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Ultrasonographic estimation of gastric volume in patients after overnight fasting and after ingestion of clear fluids two hours before surgery

Introduction: Pre-operative fasting aims to decrease the volume and increase the pH of gastric contents, hence reducing the risk of aspiration. According to the past literature gastric contents of 25 ml (0.4 ml/kg) and with pH ≤ 2.5 predisposes the patient to pulmonary aspiration hence pre-operative fasting was recommended. Use of two-dimensional ultrasonography is an accurate non-invasive tool to determine gastric volume. We compared the gastric volume using ultrasonography and pH of gastric aspirate by pH strip in patients after overnight fasting and after ingestion of 200 ml clear fluids (water) 2 h prior to surgery. Methodology: The study was conducted in 60 ASA I patients undergoing elective surgery after obtaining institutional ethical committee clearance & written informed consent from all the patients. Patients were randomized based on computer generated randomization table into one of the two groups; Group A patients with overnight fasting, and Group B patients with overnight fasting, but receiving 200 ml of clear fluids (water) 2 h before surgery. Gastric antral dimensions were noted and gastric volume was calculated. Gastric aspirate pH was measured by pH strips. Results: Age and gender distribution was comparable between the two groups. The mean gastric volume by USG was 29.7 ± 8.0 ml and 19.2 ± 4.9 ml in Group A and B respectively. The reduced gastric volume in Group B was statistically significant (< 0.00001). The mean pH of gastric aspirate in Group A was 1.4 and Group B was 2.63. The results reveal that Group B has a better result in terms of pH of the gastric contents and was statistically significant (p < 0.00001). Conclusion: We conclude that the surgical patients who fasted overnight may be allowed 200 ml of clear fluids 2 h prior to surgery as it results in lesser residual gastric fluid volume and higher mean pH at the time of surgery, resulting in a reduced risk of aspiration.