BIS - Revision history

WikiSysop at 15:38, 11 November 2025

2025-11-11T15:38:43Z

← Older revision		Revision as of 15:38, 11 November 2025
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	There is potential value in monitoring the ''<u>waveform</u>'' of the BIS monitor. Figure 1 describes common EEG frequency bands, which can be seen by observing the processed EEG waveform. In an appropriately anesthetized patient under general anesthesia, the EEG waveform should be dominated by Delta waves (1-4 Hz), Theta Waves (4-8 Hz), and Alpha waves (8-12 Hz).<ref name=":1">Chen, M., & ShangGuan, W. (2022). Monitoring anesthesia: Electroencephalography and beyond. In ''Features and Assessments of Pain, Anaesthesia, and Analgesia'' (pp. 79-89). Elsevier. <nowiki>https://doi.org/10.1016/B978-0-12-818988-7.00025-X</nowiki></ref> Beta waves (12-30 Hz) are found in wakeful patients.<ref name=":1" />		There is potential value in monitoring the ''<u>waveform</u>'' of the BIS monitor. Figure 1 describes common EEG frequency bands, which can be seen by observing the processed EEG waveform. In an appropriately anesthetized patient under general anesthesia, the EEG waveform should be dominated by Delta waves (1-4 Hz), Theta Waves (4-8 Hz), and Alpha waves (8-12 Hz).<ref name=":1">Chen, M., & ShangGuan, W. (2022). Monitoring anesthesia: Electroencephalography and beyond. In ''Features and Assessments of Pain, Anaesthesia, and Analgesia'' (pp. 79-89). Elsevier. <nowiki>https://doi.org/10.1016/B978-0-12-818988-7.00025-X</nowiki></ref> Beta waves (12-30 Hz) are found in wakeful patients.<ref name=":1" />

			[[File:EEG figure-1.jpeg\|thumb\|Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state. Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.]]

	In order to observe and interpret the unfiltered waveform, users of the BIS must de-select "Filters" from the BIS module menu on their monitor. Then, two things can be observed to suggest that the waveform is consistent with general anesthesia. First, there should be the presence of slow waves / Delta waves, lasting 0.25-1 seconds (1-4 Hz) in duration. Second, there should be an absence of high frequency waves (Beta waves, 12-30 Hz). If both of these criteria are met, the BIS waveform is suggesting that the patient is appropriately anesthetized. In most cases, the BIS numerical reading will match this interpretation, but the number can be skewed by some confounders, such as EMG artifact (especially in patients without neuromuscular blockade) and use of ketamine in the anesthetic, leading to a falsely high numerical reading that can be differentiated from "light depth of anesthesia" by observing the BIS waveform.		In order to observe and interpret the unfiltered waveform, users of the BIS must de-select "Filters" from the BIS module menu on their monitor. Then, two things can be observed to suggest that the waveform is consistent with general anesthesia. First, there should be the presence of slow waves / Delta waves, lasting 0.25-1 seconds (1-4 Hz) in duration. Second, there should be an absence of high frequency waves (Beta waves, 12-30 Hz). If both of these criteria are met, the BIS waveform is suggesting that the patient is appropriately anesthetized. In most cases, the BIS numerical reading will match this interpretation, but the number can be skewed by some confounders, such as EMG artifact (especially in patients without neuromuscular blockade) and use of ketamine in the anesthetic, leading to a falsely high numerical reading that can be differentiated from "light depth of anesthesia" by observing the BIS waveform.
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	[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]		[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]
	[[File:EEG figure-1.jpeg\|thumb\|Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state. Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.]]

Nandrad1: Added additional information about waveform frequencies and visual interpretation of processed EEG waveform

2025-11-11T14:59:08Z

Added additional information about waveform frequencies and visual interpretation of processed EEG waveform

← Older revision		Revision as of 14:59, 11 November 2025
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	{{Stub Notice}}		{{Stub Notice}}

