Case Studies in Palliative and End-of-Life Care by Margaret L. Campbell

Author:Margaret L. Campbell [Campbell, Margaret L.]
Language: eng
Format: epub
Publisher: Wiley
Published: 2012-07-31T21:00:00+00:00

Treatment

Pharmacologic

The first step in management of intractable nausea and vomiting is to identify the neuro-mechanisms which are triggering the symptoms.5 Four pathways provide input to the vomiting center in the brainstem: (1) the chemoreceptor trigger zone (CTZ), which stimulates vomiting in reaction to toxins in the bloodstream and cerebrospinal fluid; (2) the cortex, which produces nausea in reaction to sensory input, anxiety, meningeal irritation and increased intracranial pressure; 3) peripheral pathways carrying stimuli from receptors in the gastrointestinal tract, serosa, and viscera and transmitted through the vagus and splanchnic nerves, sympathetic ganglia, and glossopharyngeal nerves, and (4) the vestibular system of the labyrinth, which is stimulated by motion to trigger the vomiting center via the vestibulocochlear nerve.

It is possible for just one, many, or all of these triggers to contribute to nausea. In the patient with liver cancer, nausea and vomiting is likely caused by a combination of all of these factors. Opiods commonly used to treat the pain associated with liver cancer can contribute to stimulation of the chemoreceptor zone, gastroparesis, and sensitization of the labyrinth. For the liver cancer patient receiving chemotherapy, stimulation of the chemoreceptor zone and irritation to the gastrointestinal (GI) mucosa with resultant stimulation of the vagus and splanchnic nerves can result in nausea and vomiting. Bowel obstructions stimulate peripheral pathways as a result of the irritation of bowel by accumulated fecal matter and fluids. The accompanying toxins and impaired motility of the gastrointestinal tract trigger the peripheral pathways by stretching and irritating the walls of the gastrointestinal tract.

Mannix identifies eight key steps in the palliation of nausea and vomiting. These include:6

1. Identify the likely cause.

2. Identify the pathways by which the vomiting reflex is triggered.

3. Identify the neurotransmitter receptor involved in that pathway.

4. Prescribe the most potent antagonist for each receptor identified.

5. Choose the route of administration that ensures the drug will reach its receptors.

6. Give the drug regularly and titrate the dose carefully.

7. If symptoms persist, review the steps.

8. Consider whether the trigger for nausea and vomiting can be removed.

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