BIS Monitoring Flashcards
What are the different stages of anesthesia?
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.
Signs of Stage 1
Patient is in a twilight sleep, conscious sedation procedures, colonoscopy etc. some pt participation.
Signs of Stage 2
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.
Signs of Stage 3
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.
Recall & Awareness Definition
Recall- process of remembering or memory.
Awareness- refers to both consciousness (arousal and subj experience) and explicit recall (memory).
3 Means of Intraop awareness
1-insufficient anesth dose. 2- interruption of anesth delivery. 3- potential inherent anesth resistance (redheads, substance abuse).
When does awareness most occur during intraop phases?
Most during maintenance, less during induction, least during emergence.
What are the most at risk populations for awareness?
Trauma/unstable pts / obstetric emergency under GETA / cardiac cases under bypass
Categories of Risk Factors for Awareness: Patient conditions
trauma / hx of awareness / diff AW w/ multi ETT attempts / ASA status 3-5 / Rx resistance (benzo/opiod tolerance) / altered p450 metabolism (enzyme induced)
Categories of Risk Factors for Awareness: Procedures
Obstetric emergency under GETA / fiberoptic bronchoscopy / ermegency Sx / cardiac case under bypass
Categories of Risk Factors for Awareness: Others
operator error (vapor off) / equipment failure / TIVA interrupted / muscles relaxant during maintenance (indirect lowering of anesth dose) / N2)-opiod anesthesia
How is awareness detected?
Modified Brice questionnaire
EEG Wave Type
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.
What four components does BIS monitor examine?
Low frequency, high frequency beta activation, suppressed EEG waves, burst suppression.
Describe clinical ranges for anesthetic depths for BIS monitoring
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.
Categories Affecting BIS Values: medications
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.
Categories Affecting BIS Values: Medical Devices
Incr Value: pacemakers, forced air warmers, Sx navigation equipment, endoscopic shaver devices, electrocautery.
Categories Affecting BIS Values: Clinical Conditions
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.
What is a clinical scenario assoc with high BIS and HD instability?
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.
2006 Standards for Preventing Awareness
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.
Clinical strategies to minimize and address awareness.
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.
