From the Guidelines
Nausea and vomiting are complex processes involving multiple pathways and neurotransmitters, including serotonin, dopamine, acetylcholine, and histamine, which stimulate the vomiting center in the brain, leading to the emetic response.
Pathophysiological Mechanisms
The chemoreceptor trigger zone, vomiting center, and gastrointestinal tract have many neurotransmitter receptors that can be activated by chemotherapeutic agents or their metabolites, leading to chemotherapy-induced emesis 1.
Different Pathways Involved
The emetic response involves a multistep reflex pathway controlled by the brain, triggered by afferent impulses to the vomiting center from the:
- Chemoreceptor trigger zone
- Pharynx and gastrointestinal tract (by way of vagal afferent fibers)
- Cerebral cortex 1
Evaluation of Nausea and Vomiting
Evaluation of nausea and vomiting should consider various causes, including:
- Gastric outlet obstruction
- Bowel obstruction
- Constipation
- Opioid use
- Hypercalcemia 1
- Chemotherapy and radiation therapy 1 Treatment options may include:
- Proton pump inhibitors and histamine-2 (H2) receptor antagonists for gastritis or gastroesophageal reflux
- Corticosteroids for gastric outlet obstruction
- Dopamine receptor antagonists (e.g., prochlorperazine, haloperidol, metoclopramide, olanzapine) or benzodiazepines for nonspecific nausea and vomiting
- 5-HT3 receptor antagonists and/or anticholinergic agents and/or antihistamines for persistent nausea and vomiting 1
From the Research
Pathophysiological Mechanisms
The pathophysiology of nausea and vomiting is complex and involves multiple mechanisms, including:
- Defense mechanisms to remove toxins or irritants from the gastrointestinal tract 2, 3
- Stimulation of emetic pathways through activation of various receptor subtypes 4, 3
- Brain-gut interactions, gastrointestinal neurophysiologic, motor, sensory, and hormonal factors 5
Pathways Involved
Several pathways are involved in the evaluation of nausea and vomiting, including:
- Vagal and non-vagal pathways 4
- Brainstem nuclei, such as the nucleus tractus solitarii 6
- Autonomic nervous system, including the vagus nerve and spinal cord neurons 4, 6
- Central nervous system areas, including the anterior insular cortex, anterior cingulate cortex, and amygdala 6
Neurochemical Mechanisms
Neurochemical mechanisms play a crucial role in the pathophysiology of nausea and vomiting, including:
- Neurotransmitters and mediators, such as serotonin and dopamine 2, 3
- Corresponding receptors, such as 5-HT3 and D2 receptors 3
- Intracellular emetic signaling pathways, including postreceptor signal transduction mechanisms 3
Current Understanding and Future Directions
While significant progress has been made in understanding the mechanisms of nausea and vomiting, there is still much to be discovered, particularly in the area of chronic nausea and vomiting 5, 6. Future research should focus on elucidating the complex interactions between various mechanisms and pathways, as well as developing effective treatments for nausea and vomiting 2, 3, 6.