Causes of Nausea
- Chemical etiology
- As a result of chemical triggers detected at the chemoreceptor trigger zone
- Differential includes
- Medications and drugs – opioids, antibiotics, NSAIDs
- Chemotherapy
- Metabolic causes such as kidney/liver failure
- Electrolyte imbalance
- Visceral
- Differential includes
- Bowel obstruction
- Constipation
- Liver capsule stretch due to metastatic disease
- Anything that increases abdominal pressure
- Ascites
- Intra-abdominal masses/metastases
- GERD
- Delayed gastric emptying
- Differential includes
- Cerebral cortex
- CNS lesion
- Increased ICP
- Head trauma
- Psychogenic/anticipatory
- Vestibular
- Motion sickness
- Positional vertigo
Management of Nausea
- Choice of anti-emetic should be determined by the underlying cause of nausea
- Gut prokinetic anti-emetics
- Metoclopramide (acts on CTZ)
- Domperidone – similar to metoclopramide but doesn’t cross BBB
- Antipsychotics
- Haloperidol (acts on D2 receptors at CTZ)
- Prochloperazine
- Olanzapine
- Methotrimeprazine
- Second-line, not first-line due to widespread receptor effect leading to more side effects
- 5HT3 antagonists
- Ondansetron (expensive in outpatient)
- Granisetron
- Mainly used for chemotherapy and radiotherapy induced nausea
- Antihistamine
- Dimenhydrinate (gravol)
- Affects H1 histamine receptor
- Most effective for vestibular nausea
Main anti-emetics used depending on cause of vomiting (from A practical approach to Symptom management in palliative care)
- Drug toxin or metabolic
- Haloperidol
- Levomepromazine
- Radiotherapy
- Haloperidol
- Chemotherapy
- Ondansetron
- Dexamethasone
- Metoclopramide
- Bowel obstruction
- Cyclizine (antihistamine)
- Scopomaline (anticholinergic)
- Delayed gastric emptying
- Metoclopramide
- Domperidone
- Raised intracranial pressure
- Cyclizine
- Dexamethasone