POPCORN trial will compare the side effects and effectiveness of Morphine versus Oxycodone medication when prescribed for use as patient controlled analgesia (PCA) for pain relief for paediatric patients after-surgery. This trial is embedded into routine patient care using the hospital electronic medical record (EMR). Participants will be randomly assigned to either medication after they enrol in the study.

The main questions the POPCORN trial aims to answer are:

• 1. Is there a difference in the usage of medication to treat nausea and vomiting for those who received oxycodone PCA versus morphine PCA for post-surgery pain relief?
• 2. Is there a difference in side effects or pain relief needed between the two groups?

Study activities are as follows:

• Participants enrolled to study during their pre-operative consultation
• Participants are randomly assigned to morphine or oxycodone
• No further study-specific activities expected from participant after enrolment and randomisation
• Participant receives routine medical care as planned
• Clinicians record assessments as per routine care in electronic medical record (EMR)
• EMR data are extracted as trial data

Morphine and oxycodone are commonly used intravenous (IV) opioids in adult and paediatric post-operative patients. Traditionally, morphine has been preferentially prescribed with PCA. However, IV oxycodone is rapidly becoming more popular. Despite systematic reviews describing their use within the adult population, very little is known about the comparative side-effect profiles of morphine versus oxycodone within the paediatric post-operative population. Both options are currently in use and considered standard of care at The Royal Children's Hospital (RCH), Melbourne, Australia. However, there is limited literature to support a clinician's choice between IV oxycodone PCA versus IV morphine PCA.

The aim of this embedded randomized controlled trial is to compare the side-effect profile of IV oxycodone PCA to IV morphine PCA in post-operative paediatric patients.

This is a single site, randomised, embedded trial with two intervention arms, namely IV morphine PCA and IV oxycodone PCA. The study will not be blinded due to the need for opioid syringes to be readily identifiable on the ward. Apart from the consent and randomisation process, there will be no change to current pre-existing practices around PCA use and patient care. Adopting a health informatics approach; patient identification, consent, randomization and reporting of outcomes will be embedded within the EMR.

The primary objective is to compare antiemetic use between the two intervention arms. The secondary objectives will be a comparison of PCA side effects, efficacy and opioid use between the two arms. Outcome data must be what is already recorded as part of usual clinical care within the EMR including: antiemetic administration, respiratory depression (new oxygen and/or high dose naloxone use), urinary retention (need for in-dwelling catheter insertion), constipation (medication laxative administration), itch (RCH Itch Score (0-4 Likert scale)), nausea and vomiting, sedation (0-4 University of Michigan Scoring System), pain (Wong-Baker FACES Pain Rating Scale/Visual Analogue Scale (VAS 0-10) and total opioid consumption (mg/kg/day).

Inclusion Criteria:

• Postoperative patients who are appropriate for a PCA including those aged 6 and above and up to age 18 years.
• Those deemed appropriate for either morphine or oxycodone by their treating anaesthetist.
• American Society of Anaesthesiologists (ASA) score 1-3 inclusive
• Those whose parents or legal guardians have provided informed consent on the patient's behalf.

Exclusion Criteria:

• Any patients with an allergy, hypersensitivity, or contraindication to morphine or oxycodone.
• Patients in the age group with significant intellectual disability or physical incapacity rendering them incapable of using the PCA device
• ASA score 4 or above
• Inability or unwillingness of parent or legal guardian to provide informed consent for the study.

Beginning 12 months following analysis and article publication, the following will be made available long-term for use by future researchers from a recognised research institution whose proposed use of the data has been ethically reviewed and approved by the Murdoch Children's Research Institute's (MCRI's) independent data use review committee (not including trial sponsor-investigator) and who accept MCRI's conditions, under a collaborator agreement, for accessing participant data after de-identification (text, tables, figures, and appendices) that underlies reported results, along with trial protocol, Statistical Analysis Plan (SAP) and Participant Information and Consent Forms (PICF).

12 months following analysis and publication of the primary outcome

Requests for access to previously published anonymised datasets by the scientific community will be reviewed and determined by an independent committee within the MCRI and in accordance with institute policy.

The study will not be blinded due to the need for opioid syringes to be readily identifiable on the ward.