Post op N+V

Question 1

How common is PONV

Answer 1

25% of surgical patients

Question 2

What are the physiological pathways

Answer 2

Higher cortical centres stimulated through memory/ fear
direct stimulation of small intestine/ stomach/ oesophagus
chemoreceptor triggers: opioids and anaesthetic drugs

Question 3

What are the patient factors that increase risk of PONV

Answer 3

Younger age
being female
non-smoker
previous history of PONV

Question 4

What are the operative factors that increase risk of PONV

Answer 4

abdo, gynae or ent surgery
longer duration of surgery
inhalation agents

Question 5

What are the post op factors that increase risk of PONV

Answer 5

pain
opioid analgesia
dehydration
hypotension

Question 6

What are the adverse effects of PONV

Answer 6

Patient distress
dehydration and electrolyte imbalance
aspiration
tension on sutures
raised ICP
delayed oral intake 
delayed discharge

Question 7

What steps can be taken to prevent PONV

Answer 7

minimal use of opioids and inhaled anaesthetics

use regional anaesthesia where possible

Question 8

What are the drug options for management of PONV and give some advantages/disadvantages of each

Answer 8

Ondansetron- 5HT2 antagonist, most effective, but caution in hepatic impairment, QT prolongation, pregs/breast feeding
Metaclopramide/domperidone/prochlorperazone: dopamine antagonists, relatively ineffective for PONV, contraindicated in parkinsons
Cyclizine: anti-histamine used in middle ear surgery and motion sickness, CI: heart failure, BPH, hepatic/renal disease
Dexamethasone: unknown mechanism used to augment the other drugs

Question 9

How do you management a patient who is unresponsive to the first drug you give for PONV

Answer 9

Add another which acts on a different receptor pathway