As the anesthesiologist Henry Jay Przybylo explains in “Counting Backwards,” the word “anesthesia” means “without feeling,” but a modern general anesthetic is about much more than just rendering a patient unconscious. It also involves analgesia, the prevention of pain; anxiolysis, the relief of anxiety; and amnesia, the obliteration of memory. The latter is necessary because it is by no means certain that patients are fully unconscious when anesthetized — a problem explored at length in Kate Cole-Adams’s book “Anesthesia.”
Despite the central role that anesthetic drugs play in medicine, very little about how they work is known for certain. Equally remarkable is the fact that ether, the first agent to be used as a general anesthetic, was shown by Paracelsus in the 16th century to put chickens to sleep. He wrote that it “quiets all suffering without any harm and relieves all pain…” It remains mysterious as to why 300 years were to pass before it came to be used as a general anesthetic. Some would point to Kuhn’s scientific paradigms and argue that medicine wasn’t ready for such a shift in thinking, others that it reflects the entirely unscientific nature of premodern medicine and the blinkered self-confidence of doctors. There are, of course, many similar examples in the history of medicine — perhaps the most egregious being the failure of the medical profession to exploit Leeuwenhoek’s invention in the 17th century of the microscope and his discovery of microbial life, as discussed in David Wootton’s book “Bad Medicine.”
Several American doctors began to use ether as a general anesthetic in the 1840s. There were bitter disputes about who could claim to be the first, but what is clear is that ether was rapidly taken up by the medical profession. It is interesting to note that it was also widely used as a recreational drug in countries like Ireland and Poland, where it was used as an alternative to alcohol.
Ether is no longer used in general anesthesia, and has been replaced by different “volatile” agents — such as sevoflurane and isoflurane. The way in which these volatile anesthetic agents dissolve in oil led to the theory that they worked by interfering with the lipoprotein membranes of nerve cells, implying that all the brain’s neurons were inactivated by the drugs and that the unconsciousness of general anesthesia was complete. This theory is no longer believed and instead there is near-complete uncertainty as to how the agents do work. More recent research on injectable anesthetic drugs like propofol suggests that they interfere selectively with certain neurotransmitters and with the interaction between the cerebral cortex (where thought and perception resides) and the deep part of the cerebral hemispheres known as the thalamus, which acts as some kind of gateway between the cerebral cortex and the rest of the brain. In other words, it is by no means certain that all of your brain is “asleep” when you are anesthetized.
The possibility of “awareness under anesthesia” is obviously of deep concern to both anesthesiologists and patients and is reminiscent of the fear in previous ages of being buried alive after being mistakenly assumed dead. Awareness became a clinical problem in the 1940s with the introduction of the paralyzing drug curare. Until then, if an anesthetic was inadequate, the patient would start to wake up and to move. With curare this cannot happen and it is possible for patients to be awake and, since they are entirely paralyzed, for the anesthesiologist to be unaware of it.
Awareness undoubtedly can occur under anesthesia although there is much argument as to how often. A 2014 survey in the United Kingdom of three million cases of anesthesia suggested an incidence of 1 in 19,000 with not all the episodes causing distress. This survey relied on patients volunteering their memory of being aware, so it is possible that some chose not to report the experience and that the true incidence might be higher. The issue is further complicated by the possibility of implicit or “unconscious” memory as opposed to conscious or “explicit” memory. The “explicit” memories would be the horror stories of patients wide-awake but unable to move while being operated on, usually as a result of medical error. It seems that the paralysis is even more distressing than the pain and can lead to long-term psychiatric harm and PTSD. Implicit, unconscious memories of being awake under anesthesia are much harder to uncover.
Cole-Adams makes much of these sorts of hidden memories in her book, and of various experiments with hypnotizing patients before and after anesthesia to find them, but as she admits, the evidence is confused and contradictory. Nevertheless, some anesthesiologists are careful in what they say in front of anesthetized patients in case the patient is able to later recall what they overheard. This is quite unlike surgeons who, on the whole, are disinhibited extroverts when operating.
A good experience of anesthesia should be as routine and dull as a commercial airplane ride, with the added feature that the patient should have no memory of it. Both anesthesia and flight have become dramatically safer in recent decades and there is much in common between flying an aircraft and anesthetizing a patient — uneventful most of the time but occasionally terrifying and very occasionally fatal. The Patient Safety movement of recent years has been largely driven by anesthesiologists and analogies to aviation safety, which perhaps apply less well to surgery.
It is difficult to write an exciting book about modern anesthesia but Przybylo is thoughtful and workmanlike in his production, as he is, it is quite clear, when administering his anesthetics. Consciousness is an entirely subjective phenomenon and, perhaps inevitably given its subtitle, you will learn as much, if not more, about Cole-Adams’s own anxieties and preoccupations as you will about anesthesia in her book. The effect, as she streams her consciousness over many pages, can in itself be somewhat anesthetic.