Respiratory and Cardiovascular Emergencies

Introduction

Respiratory, cardiovascular and neurologic conditions are the most common types of medical emergencies encountered in emergency care settings in the United Kingdom (UK). It is essential that nurses working in emergency settings are able to assess and manage medical emergencies related to these body systems. This chapter introduces the knowledge and skills required to accurately and rapidly assess, and effectively manage, a variety of respiratory, cardiovascular and neurologic conditions in the emergency care setting. You will also study the most common emergency presentations of acute conditions related to the respiratory, cardiovascular and neurologic systems.  This chapter will begin your introduction into the provision of quality emergency care to patients with acute medical conditions.

Important note

This chapter assumes a basic knowledge of human anatomy and physiology. If you feel you need to revise these concepts, you are encouraged to consult a quality nursing textbook.

Respiratory emergencies

People may present to emergency care settings in the UK with a variety of respiratory conditions, with symptoms ranging from relatively mild and transient to severe and life-threatening. Respiratory compromise can result in brisk deterioration, and without rapid intervention, respiratory failure and death may result. It is essential that nurses working in emergency care settings are able to assess and manage patients with respiratory illness. 

Nurses working in emergency care settings must be familiar with their organisation's policies and procedures for respiratory assessment, and work within these. As always, the assessment of the patient with respiratory illness must begin with an assessment of airway, breathing and circulation (ABC). A more focused assessment of the respiratory system can then be undertaken; this will involve:

• A detailed assessment of the patient's respiratory system. The nurse should measure the patient's respiratory rate with the aim of identifying dyspnoea (i.e. shortness of breath). The nurse should also observe the patient for other signs of dyspnoea - including increased work of breathing (e.g. nasal flaring, retractions, accessory muscle use, tracheal tugging, grunting, difficulty speaking in compete sentences, etc.), pallor or cyanosis, and tripod positioning (e.g. leaning forward on the hands or elbows, in an attempt to open the chest). The nurse should also auscultate the patient's lungs, listening for adventitious (i.e. unexpected, additional) lung sounds.
• A rapid neurological assessment (e.g. using the Glasgow Coma Scale [GCS]). As you saw in the previous chapter of this module, tools such as the GCS assess the functioning of a patient's central nervous system, including their level of consciousness, via their response to verbal and / or painful stimuli. It is important for nurses to realise that changes to mental status in a patient with respiratory illness (e.g. confusion, disorientation, aggression, etc.) are early warning signs of deterioration.
• A rapid head-to-toe assessment. As one of the body's fundamental life-sustaining systems, complications with the respiratory system can have a variety of (sometimes subtle) systemic effects. In particular, the nurse should observe for characteristics such as 'barrel chest' (i.e. due to the hyperinflation of the lungs), and clubbing of the fingernails - both key signs of chronic hypoxia and respiratory illness.
• Additional assessments to assist with diagnosis - including chest X-rays or CT scans, a full blood count (FBC), and arterial blood gas (ABG) analysis - will also be used. 

As you saw in an earlier chapter of this module, a health history is a fundamental aspect of patient assessment - however, it is particularly important during respiratory assessment. Most importantly, nurses must ask a patient about their smoking history, as smoking is a leading cause of respiratory disease in the UK. Nurses should assess the amount of tobacco (or other substance) a patient smokes per day, and the length of time they have smoked. Nurses must also ask patients about their exposure to respiratory pathogens (e.g. influenza, tuberculosis, etc.), and respiratory hazards (e.g. asbestos, bird droppings, fumes and dust).

