Mendelson's syndrome

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Mendelson's syndrome
Classification and external resources
ICD-9-CM668.0, 997.3

Mendelson's syndrome is chemical pneumonitis or aspiration pneumonitis caused by aspiration during anaesthesia, especially during pregnancy. Aspiration contents may include gastric juice, blood, bile, water or an association of them.[1]


Mendelson's syndrome is characterised by a bronchopulmonary reaction following aspiration of gastric contents during general anaesthesia due to abolition of the laryngeal reflexes. The main clinical features are signs of general hypoxia, two to five hours after anaesthesia. Such features may include cyanosis, dyspnea, fever, pulmonary wheeze, crepitant rales, rhonchi, and tachycardia with a low blood pressure. Decreased arterial oxygen tension is also likely to be evident. Pulmonary edema can cause sudden death or death may occur later from pulmonary complications.


Historically it is said that a patient is at risk if they have:[2]

  • Residual gastric volume of greater than 25ml, with
  • pH of less than 2.5

However these are indirect measurements and are not factors that directly influence aspiration risk.[2]

Patients with a high risk should have a rapid sequence induction. High risk is defined as these factors:[2]

  1. Non-elective surgical procedure
  2. Light anaesthesia/unexpected response to stimulation
  3. Acute or chronic, upper or lower GI pathology
  4. Obesity
  5. Opioid medication
  6. Neurological disease, impaired conscious level, or sedation
  7. Lithotomy position
  8. Difficult intubation/airway
  9. Gastrointestinal reflux
  10. Hiatal hernia


The risk may be reduced by administering a non-particulate antacid (e.g. Sodium Citrate) or an H2-antagonist like Ranitidine.

If patient has developed this syndrome; only treatment is mechanical ventilation to maintain O2 saturation, patient would die otherwise. Patient is kept on mechanical ventilation until his PO2 is corrected; which is 100 mmHg for a normal human being.


It is named for Curtis Mendelson.[3][4]


  1. ^ Г.А.Рябов, СИНДРОМЫ КРИТИЧЕСКИХ СОСТОЯНИЙ. Аспирационный пневмонит (синдром Мендельсона),
  2. ^ a b c Levy, DM (2006). "Pre-operative fasting—60 years on from Mendelson". Continuing Education in Anaesthesia, Critical Care & Pain. 6 (6): 215. doi:10.1093/bjaceaccp/mkl048.
  3. ^ Enersen, OD. "Whonamedit – Mendelson's syndrome". Whonamedit? A dictionary of medical eponyms. Retrieved 2011-04-22.
  4. ^ Mendelson, CL (1946). "The aspiration of stomach contents into the lungs during obstetric anesthesia". American Journal of Obstetrics and Gynecology. 52: 191–205. PMID 20993766.

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