title: Airway pepsin levels in otherwise healthy surgical patients receiving general anesthesia with endotracheal intubation.
abstract: BACKGROUND
  Airway pepsin has been increasingly used as a potentially sensitive and quantifiable biomarker for gastric-to-pulmonary aspiration, despite lack of validation in normal control subjects. This study attempts to define normal levels of airway pepsin in adults and distinguish between pepsin A (exclusive to stomach) and pepsin C (which can be expressed by pneumocytes).
  
  
  METHODS
  We performed a prospective study of 51 otherwise healthy adult patients undergoing elective extremity orthopedic surgery at a single tertiary-care academic medical center. Lower airway samples were obtained immediately following endotracheal intubation and just prior to extubation. Total pepsin and pepsin A concentrations were directly measured by an enzymatic activity assay, and pepsin C was subsequently derived. Pepsinogen/pepsin C was confirmed by Western blot analyses. Baseline characteristics were secondarily compared.
  
  
  RESULTS
  In all, 11 (22%; 95% CI = 9.9%-33%) had detectable airway pepsin concentrations. All 11 positive specimens had pepsin C, without any detectable pepsin A. Pepsinogen/pepsin C was confirmed by Western blot analyses. In a multivariate logistic regression, men were more likely to have airway pepsin (OR, 12.71, P = .029).
  
  
  CONCLUSIONS
  Enzymatically active pepsin C, but not the gastric-specific pepsin A, is frequently detected in the lower airways of patients who otherwise have no risk for aspiration. This suggests that nonspecific pepsin assays should be used and interpreted with caution as a biomarker of gastropulmonary aspiration, as pepsinogen C potentially expressed from pneumocytes may be detected in airway samples.
authors.affiliation: Department of Anesthesia, Mayo Clinic College of Medicine, Rochester, MN.
authors.forename: J Kyle
authors.initials: JK
authors.lastname: Bohman
authors.affiliation: Department of Anesthesia, Mayo Clinic College of Medicine, Rochester, MN; Multidisciplinary Epidemiology and Translational Research in Intensive Care Study Group, Division of Critical Care Medicine, Mayo Clinic College of Medicine, Rochester, MN.
authors.forename: Daryl J
authors.initials: DJ
authors.lastname: Kor
authors.affiliation: Multidisciplinary Epidemiology and Translational Research in Intensive Care Study Group, Division of Critical Care Medicine, Mayo Clinic College of Medicine, Rochester, MN.
authors.forename: Rahul
authors.initials: R
authors.lastname: Kashyap
authors.affiliation: Multidisciplinary Epidemiology and Translational Research in Intensive Care Study Group, Division of Critical Care Medicine, Mayo Clinic College of Medicine, Rochester, MN.
authors.forename: Ognjen
authors.initials: O
authors.lastname: Gajic
authors.affiliation: Department of Critical Care Medicine, Division of Pulmonary Medicine, Mayo Clinic College of Medicine, Jacksonville, FL.
authors.forename: Emir
authors.initials: E
authors.lastname: Festic
authors.affiliation: Alfred I. duPont Hospital for Children, Wilmington, DE.
authors.forename: Zhaoping
authors.initials: Z
authors.lastname: He
authors.affiliation: Department of Critical Care Medicine, Division of Pulmonary Medicine, Mayo Clinic College of Medicine, Jacksonville, FL. Electronic address: lee.augustine@mayo.edu.
authors.forename: Augustine S
authors.initials: AS
authors.lastname: Lee
mesh_terms: D000328:Adult; D000368:Aged; D056809:Alveolar Epithelial Cells / Q000378:metabolism; D000768:Anesthesia, General; D015415:Biomarkers / Q000378:metabolism; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism; D006801:Humans; D007442:Intubation, Intratracheal; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009985:Orthopedics; D010434:Pepsin A / Q000378:metabolism*; D011446:Prospective Studies; D053120:Respiratory Aspiration / Q000175:diagnosis* / Q000378:metabolism; D012137:Respiratory System / Q000166:cytology / Q000378:metabolism*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013270:Stomach / Q000166:cytology
chemical_list: D015415:Biomarkers; D010434:Pepsin A; C020557:gastricsin