During assessment, a nurse may identify one or more of a variety of medical conditions related to the respiratory system. The most common conditions, and their management in the emergency care setting, are described following:

• Acute bronchiolitis - this is a severe inflammation of the bronchioles, caused most often by a virus (e.g. influenza, parainfluenza, respiratory syncytial virus, rhinovirus, adenovirus, etc.). Bronchiolitis is more common during the winter months, when viral illness is more prevalent in the UK population. Although bronchiolitis is most often diagnosed in children and older adults, it can occur in people of any age. Patients with bronchiolitis present with symptoms of a cold or virus, and a severe cough with dyspnoea, chest pain and fatigue. Bronchiolitis is managed using supportive therapy, including the administration of humidified oxygen and medications to ease the patient's coughing. As it originates from a viral infection, antibiotic administration (i.e. for bacterial infection) has no effect.
• Pneumonia - pneumonia is an acute inflammatory reaction in the lungs in response to the presence of pathogens, often bacteria. Patients with pneumonia present with fever, fatigue, a cough with haemoptysis (i.e. the coughing up of bloody secretions from below the level of the larynx), dyspnoea and pleuritic chest pain. On auscultation of the patient's chest, 'crackles' will be heard, and it may also be possible to identify areas of consolidation (i.e. areas with no lung sounds). It is important to highlight that older patients, who are at particular risk of developing pneumonia, may present with atypical symptoms - including a change in mental status, nausea / vomiting and headache. The treatment of pneumonia in the emergency care setting focuses on the urgent, aggressive administration of broad-spectrum antibiotics; antibiotics targeted at the specific cause of the pneumonia, identified using blood cultures or sputum samples, should also be prescribed, however antibiotic administration should not be delayed while the results of these additional assessments are obtained. Consider the following case study:

• Asthma - this is a chronic obstructive disease of the lungs, characterised by the hyper-reactive inflammation and narrowing of the airways. Although this is a chronic disease, patients can present with acute exacerbations. Patients experiencing an exacerbation will present with severe dyspnoea, coughing, wheezing, chest tightness and distress. Treatment centres on the administration of oxygen with inhaled β₂ agonists, which act to relax the narrowed airways and improve air entry. In rare cases, patients may develop status asthmaticus, a severe 'attack' of asthma which is resistant to treatment; resuscitation to prevent cardiac and respiratory arrest is key.
• Chronic obstructive pulmonary disease (COPD) - COPD, which includes the conditions emphysema (i.e. enlargement of the alveoli) and bronchitis (i.e. inflammation of the bronchioles), is a progressive and irreversible disease, often associated with smoking. Although this is a chronic disease, patients can develop acute complications. Patients with complications of COPD present with severe dyspnoea, the production of purulent sputum, pleuritic chest pain and distress. The management of COPD exacerbation focuses on supportive therapy.
• Spontaneous pneumothorax - as you saw in a previous chapter of this module, a pneumothorax involves an accumulation of air in the pleural space around the lung/s, and the resultant 'collapse' of the lung/s. Pneumothoraxes may develop following a traumatic insult; however, they can also be spontaneous, or develop during severe respiratory illness (e.g. pneumonia). You studied the typical emergency presentation and treatment of pneumothoraxes in a previous chapter of this module; you should revise this chapter now, if required.
• Pulmonary embolus (PE) - a PE is a condition where a substance, usually a blood clot or atherosclerotic plaque, occludes a large vessel in the lungs. Patients with PE present with a variety of non-specific symptoms, including worsening dyspnoea, tachycardia, cough, diaphoresis and anxiety. PE can be difficult to diagnosis, and a diagnosis is often made only after CT scans, ABG analysis, electrocardiography (ECG) and also perhaps ultrasonography. Treatment for PE centres on supportive therapy, including the administration of oxygen, intravenous fluids and analgesics. If the PE has been caused by a blood clot, antithrombolytic therapy may also be administered.
• Inhalational injury - these are injuries caused when a person inhales substances - including hot gasses produced by fire (e.g. asphyxiants [carbon monoxide, smoke]), water (i.e. in a near drowning), and / or a foreign body. Although uncommon in the UK, inhalational injuries may occasionally be seen by nurses working in emergency care settings. Patients with an inhalational injury will present with a variety of non-specific symptoms, including dyspnoea, coughing, gagging and choking, tachypnoea and pleuritic chest pain. Inhalational injuries are usually managed using supportive therapies; in severe cases, however, these therapies will be intensive and invasive.

