Nausea and Vomiting

Question 1

Define n&v

Answer 1

Retching and vomiting associted with sickness, Pain and Vagal stimulation.

Question 2

PATHO 
How does vomiting occur (3) - signal pathways
1-
2-
3- (5)

Answer 2

1. 
GIT Stimulation releases serotinin - activates 5HT receptor.
AFFERENT impulses sent to CTZ and VOMITING CENTER
EFFERENT impulses from:
2. CTZ to VC
3. VC to:
- oesophageal sphincter relaxation
- abdo muscle contraction (vomit)
- pharyngeal constriction (retching)
- salivation
- increase resp rate

Question 3

How does ONDANSATRON work

When does ondansatron not work,

Answer 3

Is a 5HT receptor inhibitor.

Blocks serotonin release and uptake in the synaptic cleft, preventing afferent signals from GIT to vomiting centre and CTZ.

Ondans does not work for car or motion sickness - this is initiated within the brain not the GIT.

Question 4

N&V Tx

Drug and preparation (adults)

Precautions 2

Answer 4

Ondansatron

4mg/ 2ml and 4mg wafer

IM neat - push

IV neat or with 8mL saline - slow push to avoid negative outcomes

Sensitivity to 5Ht receptor antagonists
Long QT syndrome
Dystonia reactions (involuntary muscle contraction)

Question 5

Negative effects of fast administration of ondansatron

Dystonic reactions

Answer 5

• bradycardia
• hypotension
• arrhythmia

Dystonia occurs due to an alteration in dopamine balance in the CTZ - this can be affected by the use of Ondansatron.

Question 6

Ondansatron for

Dose with age

IM/ IV

Answer 6

ORAL
2mg (2-6year)

4mg (>6)

IM
150 microg/kg to a max 4mg if >2

IV
Consult 150microg/kg if >2 years

Not given under 2 years