title: Mechanisms of increased right and left ventricular oxygen uptake during inotropic stimulation.
abstract: OBJECTIVE
  Few studies have investigated oxygen supply/demand relations in right ventricle (RV). The current study compared changes in myocardial oxygen uptake (MVO2) and its determinants, myocardial blood flow (MBF) and oxygen extraction (EO2), in RV and left ventricle (LV) during stimulation with inotropic drugs.
  
  
  METHODS
  Twenty-one anesthetized dogs were studied. MBF was measured with radioactive microspheres. A-VO2 difference was determined separately for RV and LV, and used to calculate MVO2 (Fick equation) and EO2. Responses to iv. infusions of isoproterenol (0.1 μg/kg/min), dobutamine (5 μg/kg/min), and amrinone (1mg/kg+10 μg/kg/min) were assessed.
  
  
  RESULTS
  Baseline MVO2 in RV was 50-60% of that in LV. The inotropes increased MVO2 in both RV and LV (range 32-63%; P<0.05). With isoproterenol, the increased MVO2 in the RV was due to increases in both MBF and EO2, whereas in LV it was due only to increases in MBF. With dobutamine and amrinone, the increased MVO2 in RV was due to increased MBF while EO2 was constant (dobutamine) or decreased (amrinone), and that in the LV was due to increased MBF while EO2 decreased.
  
  
  CONCLUSIONS
  RV possesses EO2 reserve that contributed to increased MVO2 during isoproterenol infusion, whereas LV depended on increased MBF alone. Because dobutamine and amrinone caused direct coronary vasodilation, i.e., "luxuriant perfusion," it was not necessary to recruit the EO2 reserve. Thus, it remained available to meet further increases in MVO2 or to maintain MVO2 in the face of reductions in MBF.
authors.affiliation: Department of Anesthesiology, Advocate Illinois Masonic Medical Center, Chicago, IL 60657, USA. gcrystal@uic.edu
authors.forename: George J
authors.initials: GJ
authors.lastname: Crystal
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Silver
authors.forename: M Ramez
authors.initials: MR
authors.lastname: Salem
mesh_terms: D000676:Amrinone / Q000494:pharmacology; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology; D004280:Dobutamine / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006352:Heart Ventricles / Q000187:drug effects* / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology; D013268:Stimulation, Chemical; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D002316:Cardiotonic Agents; D014665:Vasodilator Agents; D004280:Dobutamine; D000676:Amrinone; D007545:Isoproterenol
keywords: Inotropic drugs; Oxygen uptake; Right ventricle