Detection of “silent” ischemia during induction of anesthesia for coronary bypass surgery by real-time ST monitoring

Abstract

“Silent” ischemia may occur during hemodynamic changes accompanying induc tion of anesthesia in patients undergoing coronary bypass surgery and may be detected by continuous monitoring of the ECG. A real-time single-lead ST monitor was developed, validated, and used to detect ischemia during induction of anesthesia in 101 patients (85 men, 16 women; mean age, 61 ±9 years) undergoing bypass surgery. The first 72 patients were unselected, and the last 29) were included if they had stable angina and a positive exercise ECG (≥0.1 mV ST depression) so that lead selection for monitoring could be based on the exercise lest results. Ischermia during anesthesia (ST deviation, >0.1 mV) occurred in 10% of patients (10 of 101) despite routine premedication with nitrates; this percentage was identical in the unselected (7 of 72) and selected (3 of 29) patients, indicating that preoperative exercise-induced ischemia did not predict ischemia during induction of anesthesia. Perioperative Q-wave infarction developed in 5% of patients, but was more common in those with ischemia during anesthesia (2 of 10, 20%) than in those without (3 of 91, 3%; P<0.05). Silent ischemia during anesthesia for coronary bypass surgery can be detected by real-time ECG monitoring of the ST segment and may identify a small group of patients with a relatively high risk of perioperative Q-wave infarction.