Table of Contents
Introduction
Pneumonitis is a condition that causes irritation and inflammation of the lungs due to aspiration or inhalation of certain substances, chemicals, dust particles, germs, and other allergic irritants. This leads to inflammation of the air sacs, resulting in cough, breathing difficulty, and other symptoms. Aspiration can cause various syndromes depending on the nature of the aspirated material, frequency, quantity, and other host factors predisposing the individual to aspiration. Prevention of aspiration is vital, as though it is rare, it may be potentially fatal. Mendelson syndrome is a form of chemical pneumonitis that occurs when gastric contents are aspirated into the lungs under anesthesia. Managing Mendelson syndrome can be challenging if it is further complex by bacterial aspiration pneumonia; hence, timely diagnosis and immediate treatment strategies must be considered to prevent complications.
What Is Mendelson Syndrome?
Mendelson syndrome is a condition caused by severe aspiration of gastric contents into the lungs under obstetric or general anesthesia. It was first described by Curtis Lester Mendelson in 1946 in the American Journal of Obstetrics and Gynecology. He reported severe aspiration pneumonia following a vaginal delivery under general anesthesia in young and healthy obstetrical patients. Mendelson syndrome is acute chemical pneumonitis, also known as peptic pneumonia, due to pulmonary aspiration of more than 25 mL (milliliter) of gastric acid contents with a pH of less than 2.5 under any condition related to consciousness disorders. It may be similar to pulmonary edema in its presentation but has an acute onset. Mendelson syndrome develops rapidly within two to 12 hours following aspiration, resulting in cyanosis (bluish discoloration of the skin), acute respiratory distress syndrome (ARDS) (accumulation of fluid in the air sacs), and subsequent pulmonary necrosis (damage of lung tissues).
What Are the Causes of Mendelson Syndrome?
A majority of general anesthetics are used for the obstetrical population, especially during emergency cesarean sections. Anesthesiologists are prepared to induce general anesthesia in emergencies when maternal and fetal lives have potential risks. Chemical pneumonitis is more likely to occur in pregnant women due to various anatomic and physiologic changes in the body. Mendelson syndrome is an acute condition due to regurgitation and subsequent aspiration of gastric contents under any condition mainly associated with consciousness. Chemical pneumonitis may occur following the aspiration of gastric contents if the pH is below 2.5 and the volume is about 0.3 milliliters/kilogram body weight.
Aspiration commonly includes microorganisms from the oropharynx, gastric acid, liquids, and particulate matter. The lower esophageal sphincter (LES) may be displaced anteriorly, predisposing to incompetence. Production of gastrin hormone by the placenta can also lead to hypersecretion of gastric acid and delayed gastric emptying in parturients (women in labor). Circulating blood volume is increased in these individuals due to the elevation of estrogen hormone, leading to pharyngeal and laryngeal mucosal edema. Mask ventilation can be difficult in such patients, and abdominal panniculus (excess skin and fat hanging from the abdomen) and enlarged breasts may further impair mouth opening or laryngoscope introduction. However, the incidence of Mendelson syndrome has reduced over the years due to improvements in anesthetic practice and healthcare technology.
What Are the Symptoms of Mendelson Syndrome?
Symptoms of Mendelson syndrome appear immediately or shortly after aspiration, and patients may become ill as the regurgitation or aspiration may not be noticed by the healthcare specialist. This can even cause difficulty or failure in intubation procedures. Patients with Mendelson syndrome usually present with signs and symptoms such as
-
Cough.
-
Dyspnea (difficulty breathing or shortness of breath).
-
Fever.
-
Profuse pink sputum.
-
Tachycardia (increased heart rate).
-
Hypotension (low blood pressure).
-
Pulmonary edema.
-
Hypovolemia (decreased fluid volume).
-
Bronchospasm (tightening of chest muscles).
This may lead to reduced arterial oxygen levels, increased pulmonary artery pressure, lower lung compliance, and metabolic acidosis (increased acid content). Symptoms may slowly progress to lung abscess, empyema (collection of pus), and pulmonary necrosis.
How Is Mendelson Syndrome Diagnosed?
Mendelson syndrome is diagnosed based on clinical history, including a witnessed aspiration, chest radiography features, and risk factors. During the physical examination, the patient exhibits tachypnea (rapid breathing), tachycardia, and crackles on chest auscultation, especially in the lower right area, where most of the aspirated contents are present. Radiographic features may demonstrate irregular densities in the pulmonary segments, mainly on the lower right side, due to a larger diameter area. Pulse oximetry reveals tachycardia and oxygen desaturation. A computed tomography (CT scan) may show a consolidated chest. Other recommended tests include blood culture, sputum culture, culture of the aspirate, ultrasound for effusion, bronchoscopy, tracheal aspiration for sampling, etc.
How Can Mendelson Syndrome Be Managed?
The best treatment for Mendelson syndrome is prevention; however, aspiration must be recognized immediately by the healthcare team and managed swiftly to prevent further problems. The patient must be in the Trendelenberg position (a position in which the head is low and the legs are high), and the oropharynx is suctioned. Intubation must be done if the patient shows signs of hypoxia or reduced airway reflexes. A soft suction catheter is passed after the endotracheal tube to prevent dislodging of the aspirated material further into the lungs. Bronchoscopy with lavage may be considered if there is evidence of lobar collapse. Mechanical ventilation may be preferred depending on the individual’s clinical condition. Supportive measures include adequate fluid management, bronchodilator therapy, diuretics, and physiotherapy to promote drainage. Antibiotics are not recommended unless aspiration pneumonia develops and a specific microorganism is identified.
How Can Mendelson Syndrome Be Prevented?
Some of the preventive measures of Mendelson syndrome include:
-
Minimal oral intake of clear liquids for uncomplicated laboring individuals up to two hours before the administration of anesthesia.
-
Solid foods must be avoided in laboring patients, especially those with additional risk factors.
-
Antiacid therapy neutralizes gastric pH and lowers the risk of chemical pneumonitis.
-
Avoiding general anesthesia in high-risk patients.
-
Following proper anesthetic techniques and necessary precautions before administration.
Conclusion
Mendelson syndrome is a severe form of aspiration chemical pneumonitis that occurs due to regurgitation and subsequent aspiration of gastric contents under anesthesia. Certain physiological changes in pregnant women increase the risk of aspiration in this population. The incidence of pulmonary aspiration has relatively reduced in recent years because of the advances in anesthetic practice. An interprofessional team of experts specializing in pulmonary and obstetric specialists can best manage Mendelson syndrome. The prognosis of the condition mainly depends on the severity of aspiration, complications, comorbidities, and general health of the patient. However, it is recommended to take necessary precautions during labor, especially cesarean section and postpartum, to avoid further complications.
