BIS Monitoring

Question 1

What are the different stages of anesthesia?

Answer 1

Stage 1- induction until loss of consciousness. stage of analgesia/disorientation
Stage 2- loss of consciousness to onset of automatic breathing. stage of excitement/delirium.
Stage 3- Automatic breathing to respiratory paralysis. stage of surgical anesthesia.
Stage 4- respiratory paralysis until death. deep deep anesthesia, resp arrest and vasomotor collapse.

Question 2

Signs of Stage 1

Answer 2

Patient is in a twilight sleep, conscious sedation procedures, colonoscopy etc. some pt participation.

Question 3

Signs of Stage 2

Answer 3

Pt with no participation/cooperation. Contains hyperreactive AW, at risk for laryngospasm, vomit/aspiration risk. Eyelash reflex gone. Only see on emergence, not during induction.

Question 4

Signs of Stage 3

Answer 4

Consists of 4 planes. Plane 1-auto breathing, variable EOM, no swallowing reflex. Plane 2-no EOM, onset of ext IC paralysis, corneals gone, no larygneal reflex, loss of skin stim. Plane 3-desired plane for surgery, cont of ext IC paralysis, near loss of pupil reactivity. Plane 4- complete resp muscle paralysis.

Question 5

Recall & Awareness Definition

Answer 5

Recall- process of remembering or memory.

Awareness- refers to both consciousness (arousal and subj experience) and explicit recall (memory).

Question 6

3 Means of Intraop awareness

Answer 6

1-insufficient anesth dose. 2- interruption of anesth delivery. 3- potential inherent anesth resistance (redheads, substance abuse).

Question 7

When does awareness most occur during intraop phases?

Answer 7

Most during maintenance, less during induction, least during emergence.

Question 8

What are the most at risk populations for awareness?

Answer 8

Trauma/unstable pts / obstetric emergency under GETA / cardiac cases under bypass

Question 9

Categories of Risk Factors for Awareness: Patient conditions

Answer 9

trauma / hx of awareness / diff AW w/ multi ETT attempts / ASA status 3-5 / Rx resistance (benzo/opiod tolerance) / altered p450 metabolism (enzyme induced)

Question 10

Categories of Risk Factors for Awareness: Procedures

Answer 10

Obstetric emergency under GETA / fiberoptic bronchoscopy / ermegency Sx / cardiac case under bypass

Question 11

Categories of Risk Factors for Awareness: Others

Answer 11

operator error (vapor off) / equipment failure / TIVA interrupted / muscles relaxant during maintenance (indirect lowering of anesth dose) / N2)-opiod anesthesia

Question 12

How is awareness detected?

Answer 12

Modified Brice questionnaire

Question 13

EEG Wave Type

Answer 13

Beta- 13-30 Hz (light anesthesia) / Alpha 8-13 Hz (relaxation), both are high freq low amplitude. Theta 4-7 Hz (mod anesthesia, stg 3) / Delta 0.5-4 Hz (deep anesthesia, brain injury), both are low freq high amplitude. Burst suppression- poor prognosis, alternating high freq short periods of electrical suppression.

Question 14

What four components does BIS monitor examine?

Answer 14

Low frequency, high frequency beta activation, suppressed EEG waves, burst suppression.

Question 15

Describe clinical ranges for anesthetic depths for BIS monitoring

Answer 15

Awake = 85-100 / Light/Mod = 60-85 / General Anesthesia = 40-60 (want here) / Deep Hypnotic state = 20-40 / Burst Suppression = 0-20 (assoc with stage 4 anesthesia). BIS < 40 for 5+ min increases mortality.

Question 16

Categories Affecting BIS Values: medications

Answer 16

Incr Value: ketamine, etomidate (myoclonia), halothane, Ephedrine (SNS effect?) / Decr Value: NMB (abolish EMG), beta blockers (no SNS?), Alpha2 agonists (no SNS) / No change: N2O, opiods.

Question 17

Categories Affecting BIS Values: Medical Devices

Answer 17

Incr Value: pacemakers, forced air warmers, Sx navigation equipment, endoscopic shaver devices, electrocautery.

Question 18

Categories Affecting BIS Values: Clinical Conditions

Answer 18

Low Values: cardiac arrest, hypovolemia, hypotension, cerebral ischemia/hypoperfusion, hypoglycemia, hypothermia. / Low BIS d/t post ictal states, dementia, cerbral palsy, brain injury,tumor, brain death. High values with epilepsy.

Question 19

What is a clinical scenario assoc with high BIS and HD instability?

Answer 19

Unstable trauma patient. Cant use propofol, etc, prone to awareness/recall. If pt is unstable with a “deep” anesthetic profile, most likely have a physiologic problem.

Question 20

2006 Standards for Preventing Awareness

Answer 20

1-perform preop assessment to evaluate risk of awareness/recall. 2-use of multiple monitoring modalities to assess anesthetic depth. 3-utilize brain function monitoring. Weigh psych risks of awareness vs physio risks of anesthesia. Discuss expectations with pt preop.

Question 21

Clinical strategies to minimize and address awareness.

Answer 21

Pre-op - assess for risk, provide informed consent for high risk procedures. Intra-op - pre-med for amnesia, multiple modalities for assessing depth, re-amnesia for unintended consciousness. Post-op - assess for poss awareness, provide f/u care, report occurrence for quality assurance.