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

Abstract

Background and Aims: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.Methods: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.Results: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.Conclusion: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.

Gastric ultrasound as an aspiration risk assessment tool

“…Both the current articles, however, reported the presence of RGV >1.5 mL/kg or solid contents in 22% and 28% of patients, respectively. [ 1 2 ] These very high numbers are in contrast to the much lower above-mentioned percentages. [ 4 5 ] However, the authors of the current studies failed to mention previous literature,[ 4 5 ] and also did not address this difference in their discussion.…”

“…We read with interest two publications in the Indian Journal of Anaesthesia that used gastric ultrasound (GUS) to preoperatively assess gastric contents and residual gastric volumes (RGVs) in fasted adult surgical patients. [ 1 2 ] GUS is used increasingly as an aspiration risk assessment tool and we congratulate the authors for their respective contributions. However, we are concerned about the internal and external validity of both studies for the following reasons given below.…”

“…Finally, both the articles reported a statistically significant relationship between RGV and comorbidities such as chronic kidney disease and gastroesophageal reflux disease (GERD),[ 1 2 ] without defining chronic kidney disease (mild stage, end-stage) or GERD (which could be considered when reflux has been investigated, treated or both, with or without hiatal hernia). There was no record of the exact number of patients with chronic kidney disease nor of the number of patients with GERD with GRV > or <1.5 mL/kg.…”

Probing the future - Can gastric ultrasound herald a change in perioperative fasting guidelines?

“…This issue of Indian Journal of Anaesthesia features two articles on GUS. [ 17 18 ] These articles re-emphasise that the presence of associated risk factors for aspiration such as diabetes mellitus, chronic kidney disease, reflux gastro-oesophageal disease etc., contributes to delayed gastric emptying and increased residual gastric volume. However, the most concerning outcome from both articles is the detection of solid/particulate matter or unsafe residual gastric volumes in healthy adults presumably at low risk for aspiration, despite an adequate duration of fasting.…”

“…However, the most concerning outcome from both articles is the detection of solid/particulate matter or unsafe residual gastric volumes in healthy adults presumably at low risk for aspiration, despite an adequate duration of fasting. [ 17 18 ] These findings arouse some disquieting queries: Why did only a select few patients have this problem? Will further evaluation of such patients help to identify any special risk factors inherent to these presumably fit patients?…”