Near-infrared spectroscopy for the evaluation of anesthetic depth

Abstract

The standard-of-care guidelines published by the American Society of Anesthesiologists (ASA) recommend monitoring of pulse oximetry, blood pressure, heart rate, and end tidal CO2 during the use of anesthesia and sedation. This information can help to identify adverse events that may occur during procedures. However, these parameters are not specific to the effects of anesthetics or sedatives, and therefore they offer little, to no, real time information regarding the effects of those agents and do not give the clinician the lead-time necessary to prevent patient "awareness." Since no "gold-standard" method is available to continuously, reliably, and effectively monitor the effects of sedatives and anesthetics, such a method is greatly needed. Investigation of the use of functional near-infrared spectroscopy (fNIRS) as a method for anesthesia or sedation monitoring and for the assessment of the effects of various anesthetic drugs on cerebral oxygenation has started to be conducted. The objective of this paper is to provide a thorough review of the currently available published scientific studies regarding the use of fNIRS in the fields of anesthesia and sedation monitoring, comment on their findings, and discuss the future work required for the translation of this technology to the clinical setting.

Figure 1

Effect of bolus propofol induction (200 mg) on [Hb], [HbO₂], and [HbTot]. (a) Time before induction and (b) time after induction. Data collected from a 31-year-old female patient undergoing a laparoscopic hysterectomy. (G. Hernandez-Meza, personal communications, July 22, 2015, School of Biomedical Engineering, Science and Health Systems at Drexel University, Philadelphia, PA 19104).

Figure 2

Example of the effect of changes in position on female patient (58 years old) during laparoscopic salpingo-oophorectomy using general anesthesia with 2.4% sevoflurane. (a) Response of Hb, HbO₂, and HbTot during transition from (1) supine position to (2) Trendelenburg position. (b) Transition from (3) Trendelenburg position to (4) supine position. (G. Hernandez-Meza, personal communications, July 22, 2015, School of Biomedical Engineering, Science and Health Systems at Drexel University, Philadelphia, PA 19104).

Figure 3

Continuous recording of fNIRS signal response during the transition from maintenance to emergence in a 62-year-old male patient. (a) Maintenance with 2% sevoflurane, (b) anesthetic removal, and (c) response 1 minute before the patient started moving. (G. Hernandez-Meza, personal communications, July 22, 2015, School of Biomedical Engineering, Science and Health Systems at Drexel University, Philadelphia, PA 19104).