Post-operative nausea and vomiting

Question 1

Who is at risk of PONV

Answer 1

Female
History of PONV (?motion sickness)
Non smokers
Patient on opioid therapy

Question 2

Which anaesthetic/surgical factors increase risk for PONV

Answer 2

Nitrous > Volatiles > TIVA
Use of opioids
Prolonged surgery
Visceral > peripheral
Laparoscopic > laparotomy

Question 3

What is the background risk of PONV

Answer 3

~10%, inc to 20% with 1 risk factor, 40% with 2, 60% with 3 and 80% with 4

Question 4

How can an anaesthetic be altered to reduce risk of PONV

Answer 4

Consider use of regional techniques
Substitute propofol for volatiles and remifentanil for fentanyl
Minimise use of intraoperative opioids
Avoid nitrous
Minimise use of neostigmine
?? use intraoperative supplemental oxygen

Question 5

What are the classes of anti-emetic

Answer 5

5-HT3 receptor antagonists (Ondansetron)
D2 receptor antagonists (Metoclopramide, droperidol, prochlorperazine)
H1 receptor antagonists (Cyclizine, promethazine)
Steroids (Dexamethasone)
Anti-cholinergics (Hyoscine)
Propofol
Naloxone
Neurokinin-1 receptor antagonists (Aprepitant)

Question 6

Outline a process for managing PONV

Answer 6

Identify at risk patients and plan accordingly
Use monotherapy anti-emetics for those at moderate risk
Use multi-modal anti-emetic therapy for those at high risk
Prescribe post-op anti-emetics that work on a different receptor to those given intraop