PERIOPERATIVE MYOCARDIAL-ISCHEMIA IN PATIENTS UNDERGOING ELECTIVE HIP-ARTHROPLASTY DURING LUMBAR REGIONAL ANESTHESIA

Perioperative myocardial ischemia predicts unfavorable outcomes and occurs in as many as 41% of patients with coronary artery disease or cardiac risk factors undergoing noncardiac surgery. To determine the prevalence of myocardial ischemia, we studied 52 consecutive unselected patients undergoing elective hip arthroplasty during lumbar regional anesthesia. Patients were continuously monitored for 6 days using a three-channel Holter monitor. Ninety-nine episodes of myocardial ischemia occurred in 16 patients (31%), six of whom were considered preoperatively to be at low risk for coronary artery disease. Forty-four percent of the ischemic episodes were preceded or accompanied by a heart rate greater-than-or-equal-to 100/min and 56% by a heart rate greater-than-or-equal-to 90 beats/min. Ninety-six percent of the ischemic episodes were clinically silent, and 82% were not related to patient care events. Thirteen episodes of myocardial ischemia occurred preoperatively, 1 intraoperatively, and 85 postoperatively. The incidence of post-operative ischemic episodes showed a circadian variation: 44% occurred between 6 AM and noon, 33% between noon and 6 PM, 17% between 6 PM and midnight, and 6% between midnight and 6 AM. Six adverse cardiac events occurred during hospitalization (three of the six among patients with perioperative ischemia) and an additional four events during a follow-up period of 12 months (all four events occurred among patients with perioperative ischemia). Patients with perioperative myocardial ischemia had a relative risk of 2.6 (95% confidence interval 1.3-5.2) to develop an adverse cardiac event postoperatively.