A 34-year-old woman with a history of maxillary carcinoma treated by proton therapy underwent partial maxillectomy under general anesthesia. Continuous quantitative EEG monitoring—using bispectral index (BIS), spectral edge frequency (SEF), and density spectral array (DSA)—revealed BIS 33 and SEF 12 Hz, with theta–delta dominance and no burst suppression.
This chapter demonstrates how anesthesiologists can interpret these indices synergistically, recognize early warning patterns such as falling SEF or emerging burst suppression, and titrate anesthetics precisely to avoid both intraoperative awareness and excessive cortical suppression. The discussion integrates cellular neurophysiology, pharmacologic influences, and practical algorithms for real-time intraoperative decision-making.
At the end of this chapter, the reader should be able to:
Define SEF and Burst Suppression Ratio (BSR) and explain their physiologic basis.
Interpret BIS, SEF, and DSA in an integrated framework for anesthetic depth assessment.
Recognize the EEG hallmarks of burst suppression and manage excessive cortical suppression.
Apply SEF trends and DSA color evolution to anticipate emergence.
Understand how prior proton therapy or cerebral vulnerability alters EEG response to anesthetics.
During partial maxillectomy, the anesthesiologist noted BIS 33 and a steady SEF decline from 14 → 10 Hz over ten minutes. The DSA showed a blue–green theta–delta pattern without visible suppression. The patient, previously irradiated, was mildly hypocapnic (EtCO₂ = 30 mmHg). Small reductions in sevoflurane (from 2.3 % → 1.8 %) and restoration of normocapnia normalized SEF to 12–13 Hz. The case remained hemodynamically stable, and emergence was prompt.
This example illustrates how SEF trend analysis—a numeric reflection of cortical slowing—can pre-empt the onset of burst suppression and optimize anesthetic titration.
References
Johansen JW, Sebel PS. Development and clinical application of electroencephalographic bispectrum monitoring. Anesthesiology. 2000;93(5):1336-44.
Brown EN, Purdon PL, Van Dort CJ. General anesthesia and altered states of arousal: A systems neuroscience analysis. Annu Rev Neurosci. 2011;34:601-28.
Patient: 34-year-old female; previous endoscopic resection + proton beam therapy for left maxillary carcinoma.
Procedure: Partial maxillectomy.
Anesthesia:
Fentanyl 200 µg IV
Midazolam 1 mg IV
Propofol 200 mg IV bolus
Cisatracurium 10 mg IV bolus → 10 mg q30 min
Sevoflurane maintenance EtSevo ≈ 2.35 %, MAC ≈ 1.1
Monitoring: Philips IntelliVue (vitals); Covidien BIS/DSA.
Intraoperative Data: BIS 33, SEF 12 Hz, EtCO₂ 30 mmHg, MAP 79 mmHg, DSA theta–delta dominance with no suppression.
References
3. Pilge S, Zanner R, Schneider G, Kreuzer M, Kochs EF. Time delay of electroencephalogram index calculation: Analysis of cerebral state, bispectral, and narcotrend indices. Anesthesiology. 2006;104(3):488-94.
Definition and Calculation
The SEF95 represents the frequency below which 95 % of total EEG power resides. It summarizes the distribution of EEG energy: high SEF reflects predominance of faster (beta) activity, while...
