Write a short note on Mendelson’s Syndrome.

Definition

Mendelson’s syndrome is the chemical (aspiration) pneumonitis that results from aspiration of acidic gastric contents into the lungs during anaesthesia. It was originally described in obstetric patients and is a feared complication of a ‘full stomach’ under anaesthesia.

Pathophysiology & Features

Aspiration of gastric acid (classically a pH < 2.5 and volume > 25 mL is considered high-risk) causes a chemical burn of the airways and alveoli, with bronchospasm, pulmonary oedema and hypoxaemia. Features include wheeze, cyanosis, tachypnoea, tachycardia and falling oxygen saturation, sometimes progressing to acute respiratory distress and secondary infection (aspiration pneumonia).

Prevention & Management

Prevention is paramount: fasting, identifying full-stomach patients, aspiration prophylaxis, and rapid sequence induction with cricoid pressure. If aspiration occurs: head-down/lateral position, suction the airway, secure it (intubate) and give 100% oxygen, with supportive respiratory care (ventilation/PEEP as needed). Antibiotics are given for secondary infection (not routinely), and steroids are not recommended.

WHY Obstetric Patients Are High Risk

Mendelson described the syndrome in obstetric anaesthesia, and pregnant women remain a paradigm of aspiration risk: from mid-pregnancy the gravid uterus raises intra-abdominal pressure and displaces the stomach, progesterone relaxes the lower oesophageal sphincter, and labour and opioids delay gastric emptying, so a labouring woman is treated as having a full stomach. This is why obstetric general anaesthesia classically combines antacid prophylaxis with a rapid sequence induction, and why regional anaesthesia — which avoids instrumenting the airway of an unfasted patient — is generally preferred for caesarean section.

Prevention by fasting and prophylaxis is far better than treatment.

• Mendelson’s syndrome = chemical pneumonitis from aspiration of acidic gastric contents.
• High-risk aspirate: pH < 2.5, volume > 25 mL → airway burn, bronchospasm, hypoxaemia.
• Features: wheeze, cyanosis, tachypnoea, desaturation ± later infection.
• Prevent (fasting, prophylaxis, RSI + cricoid); treat with suction, intubation, O₂, support; no routine steroids.