Propofol and memory
*E-mail: Stephen.kinsella{at}ubht.nhs.ukEditor—We were unsure from Dr Veselis' editorial whether he approves of the possibility of patients being awake during general anaesthesia.1 Phrases such as ‘It will be a brave new world when we can tell a patient ... "don't worry—you won't remember this" with confidence ... ’; ‘being aware but having no memory ... is not a traumatic event ... allows ethical research to be done ... .’; and ‘ ... . the question is whether we want a monitor to detect unconsciousness or one that detects amnesia?’ suggest an openness to discussion at least.
It suits anaesthetists to tell patients that awareness is a rare complication, occurring in 1–2 per thousand.2 3 However, this figure relates to awareness with recall. We thought that it might be less reassuring to tell them that they have a 16% chance of being awake during surgery,4 or even ‘you are sure to be awake for some of the time during surgery’.5
We asked 60 anaesthetists in our department three questions:
- ‘Would it be acceptable if, during your operation carried out under general anaesthesia, you were awake for a period of time, even though you did not remember afterwards?’
- ‘Would it be acceptable if, during your operation carried out under general anaesthesia when you were completely paralysed, you were awake for a period of time, even though you did not remember afterwards?’
- ‘Would it be acceptable if, during your operation carried out under general anaesthesia when you were completely paralysed, you were awake for a period of time and in pain, even though you did not remember afterwards?’
The answers were ‘no’ in 45 (75%), 56 (93%) and 58 (97%) cases of responses. Three anaesthetists who answered yes to question (i) qualified this, commenting that being awake would be acceptable in planned circumstances or with prior consent.
A significant minority of our anaesthetists would be prepared to be awake if not paralysed and not in pain. However, there is no way to guarantee that the surgeon will not inflict pain at some future time during the operation, and this may be more likely if a light level of anaesthesia is aimed for using a ‘depth of anaesthesia’ monitor. Being awake and anxious during surgery may also lead to long-term psychological sequelae.6
We think that if most anaesthetists wish to be unconscious rather than amnesic during general anaesthesia, it will be a long time before it is possible to convince the public that this is acceptable or desirable.
Bristol UK
Editor—I am pleased that my editorial was provocative enough to undertake this interesting survey. The results indicate that these anaesthetists, as probably most do, rely on the clinical metric that has served the profession well from the first use of nitrous oxide and ether. Namely, that if a person is unconscious, they will also be amnesic even for painful stimuli. The blissful sleep of oblivion has served us well, and may be the root of the perception that amnesia without awareness is superior to amnesia for events that we are aware of at the time. As will be recalled, the first media event in the use of nitrous oxide was of a screaming patient in front of a ridiculing audience. This untoward response to anaesthesia rests heavily on our collective consciousness, and is reinforced with every new case of awareness. How can one best assuage the visceral fear of failure?
In large part, the solution to awareness is in understanding the processes of complex systems and making these reliable, as awareness is almost certainly due to the administration of too little anaesthesia, frequently as a result of human error or technical malfunction. Beyond that, I propose that if we understood how anaesthesia, or more accurately, each component of the anaesthetic state works, then we would be less terrified of its failure. Although all of us are excellent empiric purveyors of magic potions, our trade would be more secure with this knowledge in hand. As it is now, our best option is to develop reliable monitors of each anaesthetic component. Such endeavours, of course, will be easier when we understand which brain activities relate to anaesthetic actions on consciousness, memory or pain and how these might be best monitored. This state of affairs is currently exemplified by the use of neuromuscular blocking agents with neuromuscular blockade monitors, where both the physiology and monitoring are largely understood.
Short of this, it is always safer and more reassuring to err on the side of over-medication. This approach is increasingly safe as new medications with fewer side-effects and more error resistant pharmacological profiles are developed. Interestingly, these very considerations, serving as the basis for learned and heated controversies about which agent is superior, started as soon as nitrous oxide and ether were first used.
Such heuristics work well, as is attested to by their endurance from the very beginnings of anaesthesia practice. However, let us not be lulled into a sense of comfort where further knowledge of how anaesthesia works in the brain is no longer pursued just because what we do, we do well enough. The methods of practice that I envision, which cause such psychological discomfort today, will only be possible and acceptable when such knowledge is attained.
New York, USA
E-mail: veselisr{at}MSKCC.org
References
1 Veselis RA. The remarkable memory effects of propofol. Br J Anaesth 2006; 96:289–91
2 Sebel P, Bowdle T, Ghoneim M, et al. The incidence of awareness during anesthesia: a multicentre United States study. Anesth Analg 2004; 99:833–9
3 Sandin R, Enlund G, Samuelsson P, Lennmarken C. Awareness during anaesthesia: a prospective case study. Lancet 2000; 355:707–11[CrossRef][ISI][Medline]
4 Russell IF and Wang M. Absence of memory for intra-operative information during surgery with total intravenous anaesthesia. Br J Anaesth 2001; 86:196–202
5 Russell IF. The Narcotrend ‘depth of anaesthesia’ monitor cannot reliably detect consciousness during general anaesthesia: an investigation using the isolated forearm technique. Br J Anaesth 2006; 96:346–52
6 Lennmarken C, Bildfors K, Enlund G, Samuelsson P, Sandin R. Victims of awareness. Acta Anaesthesiol Scand 2002; 46:229–31[CrossRef][ISI][Medline]
CiteULike 
Connotea 
Del.icio.us What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||