Vomiting and Neasua (2) Flashcards
1
Q
Pharmacology- reminder
A
- Cyclizine (H1, mACh)
- Cinnarizine (H1)
- Promethazine (D2, H1, mACh)
- Hyoscine (mACh)
- Phenothiazine (D2)
- Metoclopramide (D2, 5-HT4) / domperidone (D2)
- Ondansetron (5-HT3)
- Cannabinoids, steroids, NK-1 antagonists
2
Q
Treatment of nausea and vomiting
Always assess first and treat underlying cause
A
- Pregnancy
- Infections- supportive treatment
- Travel
- Vertigo
- Post-operative
- Palliative care
- Chemotherapy
3
Q
Central
A
- Raised itracranial pressure
- Dilation arteries (migraines)
- Sight, smell, taste
- Stimulation labyrinthine mechanisms
4
Q
Peripheral- enteric brain plays a role in this
A
- Gastric dysrhythmias
- Motion sickness
- Delayed gastric emptying
- Gastric mucosal irritation (NSAID)
- All via vagal afferents
- Dilation and obstruction GIT
- Via sympathetic and vagal afferents
- The vagal afferent nerve is the main nerve that moderates these processes
5
Q
Control of nasea and vomiting
A
- CPG- central pattern generator which creates rhythmic outputs from non-Rhythmic inputs
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6
Q
Drug causes of nausea and vomiting
A
- Always assess first
- Identify and correct the underlying cause
- Gastric irritation- antibiotics, Iron, NSAID’s
- Gastric stasis- Anti-muscarinics, opioids, phenothiazine, TCA’s
- CTZ- antibiotics, cytotoxics, digoxin, opioids, imidazoles
- NTS contain opiate receptors which lie outside the BBB and can trigger vomiting
- 5-HT3 receptor stimulation- Antibiotics, cytotoxics, SSRI’s
- Then initiate the most appropriate anti-emetic based on the underlying cause- where the drug is acting will dictate the anti-emetic
7
Q
Post Operative Nausea and Vomiting (PONV)
A
- 20-30% patients experience this as a complication of surgery and anaesthesia
- Surgery
- Pain can trigger pain
- Surgery on GIT can trigger
- as well as drugs used
- Multiple risk factors (female, history of PONV, Peri-operative opioids, type of surgery, anaesthetic, delayed gastric emptying)
- Prophylaxis, no single class may be effective
- Metoclopramide relaticely ineffective in PONV
- Prochlorperazine or cyclizine commonly usaid
- 5-HT3 antagonists in high risk patients
- May require combination
8
Q
PONV
A
- Metoclopramide- D2 receptor
- Increase gastric emptying time- promote gastric motility(NB- use in migraine- GI motility is very low so analgesic doesn’t get absorbed)
- Not good for PONV
- PONV- cyclizine and prochlorperazine are useful
- 5-HT3 antagonists are better in high-risk patients- chance of getting PONV between 60-90%
- We use a different anti-emetic in treatmeant compared to prophylaxis- this is due to reduced effectiveness
- If an anti-emetic doesn’t work and there is no medical reason specialist advice must be used
9
Q
Chemotherapy induced nausea and vomiting (CINV)
A
- Anticipatory- conditioned response- this only occurs when the person has already had N&V with previous therapy around 3-4 cycles in (higher centres of the brain)
- Breakthrough- this is when you get emesis with sufficient anti-emetic prophylaxis- in this case, we will give them a separate agent to the prophylaxis
- Refractory- this is when the person doesn’t respond to any therapy- failure to standard and acute new therapy
- Acute emesis occurring in the 24 hours post chemotherapy
- Delayed emesis up to 120 hours post-treatment and subsides gradually
- Highly emetogenic: cisplatin, carmustine, dacarbazine
- Moderate cyclophosphamide, carboplatin, doxorubicin
10
Q
Treatment of CINV
A
- Local guidelines
- 5-HT3 antagonists parenterally for highly emetogenic regimens, orally for less emetogenic regimens
- Effect can be enhanced with dexamethasone pre-chemotherapy, together with lorazepam
- Combination of NK-1 receptor antagonist (e.g. aprepitant) together with dexamethasone in moderate to highly emetogenic regimens with resistant to other anti-emetic combinations
11
Q
Motion sickness
A
- Stimulation of via afferent pathways to vestibular nuclei, activating brainstem nuclei
- Histaminergic and muscarinic pathways
- If your visual Field is telling you one thing and your vestibular nuclei (responsible for motion and balance) is telling you something else it can trigger vomiting centre
12
Q
Motion sickness
A
- Prophylaxis prior to travelling with hyoscine
- Transdermal patch to be applied several hours before travel
- Adverse effects- dry mouth, blurred vision
- Sedating anti-histmines e.g. cinnarizine may be effective and better tolerated
- Dopamine and 5-HT3 antagonists not effective in motion sickness
13
Q
Pregnancy associated nausea and vomiting
A
- First trimester: 4 weeks post last menses to 12/52
- More than 80% experience nausea, 50% vomiting in first trimester
- Usually not harmful, 90% cases resolve by week 16 most resolve by week 20 gestation
- Distinguish from hyperemesis gravidarum (intractable vomiting 0.5-2% pregnancies)- electrolyte, fluid disturbance usually requires hospital admission
- Cause unclear stimulus may be from the placenta, not the foetus (correlates with the level of HCG)
14
Q
Treatment of N&V of pregnancy
A
- First line- non-drug treatment (small frequency meals)
- Avoid strong smells
- Consider offering drug treatment
- Anti-histamine- oral promethazine/cyclize
- 24/48 hours
- Metoclopramide/ oral prochlorperazine
- 24/48 hours
- Specialist advice
- Anti-histamine- oral promethazine/cyclize
15
Q
Vestibular disorder
A
- Treat underlying cause as well as nausea and vomiting symptoms
- Nausea and vertigo of Meniere’s often resistant to treatment
- In addition to specific treatment antihistamines e.g. cinnarizine or phenothiazines e.g. prochlorperazine e.g. prochlorperazine may help
