Fig. 1. The original fig. 1 from Tong et al. was copied from the electronic document. No changes were made to any electrocardiographic tracing that would alter the apparent strip recorder rate, and all five strips appear to have been recorded at 25 mm/s. The up-arrows appearing in strips D and E were placed by the original authors. Annotations ( letters, numbers , and down-arrows ) were added for reference within the text. Reprinted with permission from Anesthesiology.