Chewing gum for the treatment of postoperative nausea and vomiting: a pilot randomized controlled trial. Darvall JN, Handscombe M, Leslie K.  British Journal Anaesthesia 2017;118(1):83-89.

Presented by: Dr K James


 Two main areas of  which paper aims of addressing:

  1. Pilot study to test feasibility of a larger Randomised Controlled Trial
  1. Chewing gum may be non-inferior to ondansetron in inhibiting Post Operative Nausea and Vomiting (PONV)
    • Currently no existing study examining the effect of gum chewing on PONV.
    • It is postulated to reduce nausea and vomiting via the ‘sham feeding’ effect linked to vagal stimulation.
    • Meta-analysis (272 patients, 7 RCTs) demonstrated reduced time to first flatus and bowel motion and a non-significant trend towards earlier hospital discharge.
  • Chewing gum may be beneficial in the post operative care setting because:
    • It is a non-pharmacological agent,
    • There are very few side effects
    • It can be self administered

Design & setting

  • Randomized controlled non-inferiority trial to test the hypothesis:

“Chewing gum in the PACU would prove to be non-inferior to ondansetron for the treatment of PONV in female patients after laparoscopic or breast surgery and to test the feasibility of a large multicentre RCT”

  • Non Inferiority defined as a difference between groups of <15% in a per protocol analysis
  • Study was carried out in PACU, Department of Pain and Anaesthesia in Royal Melbourne Hospital,
  • Ethical approval gained 


  • Female adult patients
  • Laparoscopic or breast surgery
  • January – June 2016.
  • Written consent was gained from patients
  • Patient/doctor/anaesthetist blinded until patient experienced nausea or vomiting in PACU


  • 155 patients eligible, 53 excluded. Not all reasons for exclusion were disclosed, but a high proportion was due to failure to recruit both anaesthetist and patient.
  • 94 randomized pre-operatively
  • Control arm (n = 46)
    • Received IV anti-emetics on the occurrence of PONV in PACU (current standard of care.)
    • Ondansetron 4mg IV
  • Chewing gum arm (n = 48)
    • Chewing gum administered as first line on occurrence of PONV in PACU
    • Rescue IV anti-emetics available if required.
  • Relief of PONV graded on four point verbal descriptive scale


  • Primary outcome:
    • Full resolution of PONV after either ondansetron or chewing gum.
  • Secondary outcomes:
    • Duration of PACU stay
    • Anti-emetic rescue use
    • Patient acceptability of anti-emetic treatment.
  • Feasibility outcomes:
    • Recruitment rate
    • Protocol compliance
    • Incidence of PONV
    • Ability to chew gum


The investigators state that:

  • Chewing gum was non-inferior to ondansetron for the treatment of PONV.
    • (Symptoms resolution of 75% and 39% respectively)
  • Non-inferiority statistics demonstrated a p-value of 0.07. (Not significant)
  • No difference in secondary outcomes between groups.
  • Recruitment was satisfactory, protocol acceptable to anaesthetists and nurses, data collection was complete.


On face value, with little critical appraisal of the paper the following conclusions can be made from reading the authors conclusions:

  • Chewing gum was not inferior to ondansetron for treatment of PONV after general anaesthesia for laparoscopic or breast surgery in female patients.
  • Larger multi-centred RCT is feasible


  • Clearly states only a pilot study throughout the report
  • Transparent data collection and data representation
  • Data and results presented thoroughly. Very nice paper to read which looks very appealing.
  • Novel and interesting treatment and solution to PONV


  • It is only a pilot study, not a RCT (and they had already performed a pilot study for this debate in question)
  • A power calculation was performed, but them not adhered too.
  • They assessed whether PONV was present or absent, its severity was not assessed.
  • There was a variation in medications used intraoperatively which may have effected the results:
    • Additional opioids
    • Reversal agent
    • Intra-op. antiemetics
  • Variation in surgery:
    • Laraoscopic and breast surgery which have two very different profiles of emesis.
  • Peppermint flavour of the chewing gum used may be a confounding factor as it has been reported that peppermint settels the stomach
  • More than 50% of patients of the Chewing Gum group received pharmacological anti emetics. 

Implications and Potential for impact

  • Future RCT could be feasible
  • Interesting study, well presented
  • No conclusions can be drawn about chewing gum as an anti emetic
  • I wont be prescribing Wrigley’s Extra on anaesthetic charts!

Although the paper was written and presented very well, it is trying to find an answer to a problem that does not exist because ondansetron is very well tolerated by most patients, is cheap and not very labour intensive to administer. Conversely, chewing gum, if administered to patients who are too sleepy, could cause harm. The data is analysed in such a way that it is very difficult to follow, and indeed gain any conclusions from.