Fig. 2. (  A ) Change in blood volume (mean ± SEM) calculated as the difference in blood volume from the baseline or prebolus measurement. 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 positive change in blood volume or increase in all protocols at T20 and in all protocols except the Phen protocol thereafter. Postinfusion protocol differences were Iso > Dopa ≈ Control > Phen. (  B ) Cumulative urinary output (mean ± SEM). The 0.9% NaCl bolus caused an increase in cumulative urinary output at T20 for all protocols except the Iso protocol, and thereafter, cumulative urinary output was significantly increased in all protocols. Postinfusion protocol differences in cumulative urinary output were Dopa ≈ Phen > Control > Iso.