title: Cardiac output response to norepinephrine in postoperative cardiac surgery patients: interpretation with venous return and cardiac function curves.
abstract: OBJECTIVE
  We studied the variable effects of norepinephrine infusion on cardiac output in postoperative cardiac surgical patients in whom norepinephrine increased mean arterial pressure. We hypothesized that the directional change in cardiac output would be determined by baseline cardiac function, as quantified by stroke volume variation, and the subsequent changes in mean systemic filling pressure and vasomotor tone.
  
  
  METHODS
  Intervention study.
  
  
  METHODS
  ICU of a university hospital.
  
  
  METHODS
  Sixteen mechanically ventilated postoperative cardiac surgery patients.
  
  
  METHODS
  Inspiratory holds were performed at baseline-1, during increased norepinephrine infusion, and baseline-2 conditions.
  
  
  RESULTS
  We measured mean arterial pressure, heart rate, central venous pressure, cardiac output, stroke volume variation and, with use of inspiratory hold maneuvers, mean systemic filling pressure, then calculated resistance for venous return and systemic vascular resistance. Increasing norepinephrine by 0.04 ± 0.02 μg·kg·min increased mean arterial pressure 20 mm Hg in all patients. Cardiac output decreased in ten and increased in six patients. In all patients mean systemic filling pressure, systemic vascular resistance and resistance for venous return increased and stroke volume variation decreased. Resistance for venous return and systemic vascular resistance increased more (p = 0.019 and p = 0.002) in the patients with a cardiac output decrease. Heart rate decreased in the patients with a cardiac output decrease (p = 0.002) and was unchanged in the patients with a cardiac output increase. Baseline stroke volume variation was higher in those in whom cardiac output increased (14.4 ± 4.2% vs. 9.1 ± 2.4%, p = 0.012). Stroke volume variation >8.7% predicted the increase in cardiac output to norepinephrine (area under the receiver operating characteristic curve 0.900).
  
  
  CONCLUSIONS
  The change in cardiac output induced by norepinephrine is determined by the balance of volume recruitment (increase in mean systemic filling pressure), change in resistance for venous return, and baseline heart function. Furthermore, the response of cardiac output on norepinephrine can be predicted by baseline stroke volume variation.
authors.affiliation: Department of Intensive Care Medicine, Leiden University Medical Center, Leiden, The Netherlands. j.j.maas@lumc.nl
authors.forename: Jacinta J
authors.initials: JJ
authors.lastname: Maas
authors.forename: Michael R
authors.initials: MR
authors.lastname: Pinsky
authors.forename: Rob B
authors.initials: RB
authors.lastname: de Wilde
authors.forename: Evert
authors.initials: E
authors.lastname: de Jonge
authors.forename: Jos R
authors.initials: JR
authors.lastname: Jansen
mesh_terms: D002302:Cardiac Output / Q000187:drug effects*; D006348:Cardiac Surgical Procedures; D002496:Central Venous Pressure; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D016018:Least-Squares Analysis; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D011182:Postoperative Care; D013318:Stroke Volume; D014655:Vascular Resistance; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*; D014680:Veins
chemical_list: D014662:Vasoconstrictor Agents; D009638:Norepinephrine