A response to ‘Peri‐operative β‐blockade and haemodynamic optimisation in patients with coronary artery disease and decreasing exercise capacity presenting for major non‐cardiac surgery’ Biccard B M, Anaesthesia 2004; 59: 60–8

Biccard raises the clinically important issue of the discrepancy between the effects of acute and chronic β-blockade. Biccard suggests that the lack of evidence for a cardioprotective effect of chronic β-blockade in patients undergoing non-cardiac surgical procedures may be due to β-blocker therapy being a marker for more advanced ischaemic heart disease (IHD). However, there are data to suggest that after allowance for the confounding factor of IHD there is no protective effect. Lee et al. [1] studied 2893 patients undergoing non-cardiac surgery. There was a similar incidence of complications between the chronic β-blocker group and those not receiving chronic β-blocker therapy (13/533; 2.4% vs. 43/2360; 1.8%). β-blocker therapy was not associated with a difference in outcome when allowance was made for the confounding factor of IHD. In vascular surgical patients, we have shown [2] no effect of chronic β-blockade when the patients were stratified according to their Lee Risk Index. In ‘non-surgical’ patients those receiving β-blockers develop myocardial ischaemia at a lower heart rate (the ischaemic threshold) than those who are not β-blocked [3, 4]. It may be that patients receiving chronic β-blockade are conversely more likely to develop myocardial ischaemia unless specific steps are taking to ‘clamp’ their heart rates below the ischaemic threshold. The observations of the McSPI Research Group [5, 6] are cited by Biccard as justification for additional β-blockade to improve outcome in those chronically receiving β-blockers. These observations refer to acute peri-operative β-blockade in patients with a high incidence of associated comorbidities. Whether additional β-blockade in the peri-operative period is necessary to ‘clamp’ the heart rate in patients receiving chronic β-blockade remains unproven. However, such studies are necessary if we are to be able to care for this large group of surgical patients.