	Processed EEG monitor, translating EEG waves into a numeric scale ranging from 0 (complete EEG suppression) to 100 (fully awake). It is said that adequate anesthesia may be present with a BIS value of 40-60. Studies have shown that intraoperative BIS, compared to clinical signs, may have a reduction of intraoperative awareness (OR) 0.36, 95% CI 0.21 to 0.60; I2 = 61%; 27 studies; 9765 participants<ref name=":0">https://pubmed.ncbi.nlm.nih.gov/31557307/</ref>, time to eye opening, time to orientation, and time to discharge patient from PACU<ref name=":0" />. However, BIS guided anesthesia did not show a clinical difference to anesthesia guided by end tidal anesthetic gas concentration (ETAC). Furthermore, studies show that neuromuscular blockade alone, without other anesthetics, decrease the value of BIS.<ref>Schuller PJ, Newell S, Strickland PA, Barry JJ. Response of bispectral index to neuromuscular block in awake volunteers. Br J Anaesth. 2015 Jul;115 Suppl 1:i95-i103.</ref> Therefore, the accuracy and reliability of BIS are ~~questionable~~.		Processed EEG monitor, translating EEG waves into a numeric scale ranging from 0 (complete EEG suppression) to 100 (fully awake). It is said that adequate anesthesia may be present with a BIS value of 40-60. Studies have shown that intraoperative BIS, compared to clinical signs, may have a reduction of intraoperative awareness (OR) 0.36, 95% CI 0.21 to 0.60; I2 = 61%; 27 studies; 9765 participants<ref name=":0">https://pubmed.ncbi.nlm.nih.gov/31557307/</ref>, time to eye opening, time to orientation, and time to discharge patient from PACU<ref name=":0" />. However, BIS guided anesthesia did not show a clinical difference to anesthesia guided by end tidal anesthetic gas concentration (ETAC). Furthermore, studies show that neuromuscular blockade alone, without other anesthetics, decrease the value of BIS.<ref>Schuller PJ, Newell S, Strickland PA, Barry JJ. Response of bispectral index to neuromuscular block in awake volunteers. Br J Anaesth. 2015 Jul;115 Suppl 1:i95-i103.</ref> Therefore, the accuracy and reliability of BIS are debated.

			There is potential value in monitoring the ''<u>waveform</u>'' of the BIS monitor. Figure 1 describes common EEG frequency bands, which can be seen by observing the processed EEG waveform. In an appropriately anesthetized patient under general anesthesia, the EEG waveform should be dominated by Delta waves (1-4 Hz), Theta Waves (4-8 Hz), and Alpha waves (8-12 Hz).<ref name=":1">Chen, M., & ShangGuan, W. (2022). Monitoring anesthesia: Electroencephalography and beyond. In ''Features and Assessments of Pain, Anaesthesia, and Analgesia'' (pp. 79-89). Elsevier. <nowiki>https://doi.org/10.1016/B978-0-12-818988-7.00025-X</nowiki></ref> Beta waves (12-30 Hz) are found in wakeful patients.<ref name=":1" />

			In order to observe and interpret the unfiltered waveform, users of the BIS must de-select "Filters" from the BIS module menu on their monitor. Then, two things can be observed to suggest that the waveform is consistent with general anesthesia. First, there should be the presence of slow waves / Delta waves, lasting 0.25-1 seconds (1-4 Hz) in duration. Second, there should be an absence of high frequency waves (Beta waves, 12-30 Hz). If both of these criteria are met, the BIS waveform is suggesting that the patient is appropriately anesthetized. In most cases, the BIS numerical reading will match this interpretation, but the number can be skewed by some confounders, such as EMG artifact (especially in patients without neuromuscular blockade) and use of ketamine in the anesthetic, leading to a falsely high numerical reading that can be differentiated from "light depth of anesthesia" by observing the BIS waveform.

	[https://www.ncbi.nlm.nih.gov/books/NBK539809/ StartPearls: BIS]		[https://www.ncbi.nlm.nih.gov/books/NBK539809/ StartPearls: BIS]

WikiSysop at 14:34, 11 November 2025

2025-11-11T14:34:16Z

← Older revision		Revision as of 14:34, 11 November 2025
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	[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]		[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]
	[[File:EEG figure-1.jpeg\|thumb\|Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state. Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.]]		[[File:EEG figure-1.jpeg\|thumb\|Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state. Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.]]
	~~EEG_figure-1.jpeg~~

	~~Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state.~~
	~~Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.~~

WikiSysop at 14:33, 11 November 2025

2025-11-11T14:33:45Z

← Older revision		Revision as of 14:33, 11 November 2025
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	[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]		[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]
	[[File:EEG figure-1.jpeg\|thumb]]		[[File:EEG figure-1.jpeg\|thumb\|Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state. Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.]]
	EEG_figure-1.jpeg		EEG_figure-1.jpeg

	Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state.		Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state.
	Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.		Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.

WikiSysop at 14:32, 11 November 2025

2025-11-11T14:32:12Z

← Older revision		Revision as of 14:32, 11 November 2025
Line 10:		Line 10:

	[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]		[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]
			[[File:EEG figure-1.jpeg\|thumb]]
	EEG_figure-1.jpeg		EEG_figure-1.jpeg

	Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state.		Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state.
	Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.		Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.

