title: Myocardial ischemia during the weaning period.
abstract: OBJECTIVE
  To estimate the incidence of silent myocardial ischemia, its pattern over time and its relationship to the time and mode of weaning high-risk cardiac patients after noncardiac surgery.
  
  
  METHODS
  Prospective study with random assignment to one of three weaning modes.
  
  
  METHODS
  A surgical intensive care unit in a university hospital and a Veterans Administration hospital.
  
  
  METHODS
  Sixty-two patients meeting standard criteria for extubation were randomized to one of three modes of weaning: synchronized intermittent mandatory ventilation (n = 19), T-Bar (n = 21) or continuous positive airway pressure (n = 22).
  
  
  METHODS
  Ischemia was monitored with a continuous two-lead (V5, III) ST segment analyzer. Tracings were reviewed by a cardiologist. Ischemia was defined as greater than 1 mm ST segment depression 60 milliseconds after the J point. The monitoring period included a prewean (mean 654.0 minutes), wean (mean 46.5 minutes) and postwean (mean 1223.4 minutes) period.
  
  
  RESULTS
  Of 62 patients, 12 (19.3%) experienced ischemia at some time during the monitoring period, most often during the weaning period. Ischemia during weaning was detected in 3 of 21 (14.3%) T-Bar patients and 2 of 22 (9.1%) continuous positive airway pressure patients but in no synchronized intermittent mandatory ventilation patients.
  
  
  CONCLUSIONS
  This study demonstrates that silent myocardial ischemia occurs frequently in high-risk postoperative patients, with the highest incidence during weaning.
authors.affiliation: Mount Sinai Hospital, New York, NY.
authors.forename: A
authors.initials: A
authors.lastname: Abalos
authors.forename: A B
authors.initials: AB
authors.lastname: Leibowitz
authors.forename: D
authors.initials: D
authors.lastname: Distefano
authors.forename: N
authors.initials: N
authors.lastname: Halpern
authors.forename: T J
authors.initials: TJ
authors.lastname: Iberti
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D004562:Electrocardiography; D005260:Female; D006801:Humans; D015994:Incidence; D007385:Intermittent Positive-Pressure Ventilation / Q000009:adverse effects* / Q000379:methods; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D010101:Oxygen Consumption; D011175:Positive-Pressure Respiration / Q000009:adverse effects* / Q000379:methods; D011183:Postoperative Complications / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology / Q000503:physiopathology; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D015300:Ventilator Weaning / Q000009:adverse effects* / Q000379:methods; D014939:Work of Breathing