Prophylaxis should be considered for patients at risk. Risk factors include:

Patient factors

• previous PONV
• motion sickness
• female
• obesity
• hiatus hernia
• anxiety
• prolonged fast

Surgical Factors

• intra-abdominal
• pelvic
• middle ear
• strabismus
• laparoscopic surgery
• tonsillectomy (where there may be ingestion of blood)
• ambulatory orthopaedic surgery (up to 40% in arthroscopy)

Anaesthetic Factors

• opioids
• N2O
• excessive gastric gas (from 'hand-bagging' to maintain airway)

Post op Factors

• pain
• opioids
• hypotension
• dehydration
• ileus
• hypoxia
• hypercapnoea
• delayed return to enteral nutrition
• hypopglycaemia

• minimise risk factors where possible
• consider pre-operative oral ranitidine 150mg and/or sodium citrate 0.3M 30ml for patients with a significant hiatus hernia
• consider anaesthetic technique using TIVA, where appropriate to reduce risk of PONV depending on the number of unavoidable risk factors:

For persistent PONV unresponsive to the above therapy consider:

• metoclopramide 10mg IM/IV 8 hourly as needed
• dexamethasone 6.6mg IV 8  hourly as needed
• NB there is good evidence to support the fact that metoclopramide (in usual clinical doses) confers no prophylactic antiemetic effect
• an antiemetic prescription should accompany any opioid prescription
• PONV is multifactorial in origin, therefore multimodal antiemetic therapy may be more effective and reduce side effects
• if local anaesthetic blocks used then consider dexamethasone, as the dual action of prolongation of block (improved analgesia) and antiemesis may be favourable