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ICU SKILLS UPDATE February/March 2007 By Dianne Brown
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Page 1: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

ICU SKILLS UPDATE

February/March 2007

By Dianne Brown

Page 2: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

ICU Skills Update

Theory and Hands On Practice

1. Bispectral Index Monitoring

Page 3: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BISPECTRAL INDEX MONITOTING

Page 4: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BISPECTRAL INDEX MONITORING

The bispectral index (BIS) is a fairly recent technology used to measure the effects of anesthetics and sedatives on the brain and consciousness

Uses a complex mathematical algorithm based upon descriptive EEG parameters from the frontal cortex to suggest various levels of sedation

Page 5: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BISPECTRAL INDEX MONITORING

A sensor, placed on the patient’s forehead, sends raw EEG waveforms to the monitor, where they are analyzed and a BIS index is calculated

This value ranges from 100 (completely awake) to 0 (isoelectric EEG)

Page 6: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BISPECTRAL INDEX MONITORING

Page 7: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BISPECTRAL INDEX MONITORING

Page 8: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.
Page 9: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Understanding the relationship between BIS and EEG

When BIS monitoring is initiated, a sensor is placed across the patient’s forehead per manufacturer’s recommendations to detect one channel of EEG activity

The EEG signal is filtered and digitalized The EEG state (frequency/amplitude) is

calculated and associated with the level of sedation, arousal or anesthesia

Page 10: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Understanding the relationship between BIS and EEG

The BIS value is a single number based on the previous 15 seconds of EEG data and is updated frequently

The BIS monitor provides a single channel of an EEG tracing from the right or left frontal-temporal montage electrode placement

Page 11: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

ICU Sedation: A Bipolar Challenge

Over-sedation Patient unable to

participate in care Delayed weaning ↑Ventilator-associated

pneumonia ↑Unnecessary testing ↑ICU and hospital

length of stay ↑Costs

Under-sedation Anxiety, agitation ↑Cost, nursing time ↑Use of neuromuscular

blocking agents ↑Risk of

recall/awareness of unpleasant events

↑Unintended medical device removal

Page 12: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Potential Indications for BIS Monitoring

Use with neuromuscular blockade: BIS monitoring may help to identify patients at risk of awareness, recall and pain when paralyzed

Use of BIS values to guide sedation and analgesia Titrating sedation/analgesia in patients receiving

controlled ventilation Avoiding extremes of under and over sedation Titration of medications for medication-induced

coma

Page 13: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Factors affecting the BIS value

Sedation: decrease in BIS value Analgesia: decrease in BIS value Neuromuscular blocking agents: decrease in

BIS value related to attenuation of high-frequency muscle activity across the patient’s forehead

Painful (noxious) stimulation: if analgesia inadequate, arousal response may be produced within cerebral cortex

Page 14: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Factors affecting the BIS value

Sleep: BIS range is lower (20-70) during deep sleep, and BIS range is higher (75-92) during REM sleep

Hypothermia: decrease in BIS value Cerebral ischemia: decrease in BIS value Neurological states: decrease in BIS value

depending of location of injury and degree to which overall cerebral metabolism is affected

Page 15: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Factors affecting the BIS value

Encephalopathic states: severe anoxic/ischemia encephalopathy (decrease in BIS value)

High-frequency electrical artifact from patient care equipment, such as pacemaker or muscle activity; rapid head or eye movement (increase in BIS value)

Page 16: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Interpretation of BIS value

BIS is interpreted over time, in response to stimulation and within the context of whether therapeutic endpoints and overall goals of therapy are met

Decisions to increase or decrease titration of sedative or analgesic should be based on clinical assessment/judgement, goals of therapy, and the BIS value

Page 17: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Interpretation of BIS value

Relying on BIS alone for sedation/analgesia management is not recommended

Movement such as in response to painful stimulation may occur with low BIS values

Page 18: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BIS increases suddenly or is higher than expected

Is 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?

Page 19: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BIS decreases suddenly or is lower than expected

Has been a decrease in stimulation?

Has patient recently received 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?

Page 20: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Current Status of the Literature

BIS scores do not provide a differential diagnosis. BIS scores can be affected by many cerebral events including sedation, sleep and cerebral ischemia

BIS/EEG activity can also be affected by age, temperature, PaCO2, hyper/hypo-glycemia, electroyte imbalances, hepatic or renal function, endocrine disorders

Page 21: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Current Status of the Literature BIS scores can be affected by many forms of

artifact:

- Artifact occurs with excessive muscle activity – movement, swallowing, blinking, shivering etc.

- Artifact can also occur with concomitant use of other electrical devices and monitoring equipment - EEG

Page 22: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Current Status of the Literature

Neuromuscular activity typically elevates BIS scores. Hence the effects of NMBAs or their metabolites may cause lower BIS scores as a result of decreased muscle activity and not decreased LOC

The synergistic action of agents affecting muscle relaxation must be considered when interpreting scores

Page 23: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Current Status of the Literature

Overall conflicting research results May predict recovery of consciousness related to

sedation and possibly traumatic brain injury Several studies have found variable correlations

between BIS scores and sedation scores BIS monitoring may serve as an adjunct measure to

subjective scales of sedation monitoring in ICU patients, particularly in patients who are heavily sedated or chemically paralyzed

Page 24: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Clinical Applications

BIS is only one part of a multi-modal assessment strategy

It remains unclear as to what BIS actually measures: Awareness? Hypnosis with recall? Delirium? Extent of brain injury, brain function or generalized cerebral electrical activity?

Page 25: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Clinical Applications

Only use trended scoresWhen interpreting results, consider

multiple factors including measurements error as well as the special/individual circumstances of each patient

Page 26: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

What the numbers mean

Page 27: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BIS Number

What the numbers mean:

0 = no electrical brain activity

100 = fully awake For moderate sedation, aim for range from 60-

70, below 60 is associated with a low probability of explicit recall

For deeper sedation, aim for range from 40-60. A patient with a BIS value of less than 45 is approaching a deep hypnotic state

Page 28: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

BIS Number

For a patient receiving neuromuscular blockage, sedation, analgesia therapy, the medication should be titrated for a BIS value between 45 and 60

Page 29: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

SQI: Signal Quality Index

What the numbers mean: 0 = poor quality

100 = excellent quality Aim for range from 80-100%

Page 30: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

EMG: Electromyographic Activity

Reflects the electrical power of muscle activity or artifact

What the numbers mean: the higher the number, the greater the muscle activity

- if the EMG is high, can make the number artificially high (it incorrectly reads the increased muscle activity as increased EEG activity

Acceptable EMG is less than 55 dB Optimal EMG is less than 30 dB

Page 31: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Electrode Placement

Prep skin with alcohol prior to electrode placement

Electrode should be changed every 24 hours, alternating temples daily

Look at electrode packaging for placement instructions

Page 32: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Electrode Placement

To ensure adequate placement and impedance, check on the screen

Page 33: ICU SKILLS UPDATE February/March 2007 By Dianne Brown.

Resources

Guidelines and Procedure available in AACN Procedural Manual for Critical Care, Procedure 86, page 699