Week 7 - Awareness

Question 1

What are the two interpretations on why awareness during anesthesia occurs?

Answer 1

A “conservative” one: anesthesiologists’ error, too light a level of anesthesia, and rare resistance to anesthetic effects

A “liberal” one: occasional reports of awareness are “tip of the iceberg”

Question 2

What are the various awareness situations?

Answer 2

• Awareness/responsiveness without subsequent recall
• Recall without responsiveness
• Unconscious retention without conscious recall

Question 3

What might awareness produce?

Answer 3

“Traumatic Neurotic Syndrome” / PTSD with:

• nightmares
• irritability
• anxiety
• preoccupation with death

Question 4

What perception is the most common during awareness under anesthesia?

Answer 4

Auditory – OR sounds and conversations

*pain, other body sensations are less common

Question 5

What surgeries have higher incidences of awareness?

Answer 5

Surgeries involving lighter anesthesia

• Obstetric surgery (c-section)
• Cardiopulmonary bypass surgery
• Major trauma

Question 6

What characteristic are suggested to increase awareness?

Answer 6

• Heavy use of alcohol and other drugs
• Pain patients on high doses of opioids
• Limited hemodynamic reserve
• ASA status 4 or 5
• History of intraoperative awareness
• History of difficult intubation
• Childhood
• Obesity (?)

Question 7

What are some associated experiences of awareness during and after anesthesia?

Answer 7

During:

• inability to move
• helplessness and weakness
• hearing noises and voices

Persistence of complaints after of:

• sleep disturbances
• fear of future anesthetics

Question 8

What are 10 suggestions to help prevent awareness during anesthesia?

Answer 8

• Check the delivery of anesthetic agents to the patient
• Consider premedicating with amnesics
• Give adequate doses of induction agents
• Avoid muscle paralysis unless it is needed and even then avoid total paralysis
• Supplement N2O and opioid anesthesia with at least 0.6 MAC of volatile agent
• Administer at least 0.8-1 MAC when volatile agents are used alone
• Use amnesics when light anesthesia is the only regimen which can be tolerated by the patient
• Inform the patient about the possibility of awareness and prevent hearing of OR sounds
• Teaching and research
• Development of an awareness monitor

*muscle relaxants alone can produce BIS values indicating unconsciousness

Question 9

What are the 5 memoranda for management of an awareness event?

Answer 9

1. Detailed interview with the patient (verify account, sympathize, try to explain what happened, reassure pt about non-repetition in the future, apologize)
2. Interview should be recorded in the patients chart
3. Inform the patient’s surgeon, nurse, and hospital lawyer
4. Visit the patient daily during hospital stay and keep in contact by telephone afterwards
5. Don’t delay referral to a psychologist or psychiatrist

Question 10

What type of EEG is useful for monitoring for awareness during anesthesia?

Answer 10

Processed EEG is more useful than raw EEG

• raw EEG has too much data and no readily observable indicators of awareness
• many processed EEG measures can be derives

Question 11

What are examples of processed EEG monitors?

Answer 11

• BIS (Covidien)
• Entropy (GE Healthcare)
• Narcotrend (MonitorTechnik)
• Patient State Index, SEDLine (Masimo)
• SNAPII (Stryker)
• Cerebral State Monitor (Danmeter)