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aspiration pneumonitis (Mendelson's syndrome)

Etiology: 1) regurgitation of stomach contents & aspiration of chemical material, generally gastric juices 2) often follows anesthesia when the gag reflex is depressed Pathology: 1) low pH (< 2.5) of aspirated gastric contents 2) large volume of aspirate 3) pulmonary inflammation 4) destruction of the alveolar lining 5) transudation of fluid into the alveolar space 6) ARDS may develop 7) bacterial superinfection Clinical manifestations: 1) develops within hours 2) cough 3) wheezing 4) rales 5) tachypnea 6) dyspnea 7) hypoxia 8) low-grade fever 9) tachycardia 10) hypotension 11) sputum production is minimal; significant sputum production suggests bacterial superinfection 12) evidence of sepsis (bacterial superinfection) Laboratory: 1) complete blood count (CBC) a) WBC may be increased without bacterial infection b) bacterial superinfection generally accompanied by leukocytosis 2) arterial blood gas (ABG) may show increased P(A-a)O2 - pulse oximetry may show diminished SaO2 3) blood cultures & sputum cultures to rule out aspiration pneumonia Radiology: - chest X-ray - may be normal (in contrast to aspiration pneumonia) [3] - may change from normal to complete white-out within 8-24 hours - a case described with new lower lung opacity [7] Differential diagnosis: - aspiration pneumonia with abnormal chest X-ray [3] - develops days not hours after pulmonary aspiration Complications: - significant risk for aspiration pneumonia Management: 1) supportive care (without antibiotics) is the most appropriate therapy [4] - respiratory support - supplemental oxygen - positive pressure ventilation with more severe disease - mechanical ventilation of a last resort [3] 2) standard antibiotic therapy for community-acquired pneumonia [6] - discontinue antibiotics if cultures negative 3) withold antibiotics until evidence of bacterial superinfection, except in association with: a) intestinal obstruction b) gingivitis or periodontitis (severe) c) immunocompromised host 4) prognosis a) may resolve quickly with symptomatic therapy b) bacterial superinfection may result may develop over a period of days c) symptoms that persist or increase after 48 hours suggest aspiration pneumonia [3]

Related

aspiration pneumonia pulmonary aspiration; foreign body aspiration

General

pneumonitis syndrome

References

  1. Manual of Medical Therapeutics, 28th ed, Ewald & McKenzie (eds), Little, Brown & Co, Boston, 1995, pg 252-53
  2. Harrison's Principles of Internal Medicine, 14th ed. Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 993-4
  3. Geriatric Review Syllabus, 9th edition (GRS9) Medinal-Walpole A, Pacala JT, Porter JF (eds) American Geriatrics Society, 2016
  4. Marik PE. Aspiration pneumonitis and aspiration pneumonia. N Engl J Med. 2001 Mar 1;344(9):665-71. Review. PMID: 11228282
  5. Raghavendran K, Nemzek J, Napolitano LM, Knight PR. Aspiration-induced lung injury. Crit Care Med. 2011 Apr;39(4):818-26. Review. PMID: 21263315 Free PMC Article
  6. Medical Knowledge Self Assessment Program (MKSAP) 19 American College of Physicians, Philadelphia 2022
  7. NEJM Knowledge+