Managing acute coronary syndromes in the prehospital and emergency setting: New guidelines from the Australian Resuscitation Council and New Zealand Resuscitation Council
Darren L Walters, MBBS M Phil (UQ) Grad. Cert Mang. (Health) FRACP FCSANZ FSCAI, Associate Professor, Director of Cardiology; Carol Cunningham, BNurs, Project Officer.
The Australian Resuscitation Council (ARC) and New Zealand Resuscitation Council (NZRC) have for the first time developed guidelines for the management of acute coronary syndromes (ACS) in the prehospital and emergency setting. These guidelines result from the International Liaison Committee on Resuscitation (ILCOR) process and the development of the International Consensus on Cardiopulmonary Resuscitation and Emergency Cardiovascular Care Science with Treatment Recommendations (COSTR) document for 2010.1
The current COSTR process devoted a dedicated Task Force to address 25 acute topics related to the initial management of ACS drawing on expert reviewers from Africa, Asia, Australia, Europe, North America and South America. The 2010 COSTR has produced an expanded review of the available evidence in the area of the out-of-hospital and emergency care of ACS1. A complete systematic review of the literature is contained in the COSTR document (http://circ.ahajournals.org/cgi/content/full/122/16_suppl_2/S422).
The diagnosis and management of patients with ACS in the prehospital and emergency setting has been an area of increased research activity over the last 10 years. It is an area that has been, until recent years, overlooked in ACS guidelines that have tended to focus on immediate and definitive therapeutic interventions once a clear diagnosis has been established.2,3
Guidelines for the Management of Acute Coronary Syndromes 2006 and 2007 Addendum published by the Cardiac Society of Australia and New Zealand and the National Heart Foundation of Australia provide comprehensive guidelines for the diagnosis, treatment and long-term management of ACS.4,5 The new ARC guidelines focus on managing ACS in the prehospital and emergency setting and have been developed to complement these Cardiac Society of Australia and New Zealand and National Heart Foundation of Australia guidelines (http://www.resus.org.au/policy/guidelines/index.asp).
The ARC and NZRC guidelines on ACS encompass three broad areas: the initial presentation with ACS; the initial medical therapy of ACS and recommendations on reperfusion strategies for AMI. An overview of the new information is summarized below:
Initial presentation with ACS
There is continued recognition that in isolation the clinical history, clinical examination, biomarkers, ECG criteria and risk scores are unreliable for the accurate identification of patients who might be safely discharged early in the emergency setting.6–11 Hence, systematic strategies with a low rate of error are required to effectively evaluate patients presenting with possible ACS.
It is also recognized that there are patient-related factors that impede access to timely medical care. These factors include older age, belonging to racial and ethnic minorities, female gender, lower social status and social isolation.10,12–17 It is particularly relevant to recognize these issues when providing care to the Australian indigenous, Maori and Pacific Islander population. These groups have a high incidence of ischaemic heart disease and present at a younger age with more advanced disease.18
Chest Pain Observations Units have an important role in identifying patients who require admission for further testing and treatment.19–23 The use of a protocol that includes serial evaluation of symptoms, physical findings, ECGs and biomarker testing coupled with further provocative testing or imaging procedures is recommended.
When it is possible, earlier diagnosis and management is highly desirable in ACS where the risk is time-dependant. The use of prehospital ECG for the diagnosis of ST elevation myocardial infarction (STEMI) is recommended and can be interpreted by a variety of methods including by trained, non-medical staff in the field, remote transmission or with computer assistance.24
Initial medical therapy
The timely introduction of medical interventions is increasingly recognized as critical to improving outcomes. There is increasing capacity for emergency care providers to make diagnoses and institute treatment in the field, although a cautionary note applies to the use of a response to nitrate therapy as a reliable diagnostic manoeuvre for ACS.25
Increasingly, it is being recognized that supplementary oxygen should only be initiated for patients who are breathlessness, hypoxaemic or have signs of heart failure or shock. The use of oxygen saturation monitoring by non-invasive techniques such as pulse oximetry might be useful in guiding oxygen therapy, as hyperoxaemia can be harmful in uncomplicated myocardial infarction.26,27
Aspirin is beneficial in ACS and widely available.28 Aspirin may be given by dispatchers or bystanders provided a true allergy or a bleeding disorder can be excluded.29,30 A number of newer anti-platelet agents such as clopidogrel and prasugrel also have an important role in the early management of ACS.31,32 NSAIDs other than aspirin should not be administered, as they might be harmful in patients with suspected ACS.
Acute myocardial infarction with ST elevation or new left bundle branch block occurs typically as a result of coronary artery occlusion.1,5 In this situation reperfusion of the myocardium at the earliest possible time is the principal strategy for improving patient outcome.33,34 Clinical reperfusion networks that include emergency medical services and hospitals with an agreed approach to STEMI management are beneficial in achieving best outcomes for these patients with ACS.35,36
Primary percutaneous coronary intervention (PPCI) is the preferred reperfusion strategy for STEMI when it is performed in a timely manner by an experienced team.36,37 Fibrinolysis continues to be an important treatment modality for many patients when PPCI is not available.38,39 Acceptable first medical contact to PPCI delay varies depending on the infarct territory, age of the patient and duration of symptoms.40,41
‘Rescue’ PCI should be performed if fibrinolysis fails.42–44 Patients may be directed to PPCI-capable facilities in the prehospital setting bypassing closer Emergency Departments if PPCI can be delivered in a timely manner.45 Patients with successful fibrinolysis, but not in a PCI-capable facility, should be transferred for angiography and possible PCI ideally at 6–24 h after fibrinolysis.46 However, immediate routine PCI after fibrinolysis or combination of glycoprotein IIb/IIa and fibrinolysis (‘facilitated’) are not recommended.47
An important situation to recognize is when a patient with an out-of-hospital cardiac arrest develops return of spontaneous circulation (ROSC). The most common underlying mechanism of arrest is an ACS.48 In this patient group, there might be absence of ECG findings such as ST elevation. Similarly, there might be no pre-arrest history of chest pain.48,49 Immediate angiography and PCI is a reasonable approach in the patient with ROSC, and might be a part of a standardized protocol for the post-arrest care of these patients.1,41,50 In many leading centres, a systematic approach with coronary angiography ± PCI is adopted for a patient with out-of-hospital cardiac arrest and ROSC, unless a non-ischaemic cause of the arrest is clearly indentified.51,52
Management of the patient with ACS should begin at the point of first medical contact (doctor, nurse, paramedic or trained health-care worker) in the prehospital and emergency care setting. A number of strategies are recommended to improve patient outcomes. The ARC and NZRC have developed practical guidelines designed to assist with the initial diagnosis and management of this patient group.