Figure 40-12 The number of dermatomes blocked (sacral segments, 5; lumbar segments, 5; thoracic segments, 12) versus reduction in the shivering threshold (difference between the control shivering threshold and the spinal shivering threshold). The shivering threshold was reduced more by extensive spinal blocks than by less extensive ones (Δ threshold = 0.74 − 0.06 [dermatomes blocked]; r² = .58, P < .006). The curved lines indicate the 95% confidence intervals for the slope. (Redrawn from Leslie K, Sessler DI: Reduction in the shivering threshold is proportional to spinal block height. Anesthesiology 84:1327–1331, 1996.)