JJP is Clinical Lead of the 5th National Audit Project (NAP5) on Accidental Awareness During General Anaesthesia and an Editor of Anaesthesia. The views expressed are his own and not those of NAP5 or of the Journal. No other funding or competing interests declared. Previously posted on the Anaesthesia correspondence website: www.anaesthesiacorrespondence.com.
Version of Record online: 9 DEC 2013
© 2013 The Association of Anaesthetists of Great Britain and Ireland
Volume 69, Issue 1, pages 80–82, January 2014
How to Cite
Pandit, J. J. (2014), A reply. Anaesthesia, 69: 80–82. doi: 10.1111/anae.12548
- Issue online: 9 DEC 2013
- Version of Record online: 9 DEC 2013
I will not counter each of Russell and Wang's extensive points about my editorial . We can all agree on two things. First, responses to anaesthesia are not singular or all-or-nothing (i.e. simply awake vs unconscious), but heterogeneous, with mental states in between. Second, where a patient undergoing anaesthesia with isolated forearm technique (IFT) responds both spontaneously to the surgery and to command, then it is virtually certain that this signifies wakefulness (consciousness). Since these actions are consistent, their interpretation is straightforward. My point, which Russell and Wang do not quite address, concerns interpreting inconsistent responses; that is, when a patient responds only to command but not spontaneously. Undoubtedly, IFT is an effective monitoring technique but as I showed , when patient responses are inconsistent, the proper interpretation of IFT (and even more sophisticated brain imaging technologies) is almost impossible.
Note that in Russell's own recent papers [2, 3], none of the IFT patients moved spontaneously. Russell and Wang suggest this is because of analgesia, but analgesia is irrelevant because it does not abolish all sensations such as touch or hearing, etc. Thus a patient who is unexpectedly aware during surgery and retains the ability to move should do so, to signify their surprise at feeling touch or hearing voices, even if they are pain-free. The fact they do not move suggests a neutral experience – a state of detachment from, or acceptance of events (ie, a dysanaesthetic state).
The model of Sanders et al. they quote is very different indeed from the notion of dysanaesthesia [4, 5]. First, it is unclear if an IFT-positive response is best classed in their terminology as ‘disconnected’ consciousness (because the patient appears disconnected from surgery) or as ‘connected’ consciousness (because the patient remains connected to verbal command). Second, their model makes no allowance for a state in which the patient is lucidly aware of events but in an entirely neutral way. For them as stated, all thoughts during anaesthesia are cases of either dreaming or delirium. Dysanaesthesia is neither: it is a state where perception (the emotional interpretation of sensory information) is uncoupled from the sensations, leaving a neutral state of mind, detached from events.
If dysanaesthesia existed then we might indeed predict that some dysanaesthetic patients would respond to direct verbal command (i.e. a sensory stimulus they attend to), but not to move spontaneously on becoming aware of surgery (because the surgical stimulus is not compelling for them). Furthermore, the notion of dysanaesthesia nicely explains the disparity between the incidence of ‘awareness’ established by direct (Brice) questioning (incidence ~1:500) versus the incidence now established by spontaneous reporting (incidence ~1:15 000) . This difference arises (so the dysanaesthesia hypothesis goes) because the patients making up the difference have experienced surgery in a neutral, unemotional way that does not compel them to report it spontaneously (but they do respond truthfully about their recollection if asked in a Brice interview). This proposition is potentially testable.
Further, at least two more testable predictions arise from the hypothesis of dysanaesthesia. First, that there will be found patients who were not paralysed with neuromuscular blockade, who did not spontaneously move during surgery, but who clearly and convincingly recall surgery in a neutral way . This is not something that is readily explained by the ideas of Russell and Wang. In fact, many of the descriptions used by Russell and Wang about patients searching for their bodies, or patients choosing not to respond to verbal commands (or respond to the surgery) etc, seem to support the notion of dysanaesthesia, wherein sensations are uncoupled from perception.
A second prediction is that using appropriate doses of dexmedetomidine during anaesthesia might increase the incidence of IFT-positive responses to command. Sanders et al. have previously explicitly predicted that this drug will reduce the incidence of IFT-positive responses (a result that would be consistent with their alternative ‘disconnected-connected consciousness’ hypothesis) [4, 5]. Given clear descriptions of how patients respond to command during dexmedetomidine sedation , the dysanaesthesia hypothesis would be consistent with precisely the opposite: IFT-positive responses might in fact be obtained more frequently.
Rather than debate the hypothesis hypothetically, all readers are in a position to conduct IFT in their patients and acquire the experiences for themselves. They can then directly assess who out of Russell and Wang, or I, are more likely to be correct, and indeed test some of the explicit predictions made above.