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Nausea and Vomiting: A thread (mostly for fun)
First a little background adapted from Dylan Harris: lecturer at University of Cardiff.
First a little background adapted from Dylan Harris: lecturer at University of Cardiff.
Chemoreceptor trigger zone
Located at the blood brain barrier in 4th ventricle. Think of this as a smoke detector. It is on constant alert for toxins, poisons and nasties floating about in your blood stream. It uses Dopamine and Serotonin mainly to mediate its effects.
Located at the blood brain barrier in 4th ventricle. Think of this as a smoke detector. It is on constant alert for toxins, poisons and nasties floating about in your blood stream. It uses Dopamine and Serotonin mainly to mediate its effects.
The Vomiting Centre.
Think of this as the sprinkler system located in the medulla.
Stimulation leads to the inevitable vomiting reflex. Histamine and Acetylcholine play a role.
Think of this as the sprinkler system located in the medulla.
Stimulation leads to the inevitable vomiting reflex. Histamine and Acetylcholine play a role.
Other areas that feed into the vomiting centre:
The vestibular apparatus. The “whirly pit” after a heavy night out, labyrinthitis or motion sickness.
Mediated by histamine and acetylcholine.
The vestibular apparatus. The “whirly pit” after a heavy night out, labyrinthitis or motion sickness.
Mediated by histamine and acetylcholine.
Gastrointestinal tract:
Gastric Distention, toxic stimulation of vagal afferents or stimulation of glossopharyngeal nerve.
Mainly mediated by 5HT3 and dopamine receptors.
Gastric Distention, toxic stimulation of vagal afferents or stimulation of glossopharyngeal nerve.
Mainly mediated by 5HT3 and dopamine receptors.
Higher centres:
Fear, anxiety, apprehension and emotion.
Mediated by GABA
Fear, anxiety, apprehension and emotion.
Mediated by GABA
It’s a little more complex but armed with this knowledge we can have a good go at treating nausea.
Don’t forget history and examination first though. Then look at the drug chart and blood results.
Don’t forget history and examination first though. Then look at the drug chart and blood results.
Suspect toxins?
New drug: opioid, antibiotics
Toxin: uraemia, sepsis, DKA.
You want to target the Chemoreceptor trigger zone and
Block Dopamine.
Try: Haloperidol, Metoclopramide
New drug: opioid, antibiotics
Toxin: uraemia, sepsis, DKA.
You want to target the Chemoreceptor trigger zone and
Block Dopamine.
Try: Haloperidol, Metoclopramide
Suspect Inner ear issue, raised Intracranial pressure or intracerebral cause?
Target vestibular/cerebellar inputs and block Histamine/acetylcholine receptors.
Try: Cyclizine, Hyoscine hydrobromide, Prochlorperazine
Target vestibular/cerebellar inputs and block Histamine/acetylcholine receptors.
Try: Cyclizine, Hyoscine hydrobromide, Prochlorperazine
Suspect Gastrointestinal source?
Gastris stasis: opioids, DKA, gastroparesis
Try: Metoclopramide as a prokinetic
Damage to GI lining: radiotherapy, chemotherapy, gastroenteritis.
Try: 5HT3 antagonist ondansetron.
Gastris stasis: opioids, DKA, gastroparesis
Try: Metoclopramide as a prokinetic
Damage to GI lining: radiotherapy, chemotherapy, gastroenteritis.
Try: 5HT3 antagonist ondansetron.
Suspect emotion/fear?
Often referred to as anticipatory nausea and vomiting. Seen in patients and attending for chemotherapy after first cycle induces nausea.
Try: Benzodiazepine evening and/or morning before treatment/procedure.
Often referred to as anticipatory nausea and vomiting. Seen in patients and attending for chemotherapy after first cycle induces nausea.
Try: Benzodiazepine evening and/or morning before treatment/procedure.
Some pointers:
Metoclopramide can be very handy. I often use first line. It is non-sedating and note how it targets 2 causes of nausea.
Cyclizine will block the prokinetic of Metoclopramide: avoid using together.
Metoclopramide can be very handy. I often use first line. It is non-sedating and note how it targets 2 causes of nausea.
Cyclizine will block the prokinetic of Metoclopramide: avoid using together.
Cyclizine: Can cause psychiatric side-effects especially if given as rapid injection. Caution in elderly and those with dementia.
If you suspect something is causing Nausea from the neck upwards then Cyclizine may be an option. Its uses are limited from the neck down
If you suspect something is causing Nausea from the neck upwards then Cyclizine may be an option. Its uses are limited from the neck down
Ondansetron/ 5HT3 antagonists:
Licensed for chemotherapy/radiotherapy induced nausea.
Over used in other indications (personal opinion)
Very constipating! Commonly combined with opioids which leads to severe constipation and worsening nausea.
Licensed for chemotherapy/radiotherapy induced nausea.
Over used in other indications (personal opinion)
Very constipating! Commonly combined with opioids which leads to severe constipation and worsening nausea.
Levomepromazine:
Palliative care workhorse that hits most receptors in the vomiting set up. Sedating and causes postural hypotension.
Doses above 12mg/day are rarely needed to get the anti-emetic effect, all you will acheive is sedation at higher doses.
Results favourable
Palliative care workhorse that hits most receptors in the vomiting set up. Sedating and causes postural hypotension.
Doses above 12mg/day are rarely needed to get the anti-emetic effect, all you will acheive is sedation at higher doses.
Results favourable
Remember non-pharmacological options:
Control odours, remove sick bowls regularly, get bowels moving, treat dry mouth/candida, rationalise tablets, position (raise head in ICP)
BNF is your friend for side-effects and speak to ward pharmacist they are legends.
Control odours, remove sick bowls regularly, get bowels moving, treat dry mouth/candida, rationalise tablets, position (raise head in ICP)
BNF is your friend for side-effects and speak to ward pharmacist they are legends.
