Palliative Care: Constipation/Nausea and Vomiting/SOB/End of Life Flashcards
Outline some potential causes of constipation.
- Immobility, reduced food intake
- Reduced fluid intake, fluid loss
- Generalised weakness
- Intestinal obstruction e.g. tumour mass
- Drugs – opioids, diuretics, antimuscarinics, serotonin
antagonists (antiemetics like Ondansetron), some
chemotherapy agents + many others!
Outline some general measures to managing constipation.
- Maximise mobility
- Encourage good hydration
- Assess diet and appetite
List 3 stimulant laxatives.
- Bisacodyl
- Senna
- Sodium Picosulphate
List 3 faecal softener.
- Docusate sodium
- Lactulose (can cause bloating)
- Macrogols (Laxido, Movicol)
List 3 rectal interventions.
- Bisacodyl suppository
- Glycerol suppository
- Osmotic micro-enema (Micralax)
List 2 opioid antagonists use for opioid induced constipation.
- Methylnaltrexone (SC injection)
- Naloxegol
List the common causes of nausea/vomiting.
- Drugs: opioids/NSAIDs/SSRIs/TCAs/chemotherapeutic agents
- Surgical: Bowel obstruction
- Metabolic: inc. Ca2+/inc. urea/decreased sodium/hypoglycaemia
- Increased ICP
- Constipation
- Anxiety
- Uncontrolled pain
- Autonomic neuropathy
Outline step 1 of the 4 step antiemetic ladder.
Selected narrow spectrum drug e.g. metoclopramide (+/- dexamethasone)
Outline step 2 of the 4 step antiemetic ladder.
Alternative narrow spectrum drug e.g. haloperidol/cyclizine/ondansetron
Outline step 3 of the 4 step antiemetic ladder.
Combination of narrow spectrum drugs e.g. haloperidol and cyclizine
Outline step 4 of the 4 step antiemetic ladder.
Broad spectrum drug e.g. levomepromazine
Which antiemetic do you use in gastric paresis?
Metoclopramide (prokinetic)
Which antiemetic do you use in renal failure?
Haloperidol
Which antiemetic do you use in chemotherapy?
Ondansetron + dexamethasone
Which antiemetic do you use in intestinal obstruction?
Cyclizine (+/- haloperidol)
Which antiemetic do you use in unclear/multiple causes?
Levomepromazine (broad spectrum)
Mechanism of action of metoclopramide?
Dopamine (D2) receptor antagonist at chemoreceptor trigger zone at medulla oblongata - preventing nausea and vomiting triggered by most stimuli. Gastric prokinetic effect mediated by muscarininc, D2 antagonism, and 5HT4 receptor agonism (may contribute to antiemetic effect)
Mechanism of action of ondansetron?
Ondansetron is a highly specific and selective serotonin 5-HT3 receptor antagonist, with low affinity for dopamine receptors. The 5-HT3 receptors are present both peripherally on vagal nerve terminals and centrally in the CTZ.
Serotonin is released by the enterochromaffin cells of the small intestine in response to chemotherapeutic agents and may stimulate vagal afferents (via 5-HT3 receptors) to initiate the vomiting reflex. It is thought that ondansetron’s antiemetic action is mediated mostly via antagonism of vagal afferents with a minor contribution from antagonism of central receptors.
Mechanism of action of cyclizine?
- H1 receptor antagonist (antihistamine)
- Not fully elucidated
- Effects on vestibular system and CTZ
- Also exerts central anticholinergic (muscarinic) effects
Mechanism of action of haloperidol?
- High affinity for dopamine D2 receptor (antagonist) - acts at CTZ of MO.
Mechanism of action of levomepromazine?
- Broad spectrum
- D2 receptor antagonism
- H1 receptor antagnosim
- Acetylcholine muscarinic receptor antagonism
Outline the side-effects of metoclopramide.
- Extrapyramidal side-effects:
- Akathisia (restlessness)
- Focal dystonia (the “yips”/spasms)
- Tardive dyskinesia (D2 Rx antagonism e.g. lip smacking/sticking tongue out/rapid blinking) - Abdominal cramps
Outline the side-effects of haloperidol.
- Extrapyramidal side-effects:
- Akathisia (restlessness)
- Focal dystonia (the “yips”/spasms)
- Tardive dyskinesia (D2 Rx antagonism e.g. lip smacking/sticking tongue out/rapid blinking) - Sedation
Outline the side-effects of ondansetron.
- Constipation
- Headache
