Awareness During Awareness During AnesthesiaAnesthesia

DR.Mohammad HajeyahDR.Mohammad HajeyahKuwait Board of AnesthesiaKuwait Board of Anesthesia

R.3R.3

IS THE PATIENT IS THE PATIENT AWAKEAWAKE RIGHTNOW RIGHTNOW

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HOW MANY OF YOU THINK THAT ITS HOW MANY OF YOU THINK THAT ITS IMPORTANT TO MONITOR IMPORTANT TO MONITOR AWARENESSAWARENESS

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HOW MANY OF YOU DO MONITOR HOW MANY OF YOU DO MONITOR AWARENESSAWARENESS

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OUTLINEOUTLINE Definition Definition

IncidenceIncidence Why does it happenWhy does it happen

Types and consequences Types and consequences

Modalities of monitoringModalities of monitoring

How do we prevent and manage itHow do we prevent and manage it

Take home messageTake home message

DEFINITIONDEFINITION The situation that occurs when a patient The situation that occurs when a patient

under general anesthesia becomes aware of under general anesthesia becomes aware of some or all events during surgery or a some or all events during surgery or a procedure, and has direct recall of those procedure, and has direct recall of those events. events.

Because of the routine use of Because of the routine use of neuromuscular blocking agents during neuromuscular blocking agents during general anesthesia, the patient is often general anesthesia, the patient is often unable to communicate with the surgical unable to communicate with the surgical team if this occurs. team if this occurs.

ExplicitExplicit memory may be recalled memory may be recalled spontaneously, or may be provoked by spontaneously, or may be provoked by postoperative events or questioning.postoperative events or questioning.

ImplicitImplicit memory may not be consciously memory may not be consciously recalled, but may affect behavior or recalled, but may affect behavior or performance at a later timeperformance at a later time

INCIDINCEINCIDINCE Awareness during anesthesia is a very Awareness during anesthesia is a very

disturbing event if encountered.disturbing event if encountered.

Memories of the event are either Memories of the event are either remembered spontaneously or provoked by remembered spontaneously or provoked by post-op events.post-op events.

Recall of such events specially if awareness Recall of such events specially if awareness of paralysis and painful stimuli is the issue of paralysis and painful stimuli is the issue then ones life maybe changed permanently.then ones life maybe changed permanently.

Back in the 1970`s where nitrous oxide was used in Back in the 1970`s where nitrous oxide was used in 60-70%,incidince was 7% ( 1 in 14) pts.60-70%,incidince was 7% ( 1 in 14) pts.

In recent times awareness with recall of painful In recent times awareness with recall of painful stimuli is at 0.03% (1 in 3000 )pts.stimuli is at 0.03% (1 in 3000 )pts.

And in cases where no painful stimuli was And in cases where no painful stimuli was encountered its 0.1-0.7% (1 in 142-1000) pts.encountered its 0.1-0.7% (1 in 142-1000) pts.

Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379 ..

The closed claim analysis of the ASA. States The closed claim analysis of the ASA. States the incidence to be more common in women the incidence to be more common in women (77%).(77%).

In adults younger than 60 yrs. (89%).In adults younger than 60 yrs. (89%).

In pediatrics its (0.5-1%)In pediatrics its (0.5-1%)

In ASA physical status 1 and 2 (68%)In ASA physical status 1 and 2 (68%)

Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379379..

A study in A study in FinlandFinland done on 2,600 pts. Showed (0.4%) who done on 2,600 pts. Showed (0.4%) who experienced awareness and (0.3%) possibly experience experienced awareness and (0.3%) possibly experience awareness.awareness.

A A SwedishSwedish study found the incidence to be (0.18%) when study found the incidence to be (0.18%) when MR. was used and (0.10%) when no MR. was used.MR. was used and (0.10%) when no MR. was used.

A study done in the A study done in the university of Iowauniversity of Iowa showed the showed the incidence to be much higher in cases where incidence to be much higher in cases where cardiopulmonary and vascular functions were compromised. cardiopulmonary and vascular functions were compromised. (1.1-1.5%) in cardiac surgery and (11-43%) in major (1.1-1.5%) in cardiac surgery and (11-43%) in major trauma.trauma.

Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379.Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379.

