doi: 10.1097/ALN.0b013e31826f9223

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Sanders, Robert D. B.Sc., M.B.B.S., F.R.C.A.*; Tononi, Giulio M.D.; Laureys, Steven M.D., Ph.D.; Sleigh, Jamie M.B.Ch.B., F.R.C.A., Dip. App. Stat., M.D.

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We are grateful to Dr. Pinsker for his complimentary letter and also to the insightful question posed. We specifically use the term “connectedness” to define the potential that an external stimulus will trigger an experience.1 All experience is primarily internally generated; it may be independent of external events (such as a dream), or triggered – or modified – by external stimuli. We use “connectedness” to imply a connection between the patient’s internally manufactured consciousness and the environment so that an external event may trigger an experience. We primarily have focused our discussion on general anesthesia because of the widespread assumption that these subjects should be unconscious. We propose that, at a minimum, they should be disconnected and thus unaware of surgery.1 However, we agree there are multiple ways by which connectedness to different stimuli may be manipulated. This may include spinal anesthesia to negate the pain of peripheral surgery. Of course, this may be insufficient as, of the multiple causes for distress under anesthesia, pain is not the commonest.2 Similarly, we have proposed that reinforcement of a “thalamic” gate may be helpful, but because activation of the cortex is common during surgery,1 we propose that targeting connectedness at a cortical level (perhaps a final pathway for all stimuli) may prove the most beneficial. We also agree that if a signal enters the central nervous system, this may leave a trace, as discussed in many studies of implicit learning.3,4 We do not define this as connectedness (unless there is a change in the subject’s conscious experience), but acknowledge that this remains an important area of research and are grateful for Dr. Pinsker for highlighting this.
Robert D. Sanders, B.Sc., M.B.B.S., F.R.C.A.,* Giulio Tononi, M.D., Steven Laureys, M.D., Ph.D., Jamie Sleigh, M.B.Ch.B., F.R.C.A., Dip. App. Stat., M.D.
*Imperial College London, London, United Kingdom.
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1. Sanders RD, Tononi G, Laureys S, Sleigh JW. Unresponsiveness ≠ unconsciousness. Anesthesiology. 2012;116:946–59

2. Ghoneim MM, Block RI, Haffarnan M, Mathews MJ. Awareness during anesthesia: Risk factors, causes and sequelae: A review of reported cases in the literature. Anesth Analg. 2009;108:527–35

3. Gonsowski CT, Chortkoff BS, Eger EI 2nd, Bennett HL, Weiskopf RB. Subanesthetic concentrations of desflurane and isoflurane suppress explicit and implicit learning. Anesth Analg. 1995;80:568–72

4. Russell IF, Wang M. Absence of memory for intraoperative information during surgery under adequate general anaesthesia. Br J Anaesth. 1997;78:3–9

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