title: Bedside Assessment of the Microvascular Venous Compartment in Cardiac Surgery Patients With Valvular Diseases Undergoing Cardiopulmonary Bypass.
abstract: OBJECTIVE
  Blood volume reserve for venous return and the effects of cardiopulmonary bypass (CPB) on microvascular bed partitioning and blood flow were examined in patients with valvular diseases.
  
  
  METHODS
  Prospective, consecutive, case-control study.
  
  
  METHODS
  Single university hospital.
  
  
  METHODS
  The study comprised 20 adult cardiac surgery patients and 20 healthy volunteers.
  
  
  METHODS
  Cardiovascular and microvascular variables were collected soon after the induction of anesthesia, after commencement of CPB, 20 minutes after separation from CPB, and in the intensive care unit.
  
  
  RESULTS
  The unstressed and stressed volumes (Vu, Vs) and pressures therein (Pit, Ps) were measured in the brachioradial muscle with near-infrared spectroscopy, applying incremental venous occlusions. At the first time point, Vs and Pit showed lower and higher values, respectively, than those of control patients, but Vs increased with Vu during the study, whereas Pit remained unchanged. Fluid balance correlated with Pit (r = 0.83, p<0.001) and hemoglobin (r = 0.78, p = 0.004). A nonlinear regression was found between fluid balance and ΔVu (r = 0.90, p<0.001) [y = 1.85+37.43(-0.01×x)]. The Vu/Pit and Vs/Ps ratios were lower than those of the control patients. Blood flow correlated to Vs/Ps (r = 0.75, p<0.001). The time constant was lower than reference (p = 0.005) and increased 10 times after CPB.
  
  
  CONCLUSIONS
  Cardiac surgery patients have a limited blood volume reserve for venous return due to a reduced microvascular bed capacitance. This study demonstrated that during CPB a positive fluid balance induced an extravascular pressure increase and further reduced blood volume reserve.
authors.affiliation: Intensive Care Unit, Department of Medical and Surgical Science and Translational Medicine, Faculty of Medicine and Psychology, University of Rome "Sapienza," Roma, Italy. Electronic address: radbl@libero.it.
authors.forename: Roberto Alberto
authors.initials: RA
authors.lastname: De Blasi
authors.affiliation: Intensive Care Unit, Department of Health Science, University of Florence, University Hospital Careggi, Florence, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Romagnoli
authors.affiliation: Intensive Care Unit, Department of Medical and Surgical Science and Translational Medicine, Faculty of Medicine and Psychology, University of Rome "Sapienza," Roma, Italy.
authors.forename: Monica
authors.initials: M
authors.lastname: Rocco
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001810:Blood Volume / Q000502:physiology*; D001811:Blood Volume Determination / Q000379:methods; D001831:Body Temperature / Q000502:physiology; D002315:Cardiopulmonary Bypass / Q000379:methods*; D016022:Case-Control Studies; D003187:Compliance / Q000502:physiology; D005260:Female; D006349:Heart Valve Diseases / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D018482:Muscle, Skeletal / Q000098:blood supply; D011446:Prospective Studies; D012039:Regional Blood Flow / Q000502:physiology; D019265:Spectroscopy, Near-Infrared / Q000379:methods; D014655:Vascular Resistance / Q000502:physiology
keywords: cardiopulmonary bypass; microvascular bed; near-infrared spectroscopy; skeletal muscle; valvular disease; venous compartment