WHY DOES IT HAPPENWHY DOES IT HAPPEN

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Resistance to anesthetic agents:Resistance to anesthetic agents:

1.1. Pyrexia/SepticPyrexia/Septic

2.2. HyperthyroidismHyperthyroidism

3.3. ObesityObesity

4.4. AnxietyAnxiety

5.5. Young ageYoung age

6.6. Heavy alcohol and tobacco use.Heavy alcohol and tobacco use.

7.7. Recreational drug usage. Recreational drug usage.

8.8. Factors reducing the MAC.Factors reducing the MAC.

Why does it happenWhy does it happen

ConsequencesConsequences No one can tell you how bad it is but the patient No one can tell you how bad it is but the patient

himself.himself.

Impact can be as a medico legal law sue and also Impact can be as a medico legal law sue and also as psychiatric implications. as psychiatric implications.

Symptoms would range from simple insomnia and Symptoms would range from simple insomnia and anxiety to as severe as PTSD. development.anxiety to as severe as PTSD. development.

Those symptoms are related to being helpless, Those symptoms are related to being helpless, feeling pain,fear,and inability to communicate nor feeling pain,fear,and inability to communicate nor express themselves.express themselves.

ConsequencesConsequences

Signs of Signs of AWARENESSAWARENESS

TachycardiaTachycardia

HypertensionHypertension

Sweating Sweating

Tear formationTear formation

Pupillary dilatation and reaction to lightPupillary dilatation and reaction to light

Movement and grimacingMovement and grimacing

How do we monitor How do we monitor AwarenessAwareness Bispectral indexBispectral index

ElectroencephalogramElectroencephalogram

Auditory Evoked ResponseAuditory Evoked Response

Ocular MicrotremorOcular Microtremor

Patients State Analyzer IndexPatients State Analyzer Index

Bispectral IndexBispectral Index

BISBIS

Measures patients response to Measures patients response to sedative/hypnotics administration.sedative/hypnotics administration.

Non-invasive.Non-invasive.

Converts the generated EEG. Data into a Converts the generated EEG. Data into a number.number.

Ideal numbers under GA. Are between 40-60.Ideal numbers under GA. Are between 40-60.

BISBIS

One study stated that with BIS there was a One study stated that with BIS there was a reduction of reduction of PropofolPropofol use by 32.6% with use by 32.6% with subsequent less mean time till eye opening.subsequent less mean time till eye opening.

According to According to GlassGlass and and JohanssonJohansson; that ; that BIS uses led to a more precise dosing of BIS uses led to a more precise dosing of medication and less time till recovery leading medication and less time till recovery leading to high turnover of patients.to high turnover of patients.

BISBIS

Kurehara and CoworkersKurehara and Coworkers found claims of found claims of awareness in spite a value of 40 intra-op.awareness in spite a value of 40 intra-op.

This study concluded that BIS maybe This study concluded that BIS maybe effective in measuring hypnotic state yet effective in measuring hypnotic state yet awareness still can occur even with a low awareness still can occur even with a low BIS value.BIS value.

BISBIS A recent study concluded that values A recent study concluded that values

between 50-60 were insufficient to prevent between 50-60 were insufficient to prevent awareness during intubation with awareness during intubation with propofol propofol or or alfentanilalfentanil use. use.

Barr and colleaguesBarr and colleagues; studied BIS with ; studied BIS with Nitrous OxideNitrous Oxide use. This study concluded no use. This study concluded no changes in BIS values with different conc. Of changes in BIS values with different conc. Of Nitrous.Nitrous.

EEGEEG..

EEGEEG.. Analyzing brain waveforms changes under GA.Analyzing brain waveforms changes under GA.

Both computer-processed and un-processed EEG Both computer-processed and un-processed EEG reading are used to analyze level of awareness.reading are used to analyze level of awareness.

Problems include:Problems include:

1.1. CostCost

2.2. Complexity of readingsComplexity of readings

3.3. Complexity of equipmentsComplexity of equipments

4.4. Difficult to interpret.Difficult to interpret.

Auditory Evoked PotentialsAuditory Evoked Potentials

AEPAEP Fluctuations of the (AER) latency as a sign of Fluctuations of the (AER) latency as a sign of

awareness.awareness.

It has been reported that a positive correlation It has been reported that a positive correlation exists between AER and awareness changes.exists between AER and awareness changes.

Problems:Problems:

1.1. Good indicator with inhalational agents rather Good indicator with inhalational agents rather than narcotics.than narcotics.

