Influence of supraglottic airway device placement on cerebral hemodynamics

BACKGROUND: Supraglottic airway devices (SGDs) are of current use in anesthesia practice and in emergency conditions. It has been suggested that cerebral blood flow (CBF) can decrease after SGD insertion or cuff inflation; however, it is uncertain if this reduction is caused by the SGD or the anesthetic drugs utilized for the anesthetic procedure. During minor surgery we separated CBF measurements by an adequate time interval in order to measure the distinctive changes in cerebral hemodynamics associated with anesthesia induction, SGD insertion and cuff inflation. METHODS: Patients scheduled for minor surgery requiring general anesthesia and SGD placement were included. Middle cerebral artery mean flow velocity (FVm-mca) and the Pulsatility Index (PI) were measured through use of transcranial Doppler (TCD) at baseline, after anesthesia induction, SGD insertion and cuff inflation, once a steady cardiocirculatory state was reached and end tidal CO2 (etCO2) was within normal range. RESULTS : A total of 21 patients were included. Following anesthesia induction, in concomitance to a reduction in mean arterial pressure (MAP), there was a mean decrease in FVm-mca by 16.60 cm/s, P<0.005 and a mean increase in PI by 0.24, P<0.0015. MAP, FVm-mca and PI did not change significantly, neither after SGD placement (P>0.05), nor after SGD cuffing (P>0.05). CONCLUSIONS: SGD insertion and cuff inflation did not influence cerebral hemodynamics in anesthetized patients undergoing minor surgery. At normal etCO2 range, the CBF reduction with transient increase in PI was associated with anesthesia induction and not SGD insertion itself.