Pump flow changes do not impair sublingual microcirculation during cardiopulmonary bypass

Abstract

Objective: The 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.

Design: A prospective, observational, clinical study.

Setting: A university-affiliated teaching hospital.

Participants: Thirty adult patients undergoing elective cardiac surgery with CPB.

Interventions: Analysis of the sublingual microcirculation during CPB using a pump flow rate of 80% or 100% of the theoretic value.

Measurements and main results: Sidestream 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), SvO(2), and PaCO(2) were evaluated. No significant changes in the measured parameters were noted at the 2 different flow rates.

Conclusions: Changes 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.