2.2. Complexity of equipment and analysis.Complexity of equipment and analysis.

Ocular Micro tremorOcular Micro tremor

OMTOMT A promising new device in awareness monitoring.A promising new device in awareness monitoring.

It measures high frequency tremors of extra-ocular It measures high frequency tremors of extra-ocular muscles generated by higher brain signals from the muscles generated by higher brain signals from the brain stem. brain stem.

Those signals are in direct relation with anesthesia Those signals are in direct relation with anesthesia depth.depth.

Still under study and not fully under practical use.Still under study and not fully under practical use.

Patient State Analyzer IndexPatient State Analyzer Index

It’s a quantitative analysis of the EEG.It’s a quantitative analysis of the EEG.

Simply uses more extensive sensors to Simply uses more extensive sensors to measure EEG.measure EEG.

Few completed studies regarding this Few completed studies regarding this method.method.

How To ManageHow To Manage

Intra-operative:Intra-operative: If pt is being exposed to a noxious stimuli that If pt is being exposed to a noxious stimuli that

maybe recalled later on then anesthesia should be maybe recalled later on then anesthesia should be deepened. deepened.

If hypotension is present then anesthesia should If hypotension is present then anesthesia should be deepened while supporting hemodynamics.be deepened while supporting hemodynamics.

Benzodiazepines (Mediazolam 5mg) may reduce Benzodiazepines (Mediazolam 5mg) may reduce recall post-op. via retrograde amnesic effect.recall post-op. via retrograde amnesic effect.

Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005

How To ManageHow To ManagePost-operative:Post-operative: Pt. should be interviewed post-op if claims were made of Pt. should be interviewed post-op if claims were made of

intra-op awareness.intra-op awareness.

Exact timing and experience should be identified and Exact timing and experience should be identified and distinguished from dreaming.distinguished from dreaming.

Its important to make it clear that no confusion was made Its important to make it clear that no confusion was made between awareness and memories at induction or between awareness and memories at induction or emergence.emergence.

Always to take every claim seriously and to show sympathy Always to take every claim seriously and to show sympathy with the patient.with the patient.

If pt. started showing signs of anxiety ,depression and If pt. started showing signs of anxiety ,depression and PTSD. Then psychiatric referral shouldn’t be delayed. PTSD. Then psychiatric referral shouldn’t be delayed.

Avoiding AwarenessAvoiding Awareness BZD. Administered at induction reduces the BZD. Administered at induction reduces the

incidence of awareness specially at high risk period incidence of awareness specially at high risk period during induction.during induction.

Adequate anesthetic drugs should be Adequate anesthetic drugs should be administered. administered.

The risk of awareness is greatly reduced at a MAC The risk of awareness is greatly reduced at a MAC 0.8-1.0.0.8-1.0.

MAC. Adjustment according to patient age group MAC. Adjustment according to patient age group reduces the risk greatly.reduces the risk greatly.

Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005

Avoiding AwarenessAvoiding Awareness The use of NMBD. Inc. the risk of The use of NMBD. Inc. the risk of

awareness.awareness. Complete paralysis should be given only if Complete paralysis should be given only if

needed and doses should e measured.needed and doses should e measured. In cases that light anesthesia is suspected In cases that light anesthesia is suspected

then monitoring is justified using BIS. and/or then monitoring is justified using BIS. and/or other modalities.other modalities.

In spite of all that awareness still occurs for In spite of all that awareness still occurs for unknown reasons.unknown reasons.

Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005

Take Home MessageTake Home Message Intra-op awareness is associated with devastating Intra-op awareness is associated with devastating

psychiatric sequelae that leads to medico-legal psychiatric sequelae that leads to medico-legal consequences on the anesthetist. consequences on the anesthetist.

Awareness is twice likely if NMBD. Are used.Awareness is twice likely if NMBD. Are used.

Inadequate anesthetic dosing is the most common cause of Inadequate anesthetic dosing is the most common cause of awareness.awareness.

Most of the time signs of awareness are often masked by Most of the time signs of awareness are often masked by drugs or patients own concomitant illnesses.drugs or patients own concomitant illnesses.

Monitoring, specialy in high risk cases is justified and Monitoring, specialy in high risk cases is justified and reduces the risk of awareness greatly.reduces the risk of awareness greatly.

Thank YouThank You