History

Fact Explanation
Asymptomatic Some patients may not present with any symptoms and they are known to have silent aspiration. [3]
Symptoms of respiratory distress Patients with aspiration of gastric acid present with symptoms of respiratory distress within two to six hours of aspiration. Shortness of breath, wheezing and cyanosis are common complains. [2]
Fever Some patients develop fever. Patients can develop fever in the presence of aspiration pneumonia as well. [2]
Cough Coughing occurs secondary to acid aspiration. [2]
Risk factors In addition to pregnancy, general anesthesia, obesity, and opioid analgesics increases the risk of Mendelson's syndrome. [1]
References
  1. LEVY D M. Pre-operative fasting--60 years on from Mendelson. Continuing Education in Anaesthesia, Critical Care & Pain [online] 2006 December, 6(6):215-218 [viewed 27 August 2014] Available from: doi:10.1093/bjaceaccp/mkl048
  2. MARIK PAUL E.. Aspiration Pneumonitis and Aspiration Pneumonia. N Engl J Med [online] 2001 March, 344(9):665-671 [viewed 28 August 2014] Available from: doi:10.1056/NEJM200103013440908
  3. BHATIA P. Pregnancy and the lungs. [online] 2000 November, 76(901):683-689 [viewed 28 August 2014] Available from: doi:10.1136/pmj.76.901.683

Examination

Fact Explanation
Tachypnea Increased respiratory rate can be detected in affected patients. This usually develops two to six hours after aspiration. [1]
Wheezing Aspiration of the gastric contents causes inflammation and subsequent edema of the airway. This results in wheezing. [1]
Cyanosis Patients can develop cyanosis due to reduced oxygenation, as a result of respiratory distress. [1]
Hypotension Respiratory distress can cause hypotension. [1]
Pulmonary edema Pulmonary crackles are indicative of pulmonary edema. Reduced chest expansion, dull percussion note, increased tactile vocal fremitus and reduced breath sounds over the affected lobe are indicative of lobar consolidation in aspiration pneumonia, which is common over the lower lobe of the right lung.[2]
References
  1. MARIK PAUL E.. Aspiration Pneumonitis and Aspiration Pneumonia. N Engl J Med [online] 2001 March, 344(9):665-671 [viewed 28 August 2014] Available from: doi:10.1056/NEJM200103013440908
  2. BHATIA P. Pregnancy and the lungs. [online] 2000 November, 76(901):683-689 [viewed 28 August 2014] Available from: doi:10.1136/pmj.76.901.683

Differential Diagnoses

Fact Explanation
Pulmonary embolism Pulmonary embolism is a recognized complication of deep vein thrombosis. Pregnancy is considered a hypercoagulable state. Patients present with sudden onset chest pain, cough and hemoptysis. [1]
Amniotic fluid embolism Although rare, amniotic fluid embolism carries a high risk of mortality. Usual symptoms are sudden collapse, dyspnoea, cyanosis, and hypotension. [2]
Air embolism In air embolism small volume air bubbles enter the blood vessels. These small air bubbles expand in the right ventricle and in the pulmonary vascular tree, obstructing the pulmonary circulation. Severe acute pulmonary hypertension causes acute right heart failure. [2,3]
Obstructive lung disease Patients who are already diagnosed to have asthma, chronic bronchitis and cystic fibrosis can develop exacerbation of the symptoms during pregnancy. [2]
Pneumonia Pneumonia can be either bacterial, viral or fungal. Fever, pleuritic chest pain, cough and dyspnea are common symptoms of pneumonia. [4]
References
  1. BATTINELLI ELISABETH M., MARSHALL ARIELA, CONNORS JEAN M.. The Role of Thrombophilia in Pregnancy. Thrombosis [online] 2013 December, 2013:1-9 [viewed 28 August 2014] Available from: doi:10.1155/2013/516420
  2. BHATIA P. Pregnancy and the lungs. [online] 2000 November, 76(901):683-689 [viewed 28 August 2014] Available from: doi:10.1136/pmj.76.901.683
  3. GORDY S, ROWELL S. Vascular air embolism Int J Crit Illn Inj Sci [online] 2013, 3(1):73-76 [viewed 28 August 2014] Available from: doi:10.4103/2229-5151.109428
  4. MARRIE THOMAS J., LAU CATHERINE Y., WHEELER SUSAN L., WONG CINDY J., FEAGAN BRIAN G.. Predictors of Symptom Resolution in Patients with Community‚ÄźAcquired Pneumonia. CLIN INFECT DIS [online] 2000 December, 31(6):1362-1367 [viewed 28 August 2014] Available from: doi:10.1086/317495

Investigations - for Diagnosis

Fact Explanation
Chest X-ray Pulmonary edema is a recognized complication of Mendelson's syndrome. In addition, if the patient has aspiration pneumonia, lobar consolidation can be seen commonly over the right lower lobe. [1]
Pulse oxymetry Pulse oxymetry shows reduced oxygen saturation. [1]
References
  1. BHATIA P. Pregnancy and the lungs. [online] 2000 November, 76(901):683-689 [viewed 28 August 2014] Available from: doi:10.1136/pmj.76.901.683

Management - General Measures

Fact Explanation
Health education Patients who are awaiting surgery under general anesthesia should be clearly advised about the necessity of fasting for solids for six hours and two hours for liquids. [1]
References
  1. LEVY D M. Pre-operative fasting--60 years on from Mendelson. Continuing Education in Anaesthesia, Critical Care & Pain [online] 2006 December, 6(6):215-218 [viewed 27 August 2014] Available from: doi:10.1093/bjaceaccp/mkl048

Management - Specific Treatments

Fact Explanation
Airway management during anesthesia Airway protection with endotracheal intubation is indicated in every patient. Application of cricoid pressure during intubation is effective in minimizing the risk of Mendelson's syndrome. Maintaining the head end elevated is also helpful. [1]
Acid prophylaxis Patients who are awaiting elective Cesarean section should be given acid prophylaxis at the time of induction of anesthesia. Single dose of sodium citrate, and ranitidine are used for acid prophylaxis. [2]
References
  1. LEVY D M. Pre-operative fasting--60 years on from Mendelson. Continuing Education in Anaesthesia, Critical Care & Pain [online] 2006 December, 6(6):215-218 [viewed 27 August 2014] Available from: doi:10.1093/bjaceaccp/mkl048
  2. LANGFORD RM, BAKHSHI KN. Acid aspiration syndrome in obstetrics. Br J Anaesth [online] 1995 Feb, 74(2):239-40 [viewed 28 August 2014] Available from: http://www.ncbi.nlm.nih.gov/pubmed/7696079