Ricerc@Sapienza

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.
DESIGN: Prospective, consecutive, case-control study.
SETTING: Single university hospital.
PARTICIPANTS: The study comprised 20 adult cardiac surgery patients and 20 healthy volunteers.
INTERVENTIONS: 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.
MEASUREMENTS AND MAIN 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 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.