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.) three times at 2-min intervals (n = 84;
metoprolol group) or
morphine 5 mg i.v. followed by
metoprolol 5 mg three times i.v (n = 80;
morphine group).
Pain was assessed on a 10-grade scale before randomization and 10, 20, and 30 min thereafter. The mean
pain score decreased from 6.5 at randomization to 2.8 30 min later, with no significant difference between groups. The percentages with complete
pain relief (
pain score < or = 1) after 10, 20, and 30 min were 11, 16, and 21%, respectively, with no difference between groups.
Hypotension was less frequent in the
metoprolol group compared with the
morphine group (0 vs. 6.3%; P=0.03), as was
nausea/
vomiting (7.2 vs. 24.0%; P=0.004). At randomization intensity of
pain was associated with degree of ST elevation (P=0.009). The degree of
pain relief over 30 min was associated with decrease in heart rate (P=0.03) and decrease in ST elevation (P=0.01).In conclusion, in the prehospital phase of presumed ACS, neither a
pain-relieving strategy including an anti-ischemic agent alone nor an
analgesic plus anti-ischemic strategy in combination resulted in complete
pain relief. Fewer side effects were found with the former strategy. Other
pain-relieving strategies need to be evaluated.