WikiSysop at 14:30, 11 November 2025

2025-11-11T14:30:19Z

← Older revision		Revision as of 14:30, 11 November 2025
Line 10:		Line 10:

	[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]		[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]

			EEG_figure-1.jpeg

			Figure 1 - EEG frequency bands from slow to fast and how they relate to mental state.
			Brain wave frequency is measured in Hertz (Hz), which is the number of waves per second.

WikiSysop at 12:23, 18 August 2025

2025-08-18T12:23:52Z

← Older revision		Revision as of 12:23, 18 August 2025
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	[https://pubmed.ncbi.nlm.nih.gov/37918790/ Effect of BIS-guided anesthesia on emergence delirium following general anesthesia in children: A prospective randomized controlled trial]		[https://pubmed.ncbi.nlm.nih.gov/37918790/ Effect of BIS-guided anesthesia on emergence delirium following general anesthesia in children: A prospective randomized controlled trial]

			[https://pubmed.ncbi.nlm.nih.gov/34465469/ Anaesthetic depth and delirium after major surgery: a randomised clinical trial]

WikiSysop at 12:22, 18 August 2025

2025-08-18T12:22:58Z

← Older revision		Revision as of 12:22, 18 August 2025
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	[https://www.anaestheasier.com/bispectral-index-bis/ Anaestheasier: Bispectral Index (BIS) and depth of anaesthesia monitoring]		[https://www.anaestheasier.com/bispectral-index-bis/ Anaestheasier: Bispectral Index (BIS) and depth of anaesthesia monitoring]

			[https://pubmed.ncbi.nlm.nih.gov/37918790/ Effect of BIS-guided anesthesia on emergence delirium following general anesthesia in children: A prospective randomized controlled trial]

WikiSysop at 12:18, 28 September 2024

2024-09-28T12:18:40Z

← Older revision		Revision as of 12:18, 28 September 2024
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	[https://www.ncbi.nlm.nih.gov/books/NBK539809/ StartPearls: BIS]		[https://www.ncbi.nlm.nih.gov/books/NBK539809/ StartPearls: BIS]

			[https://www.anaestheasier.com/bispectral-index-bis/ Anaestheasier: Bispectral Index (BIS) and depth of anaesthesia monitoring]

WikiSysop at 18:32, 8 August 2024

2024-08-08T18:32:57Z

← Older revision		Revision as of 18:32, 8 August 2024
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	Processed EEG monitor, translating EEG waves into a numeric scale ranging from 0 (complete EEG suppression) to 100 (fully awake). It is said that adequate anesthesia may be present with a BIS value of 40-60. Studies have shown that intraoperative BIS, compared to clinical signs, may have a reduction of intraoperative awareness (OR) 0.36, 95% CI 0.21 to 0.60; I2 = 61%; 27 studies; 9765 participants<ref name=":0">https://pubmed.ncbi.nlm.nih.gov/31557307/</ref>, time to eye opening, time to orientation, and time to discharge patient from PACU<ref name=":0" />. However, BIS guided anesthesia did not show a clinical difference to anesthesia guided by end tidal anesthetic gas concentration (ETAC). Furthermore, studies show that neuromuscular blockade alone, without other anesthetics, decrease the value of BIS.<ref>Schuller PJ, Newell S, Strickland PA, Barry JJ. Response of bispectral index to neuromuscular block in awake volunteers. Br J Anaesth. 2015 Jul;115 Suppl 1:i95-i103.</ref> Therefore, the accuracy and reliability of BIS are questionable.		Processed EEG monitor, translating EEG waves into a numeric scale ranging from 0 (complete EEG suppression) to 100 (fully awake). It is said that adequate anesthesia may be present with a BIS value of 40-60. Studies have shown that intraoperative BIS, compared to clinical signs, may have a reduction of intraoperative awareness (OR) 0.36, 95% CI 0.21 to 0.60; I2 = 61%; 27 studies; 9765 participants<ref name=":0">https://pubmed.ncbi.nlm.nih.gov/31557307/</ref>, time to eye opening, time to orientation, and time to discharge patient from PACU<ref name=":0" />. However, BIS guided anesthesia did not show a clinical difference to anesthesia guided by end tidal anesthetic gas concentration (ETAC). Furthermore, studies show that neuromuscular blockade alone, without other anesthetics, decrease the value of BIS.<ref>Schuller PJ, Newell S, Strickland PA, Barry JJ. Response of bispectral index to neuromuscular block in awake volunteers. Br J Anaesth. 2015 Jul;115 Suppl 1:i95-i103.</ref> Therefore, the accuracy and reliability of BIS are questionable.

			[https://www.ncbi.nlm.nih.gov/books/NBK539809/ StartPearls: BIS]