Mendelson's syndrome is chemical pneumonitis

Chemical pneumonitis

Aspiration pneumonitis or chemical pneumonitis is inflammation of the lung caused by aspirating or inhaling irritants. It is sometimes called a "chemical pneumonia", though it is not infectious...

 caused by aspiration

Pulmonary aspiration

Pulmonary aspiration is the entry of material from the oropharynx or gastrointestinal tract into the larynx and lower respiratory tract...

 during anaesthesia, especially during pregnancy

Pregnancy

Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...

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Presentation

Mendelson's syndrome is characterised by a bronchopulmonary reaction following aspiration of gastric contents during general anaesthesia due to abolition of the laryngeal

Laryngeal

Laryngeal may mean*pertaining to the larynx*in Indo-European linguistics, a consonant postulated in the laryngeal theory*in phonetics, an alternate term for glottal sounds....

 reflexes. The main clinical features are signs of general hypoxia

Hypoxia (medical)

Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

, two to five hours after anaesthesia. Such features may include cyanosis, dyspnoea, fever, pulmonary wheeze, crepitant rales, rhonchi, and tachycardia with a high blood pressure. Decreased arterial oxygen tension is also likely to be evident. Pulmonary edema

Pulmonary edema

Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...

 can cause sudden death or death may occur later from pulmonary complications.

Risk

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

• Residual gastric volume of greater than 25ml, with
• pH
  PH
  In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
  
   of less than 2.5

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

Patients with a high risk should have a rapid sequence induction

Rapid sequence induction

Rapid Sequence Induction is a medical procedure involving the expeditious induction of general anesthesia and subsequent intubation of the trachea. RSI is generally used in an emergency setting or for patients who have an increased risk of aspirating stomach contents into the lungs...

. High risk is defined as these factors:

1. Non-elective surgical procedure
2. Light anaesthesia/unexpected response to stimulation
3. Acute or chronic, upper or lower GI pathology
4. Obesity
   Obesity
   Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
   
   
5. Opioid
   Opioid
   An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...
   
    medication
6. Neurological disease, impaired conscious level, or sedation
7. Lithotomy position
   Lithotomy position
   The lithotomy position is a medical term referring to a common position for surgical procedures and medical examinations involving the pelvis and lower abdomen, as well as a common position for childbirth in Western nations...
   
   
8. Difficult intubation/airway
9. Gastrointestinal reflux
10. Hiatal hernia

Treatment

The risk may be reduced by administering a non-particulate antacid

Antacid

An antacid is a substance which neutralizes stomach acidity.-Mechanism of action:Antacids perform a neutralization reaction, increasing the pH to reduce acidity in the stomach. When gastric hydrochloric acid reaches the nerves in the gastrointestinal mucosa, they signal pain to the central nervous...

 (e.g. Sodium Citrate) or an H₂-antagonist like Ranitidine

Ranitidine

Ranitidine is a histamine H2-receptor antagonist that inhibits stomach acid production. It is commonly used in treatment of peptic ulcer disease and gastroesophageal reflux disease . Ranitidine is also used alongside fexofenadine and other antihistamines for the treatment of skin conditions...

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