There are a variety of less-serious medical conditions related to the respiratory system which may result in people presenting to emergency care settings in the UK. These conditions include influenza, acute viral rhinitis (i.e. cold), epistaxis (i.e. nosebleed), sinusitis, acute pharyngitis / laryngitis, peritonsillar abscess, among others. In most cases these are mild and self-limiting conditions, and supportive therapy - including analgesia, decongestants and, where appropriate, antibiotics - may be prescribed. It is also important to bear in mind that many respiratory conditions - including influenza, rhinitis, tuberculosis, pulmonary fungal infections, etc. - are highly contagious, and emergency nurses must take steps, such as the wearing of particulate masks, to protect themselves from illness.

Any of the conditions described above can lead to acute respiratory distress syndrome (ARDS), or the failure of the respiratory syndrome. This is a significant complication seen occasionally in the emergency care setting. There are two types of ARDS:

• Hypoxaemic respiratory failure - also referred to as oxygenation failure, which is caused by an imbalance between ventilation and perfusion in the lungs. In severe cases, this may result in shunt, where blood leaves the heart without having participated in gas exchange (e.g. no oxygen in, no carbon dioxide out).
• Hypercapnoeic respiratory failure - also referred to as ventilation failure, which is caused by an imbalance between the supply of, and demand for, oxygen in the lungs. Although this often presents as an acute condition, it may also be chronic.

The administration of high-flow oxygen via a non-rebreather mask is fundamental to the management of all the respiratory conditions described in this section. A patient with a respiratory condition must also have their blood oxygen saturation (SaO₂) continuously monitored, using a pulse oximeter. Usually, a pulse oximeter takes readings of blood oxygen concentration via a probe attached to the finger; however, it is important to remember that artificial fingernails, nail polish, cold extremities and physical damage to the fingers (current or past) may result in false pulse oximeter readings. In these situations, the probe may need to be attached to an alternative location on the body - such as the toe or earlobe. Although it is a fundamental aspect of nursing care in all settings, the psychosocial care of a patient with a respiratory condition - and particularly one which results in distressing dyspnoea, where patients may experience acute anxiety and have feelings of imminent death - is important for nurses in the emergency care setting.

Cardiovascular emergencies

As with the respiratory conditions described in the previous section of this chapter, cardiac conditions are commonly seen in emergency care settings in the UK. Unlike respiratory conditions, however, patients with cardiac conditions often present with symptoms that are mild, transient and non-specific. If these conditions are not rapidly assessed, and the cardiac illness identified and properly managed, significant disability or death can result.

Nurses working in emergency care settings must be familiar with their organisation's policies and procedures for cardiovascular assessment, and work within these. As always, the assessment of a patient with cardiac illness must begin with an assessment of airway, breathing and circulation (ABC). A more focused assessment of the cardiovascular system can then be undertaken; this will involve:

• A detailed assessment of the patient's cardiovascular system. The nurse should measure the patient's heart rate with the aim of identifying tachycardia (i.e. increased heart rate), as well as the quality of the patient's peripheral pulses and their blood pressure. The nurse should also observe the patient for other signs of cardiac dysfunction - including pallor and / or cyanosis, diaphoresis and dyspnoea - and ask the patient about feelings of dizziness, palpitations and nausea, etc. The nurse should also auscultate the patient's heart, listening for adventitious (i.e. unexpected, additional) heart sounds.
• A rapid head-to-toe assessment. As one of the body's fundamental life-sustaining systems, complications with the cardiovascular system can have systemic effects. In particular, nurses should assess the patient for sensory and motor deficits, and altered mental status with neurological symptoms (e.g. aphasia, hemiparesis, etc.). It is important for nurses working in emergency care settings to remember that, although they are an 'acute' condition, most acute coronary syndromes occur progressively over several hours, and a patient may present complaining of general and non-specific symptoms rather than those that are clearly cardiac-related.
• An assessment of the patient's chest pain, using the 'OPQRST' mnemonic introduced in an earlier chapter of this module. Pain due to cardiac dysfunction is often described as 'crushing' or 'squeezing' and it may not necessarily be felt in the chest (i.e. it may radiate to the left arm, jaw / throat, back or even the thighs / groin).

