Randomised clinical trial to compare ultrasonography guided gastric volume in patients after overnight fasting and after ingestion of clear fluids two hours before surgery

Abstract

Aspiration of the gastric contents in the peri-operative period is a serious complication of surgery and anaesthesia. 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 (0.4ml/kg) and with pH </= 2.5 predisposes the patient to pulmonary aspiration hence pre-operative fasting was recommended. But prolonged fast doesn’t guarantee empty stomach. Use of two-dimensional ultrasonography is an accurate non-invasive tool to determine gastric volume. With an aim to reduce the hours of pre-operative fasting without increasing the risk of aspiration pneumonia we compared the gastric volume using ultrasonography and pHof gastric aspirate by pH strip in patients after overnight fasting and after ingestion of 200 ml clear fluids (water) 2 hours prior to surgery. 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. Thorough pre anaesthetic evaluation was done, investigations were noted. After having achieved the inclusion and exclusion criteria and having obtained informed consent, patients were randomized based on computer generated randomization table into one of the two groups. Group A: Patients with Overnight fastingGroup B: Patients receiving 200 ml of clear fluids (water) 2 hours before surgery.Gastric antral dimensions were noted and gastric volume was calculated.We observed that the age and gender distribution were comparable between the two groups. The mean gastric volume by USG in group A is 29.7±8.0ml and group B is 19.2±4.9 ml. The reduced gastric volume in group B is statistically significant (<0.00001).The mean pH of gastric aspirate in group A is 1.4 and group B is 2.63. The results reveal that group B has a better results in terms of pH of the gastric contents and is statistically significant (p<0.00001).The mean gastric volume in patients who had consumed 200 ml of clear fluid 2 hours prior (group B) was lesser than patients who fasted overnight (group A).The mean pH in patients who had consumed 200 ml of clear fluid 2 hours prior (group B) was higher than patients who fasted overnight (group A).