In this particular posting, I want, if I may, to focus for a short time on a problem, which for many people amounts to so much more than just a “temporary physical sensation”. Sometimes patients who are being treated with chemotherapeutic drugs which can cause nausea and vomiting, find that just a thought popping into the mind, or a smell or a visual cue, can promptly and alarmingly induce uncontrollable feelings of nausea and not uncommonly, actual vomiting. Moreover, this can happen at any time, even in the resting period between courses or pulses of treatment. Let me give you an example of the sort of thing I mean.
One Christmas a few years back some of my colleagues and I who play brass instruments (trumpets, horns, trombones etc) were carol playing in the busy Sauchiehall Street shopping centre in Glasgow. This we were doing in aid of a cancer charity, our aim being to supplement much needed funding. At one point, a patient known to most of us (and who happily was by now off treatment and enjoying complete remission from her disease) approached to inquire where the collecting boxes were. Accordingly, we pointed her in the direction of two or three other colleagues – members of nursing staff – who were collecting nearby. The lady concerned had a favourite ward sister and ‘spying’ her with her collecting can, she promptly and very purposefully headed off in that direction.
As she approached, sister greeted her warmly but then to her – and everyone else’s dismay – the patient immediately backed off, heading for an alley nearby where she was promptly physically sick. Needless to say our doughty colleague was subjected to a great deal of good-natured ribaldry for quite a few days after that. Was it the voice – combined perhaps with a familiar figure in hospital uniform – that had triggered such an entirely unexpected (and for the poor lady concerned, embarrassing) response? Well whatever it was, it instantly overwhelmed her to the point of completely ‘side-lining’ her undoubted feelings of genuine friendship, warmth and gratitude. We call this “psychogenic” or “anticipatory” nausea and vomiting and to understand it more fully, we will, if you will bear with me, need to take account of a few facts about well known human physiological behaviour.
As we have already begun to see, the expulsion of an imbibed or ingested toxin or poison is a perfectly normal defence response. Most of us will, from time to time, have also observed it in animals, especially dogs and other domestic pets. Moreover, we know that where it occurs in man, toxin detection takes place at the level of the gut and/or within the Central Nervous System (CNS), in what has already been referred to as the chemoreceptor trigger zone. Historically, the function of nausea is less clear. However, it probably functions to quickly establish a strong conditioning mechanism. This, in its most primitive form, was probably meant to warn us off and away from what ‘triggered’ it in the first place, i.e. toxins and other harmful substances.