Consider the following case study:

• Additional assessments to assist with diagnosis - including chest X-rays or CT scans, blood tests to assess for cardiac biomarkers (i.e. chemicals, such as troponin, which are released into the blood after damage to the heart muscle), and perhaps an ultrasound. An electrocardiogram (ECG) to visualise the electrical activity in the heart is a standard part of the assessment for all patients presenting to emergency care settings in the UK with suspected cardiovascular conditions.

During assessment, a nurse may identify one or more of a variety of medical conditions related to the cardiovascular system. The most common conditions, and their management in the emergency care setting, are described following:

• Myocardial infarct (MI) - a MI occurs when one of the arteries in the heart becomes occluded, and the distal areas of the cardiac muscle become acutely hypoxic. An MI may be diagnosed by ECG and, depending on where changes in the electrical activity of the cardiac muscle occur, it may be classified as one of two types: (1) an ST-Segment MI (STEMI), or (2) a Non ST-Segment MI (Non-STEMI). Patients experiencing an MI present with chest or radiating pain, nausea, dyspnoea, diaphoresis, fatigue and dizziness, and they may be very anxious. There are a variety of options for the management of MI in emergency care settings, and because this is such a common and critical presenting condition these will be explored in greater detail in the example essay which accompanies this chapter.
• Angina pectoris - angina occurs when the arteries in a patient's heart become partially occluded, often due to narrowing or atherosclerotic damage. Angina may be classified into one of two types, which differ according to the timing and severity of symptoms: (1) stable, where chest pain occurs in a pattern following a predictable amount of exertion, or (2) unstable, where chest pain may occur unpredictably at any time, including without exertion. It is more likely that patients with unstable angina will present to emergency care settings with acute exacerbations.

Patients experiencing an acute exacerbation will present with many of the same symptoms as for an MI (described earlier in this section); therefore, differential diagnosis is essential. Whereas an MI will be evident on an ECG, angina pectoris will not. Medications - including those to dilate the blood vessels, thin the blood and control heart rate and blood pressure - are the primary treatments for angina.

• Dysrhythmias - 'dysrhythmia' is a term used to describe an abnormality in the normal rhythm of the heart. There are a variety of common dysrhythmias; these are classified into two categories: (1) tachycardias (heart rate >100 beats per minute - including atrial flutter, atrial / ventricular fibrillation, and long QT syndrome), and (2) bradycardias (heart rate <60 beats per minute - often caused by a conduction block). Dysrhythmias may be due to a variety of causes; however, acute coronary syndromes, such as MI and angina (discussed earlier in this section), are common causes, and a patient should be assessed for these underlying conditions. Medications are usually used to manage dysrhythmias, however in emergency situations where cardiac arrest is imminent, a defibrillator shock may also be used.
• Pericarditis - this occurs when the pericardium, the fibrous sac surrounding the heart, is inflamed, often due to infection. Pericarditis can lead to a range of significant complications, including MI and cardiac arrest. Patients with pericarditis experience a range of non-specific symptoms of infection, dyspnoea and severe chest pain, and dysrhythmias may also be evident. Pericarditis is usually managed with supportive therapy - including, in some cases, short-term sedation - and aggressive antibiotic therapy if the causative pathogen is bacterial in origin.
• Aortic aneurysm - an aneurysm is a dilated area of a vessel. Often, aneurysms occur in the large, highly-pressurised aorta which carries oxygenated blood from the lungs / heart to the rest of the body. Aneurysms may occur anywhere along the length of the aorta, and if they rupture (or dissect) massive haemorrhage and rapid deterioration may result. In managing a patient with a ruptured aortic aneurysm, nurses should focus on using the resuscitation techniques described in a previous chapter of this module, in preparation for emergency surgery to (if possible) repair the rupture. It is important to note that patients who experience a major rupture of an abdominal aortic aneurysm outside of hospital generally have a poor prognosis.
• Hypertensive crisis - a hypertensive crisis occurs when a patient's blood pressure is so high that there is a risk of acute end-organ damage. It may occur for a variety of reasons, but is often due to dysfunction in the endocrine and / or renal systems. Medications are the primary treatment for hypertensive crises; the close monitoring of patients is also important so that complications - including, for example, renal or liver failure - can be rapidly identified and managed.

