Australasian MARS – Multicentre Aspiration Risk Study
What is MARS?
MARS is an Australasian multicentre observational cohort study looking at rates of pulmonary aspiration under anaesthesia.
The study aims to assess whether permitting clear fluid drinks until the start of anaesthesia (“Sip Til Send”) is non-inferior compared to advising patients to stop drinking 1 or 2 hours before anaesthesia (restrictive fluid fasting).
Sip Til Send
Despite national guidelines advising patients to consume clear fluids until 1 to 2 hours before an anaesthetic, in practice patients often go without fluids for much longer – commonly averaging 7 to 13 hours. This can cause thirst, dehydration, heightened anxiety, nausea, delirium in the elderly, and issues with blood sugar management.
Sip Til Send fasting has become an effective and popular strategy to shorten fluid fasting duration before anaesthesia, improving the patient experience and avoiding the problems related to dehydration. Between 2023 and 2025, approximately 50 Australasian hospitals transitioned to offering their patients Sip Til Send.
Why do we need MARS?
Pulmonary aspiration under anaesthesia is rare and in most cases the consequences are mild, but it remains an important cause of severe complications during anaesthesia.
The MARS project is designed to provide the best available evidence regarding aspiration rates with safety of Sip Til Send, particularly in adult cohorts and in emergency settings where there is very limited evidence.
Study design
The MARS project will audit more than 250,000 anaesthetics in adults and children undergoing elective and emergency procedures, collecting detailed records from any aspiration events.
Registered study sites
As of January 2026, there are 45 hospitals registered for the MARS project.
Hospital recruitment
The study is no longer recruiting new study sites.
Study progress
April 2025
Multicentre ethics approval granted by respective authorities in Australia and New Zealand and recognised by all hospitals in their respective countries.
Limited funding secured to facilitate the study’s design and implementation.
May 2025
Commencement of local governance approval applications.
April 2026
Data received from 100,000 anaesthetics
Study co-ordination
Co-ordinating Centre:
Department of Anaesthesia and Perioperative Medicine – Cairns and Hinterland Hospital and Health Service, Queensland, Australia
Lead Investigators:
Dr Phuong Markman, Staff specialist anaesthetist, Cairns Hospital, Australia
Dr Ruth Blank, Staff specialist anaesthetist, Cairns Hospital, Australia
New Zealand Coordinator:
Dr Alec Beresford, Specialist Anaesthetist – Health NZ Waitaha Canterbury – Christchurch hospital, New Zealand
Supervisor:
Professor David Story. President, ANZCA. Head, Dept of Critical Care, The University of Melbourne.
