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August 2000
Postoperative Prophylactic Administration of �-Adrenergic Blockers in Patients at Risk for Myocardial Ischemia
Urban MK, Markowitz SM, Gordon MA, Urquhart BL, Kingfield P: Anesth Analg 2000;90:1257-61.
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Commentary by Katherine Grichnik, M.D.
[see abstract below]
This is an interesting article which adds to the weight of evidence in favor of using beta-adrenergic blockade for the management of perioperative ischemia. It further supports the theory that postoperative (in contrast to preoperative and intraoperative) ischemic events result in cardiac morbidity. We can all apply this data to the perioperative care of our patients with probable coronary artery disease (CAD) in an effort to reduce postoperative cardiac morbidity and mortality.
The authors examined 107 patients with known or probable CAD (as described by Mangano et al [1]) who were randomized prospectively to receive postoperative
beta-blocker therapy as needed to keep heart rate (HR) below 80. Patients excluded were those with EKGs that were difficult to read (LBBB, LVH with repolarization abnormalities, and atrial arrhythmias), EF less than 30%, symptomatic valvular heart disease and symptomatic bronchospastic disease. All patients had the same surgery (total knee replacement) with the same anesthetic (lumbar epidural anesthesia with mild sedation) done by only 2 researchers and the same type of postoperative analgesia (epidural analgesia). No patients received preoperative or intraoperative beta blockade. Postoperatively, the treatment group patients received an esmolol infusion in an ICU for 12-24 hours followed by oral metoprolol until discharge from the hospital.
In the entire postoperative period, there tended to be differences in ischemia, MIs and cardiac morbidity seen between the control group and the beta blocker group, although these differences did not reach statistical significance. There were significant differences in ischemia from 18-24 hours postoperatively, and in the number of ischemic events.
It is important to note that several of the patients in the control group received beta blockers outside of the study protocol in order to treat hypertension, tachycardia and/or ischemia. Further, due to bradycardia, two of the treatment group patients did not receive beta blockade.
Just as important to take away from this article is the striking finding of an equal number of ischemic events between the two groups preoperatively and intraoperatively. Thus pre- and intra-operative ischemia were not determinants of the differences in cardiac morbidity seen postoperatively. This supports the notion that postoperative ischemic events determine the ultimate cardiac morbidity suffered by the patient.
I applaud the use of beta-blockade as prophylaxis against cardiac events in patients undergoing surgical procedures outside of vascular and cardiac procedures. Some patients presenting for orthopedic surgery may carry the same risk as a vascular or cardiac surgical patient with respect to risk of CAD and morbidity from CAD. This study addresses our continued efforts to be perioperative physicians and actively participate in the care of our patients postoperatively to positively influence overall outcomes.
References:
Mangano DT, Browner WS, Hollenberg M, London MJ, Tubau JF, Tateo IM. Association of perioperative myocardial ischemia with cardiac morbidity and mortality in men undergoing noncardiac surgery. The Study of Perioperative Ischemia Research Group. New Engl J Med 323:1990; 1781-8.
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ABSTRACTS
Postoperative Prophylactic Administration of �-Adrenergic Blockers in Patients at Risk for Myocardial Ischemia.
AUTHORS:
Urban MK, Markowitz SM, Gordon MA, Urquhart BL, Kingfield P
SOURCE:
Anesth Anal 2000;90:1257-61.
ABSTRACT
Perioperative myocardial ischemia (MI) is associated with postoperative cardiac morbidity. Postoperative sympatholysis may reduce the incidence of MI. This study evaluated such a reduction postoperatively with the administration of prophylactic beta-blockers in patients undergoing elective total knee arthroplasty with epidural anesthesia and postoperative epidural analgesia. One hundred seven patients were preoperatively randomized into two groups, control and beta-blockers, who received postoperative esmolol infusions on day of surgery and metoprolol for the next 48 h to maintain a heart rate less than 80 bpm.
Patients were followed for ST segment depression by using a Holter monitor and adverse cardiac outcomes. Postoperative electrocardiographic ischemia was significantly more prevalent in the control group compared with the beta-blocker group during esmolol blockade (0 of 52 vs 4 of 55; P = 0.04) and tended to be more common in the control group the next two days (8 of 55 vs 3 of 52; P = 0.135). In addition, the number of ischemic events (control, 50; beta-blockers, 16) and total ischemic time (control, 709 min; beta-blocker, 236 min) were also significantly different from the control group. Myocardial infarctions and cardiac events were more common in the control group, but these differences were not significant. Our results suggest that the use of prophylactic beta-blocker therapy may reduce the incidence of postoperative MI. Implications: Prophylactic beta adrenergic blockade administered after elective total knee arthroplasty was associated with a reduced prevalence and duration of postoperative myocardial ischemia detected with Holter monitoring.
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