2. Awareness During Anesthesia DR.Mohammad Hajeyah Kuwait Board of Anesthesia R.3

4. IS THE PATIENT AWAKE RIGHTNOW IS THE PATIENT AWAKE RIGHTNOW ?

5. HOW MANY OF YOU THINK THAT ITS IMPORTANT TO MONITOR AWARENESS HOW MANY OF YOU THINK THAT ITS IMPORTANT TO MONITOR AWARENESS ?

6. HOW MANY OF YOU DO MONITOR AWARENESS ?

7. OUTLINE  Definition  Incidence  Why does it happen  Types and consequences  Modalities of monitoring  How do we prevent and manage it  Take home message

8. DEFINITION  The situation that occurs when a patient under general anesthesia becomes aware of some or all events during surgery or a procedure, and has direct recall of those events. patientanesthesiasurgerypatientanesthesiasurgery  Because of the routine use of neuromuscular blocking agents during general anesthesia, the patient is often unable to communicate with the surgical team if this occurs. neuromuscular

9.  Explicit memory may be recalled spontaneously, or may be provoked by postoperative events or questioning.  Implicit memory may not be consciously recalled, but may affect behavior or performance at a later time

11. INCIDINCE  Awareness during anesthesia is a very disturbing event if encountered.  Memories of the event are either remembered spontaneously or provoked by post-op events.  Recall of such events specially if awareness of paralysis and painful stimuli is the issue then ones life maybe changed permanently.

12.  Back in the 1970`s where nitrous oxide was used in 60-70%,incidince was 7% ( 1 in 14) pts.  In recent times awareness with recall of painful stimuli is at 0.03% (1 in 3000 )pts.  And in cases where no painful stimuli was 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:373-379. Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379.

13.  The closed claim analysis of the ASA. States the incidence to be more common in women (77%).  In adults younger than 60 yrs. (89%).  In pediatrics its (0.5-1%)  In ASA physical status 1 and 2 (68%) 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.

15.  A study in Finland done on 2,600 pts. Showed (0.4%) who experienced awareness and (0.3%) possibly experience awareness.  A Swedish study found the incidence to be (0.18%) when MR. was used and (0.10%) when no MR. was used.  A study done in the university of Iowa showed the incidence to be much higher in cases where cardiopulmonary and vascular functions were compromised. (1.1-1.5%) in cardiac surgery and (11-43%) in major trauma. Sigalovsky N. Awareness under General Anesthesia. AANA Journal/October 2003/Vol.71,No. 5,p:373-379.

16. WHY DOES IT HAPPEN WHY DOES IT HAPPEN ?

18.  Resistance to anesthetic agents: 1. Pyrexia/Septic 2. Hyperthyroidism 3. Obesity 4. Anxiety 5. Young age 6. Heavy alcohol and tobacco use. 7. Recreational drug usage. 8. Factors reducing the MAC. Why does it happen

19. Consequences  No one can tell you how bad it is but the patient himself.  Impact can be as a medico legal law sue and also as psychiatric implications.  Symptoms would range from simple insomnia and anxiety to as severe as PTSD. development.  Those symptoms are related to being helpless, feeling pain,fear,and inability to communicate nor express themselves.

21. Consequences

22. Signs of AWARENESS  Tachycardia  Hypertension  Sweating  Tear formation  Pupillary dilatation and reaction to light  Movement and grimacing

23. How do we monitor Awareness  Bispectral index  Electroencephalogram  Auditory Evoked Response  Ocular Microtremor  Patients State Analyzer Index

24. Bispectral Index

25. BIS  Measures patients response to sedative/hypnotics administration.  Non-invasive.  Converts the generated EEG. Data into a number.  Ideal numbers under GA. Are between 40-60.

26. BIS  One study stated that with BIS there was a reduction of Propofol use by 32.6% with subsequent less mean time till eye opening.  According to Glass and Johansson; that BIS uses led to a more precise dosing of medication and less time till recovery leading to high turnover of patients.

27. BIS  Kurehara and Coworkers found claims of awareness in spite a value of 40 intra-op.  This study concluded that BIS maybe effective in measuring hypnotic state yet awareness still can occur even with a low BIS value.

28. BIS  A recent study concluded that values between 50-60 were insufficient to prevent awareness during intubation with propofol or alfentanil use.  Barr and colleagues; studied BIS with Nitrous Oxide use. This study concluded no changes in BIS values with different conc. Of Nitrous.

30. EEG.

31. EEG.  Analyzing brain waveforms changes under GA.  Both computer-processed and un-processed EEG reading are used to analyze level of awareness.  Problems include: 1. Cost 2. Complexity of readings 3. Complexity of equipments 4. Difficult to interpret.

32. Auditory Evoked Potentials

33. AEP  Fluctuations of the (AER) latency as a sign of awareness.  It has been reported that a positive correlation exists between AER and awareness changes.  Problems: 1. Good indicator with inhalational agents rather than narcotics. 2. Complexity of equipment and analysis.

34. Ocular Micro tremor

35. OMT  A promising new device in awareness monitoring.  It measures high frequency tremors of extra-ocular muscles generated by higher brain signals from the brain stem.  Those signals are in direct relation with anesthesia depth.  Still under study and not fully under practical use.

36. Patient State Analyzer Index  It’s a quantitative analysis of the EEG.  Simply uses more extensive sensors to measure EEG.  Few completed studies regarding this method.

37. How To Manage Intra-operative:  If pt is being exposed to a noxious stimuli that maybe recalled later on then anesthesia should be deepened.  If hypotension is present then anesthesia should be deepened while supporting hemodynamics.  Benzodiazepines (Mediazolam 5mg) may reduce recall post-op. via retrograde amnesic effect. Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005

38. How To Manage Post-operative:  Pt. should be interviewed post-op if claims were made of intra-op awareness.  Exact timing and experience should be identified and distinguished from dreaming.  Its important to make it clear that no confusion was made between awareness and memories at induction or emergence.  Always to take every claim seriously and to show sympathy with the patient.  If pt. started showing signs of anxiety,depression and PTSD. Then psychiatric referral shouldn’t be delayed.

39. Avoiding Awareness  BZD. Administered at induction reduces the incidence of awareness specially at high risk period during induction.  Adequate anesthetic drugs should be administered.  The risk of awareness is greatly reduced at a MAC 0.8-1.0.  MAC. Adjustment according to patient age group reduces the risk greatly. Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005

40. Avoiding Awareness  The use of NMBD. Inc. the risk of awareness.  Complete paralysis should be given only if needed and doses should e measured.  In cases that light anesthesia is suspected then monitoring is justified using BIS. and/or other modalities.  In spite of all that awareness still occurs for unknown reasons. Hardman J.G., Aitkenhead A.R. Awareness during Anesthesia. Advance Access Publication, October 2005

41. Take Home Message  Intra-op awareness is associated with devastating psychiatric sequelae that leads to medico-legal consequences on the anesthetist.  Awareness is twice likely if NMBD. Are used.  Inadequate anesthetic dosing is the most common cause of awareness.  Most of the time signs of awareness are often masked by drugs or patients own concomitant illnesses.  Monitoring, specialy in high risk cases is justified and reduces the risk of awareness greatly.

43. Thank You