Fig. 1. Comparison of variations of uterine blood flow (UBF) responses. Light lines describe curves of two standard deviations around the mean response, or heavy lines . With ephedrine and mephentermine, UBF rarely decreased below spinal hypotensive levels. With metaraminol, UBF frequently decreased further during therapy. Reprinted with permission from James FM III, Griess FC, Kemp RA: An evaluation of vasopressor therapy for maternal hypotension during spinal anesthesia. Anesthesiology 1970; 33:25–34.