal comfort (millimeters on a visual analog scale [VAS]) after epidural lidocaine injections in six volunteers in a cool operating room environment. Epidural injections were given after a 15-min control period. Shivering (not shown) started when tympanic temperature decreased approximately 0.5°C and continued until core temperature returned to within 0.5°C of control. Thermal comfort increased after epidural injections in each volunteer; maximal comfort occurred at the lowest core temperature. Results are presented as mean ± SD. From Sessler and Ponte 43; used with permission. Copyright © 1990, the American Society of Anesthesiologists, Inc. and Lippincott Williams & Wilkins.