Curriculum in CardiologyThe on- and off-target effects of morphine in acute coronary syndrome: A narrative review
Section snippets
STEMI guidelines (Table I)
The 2013 ACCF/AHA guidelines state that ‘In the absence of a history of hypersensitivity, morphine sulfate is the drug of choice for pain relief in patients with ST-segment elevation MI (STEMI)’, as, ‘it can alleviate the work of breathing, reduce anxiety, and favourably affect ventricular loading conditions’.4 However, the ACCF/AHA STEMI guideline provides no formal class of recommendation (COR) or level of evidence (LOE) designation.
According to the latest ECS guidelines for the management of
Pharmacologic considerations
Derived from the flowering poppy plant, Papaver somniferum, opioids have been used as analgesics for centuries. In the modern era, the pharmacology of endogenous opiates and opiate receptor systems was established in a number of elegant experiments on rodents and other mammals performed in the 1970s.11, 12, 13 All opiate receptors demonstrate considerable structural homology both with one another and with other G-protein coupled receptors.14 Opiate drugs exert their analgesic effects at
Analgesia
Chest pain is the most frequent presenting complaint in acute MI.17 A relationship between the duration of the pain and infarct size has been hypothesized. However, in the individual patient, one cannot predict the size of the infarction from the severity of the pain.18, 19 Theoretically, pain, via sympathetic nervous system activation, can increase myocardial oxygen demand and subsequently infarct size. Therefore pain control in ACS is of critical importance.
There are few head-to-head trials
Nausea and vomiting
Nausea and vomiting are common side effects of morphine. Studies have shown vomiting can occur in up to 15% of patients who are administered morphine compared to 2% in those who do not receive the medication in the setting of acute MI.9 The emetogenic effects of opioids are thought to occur through multiple mechanisms but principally by direct stimulation of the chemoreceptor trigger zone (CTZ), inhibition of gut motility, and stimulation of the vestibular apparatus.26, 27 Opioid’s inhibition
Future implications
Despite the enormous burden of ACS in western civilisations and the data described above, there is a dearth of prospective outcomes research on the optimal analgesic strategy for pain relief in MI. However, the design of the necessary randomized placebo control trials is substantially hindered by the ethical requirement for adequate analgesia. While the recently reported IMPRESSION trial was the first randomized placebo controlled study to assess morphine in this context, it lacked power to
Conclusion
Morphine remains the mainstay analgesic for severe chest pain in MI. Clinicians should be aware of emerging concerns regarding morphine administration in ACS, namely the adverse effect on gastrointestinal absorption of oral antiplatelet agents and the potential for increases adverse outcomes demonstrated in observational data. While morphine should be used where necessary, we believe that, pending the necessary randomized trials, this agent should be reserved only for ACS patients with chest
Acknowledgements
The authors report that they have nothing to disclose. No extramural funding was used to support this work. The authors are solely responsible for the design and conduct of this study, all study analyses, the drafting and editing of the paper and its final contents
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The authors report that they have nothing to disclose.