Perioperative β-blockers

Earlier perioperative trials of β-blockers involved small numbers of patients undergoing a wide range of surgical procedures. In addition, different β-blockers were used without titration to a desired effect (target heart rate). This high degree of heterogeneity resulted in variable opinion regarding the use of β-blockers in the perioperative phase. Published meta-analyses included these small and relatively heterogeonus trials and resulted in similar variable conclusions. Timing, location, and route of administration also complicate the desicion regarding the use of β-blockers perioperatively.

Areas of agreement

β-blockers should be continued in patients undergoing surgery who are already receiving β-blockers for any ACC/AHA class 1 recommendation. Interruption of therapy in these patients may lead to recurrent angina, arrhythmias, rebound hypertension, or other cardiovascular (CV) complications that may increase perioperative morbidity and mortality. The use of β-blockers is considered class 1 and class IIa in patients undergoing high risk vascular surgery with known coronary heart disease or have one or more clinical cardiovascular (CV) risk factors, respectively (Level of evidence= B, LOE B). This includes patients who were found to have myocardial ischemia on preoperative testing.

Weak evidence

The weakest evidence for the use of perioperative β-blockers is for patients undergoing intermediate-risk surgery who have at least one clinical risk factor and for patients undergoing vascular surgery who have no clinical risk factors.

Potential hazards

This was underscored by the POISE trial (Perioperative Ischemic Evaluation). This multicenter, randomized, placebo-controlled trial included 8351 patients who underwent intermediate or high risk surgery. Patients were randomized to receive either placebo or a fixed dose of 100 mg of metoprolol, which was administered 2 to 4 hours before surgery and again within 6 hours after surgery. A maintenance dosage of 200 mg/day of the drug was administered postoperatively for 30 days. Patients were continued on this dosage as long as their heart rate remained at least 50 beats/min and their systolic blood pressure exceeded 100 mm Hg. Despite the significant reduction in the primary composite end points (cardiovascular death, cardiac arrest, and nonfatal myocardial infarction) with metoprolol therapy vs placebo (5.8% vs 6.9%, respectively; hazard ratio [HR], 0.84; P=.04), the total 30-day mortality rate was greater in the metoprolol-treated patients than in the placebo group (3.1% vs 2.3%, respectively; HR, 1.33; P=.03), as was the incidence of clinically important hypotension (15% vs 9.7%; HR, 1.55; P<.001), severe bradycardia (6.6% vs 2.4%; HR, 2.74; P<.001), and stroke (1.0% vs 0.5%; HR, 2.17; P=.005). Stroke, hypotension, and bradycardia were all predictors of increased mortality.

Barriers to the effective use of perioperative β-blockers

• The titration of β-blockers dosage to achieve target resting heart rate of less 65 beats/min can pose logestical problems.
  • Many patients present to the preoperative medical clinic just one or few days prior to their scheduled procedure.
  • Titration of β-blockers dosage can results in hypotension, bradycardia, and other side effects.
  • The variable metabolic effects produced by β-blockers during their first pass through the hepatic venous circulation after absorption result in variable serum levels (and clinical effects) depending on the individual patient.

Recommendations

• The use of perioperative β-blockers should be limited to class 1 or class IIa recommendations (see above).
• Patients should be seen earlier during the preoperative period for carefull titration of β-blockers.
• Clinicians should pay attention in regards to the use of concurrent medications that result in bradycardia and/or hypotension.

Johnfanisrour 02:03, 12 January 2009 (UTC) john fani srourJohnfanisrour 02:03, 12 January 2009 (UTC)