Microcirculatory changes during cardiac surgery with cardiopulmonary bypass.

OBJECTIVE: To evaluate microcirculation in intermediate and high mortality risk patients undergoing cardiac surgery (CS) with cardiopulmonary bypass (CPB).

PATIENTS AND METHODS: The study included 22 patients with a Euroscore >3. Using the Videomicroscopy Side Stream Dark Field system, and evaluation was made of, capillary density, proportion of perfused capillaries, density of perfused capillaries, microcirculatory flow index (MFI), and heterogeneity flow index. Three to five video sequences were recorded: after induction of anaesthesia (T1), at the beginning of the CPB (T2), before finalising CPB (T3), at the end of the surgery, and before the patient was transferred to Intensive Care Unit (T4). Mean arterial pressure decreased, while the blood lactate increased significantly, when comparing the initial and final values (P<.05). MFI increased significantly in T3 and T4 (P<.05) with regards to the initial values. When the patients with and without postoperative complications were compared, significant differences were found in, Euroscore, left ventricular ejection fraction, and MFI in T3.

CONCLUSIONS: in patients with intermediate/high preoperative risk, CS and CBP can involve an increase in MFI and blood lactate at the end of the study. These alterations suggest the possibility of a functional microcirculatory shunt at tissue perfusion level, secondary to the surgical injury and the CPB. Further investigation is needed to have a better understanding of the mechanisms involved.