Noninvasive neuromonitoring in the operating room and its role in the prevention of delirium.

Delirium is a frequent and serious complication after surgery. It has a variable incidence between 20% and 40% with the highest incidence in elderly people undergoing major or cardiac surgery. The development of postoperative delirium (POD) is associated with increased hospital stay lengths, morbidity, the need for home care, and mortality. Studies have appeared in the last decade that evaluate the use of noninvasive monitoring to prevent its development. The evaluation of the depth of anesthesia with processed EEG allows to avoid awareness and burst suppression events. The cessation of brain activity is associated with the development of delirium. Another noninvasive monitoring technique is NIRS for cerebral tissue hypoxia detection by measuring regional oxygen saturation. The reduction of this parameter does not seem to be associated with the development of POD but with postoperative cognitive dysfunction. There are few studies in the literature and with conflicting results on the use of the pupillometer and transcranial Doppler in predicting the development of postoperative delirium.

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 trans-cranial Doppler (TCD) at baseline, after anesthesia induction, SGD insertion and cuff inflation, once a steady cardio-circulatory 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.

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 trans-cranial Doppler (TCD) at baseline, after anesthesia induction, SGD insertion and cuff inflation, once a steady cardio-circulatory 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). CONCLUSION: 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.