PONV

Question 1

3 Steps in PONV guideline

Answer 1

1. Identify risk (Apfel score)
2. Reduce baseline risk factors
3. Administer prophylaxis if medium or high risk

Question 2

What is the scoring system for PONV?

Answer 2

Scoring system for PONV (Apfel simplified risk score)

1. Female (2.57)
2. Non-smoker (1.82)
3. Hx PONV (2.09)
4. Post-operative opioids

Risk:
0 = 10% (Low)
1 = 20% (Low)
2 = 40% (Medium)
3 = 60% (High)
4 = 80% (High)

Question 3

What is the scoring system for post-discharge n&v in ambulatory surgery?

Answer 3

Scoring system for post-discharge vomiting in ambulatory surgery

1. Female
2. Hx PONV
3. Age < 50
4. Post-operative opioids
5. Post-operative nausea

Risk:
0 = 10%
1 = 20%
2 = 30%
3 = 50%
4 = 60%
5 = 80%

Question 4

What is the scoring system for post-operative vomiting in children

Answer 4

Scoring system for post-operative vomiting in children

1. Surgery > 30 min
2. Age > 3yrs
3. Strabismus surgery
4. Hx PONV or FHx

0 = 10%
1 = 10%
2 = 30%
3 = 50%
4	= 70%

Question 5

How can we reduce the basline risk factors for PONV?

Answer 5

a. Use regional anaesthesia
b. Use TIVA
c. Avoid N2O
d. Avoid volatiles
e. Minimise opioids
f. Hydration

Question 6

What are the 5 classes of recommended anti-emetics for PONV?

Answer 6

a. 5-HT3 antagonists
b. NK-1 antagonists eg aprepitant
c. Corticosteroid
d. Butyrophenone
e. Antihistamine

Question 7

Which 5-HT3 anatagonist is most efficacious and at what point in surgery should they be given?

Answer 7

All equivalent efficacy. All most effective when given at end of surgery.

Question 8

Ondansetron - dose, efficacy, side effects

Answer 8

Ondansetron:
Recommended dose 4mg IV (equal to 8mg oral dose).
Better anti-vomiting than anti-nausea effects. NNT=6 for preventing vomiting, NNT=7 for preventing nausea (over a 24 hour period) .
NNH=36 (Headache), NNH=31 (↑ LFT), NNH=23 (Constipation)

Question 9

Dexamethasone dose and benefits in PONV

Answer 9

Dexamethasone 4-5mg recommended at induction. 4mg is minimum effective dose. 
Higher doses (>.1mg/kg), in addition to anti-nausea properties, also decrease opioid requirement, sore throat, insomnia and fatigue. Therefore 8mg may be considered although further confirmation is needed.

Question 10

Droperidol dose, efficacy, and side effects

Answer 10

Droperidol 0.625-1.25 is as efficacious as ondansetron, NNT=5, and superior to metoclopramide. Most effective when administered at END of surgery. QTc effects are equivalent between droperidol, ondansetron, and both together.

Question 11

Hyoscine for PONV prophylaxis - efficacy and side effects

Answer 11

Transdermal hyoscine applied at least 2 hours prior to surgery. NNT = 6. Side-effects visual disturbance NNH=5.6, dry mouth NNH=13, dizziness NNH=50.

Question 12

Role of metoclopramide in PONV prophylaxis

Answer 12

Metoclopramide is a weak antiemetic and is not effective at doses of 10mg or less. NNT=16 for 25mg, NNT=11 for 50mg. EPSES are 0.6%

Question 13

Role of Midazolam for PONV prophylaxis

Answer 13

Midazolam 2mg at the end of surgery is as effective as ondansetron.