The document discusses explicit and implicit memory, as well as awareness during general anesthesia. It notes that awareness ranges from 0.01-2% depending on the surgery and can result from an imbalance between anesthetic requirement and delivery. It provides strategies to prevent awareness, including proper training, identifying at-risk patients, monitoring equipment, administering adequate doses, and responding quickly to signs of inadequate anesthesia. EEG monitors like BIS and Entropy can also be used to measure the depth of anesthesia, though they have limitations and don't eliminate the risk of awareness.

1. By
Abdelrahman Mahmoud Soliman

2.  Explicit memory—Conscious recollection of
previous experiences (“awareness” is evidence
of explicit memory).
 Implicit memory—Changes in performance or
behavior that are produced by previous
experiences but without any conscious
recollection of those experiences
(“unconscious memory formation” during
general anesthesia)

3.  Awareness—Postoperative recall of events
occurring during general anesthesia.
 Dreaming—Any experience (excluding
awareness) that patients are able to recall
postoperatively that they think occurred
during general anesthesia and that they
believe is dreaming.

4.  Incidence of awareness ranges from 0.01- 2%
in different studies according to type of
surgery and anesthetics.
 1 in 100 in cardiac surgery
 1 in 20 in trauma surgery
 1 in 250 in emergency C-Section under GA
 Awareness is doubled with use of muscle
relaxant.

5.  PTSD.
 Anxiety.
 Fear of future surgery.
 Legal responsibilities.

6.  Awareness results from an imbalance
between anesthetic requirement and
anesthetic delivery
1. Normal Requirement—Low Delivery
 Errors in knowledge.
 Anesthetic machine failure.

7. 2. Low Requirement—Very Low Delivery
 Trauma patients.
 C- section under GA.
 Hypovolemic patients.

8. 3. High Requirement—Normal Delivery
 Normal variability in the population.
 Patients tolerant to sedative, hypnotic and
analgesic drugs.
 Alcohol use
 Hyperthyroidism and hyperthermia.

9. 1. Anesthesia training and continuing
education
 Physiology and pharmacology
 Equipment and clinical measurement.

10. 2- Preoperative Phase
 Identify patients at risk
 Conduct preoperative checklist-based
equipment check.
 Inform, consent, reassure as appropriate.

11. 3- Intraoperative phase
 scan equipment regularly during each case.
 Take care to avoid wrong drug
administration
 Administer adequate hypnotic drug
 Minimize use of muscle relaxant
 Respond rapidly to suspected inadequate
anesthesia
 Consider using an EEG-based monitor

12. 4- postoperative phase
 Conduct a postoperative interview.
 Provide counseling for aware patients.

13.  Use of benzodiazipines can decrease the
postoperative recall in case of unanticipated
awareness.
 Respond rapidly to signs of inadequate
anesthesia by deeping level of anesthesia.
 Benzodiazipines although have no retrograde
amnesic properties can decrease
postoperative recall.

14. 1. Clinical signs

15. 2- End tidal agent monitoring:
The minimum alveolar concentration (MAC): the
minimum concentration at ambient pressure
to prevent movement in 50% of non
premedicated subjects to standard painful
stimulus (skin incision).

16. Increase MAC:
Pyrexia, hyperthyroidism, obesity, young age,
tobacco, chronic alcohol, chronic sedative
use.
Decrease MAC
Pregnancy , hypotension, old age,
hypothyroidism, hypothermia, opioids,

17. 1. EEG:
Can be used as a measure of the depth of
anesthesia for several reasons:
 Represent cortical activity which affected by
anesthetics drugs, CMR and CBF, both are
affected by anesthetics drugs and surgical
stimulation.
 It fails to measure clinical depth of
anesthesia.

18.  Based on Fourier spectral analysis and
bispectral analysis
 Monitor provide number on a scale 0-100
 85-100: awake, light sedation.
 85-60: deep sedation, impairment of memory
processing, arousable on stimulation.
 40-60: surgical anesthesia, decrease
probability of postoperative recall

19.  0-40: burst suppression > cortical electrical
silence.
 It is recommended to be maintained 40- 55
 BIS decrease the incidence but don’t eliminate
awareness risk

20.  BIS limitation
 Interindividual variability in depth of
anesthesia for a given BIS value.
 Minimally affected by opioids, therefore may
not reflect balanced anesthetic regimen.
 Changes in consciousness from ketmine and
nitrous oxide are not faithfully represented.

21.  Based analysis of irregularities in EEG signals
which decreased as level of anesthesia
increase, incorporating Fourier analysis.
 EMG from facial muscles.
Two readings are displaced
1- State enotropy ( SE): 0-91 based on EEG
2- Rsponse enotropy ( RE): 0-100 based on
EMG

22.  RE is hypothesized to represent analgesic
component.
 Studies showed that the device produce
results comparable to those of BIS.
 Anesthetic range from 40-60.

23.  Other monitors
 Evoked potentials
 Patient state index
 narcoted