1、ICU SKILLS UPDATEFebruary/March 2007By Dianne BrownICU Skills UpdateTheory and Hands On PracticeBispectral Index MonitoringBISPECTRAL INDEX MONITOTINGBISPECTRAL INDEX MONITORINGThe bispectral index (BIS) is a fairly recent technology used to measure the effects of anesthetics and sedatives on the br

2、ain and consciousnessUses a complex mathematical algorithm based upon descriptive EEG parameters from the frontal cortex to suggest various levels of sedation BISPECTRAL INDEX MONITORINGA sensor, placed on the patients forehead, sends raw EEG waveforms to the monitor, where they are analyzed and a B

3、IS index is calculatedThis value ranges from 100 (completely awake) to 0 (isoelectric EEG)BISPECTRAL INDEX MONITORINGBISPECTRAL INDEX MONITORINGUnderstanding the relationship between BIS and EEGWhen BIS monitoring is initiated, a sensor is placed across the patients forehead per manufacturers recomm

4、endations to detect one channel of EEG activityThe EEG signal is filtered and digitalizedThe EEG state (frequency/amplitude) is calculated and associated with the level of sedation, arousal or anesthesiaUnderstanding the relationship between BIS and EEGThe BIS value is a single number based on the p

5、revious 15 seconds of EEG data and is updated frequentlyThe BIS monitor provides a single channel of an EEG tracing from the right or left frontal-temporal montage electrode placementICU Sedation: A Bipolar ChallengeOver-sedationPatient unable to participate in careDelayed weaning Ventilator-associa

6、ted pneumoniaUnnecessary testing ICU and hospital length of stayCostsUnder-sedationAnxiety, agitationCost, nursing timeUse of neuromuscular blocking agentsRisk of recall/awareness of unpleasant eventsUnintended medical device removalPotential Indications for BIS MonitoringUse with neuromuscular bloc

7、kade: BIS monitoring may help to identify patients at risk of awareness, recall and pain when paralyzedUse of BIS values to guide sedation and analgesiaTitrating sedation/analgesia in patients receiving controlled ventilationAvoiding extremes of under and over sedationTitration of medications for me

8、dication-induced comaFactors affecting the BIS valueSedation: decrease in BIS valueAnalgesia: decrease in BIS valueNeuromuscular blocking agents: decrease in BIS value related to attenuation of high-frequency muscle activity across the patients foreheadPainful (noxious) stimulation: if analgesia ina

9、dequate, arousal response may be produced within cerebral cortexFactors affecting the BIS valueSleep: BIS range is lower (20-70) during deep sleep, and BIS range is higher (75-92) during REM sleepHypothermia: decrease in BIS valueCerebral ischemia: decrease in BIS valueNeurological states: decrease

10、in BIS value depending of location of injury and degree to which overall cerebral metabolism is affectedFactors affecting the BIS valueEncephalopathic states: severe anoxic/ischemia encephalopathy (decrease in BIS value)High-frequency electrical artifact from patient care equipment, such as pacemake

11、r or muscle activity; rapid head or eye movement (increase in BIS value)Interpretation of BIS valueBIS is interpreted over time, in response to stimulation and within the context of whether therapeutic endpoints and overall goals of therapy are metDecisions to increase or decrease titration of sedat

12、ive or analgesic should be based on clinical assessment/judgement, goals of therapy, and the BIS valueInterpretation of BIS valueRelying on BIS alone for sedation/analgesia management is not recommendedMovement such as in response to painful stimulation may occur with low BIS valuesBIS increases sud

13、denly or is higher than expectedIs the sedative sufficient?Has the sedation been decreased?Is there an increase in stimulation?Is there any muscle shivering or pt motion?Is the NMBA wearing off?BIS decreases suddenly or is lower than expectedHas been a decrease in stimulation?Has patient recently re

14、ceived NMBA?Has there been an increase in sedation?Is the patient sleeping?Has the pt recently received analgesic?Has there been a sudden significant drop in BP?Current Status of the LiteratureBIS scores do not provide a differential diagnosis. BIS scores can be affected by many cerebral events incl

15、uding sedation, sleep and cerebral ischemiaBIS/EEG activity can also be affected by age, temperature, PaCO2, hyper/hypo-glycemia, electroyte imbalances, hepatic or renal function, endocrine disordersCurrent Status of the LiteratureBIS scores can be affected by many forms of artifact: - Artifact occu

16、rs with excessive muscle activity movement, swallowing, blinking, shivering etc. - Artifact can also occur with concomitant use of other electrical devices and monitoring equipment - EEGCurrent Status of the LiteratureNeuromuscular activity typically elevates BIS scores. Hence the effects of NMBAs o

17、r their metabolites may cause lower BIS scores as a result of decreased muscle activity and not decreased LOCThe synergistic action of agents affecting muscle relaxation must be considered when interpreting scoresCurrent Status of the LiteratureOverall conflicting research resultsMay predict recover

18、y of consciousness related to sedation and possibly traumatic brain injurySeveral studies have found variable correlations between BIS scores and sedation scoresBIS monitoring may serve as an adjunct measure to subjective scales of sedation monitoring in ICU patients, particularly in patients who ar

19、e heavily sedated or chemically paralyzedClinical ApplicationsBIS is only one part of a multi-modal assessment strategyIt remains unclear as to what BIS actually measures: Awareness? Hypnosis with recall? Delirium? Extent of brain injury, brain function or generalized cerebral electrical activity?Cl

20、inical ApplicationsOnly use trended scoresWhen interpreting results, consider multiple factors including measurements error as well as the special/individual circumstances of each patientWhat the numbers meanBIS NumberWhat the numbers mean: 0 = no electrical brain activity 100 = fully awakeFor moder

21、ate sedation, aim for range from 60-70, below 60 is associated with a low probability of explicit recallFor deeper sedation, aim for range from 40-60. A patient with a BIS value of less than 45 is approaching a deep hypnotic stateBIS NumberFor a patient receiving neuromuscular blockage, sedation, analgesia therapy, the medication should be titrated for a BIS value between 45 and 60SQI: Signal Quality IndexWhat the numbers mean: 0 = poor quality 100 = excellent qualityAim for range from 80-100%EMG: Electromyographic Activit