Liberal liquid fasting regimens and the risk of pulmonary aspiration

Since the end of the last century, patients have been allowed to drink clear liquids until 2 h before the induction of anaesthesia. However, conventional ‘nil by mouth after midnight’ principles remain commonplace globally, with data suggesting it is associated with median liquid fasting times of up to 12 h 1. Due to unpredictable operating theatre schedules, a fixed cut-off time target for drinking, such as 2 h, is difficult to implement 2. For example, a delay of the previous surgical procedure could result in longer liquid fasting times, whereas a cancellation of the previous procedure might make the next patient unavailable if they have just had something to drink. Maintaining a ‘nil by mouth after midnight’ policy was thought to ensure that fasting status would not contribute to delayed surgery. To adhere more closely to the recommended guidelines, an increasing number of clinicians are allowing their patients to drink clear liquids until they are sent for their procedure, using liberal liquid policies like ‘Sip til Send’. The rationale behind this is that clear liquids leave the stomach rapidly and pulmonary aspiration of clear fluid with a more neutral pH has not been shown to have pathological significance 3. Furthermore, eliminating the strict 2-h limit makes it easier to bring fasting times closer to the recommended 2 h. We conducted a directed literature review to synthesise and summarise published data on adult patients to date (online Supporting Information Table S1). We found that liberal liquid policies were associated with a clear liquid fasting time of approximately 1.8 h. Pulmonary aspiration was reported in 13/121,457 patients with a liberal fasting regimen, corresponding to an incidence of 1:10,000 with conservative fasting. As well as hydration, liberal liquid regimens are associated with a lower incidence: of hunger; thirst; pain; nausea; loss of muscle strength; fatigue; delirium; peri-operative stress; and the need for intra-operative intravenous fluids. In a recent study, patients were informed about every change in the operating theatre schedule, and liquid fasting was adjusted several times daily 4. Patients had a liquid fasting time of 3 h, but an equal drinking volume compared with patients allowed to drink until sent for their procedure, with a median liquid fasting time of 2 h. Restricting the time may lead to ‘anticipatory drinking’. Patient wellbeing was better in the liberal group, which might reflect stress reduction and the opportunity for patients to adjust their drinking behaviour exactly to their needs. In light of the growing evidence indicating that prolonged liquid fasting is harmful, a recent consensus statement on peri-operative fasting endorses the implementation of liberal liquid regimes within institutional protocols 5. Some critics still demand more robust evidence that concepts like ‘Sip til Send’ have no impact on the incidence of pulmonary aspiration. Randomised controlled trials and large prospective observational studies are scarce because this would be unfeasible given the rarity of this outcome. Even in a non-inferiority study, approximately 123,000 patients per group would be needed to detect a two-fold increase in the baseline incidence of aspiration of 1:10,000 (power 80%, α = 0.05). However, published data consistently highlight the safety of liberal liquid regimes (online Supporting Information Table S1). The coming years of peri-operative practice should focus on the implementation of liberal liquid strategies for patient and institutional benefits. Table S1. Liberal liquid regimes in adults and the risk of pulmonary aspiration. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.