Myocardial ischemia during the weaning period.
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.
Abalos
A
A
Mount Sinai Hospital, New York, NY.
Leibowitz
A B
AB
Distefano
D
D
Halpern
N
N
Iberti
T J
TJ
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