Figure 4. Systemic norepinephrine (NE) spillover (nanograms per minute) and systemic NE clearance (liters per minute) at baseline (time 0) and after intraarterial infusion of isoproterenol 30 and 80 ng/min awake (squares) and during 1.0 minimum alveolar concentration (MAC) halothane anesthesia (circles). Data are expressed as mean values plus/minus SEM.