Figure 7-24 Effects of nitrous oxide (N₂ O) on the preload recruitable stroke work (PRSW) slope in the presence of isoflurane (I, top panel) and sufentanil (S, bottom panel) are shown as a percentage of the control (I or S only, respectively). *, Significantly (P < .05) different from I or S only; †, significantly (P < .05) different from I or S plus 30% nitrous oxide. (Adapted from Pagel PS, Kampine JP, Schmeling WT, Warltier DC: Effects of nitrous oxide on myocardial contractility as evaluated by the preload recruitable stroke work relationship in chronically instrumented dogs. Anesthesiology 73:1148–1157, 1990.)