Flashcards in Management of Nausea and Vomiting Deck (54)
What is nausea?
The unpleasant feeling of the need to vomit
What may (or may not) nausea be accompanied by?
What is vomiting?
The forceful expulsion of gastric contents through the mouth
What % of patients who undergo chemotherapy experience nausea or vomiting?
What % of patients who undergo chemotherapy experience anticipatory vomiting?
What are the categories of factors that influence the incidence and severity of chemotherapy induced emesis?
- Specific chemotherapeutic drug
- Patient variables
What factors about the specific chemotherapeutic drug can influence chemotherapy induced emesis?
- Schedule of administration
What patient variables increase the risk of chemotherapy induced emesis?
- Young patients
What brainstem sites have key roles in the vomiting reflex pathway?
- Chemoreceptor trigger zone
- Vomiting centre
Where is the chemoreceptor trigger zone situated?
In the area postrema
What is the area postrema?
A circumventricular structure at the caudal end of the fourth ventricle
Is the area postrema inside or outside the blood brain barrier?
What is the result of the area postrema being outside the blood brain barrier?
It can respond directly to chemical stimuli in the blood or CSF
Where is the vomiting centre found?
In the lateral reticular formation of the medulla
What is the role of the vomiting centre?
- Co-ordinates the motor mechanisms of vomiting
- Responds to different afferent inputs
What afferent inputs does the vomiting centre respond to?
- Vestibular system
- Periphery (pharynx and GIT)
- Higher brainstem cortical structure
How do chemotherapeutic agents exert their emetic actions?
Chemotherapy agents, or their metabolites, can directly activate the medullary chemoreceptor trigger zone or vomiting centre. They can also act peripherally to cause vomiting.
What neuroreceptors play a critical role in chemotherapy-induced emesis?
Several neurotransmitters, including dopamine receptor type 2 and serotonin type 3 (5-HT3)
What can trigger anticipatory vomiting?
- Colour or smell of chemotherapeutic drugs
- Stimuli associated with chemotherapy, such as cues in treatment room or the person administering the chemotherapy
What is the mechanism of anticipatory vomiting?
The triggers activate higher brain centres and trigger emesis
How do chemotherapeutic drugs act peripherally to cause vomiting?
They cause cell damage in the GI, releasing serotonin from the enterochromaffin cells of the small intestinal mucosa
How does the release of serotonin from damage enterochromaffin cells cause vomiting in chemotherapy?
The released serotonin activates 5HT3 receptors on vagal and splanchnic afferent fibres, which then carry sensory signals to the medulla, leading to an emetic response
How can you identity the cause of nausea and vomiting clinically?
Often, there are common patterns/syndromes
What % of patients will have more than 1 cause of N&V?
Up to 25%
What are the different causes of N&V that lead to different patterns?
- Impaired gastric emptying
- Chemical/metabolic disturbances
- Raised ICP
- Malignant bowel obstruction
What are the clinical features of nausea caused by impaired gastric emptying?
- Epigastric discomfort
- Reduced appetite/satiety
- Post-prandial or bloating/audible splash
- Intermittent vomiting that eases nausea
- Large volume vomits that may contain food
What are the causes impaired gastric emptying in cancer?
- Causes associated with cancer
- Autonomic neuropathy
What are the causes of impaired gastric emptying associated with the cancer?
- Locally advanced cancer
- Lymph node enlargement
- Liver mets
Give 2 examples of drugs that can cause delayed gastric emptying