Fig. 3. (  A ) Calculated extravascular expansion calculated as the difference between volume infused minus change in blood volume and cumulative urinary output at each time point. Change in blood volume and cumulative urinary output were both set to zero at the start of infusion. Control = no-drug control; Dopa = dopamine; Iso = isoproterenol; Phen = phenylephrine; NS = normal saline bolus. Statistical comparisons are as described for  figure 1 . The 0.9% NaCl bolus caused a similar and significant increase at T20 in all protocols except the Dopa protocol. Thereafter, the decreases below baseline in the Dopa and Phen protocols were significant starting at T120, whereas the increased extravascular expansion in the Iso protocol remained significant, and the Control protocol was the same as baseline. Postinfusion protocol differences in extravascular expansion were Iso > Control > Dopa ≈ Phen. (  B ) Calculated volume expansion efficacy (mean ± SEM) as measured by milliliters of blood volume expansion from T0 divided by milliliters infused. Immediately after the 0.9% NaCl bolus at T20, there was no difference between protocols, but from T60 on, postinfusion differences were Iso > Control ≈ Dopa > Phen, and these differences held throughout the entire postinfusion period.