Neurological emergencies

In addition to traumatic injury, neurologic emergencies may also originate from physiological and medical causes. These can result in rapid disability and death; therefore, it is essential for nurses working in emergency care settings to be able to assess and manage these conditions.

During assessment, a nurse may identify one or more of a variety of medical conditions related to the neurologic system. The most common conditions, and their management in the emergency care setting, are described following:

• Headache, including migraine - headaches are one of the most common neurological conditions seen in emergency care settings in the UK. People typically present to emergency care settings with migraines, severe headaches. Migraines may be classified as: (1) vascular, which are caused by acute cerebral vasodilation, or (2) muscular, which are due to skeletal muscle contractions in the head or neck. There are a variety of 'triggers' for migraines - including physiological conditions (e.g. dehydration, uraemia, hepatic disorders, hypoglycaemia, allergic reactions, etc.) or environmental conditions (e.g. stressful situations, physical exertion, heat, bright lights, certain foods, etc.) - however they may also occur spontaneously. The management of migraines in the emergency care setting centres on the use of analgesics - either non-steroidal anti-inflammatory medications or opioids. It is important to highlight that headaches are a common symptom of other acute neurological illnesses, including haemorrhagic stroke and brain tumours, and a patient should be investigated for these underlying causes. 
• Seizures - a seizure is caused by abnormal, excessive electrical activity in the brain. Seizures may have a variety of causes, including physiological disorders such as epilepsy, hypoglycaemia, acute alcohol withdrawal and conditions of the central nervous system (e.g. meningitis, tumours, stroke, etc.). Most seizures are self-limiting, and although distressing for the patient they do not usually require emergency intervention. Treatment focuses on ensuring airway patency, use of oxygen, administering anti-epileptic medication (as prescribed), and managing the underlying cause (if possible). If the cause of the seizure is undetermined, further investigations must take place when the patient is stable.
• Stroke - the term 'stroke' is used to describe the loss of neurological functioning resulting from an acute disruption of blood flow to, and hypoxia in, a section of the brain. Strokes may be classified as: (1) ischaemic, when a vessel in the brain becomes occluded (often by a blood clot or atherosclerotic plaque), or (2) haemorrhagic, when a vessel in the brain ruptures and bleeds. In both types of strokes, patients will present with unilateral weakness or paralysis (e.g. a facial droop, loss of motor coordination in the arm / leg, etc.), difficulty with speech / gait / coordination, a severe headache, altered vision, sensory impairments and / or a changed mental status. The treatment of stroke depends on its cause; for ischaemic strokes, tissue plasminogen activator (tPA) is administered in an attempt to dissolve the clot and surgical stenting may also be required, while haemorrgagic strokes are often treated with a surgical implant to control the bleed.

Differential diagnosis between ischaemic and haemorrhagic strokes is essential prior to commencing treatment; consider the following case study:

Despite the importance of waiting for a differential diagnosis, it is important to highlight that strokes must be treated rapidly if their long-term complications are to be mitigated. If a stroke patient presents late, supportive therapy only may be used.

• Meningitis - this is the inflammation of the meninges (i.e. the tissues surrounding the brain and spinal cord), caused most often by a bacteria, viral or fungal pathogen. Although meningitis is most frequently diagnosed in children and older adults, it can occur in people of any age. Patients with meningitis usually present with the signs of acute infection - including fever, headache, photophobia, lethargy and nausea / vomiting - and they may also have seizures. Patients will sometimes, but not always, have a petechial rash which is considered 'characteristic' of meningitis. Meningitis is diagnosed conclusively using a lumbar puncture (i.e. a collection of the cerebrospinal fluid, for microbial culture); this is essential in identifying the type of pathogen causing the infection. Aggressive antibiotic therapy (for bacterial infection), as well as the administration of antipyretic and anticonvulsant medication, is usually recommended. Regular neurological assessment is essential in identifying patient deterioration. It is important to highlight that some types of bacterial meningitis in particular are contagious, and extreme care should be taken by nurses.

