Myocardial ischaemia during tracheal extubation in patients after cardiac surgery: an observational study.

This study examines whether there is a temporal relationship between tracheal extubation and myocardial ischaemia in haemodynamically stable patients extubated within 6 h of cardiac surgery. Fifty-two patients were studied during three time periods: 1, from 2 h until 30 min before extubation (90 min); 2, from 30 min before until 30 min after extubation (60 min); 3, from 30 min until 2 h after extubation (90 min). Significant ST segment changes were defined as a reversible ST segment depression of 2 mm or greater or an elevation of 3 mm or greater from baseline, lasting for 1 min or more. Fourteen patients (26.9%) had ST segment changes. The ischaemic burden in periods 2 and 3 was increased compared with that in period 1; the mean (SD) was: period 1, 19.2 (18.8) min; period 2, 35.4 (24.9) min; period 3, 39.6 (24.5) min; however, the mean ST deviation (mm) did not change. ST segment changes were associated with an increased heart rate; they were not related to arterial pressure. We conclude that there is a temporal relationship between ST segment changes and tracheal extubation after cardiac surgery.