Effectiveness of standard fasting guidelines as assessed by gastric ultrasound examination: A clinical audit

An audit was conducted between July 2017 and November 2017 to assess the adequacy of American Society of Anesthesiologists (ASA) fasting guidelines on 246 patients by means of gastric ultrasonography (USG). The relevance of this audit is that many of our patients have one or more risk factors for aspiration such as diabetes mellitus, chronic kidney disease (CKD), gastro-oesophageal reflux disease (GERD), and obesity.

This audit was a prospective observational study which included all patients posted for surgery within the audit period. Patients were fasted according to ASA fasting guidelines. Their gastric content was assessed preoperatively using USG. The residual gastric volume was calculated using a validated formula. Statistical correlation between gastric volumes and the risk factors were analysed.

Of 246 patients, 69 (28.04%) had high residual gastric volume. We found no correlation between hours of fasting and residual gastric volume (P = 0.47). We found a linear correlation between rising body mass index and residual gastric volume (P < 0.0001). Patients with GERD had 2.3 times higher risk. The CKD patient subgroup had 24 patients (30%) with high residual gastric volume. No incidents of aspiration were noted.

In our audit, we found that risk factor association has a greater effect on residual gastric volume than hours of fasting. While the current fasting guidelines are adequate for healthy individuals, they are not conclusive in patients with risk factors. Ultrasound assessment of preoperative gastric volume is an effective screening tool in patients with risk factors.