An overview of the International Conference on Nausea and Vomiting assembled from my notes.
Models of Nausea and Vomiting discussed:
- Chemotherapy N&V
- Postoperative N&V
- N&V in Pregnancy (hyperemesis gravidarum)
- Cyclic Vomiting Syndrome
- Motion Sickness (both from motion and optokinetic stimulation)
- Cannabinoid Hyperemesis
Models of Emesis not discussed:
- Alcohol — gastric or vestibular?
- Regurgitation (e.g. in canids)
- Regurgitation (e.g. in ruminants)
Of course, ruminant regurgitation is not really emesis, but it might involve some of the same central pattern generators.
The issue of Bulimia raises the question of whether vomiting is always correlated with nausea. The tone of the conference was that nausea can occur without vomiting, and in fact it is harder to suppress nausea compared to suppressing emesis. One questioner did raise the point that vomiting can be a release for some people; it perhaps goes without saying that for many people vomiting, and even the very idea of vomiting, is itself nauseogenic. On the other hand, bulimia is a voluntary, if induced, activity, and may come to have a conditioned pleasurable component. (Although I recall data from the Kissilef lab in which binging and purging subjects would overeat to the point of self-reported nausea, and then purge). So, I am curious if anti-emetics have been used in the treatment of bulimics.
Major issues raised at the conference:
Control of conditioned emesis vs. acute emesis. The best treatment seems to block acute emesis to prevent acquisition of conditioned emesis, eg. in chemotherapy patients.
Quality of Life as an Outcome: This is very encouraging: oncologists are recognizing that nausea and vomiting cause a major degradation in quality of life during chemotherapy, and therefore N&V should be targeted.
Nausea as a Target: emesis seems well under control with the latest batch of 5HT3 and NK1 antagonists (+ dexamethasone), but nausea is much harder to control (and understand.)
Measures of Nausea: The ability to track and treat nausea is hampered by inadequate tools for assessment. There are a multiplicity of indices and visual analog scales; although the community seemed aware of the leading work on pain measurement, it seems unlikely that good psychophysical work a la Linda Bartoshuk (UF) has been attempted. Bovberg made a stirring call for increased ecological momentary assessment approaches to measuring nausea and vomiting “in real time”.
Central Networks subserving Nausea: We have some handle on the central pattern generators of the brainstem mediating the emetic response, but understanding nausea lacks way behind, both neurologically and I think conceptually as well. I can see some convergence of cognitive/limbic studies of disgust creeping down the brainstem to meet the emetic forces of nausea moving up. But some clear definitions of nausea, psychophysics, and neural or physiological correlates will be required for real progress (see history of fear conditioning).
Predicting Susceptibility to Nausea and Vomiting: Some intriguing genetic data was presented by Janicki and Fezjo, but it is clearly early days.