Impact of stepwise hyperventilation on cerebral tissue oxygen saturation in anesthetized patients: a mechanistic study.

Background: While the decrease in blood carbon dioxide (CO2 ) secondary to hyperventilation is generally accepted to play a major role in the decrease of cerebral tissue oxygen saturation (SctO2 ), it remains unclear if the associated systemic hemodynamic changes are also accountable.

Methods: Twenty-six patients (American Society of Anesthesiologists I-II) undergoing nonneurosurgical procedures were anesthetized with either propofol-remifentanil (n = 13) or sevoflurane (n = 13). During a stable intraoperative period, ventilation was adjusted stepwise from hypoventilation to hyperventilation to achieve a progressive change in end-tidal CO2 (ETCO2 ) from 55 to 25 mmHg.

Deep tissue fluorescence imaging and in vivo biological applications.

We describe a novel technical approach with enhanced fluorescence detection capabilities in twophoton microscopy that achieves deep tissue imaging, while maintaining micron resolution. Compared to conventional two-photon microscopy, greater imaging depth is achieved by more efficient harvesting of fluorescence photons propagating in multiple-scattering media. The system maintains the conventional two-photon microscopy scheme for excitation.

Tissue phantoms in multicenter clinical trials for diffuse optical technologies.

Tissue simulating phantoms are an important part of instrumentation validation, standardization/training and clinical translation. Properly used, phantoms form the backbone of sound quality control procedures. We describe the development and testing of a series of optically turbid phantoms used in a multi-center American College of Radiology Imaging Network (ACRIN) clinical trial of Diffuse Optical Spectroscopic Imaging (DOSI).

Impact of phenylephrine administration on cerebral tissue oxygen saturation and blood volume is modulated by carbon dioxide in anaesthetized patients.

Background: Multiple studies have shown that cerebral tissue oxygen saturation (Sct(O(2))) is decreased after phenylephrine treatment. We hypothesized that the negative impact of phenylephrine administration on Sct(O(2)) is affected by arterial blood carbon dioxide partial pressure (Pa(CO(2))) because CO(2) is a powerful modulator of cerebrovascular tone.

Methods: In 14 anaesthetized healthy patients, i.

Head-up tilt and hyperventilation produce similar changes in cerebral oxygenation and blood volume: an observational comparison study using frequency-domain near-infrared spectroscopy.

Purpose: During anesthesia, maneuvers which cause the least disturbance of cerebral oxygenation with the greatest decrease in intracranial pressure would be most beneficial to patients with intracranial hypertension. Both head-up tilt (HUT) and hyperventilation are used to decrease brain bulk, and both may be associated with decreases in cerebral oxygenation. In this observational study, our null hypothesis was that the impact of HUT and hyperventilation on cerebral tissue oxygen saturation (SctO2) and cerebral blood volume (CBV) are comparable.