Brain measures of nociception using near-infrared spectroscopy in patients undergoing routine screening colonoscopy

Abstract

Colonoscopy is an invaluable tool for screening and diagnosis of many colonic diseases. For most colonoscopies, moderate sedation is used during the procedure. However, insufflation of the colon produces a nociceptive stimulus that is usually accompanied by facial grimacing/groaning while under sedation. The objective of the current study was to evaluate whether a nociceptive signal elicited by colonic insufflation could be measured from the brain. Seventeen otherwise healthy patients (age 54.8±9.1; 6 female) undergoing routine colonoscopy (i.e., no history of significant medical conditions) were monitored using near-infrared spectroscopy (NIRS). Moderate sedation was produced using standard clinical protocols for midazolam and meperidine, titrated to effect. NIRS data captured during the procedure was analyzed offline to evaluate the brains’ responses to nociceptive stimuli evoked by the insufflation events (defined by physician or observing patients’ facial responses). Analysis of NIRS data revealed a specific, reproducible prefrontal cortex activity corresponding to times when patients grimaced. The pattern of the activation is similar to that previously observed during nociceptive stimuli in awake healthy individuals, suggesting that this approach may be used to evaluate brain activity evoked by nociceptive stimuli under sedation, when there is incomplete analgesia. While some patients report recollection of procedural pain following the procedure, the effects of repeated nociceptive stimuli in surgical patients may contribute to postoperative changes including chronic pain. The results from this study indicate that NIRS may be a suitable technology for continuous nociceptive afferent monitoring in patients undergoing sedation and could have applications under sedation or anesthesia.

Using prerecorded hemodynamic response functions in detecting prefrontal pain response: a functional near-infrared spectroscopy study

“…[3][4][5] Previous work using fNIRS in studying pain mainly delineated a significant deoxygenation process (normally a decrease in HbO concentration) in the anterior prefrontal cortex (aPFC) in response to noxious stimuli, including cutaneous pain, [6][7][8] tooth pain, 9 and visceral pain. 10,11 Such observations are in line with recent reports of deactivations in aPFC blood oxygenation level-dependent (BOLD) signals following pain using functional magnetic resonance imaging (fMRI). [12][13][14][15] Our previous fNIRS studies reported that the hemodynamic response to noxious stimuli was stronger than the response to innocuous stimuli with regard to peak amplitude changes 6 and that the HbO decrease is most strongly present in the medial portion of the aPFC.…”

Frontal Lobe Hemodynamic Responses to Painful Stimulation: A Potential Brain Marker of Nociception

“…Providing adequate anesthesia during surgery is routine, but we do not have a good measure of nociceptive stimuli that may act on brain systems. Our prior report suggests that during anesthesia, activation of certain brain regions may take place during nociceptive stimulation[1]. Frontal lobe activation during nociceptive stimulus has been reported by others.…”

“…Furthermore, additional features may contribute to the observed signal including arousal (salience) or anxiety. (2) Potential Variability of Measures in a Clinical Setting : While we have reported on the use of NIRS in measuring pain under anesthesia[30] or sedation[1], there are still issues related to the measures of evoked pain that need clarification including: 2.1. Habituation of a pain response; 2.2.…”

“…Here we wished to extend these findings using functional near infrared spectroscopy (fNIRS) with more complete coverage of the frontal lobe in order to determine an optimal frontal area in which such signals are most easily defined. As summarized in our prior report[1], frontal lobe activity is involved in nociceptive signaling. This has implications for placement of probes with regard to signal detection and ease of placement in conditions such as evaluation of pain in clinical conditions (e.g., under anesthesia).…”

“…As this light travels, it is altered by oxygenated and deoxygenated hemoglobin, which are among the dominant absorbers of near-infrared light in biological tissue [6]. The backscattered light is detected by photodiodes and through the application of the modified Beer-Lambert Law it is possible to calculate changes in cerebral concentrations of deoxygenated (HbR) and oxygenated (HbO) hemoglobin, as well as total hemoglobin concentration (HbT) [1]. …”