title: Myocardial ischemia and weaning failure in patients with coronary artery disease: an update.
abstract: OBJECTIVE
  To determine the frequency and effects of weaning-related myocardial ischemia on weaning outcomes in patients with coronary artery disease.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Medical and cardiac intensive care units of a 300-bed teaching community hospital.
  
  
  RESULTS
  Three-lead ST segments, heart rate-systolic blood pressure products, and respiratory rate/tidal volume ratios were obtained for patients with coronary artery disease just before and during their initial trials of weaning from mechanical ventilation. ST segments were interpreted by a blinded cardiologist. Eighty-three patients with a mean age of 72.4 +/- 1.1 years (mean +/- SEM), a mean Acute Physiology and Chronic Health Evaluation II score of 16.4 +/- 0.8, and a mean duration of mechanical ventilation of 4.6 +/- 0.9 days were studied. Eight patients showed electrocardiographic evidence of ischemia during weaning, and seven of these patients failed to be liberated on their first day of weaning. The presence of ischemia significantly increased the risk of weaning failure (risk ratio, 2.1; 95% confidence interval, 1.4-3.1). The rate-pressure product for the group as a whole increased significantly during weaning, from 11.9 +/- 0.4 to 13.5 +/- 0.5 mm Hg x beats/min x 10(3) (p < .01). The increase in rate-pressure product tended to be greater in patients who became ischemic (12.8 +/- 0.9 to 17.3 +/- 2.0 mm Hg x beats/min x 10(3)) than in patients who were not ischemic during weaning (11.8 +/- 0.4 to 13.0 +/- 0.5 mm Hg x beats/min x 10(3); p = .05). The rate/volume ratio did not change significantly during weaning, but the rate/volume ratios after both 1 min (65.6 +/- 4.6 vs. 98.0 +/- 9.4 breaths/min/L; p < .05) and 30 mins (68.6 +/- 4.3 vs. 91.1 +/- 8.9 breaths/min/L; p < .05) of unassisted breathing were lower in successful than in unsuccessful patients.
  
  
  CONCLUSIONS
  Electrocardiographic evidence of myocardial ischemia occurs frequently and is associated with significantly increased risk of first-day weaning failure in patients with coronary artery disease.
authors.affiliation: Division of Pulmonary Medicine, Bridgeport Hospital, CT 06610, USA.
authors.forename: S
authors.initials: S
authors.lastname: Srivastava
authors.forename: W
authors.initials: W
authors.lastname: Chatila
authors.forename: Y
authors.initials: Y
authors.lastname: Amoateng-Adjepong
authors.forename: S
authors.initials: S
authors.lastname: Kanagasegar
authors.forename: B
authors.initials: B
authors.lastname: Jacob
authors.forename: S
authors.initials: S
authors.lastname: Zarich
authors.forename: C A
authors.initials: CA
authors.lastname: Manthous
mesh_terms: D018806:APACHE; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003325:Coronary Care Units; D003327:Coronary Disease / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy; D004562:Electrocardiography; D004868:Equipment Failure; D005260:Female; D006764:Hospitals, Community; D006785:Hospitals, University; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000209:etiology* / Q000378:metabolism / Q000503:physiopathology; D010101:Oxygen Consumption; D011446:Prospective Studies; D015300:Ventilator Weaning; D014939:Work of Breathing