New Study Suggests That Masimo SedLine® Brain Function Monitoring May Aid Early Identification of Patients at Risk of Developing Postoperative Delirium

Masimo (NASDAQ: MASI) today announced the findings of a prospective study published in Anesthesia & Analgesia in which Dr. Claudia Spies and colleagues investigated the relationship between parameters derived from electroencephalogram (EEG) spectra, measured using Masimo SedLine^® Brain Function Monitoring, and postoperative delirium (POD) in older patients undergoing elective surgery.

The researchers found that the incidence of POD correlated with several spectral dynamics, in particular spectral edge frequency (SEF), suggesting that such EEG-based markers may help in early identification of patients at risk of developing POD.¹

POD is a frequent complication in geriatric patients, often associated with worse short- and long-term outcomes and long-term cognitive dysfunction. Noting that the incidence of POD is associated with prolonged EEG burst suppression during general anesthesia, the researchers sought to investigate whether specific preoperative, preexisting EEG signatures might be related to a higher risk of developing POD.

The investigators enrolled 237 patients ≥ 65 years scheduled for elective surgery of at least 60 minutes at the Charité-Universitätsmedizin Berlin (Campus Virchow Klinikum and Campus Mitte) between November 2014 and December 2016. Using Masimo Root^® with SedLine, frontal EEGs were recorded from before induction of anesthesia until return of consciousness. The researchers used the SedLine data to analyze a variety of EEG-derived parameters, including SEF (the frequency below which 95% of the power in the EEG is located), Patient State Index (a processed EEG parameter related to the effect of anesthetic agents), and duration of burst suppression, and also performed multitaper spectral analyses to calculate overall frontal power spectra across various frequency bands. Screening for POD was performed twice every day until the seventh day after surgery (or until hospital discharge) based on a variety of standard criteria, including the Nursing Delirium Screening Scale and Confusion Assessment Method. Patients with one or more positive screenings were classed as POD patients, and the remaining ones as NoPOD patients.

Of the 237 patients, 41 (17%) developed POD. The researchers found that two aspects of the preoperative EEG of POD patients was associated with lower values: SEF (POD group: 13.1 ± 4.6 Hz; NoPOD group: 17.4 ± 6.9 Hz; p = 0.002) and γ-band power (POD: -24.33 ± 2.8 dB; NoPOD: -17.9 ± 4.81 dB). Postinduction absolute α-band power was also significantly lower: POD: -7.37 ± 4.52 dB; NoPOD: -5 ± 5.03 dB. In POD patients, the ratio of preoperative to postinduction SEF was ~1; in NoPOD patients it was > 1, indicative of a slowing EEG with loss of consciousness. Finally, POD was independently associated with preoperative SEF (p = 0.025, odds ratios = 0.892, 95% CI 0.808 – 0.986), preoperative γ-band power (p = 0.029, OR = 0.568, 95% CI 0.342 – 0.944) and SEF ratio (p = 0.009, OR = 0.108, 95% CI (0.021 – 0.568).

The researchers concluded, “Lower preoperative SEF, absence of slowing in EEG while transitioning from preoperative state to unconscious state, and lower EEG power in relevant frequency bands in both these states are related to POD development. These findings may suggest an underlying pathophysiology and might be used as EEG-based marker for early identification of patients at risk to develop POD.”

The authors also noted, “Preoperative spectral EEG signatures and reduced EEG dynamics at loss of consciousness are associated with the development of POD in older patients, where changes in EEG signatures are most likely related to reduced GABA-ergic neuronal activation in POD patients. These findings can be described as predisposing EEG factors for POD, which might be used as a potential EEG-based marker for early identification of patients at risk to develop POD.”

David Drover, MD, Professor of Anesthesiology at Stanford Health Care, commented, “This study not only further supports existing knowledge but expands our understanding of how brain function monitoring can help clinicians improve postoperative outcomes in the elderly patient.”

Postoperative delirium is an acute state of mental confusion characterized by alterations in attention, consciousness, and disorganized thinking. A common and serious complication, POD afflicts up to 60% of patients after major surgery,^2-5 is most common in the elderly,^2-5 and occurs in up to 91% of the critically ill.⁶ POD is associated both with worse short- and long-term outcomes and higher costs,^3,6-9 and numerous medical bodies—including the American Society of Anesthesiologists (ASA), the United Kingdom National Institute for Health and Care Excellence, the American Geriatric Society, and the American College of Surgeons—have made the prevention of POD a public health priority.^10-13 The ASA’s Brain Health Initiative, dedicated to minimizing the impact of pre-existing cognitive deficits and optimizing the cognitive recovery and perioperative experience for adults 65 years and older undergoing surgery, describes POD as a “major public health issue.”¹⁴ The incidence of POD has been associated both with preoperative vulnerabilities and—of key importance to studies such as this—the cumulative duration of intraoperative EEG burst suppression. As numerous studies have found, processed EEG monitoring during surgery, by helping clinicians minimize the duration of burst suppression, may lower the rate of POD.^15-19