One Year Randomised Clinical Trial To Compare Ultrasonography Guided Gastric Volume In Patients After Overnight Fasting And After Ingestion Of Clear Fluids Two Hours Prior To Surgery

Abstract

Perioperative aspiration of gastric contents is a rare but serious complication of anaesthesia. The overall incidence in a mixed surgical population ranges between 0.1% and 19% depending on patient and surgical Factors and it has been the same over decades. Aspiration pneumonia is associated with significant morbidity, including prolonged mechanical ventilation and carries a risk of mortality as great as 5%. Sedation and general anaesthesia depress or impede the physiological mechanisms that protect against aspiration (the tone of the lower oesophageal sphincter and upper airway reflexes). Fasting before general anaesthesia aims to reduce the volume and acidity of stomach contents during surgery, thus reducing the risk of regurgitation/aspiration. Previous studies have shown that pH <2 and volume of gastric aspirate >25 ml (0.4ml/kg) predisposes a patient to pulmonary aspiration, hence a strict over -night fasting regimen was instituted. But prolonged fast doesn’t guarantee empty stomach. Use of two-dimensional ultrasonography is an accurate non-invasive tool to determine gastric volume . Hence in an attempt to reduce the fasting hours of a patient pre-operatively without increasing the risk of pulmonary aspiration 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 hours prior to surgery METHODS: The study was conducted in 60 patients undergoing elective surgery belonging to ASA 1 after obtaining Institutional ethical committee clearance & written informed consent from all the patients. Thorough pre anaesthetic evaluation was done, investigations were noted. After having met 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 fasting • Group B: Patients receiving 200 ml of clear fluids (water) 2 hours before surgery. Gastric antral dimensions were noted and gastric volume was calculated . RESULTS: 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. Which shows that group B has a better outcome in terms of gastric pH and is statistically significant (p<0.00001). CONCLUSION: The mean gastric volume in patients who had 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 200 ml of clear fluid 2 hours prior (group B) was higher than patients who fasted overnight (group A).