Acute chest pain. Characteristics, assessment and treatment

Abstract

Adequate treatment of pain in the acute phase of acute myocardial infarction is an important objective. In the present thesis, the analgesic effects and the pharmacokinetics of morphine and high-dose intravenous metoprolol, were assessed in patients with acute chest pain. Localization of pain, pain intensity, pain memory and predictors for consumption of analgesics were also determined in the patient groups. Patients with acute myocardial infarction localized their pain to similar body regions as compared to those without myocardial infarction. However, patients with myocardial infarction reported pain more frequently in the upper right square of the chest and the right and left arms. Intravenous high-dose metoprolol treatment was well tolerated in patients with acute chest pain. There was a rapid and almost complete pain relief in the patients without signs of transmural ischemia compared to the patients with electrocardiographic signs of transmural myocardial infarction at arrival. The need for adjunct morphine treatment in patients with suspected myocardial infarction differed among subgroups. In particular, higher doses were needed in those with a strong suspicion of myocardial infarction on arrival to hospital. Intravenous morphine administration induced analgesia approximately 20 minutes after injection. In patients given an initial dose of a beta-blocker, a more extensive pain relief was observed in the group treated with morphine than in the patients given additional beta-blocker treatment. There was a great variability in the plasma concentrations of metoprolol and morphine as well as their metabolites. Pain intensity in patients with myocardial infarction was recalled after 6 months with reasonable accuracy. However, there was a consistent overestimation of pain at recall. In conclusion; 1) The body surface distribution of pain is not of great diagnostic utility in distinguishing whether patients will develop a confirmed myocardial infarction or not. 2) There is commonly a pronounced variability in chest pain in patients admitted to hospital due to suspected myocardial infarction. 3) In patients with acute chest pain due to suspected myocardial infarction, both intravenous morphine and metoprolol induce rapid relief of pain. 4) Morphine metabolites may contribute to the pharmacodynamic effects of systemic morphine. 5) After an initial dose of beta-adrenergic blockade, a more extensive pain relief was observed when adding morphine, indicating that both an antiischemic and analgetic agent are required in pain management in patients with acute chest pain due to suspected myocardial infarction.