Bedside Assessment of the Microvascular Venous Compartment in Cardiosurgery Patients with Valvular Diseases Undergoing Cardiopulmonary Bypass

• Published in: Journal of cardiothoracic and vascular anesthesia 2016
• Main Authors: De Blasi, Roberto Alberto, Romagnoli, Stefano, Rocco, Monica
• Format: Article
• Language: English
• Subjects: Anesthesia & Perioperative Care; Critical Care
• ISSN: 1053-0770
• DOI: 10.1053/j.jvca.2016.06.001

Objective We aimed to investigate, in patients with valvular diseases, the blood volume reserve for venous return and the effects of cardiopulmonary bypass (CPB) on microvascular bed partitioning and blood flow. Design Prospective consecutive case-control study. Setting Single university hospital. Participants 20 adult cardiosurgery patients, 20 healthy volunteers. Interventions Cardiovascular and microvascular variables were collected soon after the induction of anesthesia, after commencement of CPB, 20 min after separation from CPB and in the intensive care unit. Measurements and Main Results We measured in the brachio-radial muscle the unstressed and stressed volumes (Vu, Vs) and pressures therein (Pit, Ps), with near infrared spectroscopy, applying incremental venous occlusions. At the first time-point, Vs and Pit showed respectively lower and higher values than controls, but Vs increased with Vu during the study whereas Pit remained unchanged. Fluid balance correlated with Pit (r = 0.83, p < 0.001) and Hb (r = 0.78, p = 0.004). A non-linear 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, Vs/Ps ratios showed values lower than controls. Blood flow correlated to Vs/Ps (r = 0.75, p < 0.001). Time constant was lower than reference (p = 0.005) and increased ten times after CPB. Conclusions Cardiac surgery patients have a limited blood volume reserve for venous return due to a reduced microvascular bed capacitance. Our study demonstrates that during CBP a positive fluid balance induces an extravascular pressure increase and further reduces blood volume reserve.