Nausea and vomitting

Question 1

Consequences of post-op N+V

Answer 1

• Increased anxiety for future procedures
• Increased recovery time and hospital stay
• Severe causes: aspiration pneumonia, metabolic alkalosis etc

Question 2

RF of PONV - patient factors

Answer 2

• Female
• Age - declines as age
• Previous PONV or motion sickness
• Use of opioid analgesia
• Non-smoker

Question 3

Surgical risk factors for PONV

Answer 3

• Intra-abdominal laparoscopic surgery
• Intracranial or middle ear surgery
• Squint surgery
• Gynae surgery - esp ovarian
• Prolonged operative time
• Poor pain control post op

Question 4

Anaesthetic risk factors for PONV

Answer 4

• Opiate analgesia or spinal anaesthesia
• Inhalational agents (eg Isoflurane, nitrous oxide)
• Prolonged anaesthetic time
• Intra-operative dehydration or bleeding
• Overuse bag and mask ventilation - leads to gastric dilatation

Question 5

Two areas in nervous system that play key role in controlling nausea and vomitting

Answer 5

• Vomitting centre
• Chemoreceptor trigger zone

Question 6

Where is the vomitting centre and what does it do?

Answer 6

• Lateral reticular formation of medulla oblongata
• Controls and co-ordinates the movements involved in vomitting

Question 7

Where is the chemoreceptor trigger zone?

Answer 7

• Area postrema - inferior aspect of 4th ventricle
• Outside the blood brain barrier so can respond to stimuli in circulation

Question 8

What does the vomitting centre receive input from?

Answer 8

• Chemoreceptor trigger zone
• GI tract
• Vestibular system
• Higher cortical structures - eg sight, smell, pain
  = nausea

Question 9

What happens if stimuli are sufficient in stimulating vomitting centre?

Answer 9

• It acts on diaphragm, stomach and abdominal muscles to initiate vomitting

Question 10

Neurotransmitters involved in vomitting and where

Answer 10

• CTZ - Dopamine and 5HT3
• Vestibular - acetylcholine and histamine
• GI - dopamine
• Vomitting centre - histamine and 5HT3

CD number 3, HeAr, eating makes you happy, VH5 like VO5 brand

Question 11

How to manage patient who is drowsy or vomitting?

Answer 11

• Assess A-E first then consider need for NG tube
• Due to risk of aspiration

Question 12

Questions to consider when assessing someone with PONV?

Answer 12

• What was the op - high risk for PONV?
• Anaesthetic agents/post op drugs?
• Other factors eg infection, GI causes, metabolic, neurological
• Antiemetic therapy best suited?

Question 13

Prophylactic measures to try and prevent PONV

Answer 13

• Anaesthetic - reduce opiates, volatile gases and spinal anaesthetic
• Prophylactic antiemetics
• Dexamethasone at induction

Question 14

Conservative management of PONV

Answer 14

• Fluids
• Analgesia
• NG tube considered to aid gastric decompression

Question 15

Management of PONV with impaired gastric emptying

Answer 15

• Prokinetic agent
• eg Metoclopramide or Domperidone (dopamine antagonists)
• UNLESS you suspect bowel obstruction

Question 16

Management of PONV caused by metabolic or biochemical imbalance eg uraemia, electrolyte problem or cytotoxic agents

Answer 16

• Metoclopramide for METabolic

Question 17

Management of opitae induced PONV

Answer 17

• Ondansetron - 5HT3 receptor antagonist
• OR cyclizine (H1 receptor antagonist)

Question 18

Anti emetics and where they act on the pathway

Answer 18

Draw it out :)