We’ve discussed on numerous occasions the changing role of periopative beta blockers (see “December 2009 Updated Perioperative Beta Blocker Guidelines” for links to all those columns). Since the POISE trial showed better cardiovascular outcomes came at the cost of increased mortality and stroke risk, perioperative beta blocker use has plummeted. Nevertheless, many investigators and practitioners remain convinced that appropriate periopertive use of beta blockers may result in better outcomes and have sought to identify subgroups that might benefit from beta blockers or subgroups that may be at greater risk from beta blockers.
A new study (Beattie et al. 2010) sheds some light on why some patients may fare worse on beta blockers during major surgery. They looked retrospectively at a large population underoing noncardiac surgery and used propensity scoring to get cohorts for comparison. They found that a composite of major cardiac outcomes was worse in patients experiencing an acute perioperative reduction in hemoglobin levels of more than 35%. Lesser degrees of acute anemia were not associated with these same adverse outcomes. The authors and the accompanying editorialist (Weiskopf et al. 2010) discuss how the normal physiologic mechanisms that respond to acute blood loss are impaired by beta blockade.
W Scott Beattie WS, Wijeysundera DN, Karkouti K. Acute Surgical Anemia Influences the Cardioprotective Effects of β-Blockade: A Single-center, Propensity-matched Cohort Study. Anesthesiology 2010; 112:12–5
Weiskopf RB. Perioperative Use of β-Adrenergic Antagonists and Anemia: Known Knowns, Known Unknowns, Unknown Unknowns; and Unknown Knowns. Anesthesiology 2010; 112: 25–33