title: Postcardiopulmonary bypass hypoxemia: a prospective study on incidence, risk factors, and clinical significance.
abstract: OBJECTIVE
  To evaluate the clinical significance of low arterial oxygen tension-inspired oxygen concentration (PaO2-FIO2) ratio, as a measure of hypoxemia, in the early period after cardiac surgery with cardiopulmonary bypass (CPB); and to evaluate the preoperative, intraoperative, and postoperative factors contributing to the development of hypoxemia within the first 24 hours after cardiac surgery with CPB.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  University hospital.
  
  
  METHODS
  Patients who underwent elective or emergency cardiac surgery with CPB (n = 466).
  
  
  METHODS
  Preoperative clinical and laboratory data were recorded, as were intraoperative and postoperative data regarding the PaO2-FIO2 ratio, fluid and drug therapy, and chest radiograph. Data analysis evaluated hypoxemia as depicted by the PaO2-FIO2 ratios at 1, 6, and 12 hours after surgery. Thereafter, the effect of the PaO2-FIO2 ratios on time to extubation, lung injury, and length of hospital stay was evaluated. The risk factors were analyzed in 3 separate periods: preoperative, intraoperative, and postoperative. Univariate and multivariate analyses were performed on each period separately. All data were analyzed in 2 consecutive steps: univariate analysis and multivariate analysis.
  
  
  RESULTS
  PaO2-FIO2 ratios after CPB were significantly lower compared with baseline values. Six patients (1.32%) met the clinical criteria compatible with acute lung injury. All 6 patients had prompt recovery. Significant risk factors for hypoxemia were age, obesity, reduced cardiac function, previous myocardial infarction, emergency surgery, baseline chest radiograph with alveolar edema, high creatinine level, prolonged CPB time, decreased baseline PaO2-FIO2, use of dopamine after discontinuation of CPB, coronary artery bypass grafting, use of left internal mammary artery, higher pump flow requirement during CPB, increased level of hemoglobin or total protein content, persistent hypothermia 2 and 6 hours after surgery, requirement for reexploration, event requiring reintubation, and chest radiograph with alveolar edema 1 hour after surgery. Six hours after surgery, a lower PaO2-FIO2 ratio correlated significantly with time to extubation and lung injury.
  
  
  CONCLUSIONS
  This study shows that despite improvements in the technique of CPB, hypoxemia depicted by low PaO2-FIO2 ratios is common in patients after CPB. It is short lived, however, and has minimal effect on the postoperative clinical course of these patients.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Hadassah University Hospital, Hebrew University--Hadassah Medical School, Jerusalem, Israel.
authors.forename: Y G
authors.initials: YG
authors.lastname: Weiss
authors.forename: G
authors.initials: G
authors.lastname: Merin
authors.forename: E
authors.initials: E
authors.lastname: Koganov
authors.forename: A
authors.initials: A
authors.lastname: Ribo
authors.forename: A
authors.initials: A
authors.lastname: Oppenheim-Eden
authors.forename: B
authors.initials: B
authors.lastname: Medalion
authors.forename: M
authors.initials: M
authors.lastname: Peruanski
authors.forename: E
authors.initials: E
authors.lastname: Reider
authors.forename: J
authors.initials: J
authors.lastname: Bar-Ziv
authors.forename: W C
authors.initials: WC
authors.lastname: Hanson
authors.forename: R
authors.initials: R
authors.lastname: Pizov
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000453:epidemiology* / Q000209:etiology; D015994:Incidence; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000209:etiology; D012307:Risk Factors