Cardiac surgery induces profound sympathetic nervous system and inflammatory responses. This so-called ‘stress response’ to surgery causes a multitude of adverse haemodynamic, metabolic, haematological, endocrine and immunological effects. In the setting of cardiac surgery, the attenuation of pain and sympathetic autonomic activity has many theoretical attractions. The introduction of high-dose opioid techniques into cardiac anaesthesia was based, in part, on the belief that they would inhibit the stress response. Failure to block the stress response completely, combined with equivocal evidence of clinical benefit and the need for prolonged postoperative mechanical ventilation, made the technique unpopular. The demonstration that thoracic sympathetic blockade improves the blood flow in severely diseased coronary arteries, the emergence of less invasive cardiac surgical techniques and economic pressures have prompted renewed interest in regional anaesthetic techniques.