Nausea and Emesis

Which centre of the brain controls vomiting ?

Medulla - more specifically the chemoreceptor trigger zone

• H1 muscarinic receptors

• NK1 receptors

4 ways vomiting is triggered ?

1. CTZ zone triggered by blood borne drugs, metabolic process

2. Vagus nerve in gut is triggered - irritation

3. Vestibular System - inner ear - motion sickness

4. Cortex higher centre - frontal lobe triggered by emotion stress or anxiety, smell, raise ICP

Which receptors are drug targets for nausea ?

• dopamine 2 receptor

• 5-HT3 receptor

• Histamine 1 receptor

• Muscarinic (ACh)

• NK1 receptor

Which kind of drugs act upon receptors for nausea ?

Antagonists - mostly P medicines

What type of antagonists act upon dopamine 2 receptor and for which type of nausea is this useful ?

• Metoclopramide, prochlorperazine, haloperidol and domeperidone

• For nausea associated with migraines

Which receptors are linked to motion sickness ?

• muscarinic ACh receptors

Which receptor is linked to chemotherapy induced nausea ?

• NK1 receptors

What are the 5 main aetiologies of nausea ?

1. Gut - gastroenteritis

2. Brain/cortex - migraine

3. Vestibular - motion sickness

4. Metabolic/endocrine - pregnancy

5. Drugs and toxins - opioids, chemotherapy

Key questions to ask when taking a history for nausea

1. Who are we treating ?

2. What is coming up ?

3. Other symptoms ?

4. Medicine history ?

5. How one and often ?

6. Keeping fluids down ?

7. Triggers ?

8. Pregnancy? Other conditions ?

Red flags for referal to A&E

• blood in vomit or green bile - poisoning

• Stiff neck and light sensitivity - sudden and severe headache or abdominal pain

• Breathing difficulty; nausea chest pain that radiates to arm or jaw

Urgent same day referral

• babies under 12 months - children that stopped feeding - dehydrated and not improving

• Cannot keep fluids down - vomiting for more than 2 days - diarrhoea for more than 7 days

• Chemotherapy patient

Routine GP referal

• nausea that’s not improving after a few days and keeps coming back

• Aged 55+ with nausea/vomiting and weight loss

spotting dehydration in under 5’s - SHOCK SYNDROME

• decreased consciousness

• pale or mottled skin

• cold hands and feet

• weak pulses, prolonged capillary refill

• fast heart rate and breathing

• low blood pressure

spotting dehydration in under 5’s - clinical dehydration

• appears unwell or deteriorating

• irritable or lethargic

• decreased urine output

• sunken eyes - dry mouth

• fast heart rate and breathing

• reduced skin turgor

spotting dehydration in under 5’s - healthy and no worries

• appears well and alert

• normal urine output

• normal skin colour, warm hands and feet

• eyes not sunken, moist mouth

• normal heart rate and breathing

who has a lower threshold for referral when it comes to dehydration and vomiting ?

• babies and children under 5

• call 999 - pale, mottled or cold skin, non blanching rash, very lethargic

• same day referral - baby under 12 mnths with D&V, no wet nappy for 8+hrs, stopped drinking/feeding, fever >38*C

key sign of dehydration in babies

• sunken fontanelle on head

Prescribers steps of action when treating vomiting and diarrhoea

counselling points for oral rehydration salts (dioralyte)

How to prepare dioralyte ?

Dioralyte dosing - adults, children and infants

Why does motion sickness occur ?

non drug measures when treating motion sickness

which receptors and organs are involved in motion sickness ?

• inner ear - vestibular apparatus - senses motion

• eyes - see stillness

• H1/muscarinic receptors - vomiting centre of the brain

Is the drug Hyoscine hydrobromide, cinnarizine or promethazine ?

Hyoscine : who to avoid and counselling points

cinnarizine and Promethazine are antihistamines - what are the counselling points when prescribing these meds ?

what did the MRHA find in 2023 about hyoscine patches ?

• they can cause serious anticholinergic effects including hyperthermia - the effects may last 24h+ after removal

what is the only OTC antiemetic used for migraines and who to sell this to ?

what are the contraindications for Buccastem M and what are the side effects

which antiemetic became a POM in 2014 ?

domperidone

what does NICE recommend when treating gastroenteritis in young children ?

• rehydrate

• Do NOT prescribe antiemetics