Figure 40-13 Systemic oxygen consumption without (circles) and with (squares) epidural anesthesia. The horizontal standard deviation bars indicate variability in the thresholds among the volunteers; although errors bars are shown only once in each series, the same temperature variability applies to each data point. The slopes of the oxygen consumption-versus-core temperature relationships (solid lines) were determined by linear regression. These slopes defined the gain of shivering with and without epidural anesthesia. Gain was reduced 3.7-fold, from -412 mL/min/°C (r² = .99) to -112 mL/min/°C (r² = .96). (Redrawn from Kim J-S, Ikeda T, Sessler D, et al: Epidural anesthesia reduces the gain and maximum intensity of shivering. Anesthesiology 88:851–857, 1998.)