Pump Flow Changes Do Not Impair Sublingual Microcirculation During Cardiopulmonary Bypass

ObjectiveThe flow rate of the cardiopulmonary bypass (CPB) pump used in cardiac surgery often undergoes inherent fluctuations ranging from 10% to 20% of its theoretic value. However, the effects of such alterations remain unknown. In the present study, the authors investigated whether such variations could induce changes in the microvascular flow, which is considered a primary indicator of poor perfusion.DesignA prospective, observational, clinical study.SettingA university-affiliated teaching hospital.ParticipantsThirty adult patients undergoing elective cardiac surgery with CPB.InterventionsAnalysis of the sublingual microcirculation during CPB using a pump flow rate of 80% or 100% of the theoretic value.Measurements and Main ResultsSidestream dark field (SDF) imaging was used to record 2 video clips of the sublingual microcirculation in each patient. The videos were recorded at the same site at 80% and 100% of the theoretic flow rate. Microvascular analysis displaying the De Backer score, the microvascular flow index, the total vessel density, the perfused vessel density, and the proportion of perfused vessels was performed. Moreover, the mean arterial pressure (MAP), SvO2, and PaCO2 were evaluated. No significant changes in the measured parameters were noted at the 2 different flow rates.ConclusionsChanges in the CPB pump flow rate within 20% (80%-100%) of its theoretic value do not alter the sublingual microcirculation. Thereafter, it is conceivable that during perioperative adjustments of the CPB pump rate, blood flow autoregulation mechanisms are activated so that limited changes in the pump flow can be considered safe not only at the sublingual site but also for the entire microcirculation.