En
doscopic proce
dures performe
d in the Unite
d States routinely involve the use of conscious se
dation as stan
dar
d of care. The use of se
dation re
duces patient
discomfort an
d anxiety while improving the technical quality of the proce
dure, an
d as a result, over 98% of clinicians have a
dopte
d the practice. The tremen
dous benefits of se
dation are offset by heightene
d costs, increase
d patient
discharge time, an
d car
diopulmonary complication risks. The inherent liabilities of putting patients un
der se
dation have necessitate
d a large number of physiological monitoring systems in or
der to ensure patient comfort an
d safety. Currently American Society of Anesthesiologist (ASA) gui
delines recommen
d monitoring of pulse oximetry, bloo
d pressure, heart rate, an
d en
d-ti
dal CO
2; although important safeguar
ds, these physiological measurements
do not allow for the reliable assessment of patient se
dation. Proper monitoring of patient state ensures proce
dure quality an
d patient safety; however no 鈥済ol
d-stan
dar
d鈥?is available to
determine the
depth of se
dation which is comparable to the anesthesiologist's professional ju
dgment.
Developments in functional near-infrared spectroscopy (fNIRS) over the past two decades have introduced cost-effective, portable, and non-invasive neuroimaging tools which measure cortical hemodynamic activity as a correlate of neural functions. Anesthetic drugs, such as propofol, operate by suppressing cerebral metabolism. fNIRS imaging methods have the ability to detect these drug related effects as well as neuronal activity through the measurement of local cerebral hemodynamic changes.
In the present study, 41 patients were continuously monitored using fNIRS while undergoing outpatient elective colonoscopy with propofol sedation. The preliminary results indicated that oxygenated hemoglobin changes in the dorsolateral prefrontal cortex, as assessed by fNIRS were correlated with changes in response to bolus infusions of propofol, whereas other standard physiological measures were not significantly associated.