Aspects on the intensity and the relief of pain in the prehospital phase of acute coronary syndrome: experiences from a randomized clinical trial.

The primary aim of this study was to evaluate the pain relief and tolerability of two pain-relieving strategies in the prehospital phase of presumed acute coronary syndrome (ACS), and the secondary aim was to assess the relationship between the intensity and relief of pain and heart rate, blood pressure, and ST deviation. Patients with chest pain judged as caused by ACS were randomized (open) to either metoprolol 5 mg intravenously (i.v.