Post Operative Nausea & Vomiting (PONV)
Last updated 10/04/15
Definition
- Nausea and/or vomiting which develops in the post-operative period
Features
- Common complication of General Anaesthesia (GA)
- Vomiting 30% patients
- Nausea 50% patients
- Distressing for patients
- Risk of side effects of anti-emetics needs to be weighted against benefit of reduced PONV
- Apfel Score
- Assesses risk factors and estimates likelihood of PONV
- Based on adults not paediatrics
- Scores
- Female = 1 point
- Non-smoker = 1 point
- History of PONV or motion sickness = 1 point
- Use of opiates = 1 point
- Interpretation
- 0-1 risk factors = low risk
- 0 = 10% PONV risk
- 1 = 20% PONV risk
- 2 = 40% PONV risk = medium risk
- 3+ risk factors = high risk
- 3 = 60% PONV risk
- 4 = 80% PONV risk
Causes
- Multifactorial
- Causes of vomiting
- Pharyngeal stimulation
- Abdominal surgery, gastrointestinal distension
- Pain
- Adult Risk Factors
- Female
- Non-smoker
- <50yrs old
- History of PONV
- History of motion sickness
- GA (as compared to regional anaesthesia)
- Volatile inhalational agents
- Peaks 2-6hrs after surgery
- Primary cause for PONV in first 2hrs
- Dose dependant response
- Particularly N2O
- Opiates
- Long duration of anaesthesia
- Cholecystectomy, Laparoscopy, Gynaecological surgery
- Paediatric Risk Factors
- Surgery >30min
- >3yrs old
- History of PONV in patient, parent or sibling
- Strabismus surgery
- Estimation of Risk
- No risk factors 9% risk of PONV
- 1 risk factor 10% risk of PONV
- 2 risk factor 30% risk of PONV
- 3 risk factor 55%% risk of PONV
- 4 risk factor 70% risk of PONV
Complications
- Prolonged hospital stay
- Incisional suture dehescience
- Aspiration
Investigations
- Consider only if diagnosis uncertain or suspected complications
Management
- Prevention
- Management of risk factors
- Choose regional anaesthesia over GA where possible (x9 risk)
- Judicious use of opiates
- Adequate hydration
- Avoid N20 and volatile inhalants, consider Total Intravenous Analgesia (TIVA)
- Use of TIVA with oxygen and air reduces PONV by 25%
- Particularly if considered high risk (Apfel score)
- Prophylaxis
- Evidence does not support giving to all patients undergoing surgery
- Risk Assessment
- Apfel Score as above (or similar for paediatrics)
- Low risk: observe for PONV and manage
- Medium risk: choose 1 or 2 interventions
- High risk: 3+ interventions/multimodal
- Antiemetics
- Combination therapy preferable to single agent
- Multimodal agents are additive in effect
- Common combinations
- 5-HT3 (Serratonin) Receptor Antagonists
- Ondansetron
- 4mg IV given at the end of surgery
- 50-100mcg/kg for paediatrics
- Reduces incidence of PONV by 25%
- First line agent
- More effective at preventing vomiting than nausea
- May cause Long QT
- Granisetron
- 0.35 - 3mg (typically 1mg) IV given at the end of surgery
- 40mcg/kg up to 0.6mg for paediatrics
- Neurokinin 1 (NK-1) Antagonists
- Aprepitant
- 40mg IV single dose at induction
- Half life 40hrs
- More effective at 48hrs than Ondansetron
- Corticosteroids
- Dexamethasone
- 4-5mg IV given at induction
- 150mcg/kg for paediatrics
- Avoid if labile/brittle diabetics as will increase BSL for 6-12 hrs post dose
- Reduces incidence of PONV by 25%
- Not effective as treatmetn, only for prophylaxis
- Butyrophenones
- Droperidol
- 0.625-1.25mg IV given at the end of surgery
- Reduces incidence of PONV by 25% (1.25mg)
- Cautious use in children: only if other therapy fails and is admitted
- 10-15mcg/kg for paediatrics
- Often combined with opiate in PCAs to manage nausea and vomiting
- Antihistamines (Phenothiazines)
- Propofol
- Has antiemetic properties at very low doses (subhypnotic levels)
- 20mg bolus can be used as stat management of PONV
- Agent of choice for TIVA as a prevention strategy for PONV
- Midazolam
- 2mg IV given 30 minutes before end of surgery as effective as Ondansetron 4mg IV
- Metoclopramide (Maxalon)
- Weak antiemetic
- 20mg+ doses required for effect
- Not recommended as agent for PONV
- PC6 Acupuncture point
- Meta-analysis demonstrating effectiveness
- Suitable for adults or children
- Can be used before or after induction
- IV Hydration
- Reduces baseline risk of PONV
- No difference in choice of fluids
- Treatment of PONV
- Antiemetics
- Choose from a different class if an agent was used for prophylaxis
- Limited evidence of increased therapeutic efficacy in repeating dose of same agent given intra-operatively within 6hrs of last dose
- Do not readminister Dexamethasone
- Reduced doses are required for treatment of PONV as compared to prophylaxis
- Propofol 20mg IV bolus
- Effect is brief
- Typically only used in recovery setting
- Requires monitoring
- Prochlorperazine (Stametil)