The following is true of Mendelson's syndrome
In Mendelson's syndrome, the critical pH is 2.5 and the critical volume is 25ml (0.3ml/kg body wt). Opioids will decrease the tone of LES and increase the risk rather than decrease. In 1946, Mendelson was the first to describe aspiration pneumonitis attributable to the pulmonary aspiration of acidic gastric secretions in pregnant women undergoing anesthesia. This potentially fatal complication, occasionally referred to as Mendelson syndrome, has since been the intense focus of preventive effos among the anesthesia community. Prevention of aspiration of gastric contents is primarily accomplished by adherence to established preoperative fasting guidelines, premedication with drugs that may decrease the risk of aspiration pneumonitis, and specialized induction techniques. Traditionally, patients who were scheduled for elective procedures requiring sedation, regional anesthesia, or general anesthesia were instructed to remain NPO (Latin for nulla per os or nothing by mouth) after midnight to ensure an empty stomach to decrease the risk of regurgitation. Based on evidence that allowing ingestion of clear liquids 2 to 4 hours before surgery resulted in lower gastric volumes and higher gastric pH, the ASA published Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration in 1999 that liberalized the traditional NPO policy and allowed clear liquids up to 2 hours before beginning elective procedures requiring anesthesia. The guidelines, updated in 2011, recommend 4 hours of fasting from breast milk 6 hours of fasting from solid foods, infant formula, and nonhuman milk. Fried or fatty foods may require longer fasting times (e.g., 8 hours or more). Although the ASA guidelines do not specifically address chewing gum, hard candies, or smoking, guidelines published by the European Society of Anaesthesiology on the topic do not recommend delaying the sta of anesthesia if a patient has consumed any of these immediately before the induction of anesthesia. The routine use of drugs as prophylaxis against aspiration pneumonitis is not recommended by the ASA guidelines but may be beneficial in patients with specific risk factors for aspiration, such as a full stomach, symptomatic gastroesophageal reflux disease (GERD), hiatal hernia, presence of a nasogastric tube, morbid obesity, diabetic gastroparesis, or pregnancy. The goal of aspiration prophylaxis is twofold: to decrease gastric volume and to increase gastric fluid pH. Commonly used agents include nonpaiculate antacids (e.g., Bicitra), promotility drugs (e.g., metoclopramide), and H2-receptor antagonists. These drugs may be used alone or in combination. Ref: Miller's anesthesia 8th edition Ref: Morgan & Mikhail's clinical anesthesiology 6e
Critical Volume of aspirate is 50 ml
Critical pH of gastric aspirate is 1.5
Onset of symptoms generally occurs within 2 hours
Opioids have been shown to improve outcome
Complications of anaesthesia