Methodologic considerations for studies of chronic nausea and vomiting in adults and children.

Methods to characterize and quantify severity of chronic nausea and vomiting and to elucidate their underlying mechanisms have received significant attention for both adult and pediatric patients. Validated dyspepsia symptom surveys include measures of nausea and vomiting intensity in relation to other upper gut symptoms. Visual analog scales quantify nausea intensity in real-time in physiologic studies and have been employed as enrollment criteria in clinical trial settings. A new nausea and vomiting survey has been administered to gastroparesis patients to provide insight into timing, triggers, and autonomic and psychological correlates of these symptoms. Several gastric sensorimotor and extragastric abnormalities are proposed to contribute to nausea and vomiting pathogenesis, but their relations to symptom severity are either limited or uninvestigated. Gastric emptying delays are prevalent in patients with chronic nausea and vomiting, as are blunting of fundic accommodation, aberrant gastric slow wave rhythms, and heightened perception of noxious and physiologic luminal stimulation. Potential extragastric correlates of nausea and vomiting include transit delays distal to the stomach, autonomic abnormalities, altered central nervous system activation, metabolic dysregulation, and psychological dysfunction. One goal of novel survey development will be to relate these physiologic correlates to specific symptom presentations to gain insight into mechanisms of nausea in different clinical conditions. Pediatric patients represent special challenges because of the different disorders that cause nausea and vomiting in children and differences in understanding disease manifestations, the ability to communicate symptom intensity and characteristics, and immature coping mechanisms compared to adults.