PERIOPERATIVE β BLOCKER THERAPY
Management of β-blockers perioperatively is a key anesthesia performance indicator and is closely monitored by various “quality management” agen-cies. Although studies regarding the perioperative administration of β-blockers have yielded conflict-ing results as to benefit, maintenance of β-blockers in patients already being treated with them is essential, unless contraindicated by other clinical concerns.
β-Blocker therapy in the perioperative periodhas the potential to reduce the perioperative cardio-vascular complications (myocardial ischemia, stroke, cardiac failure) due to counteraction of catechol-amine-induced tachycardia and hypertension. How-ever, these beneficial effects have not been widely demonstrated in recent clinical trials. Perioperative β-blocker therapy was associated with a reducedrisk of in-hospital death in a small group of high-risk patients (ie, those with a Revised Cardiac Score Index of 3 or higher), but showed no improvement or even an increase in stroke and overall mortality in low-risk patients undergoing noncardiac surgery.
Current American Heart Association/American College of Cardiology guidelines recommend continuation of β-blocker therapy during theperioperative period in patients who are receiving β-blockers for the treatment of angina, symptomaticarrhythmia, heart failure, and hypertension. In addi-tion, β-blocker therapy should be initiated in patients undergoing vascular surgery who are at high risk of cardiac events because of findings of myocardial ischemia during perioperative testing. The guide-lines also note that β-blockers titrated to heart rate and blood pressure are “reasonable” in patients undergoing vascular surgery who have more than one cardiac risk factor. Additionally, the guidelines suggest that perioperative β-blockers are likewise “reasonable” in patients undergoing intermediate-risk procedures who have more than one cardiac dis-ease risk factor. The routine administration of high-dose β-blockers in the absence of dose titration may be harmful in patients not currently taking β-blockers who are undergoing noncardiac surgery. 11 Discontinuation of β-blocker therapy for 24–48 hr may trigger a withdrawal syndrome characterized by hypertension (rebound hyperten-sion), tachycardia, and angina pectoris. This effect seems to be caused by an increase in the number of β-adrenergic receptors (up-regulation).