No association between preprocedural fasting and witnessed pulmonary aspiration: A systematic review and meta-analysis

Background

Preprocedural fasting has been a standard component of preoperative care since 1946 when an association between gastric volume and aspiration was made. A large body of literature exists examining various fasting regimen effects on surrogate outcomes, but few studies have investigated aspiration itself as the primary outcome.

Methods

Randomized clinical trials comparing outcomes from preprocedural fasting regimens and observational studies of witnessed aspiration events published between January 1, 2016, and December 1, 2023, were reviewed. The main primary outcome was clinical aspiration. Secondary outcomes included gastric volume and pH. Random effects meta-analysis was performed on the outcomes data. Trial sequential analysis was performed to determine the likelihood that further studies of fasting effects on aspiration events will change conclusions drawn from the current analysis.

Results

Of the 3,580 initial references found in the initial search, 17 were included in the analysis. Of these, 9 reported outcomes for aspiration events. Clinical aspiration was not affected by the various preprocedural fasting regimens. Odds ratio for aspiration events = 1.17 (95% confidence interval: 0.32–4.23, P = .81, I² = 0%, n = 8 studies, 801 patients in experimental groups, and 990 patients in control groups). Aspiration was rare, occurring in 4 of 801 patients (incidence of 0.50%) in experimental groups and 7 of 990 patients (0.71%) in control groups. Trial sequential analysis of aspiration studies showed little likelihood of finding a significant effect of new fasting regimens on aspiration. Most studies reported gastric volume and/or pH as a surrogate outcome for aspiration. The surrogate outcomes gastric volume and pH have never been shown to correlate with human anesthesia-related aspiration.

Conclusion

There was no association between liberal fasting policies and witnessed aspiration. Further study of more liberal fasting policies is unlikely to find an association. Most of the prior fasting-aspiration-fasting literature relied on surrogate outcomes that have never been shown to correlate with clinical aspiration. The lack of evidence demonstrating a relationship between fasting and aspiration suggests that fasting policies might be liberalized. Preprocedural fasting might be replaced by bedside gastric ultrasound examination of gastric volume.