Aortic cross-clamping phase of cardiopulmonary bypass is related to decreased microvascular reactivity after short-term ischaemia of the thenar muscle both under intravenous and volatile anaesthesia: a randomized trial.

Objectives: The purpose of the present study was to assess, by near-infrared spectroscopy with an INVOS oximeter during the vascular occlusion test (VOT), the influence of cardiopulmonary bypass (CPB) on tissue saturation in the thenar muscle. The secondary aim was to compare the effects of propofol and sevoflurane anaesthesia on tissue saturation.

Methods: This was a prospective, randomized, open-label study. Sixty cardiac surgery patients received either propofol or sevoflurane anaesthesia. Three-minute VOT was performed at the following time points: 30 min after anaesthesia induction, directly after sternotomy, 20 and 40 min after aortic cross-clamping, 20 min after aortic cross-clamp removal and 45 min after weaning of cardiopulmonary bypass. Group and time effects on tissue saturation were analysed with RM-ANOVA and the post hoc Tukey test.

Results: In both groups at baseline, the lowest and the highest tissue saturation and the rate of saturation recovery during the reperfusion phase of the vascular occlusion test were lower during aortic cross-clamping in comparison to the values before CPB. Lower nadir tissue saturation during ischaemia was observed under propofol in comparison to sevoflurane anaesthesia (P = 0.018).

Conclusions: This study demonstrated that the aortic cross-clamping phase of CPB cardiac surgery is associated with lower values of tissue saturation and a decreased rate of saturation recovery under both propofol and sevoflurane anaesthesia. Aortic cross-clamp release is followed by accelerated tissue desaturation during VOT. Propofol anaesthesia for CPB cardiac surgery results in greater reduction of nadir tissue saturation during the ischaemic phase of VOT in comparison to that of sevoflurane.

Trial Registration Number: NCT02593448.