Pre-hospital opiate and aspirin administration in patients with suspected myocardial infarctionBMJ 1994; 308 doi: https://doi.org/10.1136/bmj.308.6931.760a (Published 19 March 1994) Cite this as: BMJ 1994;308:760
- H R Wyllie,
- F G Dunn
- Correspondence to: Dr Dunn.
The benefit of immediate oral aspirin in the treatment of acute myocardial infarction is now established, having an equivalent impact to that of intravenous thrombolytic therapy in reducing early mortality.*RF 1-3* Though practical problems still exist with pre-hospital thrombolysis, aspirin can easily be given in this setting. Pain relief is a fundamental component and opiate analgesia is thought to be the most effective treatment. It is accepted that the route of administration should be intravenous rather than intramuscular, which can result in erratic absorption,4 haematoma formation, and a spurious increase in creatine kinase activity.5
The aim of this study was to assess the frequency with which aspirin was given acutely in patients suspected of acute myocardial infarction and the frequency and route of opiate analgesia given at home.
Patients, methods, and results
From August 1992 to February 1993, 160 patients (110 male) admitted to the coronary care unit at this hospital with suspected myocardial infarction were studied. Patients were interviewed at the time of arrival by means of a questionnaire administered by the admitting medical or senior nursing personnel. All relevant details regarding the patients, use of opiate analgesia and aspirin, and presence of chest pain were recorded. Serial cardiac enzyme measurements and electrocardiograms were used to establish a final diagnosis.
One hundred and thirty three of the patients (83%) were referred by general practitioners either directly to coronary care (n=91) or via the casualty department (n=42). A total of 66 of them had a discharge diagnosis of myocardial infarction. The administration of opiates and aspirin to the total group and to the subgroup with infarcts is summarised in the table. Isolated rises in creatine kinase activity were observed in four out of 10 patients who did not have a myocardial infarction but who had received intramuscular analgesia. No haematomas were detected in the seven patients who received both intramuscular opiate and thrombolytic therapy.
This study had two main findings with respect to pain. Firstly, a substantial number of patients suspected of having a myocardial infarction still do not have adequate pain relief on admission to hospital. Secondly, patients who receive no analgesia or who are given intramuscular analgesia are more likely to be in pain than are those given intravenous analgesia. We did not measure the severity of pain on admission but think that had we done so this would have borne out the view that those not receiving intravenous analgesia had less satisfactory control of pain.
Despite the absence of haematoma in this study, we think that this is still a concern in view of the widespread use of thrombolytic therapy and a further reason why intramuscular analgesia should not be given.
Only four of 133 patients received aspirin at home. Possibly the number noted was falsely low owing to prior regular aspirin therapy. However, the benefits attributed to aspirin in acute myocardial infarction are in connection with the use of 150 mg or more being chewed at the time of the acute event.2,3 Therefore, until further information is available aspirin should be given acutely to all patients suspected of myocardial infarction, regardless of their regular treatment.
This study has shown that the current frequency and mode of administration of opiate analgesia at home is suboptimal. We recommend that aspirin should be given as per the international study of infarct survival regimen3 to all patients suspected of having an acute myocardial infarction. Opiate analgesia should be given more frequently and via the intravenous route.