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Segmental wall motion was assessed only if > 70% of its entire endocardial outline was visible throughout systole and diastole. Wall motion was graded as: 0 = normal, 1 = mild hypokinesis, 2 = severe hypokinesis with myocardial thickening, 3 = akinesis, and 4 = dyskinesis. Image position and quality also were graded. After all TEE images were scored, baseline wall motion for each quadrant was determined using the most normal wall motion in each quadrant at any time (minimum 1-min duration) during TEE monitoring. When regional wall motion deteriorated, the following criteria were used to define an echocardiographic ischemic episode: (1) deterioration in wall motion greater or equal to 2 grades and (2) deterioration from akinesis to dyskinesis (in a segment with normal wall thickness). Apparent deterioration in wall motion accompanied by a major shift in image position (i.e., from midpapillary to basal short-axis) was not considered significant (to avoid including preexisting wall-motion abnormalities at different anatomic levels). Onset of an ischemic episode began when a significant change first occurred in one or more quadrants and ended when the last quadrant normalized by at least one grade toward baseline. Interexamination and intraobserver variabilities in our laboratory have been reported previously. Postoperative Analgesia Postoperative analgesia was provided by intravenous morphine sulfate, delivered by a patient-controlled analgesia (PCA) pump. The initial PCA setting was a 1-mg bolus dose with a lock-out interval of 6 min. For inadequate analgesia, additional 2-mg doses of morphine were administered intravenously as needed. If analgesia remained inadequate after the additional 2-mg bolus doses, the PCA dose was increased in increments of 0.5 mg. Analgesia was assessed using a visual analog scale (VAS), comprised of a 100-mm horizontal line with one pole representing “no pain” and the other “worst pain imaginable.” The scale was administered every 4 h postoperatively for the first 48 h, as long as the patient was awake. Patients assessed their pain at rest and rated the severity of the worst pain since the last assessment. To determine the intraoperative isoflurane requirements, the curve for the area under the end-tidal isoflurane concentration versus time was integrated and divided by the intraoperative time. Hemodynamic response to the 1-h dexmedetomidine infusion preceding induction of anesthesia was analyzed by comparing the values (5-min average) for systolic blood pressure and heart rate immediately before infusion with those obtained 1 h after the start of infusion. The response to intubation was analyzed by comparing the hemodynamic values immediately preceding intubation to the highest values obtained within 5 min after intubation. Hemodynamic response to emergence from anesthesia was analyzed by comparing preoperative noninvasive baseline values for systolic blood pressure and heart rate with the highest values obtained after discontinuation of anesthesia, before leaving the operating room. The percent change in rate-pressure product (HR*SBP) in response to the 1-h dexmedetomidine infusion preceding induction of anesthesia was calculated by comparing the rate-pressure product (5-min average) at the end of the 1-h infusion to the rate-pressure product immediately preceding the study drug infusion. The percent change in rate-pressure product in response to intubation was calculated by comparing the highest rate-pressure product within 5 min after intubation to the rate-pressure product immediately preceding (5-min average) the study drug infusion and in response to emergence by comparing the highest rate-pressure product after discontinuation of anesthesia, before leaving the operating room, to the rate-pressure product immediately preceding (5-min average) the study drug infusion. Nonparametric tests were used to analyze the data unless otherwise indicated. Kruskal-Wallis test was used to analyze the overall comparisons among the four groups. When a significant difference was found, the placebo group was compared to the dexmedetomidine groups using the Wilcoxon two-sample test without correction for multiple
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