Australasian MARS: Multicentre Aspiration Risk Study. A comparison of pulmonary aspiration rates for patients undergoing anaesthesia allowed to drink clear fluids before surgery versus those managed with traditional, fluid-restrictive fasting protocols

The intervention being studied is liberal preoperative fluid fasting, consisting of allowing clear fluids until the time of surgery, also known as "Sip Til Send". The study is observational in nature, there is no change to any hospital's current fasting protocol due to participation in the study and no alteration to routine patient care. The project will require a study population of more than 200,000 anaesthetics for adequate statistical power, and has ethics approval for a waiver of patient consent due to the impracticality of consenting this number of patients for the de-identified data collection. Pulmonary aspiration events occurring during anaesthesia are identified clinically by the treating anaesthetist caring for the patient. The events can then be flagged to the principal investigator at each hospital site via internal audit mechanisms. The audit mechanism varies depending on the hospital size and what electronic systems are in use, but many sites are using dedicated QR codes present in all anaesthetising locations. The data collected for each aspiration event will be extracted anonymously from patient medical records by the local principal investigator. The information will include patient characteristics, details of when and how the event occurred during anaesthesia, risk factors for aspiration, and the severity of the event (e.g. whether it resulted in unplanned hospital or ICU admission, ventilator therapy, antibiotics or mortality). In addition, the study will involve high volume, de-identified data extraction from electronic operating records of the total number of anaesthetic cases ("denominator") in order to be able to calculate an overall incidence of aspiration. Basic information will be extracted for the total number of cases including - Age on date of procedure - Date of procedure - Name of procedure and specialty - Urgency of case (elective/emergency) - Type of anaesthetic (general, sedation, regional) - American Society of Anaesthesiologists Physical Status Classification score - Time of last fluid intake Data will be extracted at 3-monthly intervals from each participating site, to allow assessment of progress towards the target sample size. The estimated total prospective data collection period is around 9 months, with no ongoing follow up or further data extraction required after this time. As the ideal comparison group for this study would be pre- and post-intervention data from the same hospitals, MARS will incorporate retrospective data when available. As pulmonary aspiration rates under Sip Til Send are unknown, many hospitals adopting this novel fasting practice chose to audit local aspiration rates and monitor for adverse events during its implementation, prior to and independent of the MARS project. We will therefore include this data where available, if it was collected using a reliable audit method which is continuous with the method that will be used for prospective data collection. The audit must have been clearly publicised within the department with instructions to report every suspected aspiration and not only cases of special interest, medico-legal significance or educational value (which may be the case with traditional morbidity and mortality reporting or incident management systems). The duration of retrospective data collected for MARS will be determined by the period for which reliable data is available, and will be different for each hospital depending on when they started to audit aspiration events.