Conclusion

Respiratory, cardiovascular and neurologic conditions are the most common types of medical emergencies encountered in emergency care settings in the UK; it is therefore essential that nurses working in these settings are able to assess and manage medical emergencies related to these body systems. This chapter has introduced the knowledge and skills required to accurately and rapidly assess, and effectively manage, a variety of respiratory, cardiovascular and neurologic conditions in the emergency care setting. It has also described the most common emergency presentations of conditions related to the respiratory, cardiovascular and neurologic systems.  This chapter has begun your introduction into the provision of quality emergency care to patients with acute medical conditions; in the following chapter of this module, you will extend on your skills and knowledge. 

Reference list

Arbour, R.B. (2007). Respiratory Failure and Acute Respiratory Distress Syndrome. In S. Lewis, M.M. Heitkemper, S.R. Dirksen, P.G. O'Brien & L. Bucher (Eds.). Medical-Surgical Nursing: Assessment and Management of Clinical Problems - International Edition. (7th edn.): St Louis: Mosby-Elsevier.

Howard, P.K. & Steinmann, R.A. (Eds.). (2010). Sheehy's Emergency Nursing: Principles and Practice. Naperville, IL: Mosby Elsevier.

Jones, G., Endacott, R. & Crouch, R. (2007). Emergency Nursing Care: Principles and Practice. Cambridge: Cambridge University Press.

National Institute of Health and Clinical Excellence. (2008). Stroke and Transient Ischaemic Attack in Over-16s: Diagnosis and Initial Management. Retrieved from: https://www.nice.org.uk/guidance/cg68/resources/stroke-and-transient-ischaemic-attack-in-over-16s-diagnosis-and-initial-management-975574675141

National Institute of Health and Clinical Excellence. (2010). Chronic Obstructive Pulmonary Disease in Over 16s: Diagnosis and Management. Retrieved from: https://www.nice.org.uk/guidance/cg101/resources/chronic-obstructive-pulmonary-disease-in-over-16s-diagnosis-and-management-35109323931589

National Institute of Health and Clinical Excellence. (2010). Chest Pain of Recent Onset: Assessment and Diagnosis. Retrieved from: https://www.nice.org.uk/guidance/cg95

National Institute of Health and Clinical Excellence. (2012). Headaches in Over-12s: Diagnosis and Management. Retrieved from: https://www.nice.org.uk/guidance/cg150/resources/headaches-in-over-12s-diagnosis-and-management-35109624582853

National Institute of Health and Clinical Excellence. (2013). Myocardial Infarction with ST-Segment Elevation: Acute Management: Retrieved from: https://www.nice.org.uk/guidance/cg167?unlid=688318161201611953530

National Institute of Health and Clinical Excellence. (2014). Pneumonia in Adults: Diagnosis and Management. Retrieved from: https://www.nice.org.uk/guidance/cg191/resources/pneumonia-in-adults-diagnosis-and-management-35109868127173

National Institute of Health and Clinical Excellence. (2014). Acute Heart Failure: Diagnosis and Management. Retrieved from: https://www.nice.org.uk/guidance/cg187

National Institute of Health and Clinical Excellence. (2014). Atrial Fibrillation: Management. Retrieved from: https://www.nice.org.uk/guidance/cg180

National Institute of Health and Clinical Excellence. (2015). Bronchiolitis in Children: Diagnosis and Management. Retrieved from: https://www.nice.org.uk/guidance/ng9/resources/bronchiolitis-in-children-diagnosis-and-management-51048523717

National Institute of Health and Clinical Excellence. (2016). Epilepsies: Diagnosis and Management. Retrieved from: https://www.nice.org.uk/guidance/cg137/resources/epilepsies-diagnosis-and-management-35109515407813

Example essay

A patient is admitted to a Type 1 A&E Department complaining of acute-onset, crushing chest pain. Following troponin assays and an electrocardiogram (ECG), the patient is diagnosed with an ST-segment elevation myocardial infarction (STEMI). With reference to the relevant National Institute for Health and Clinical Excellence (NICE) guideline and the current literature, identify and critically discuss the key interventions to be used in the emergency care of this patient.

A myocardial infarct occurs when one of the arteries in the heart becomes occluded, often by the formation of a thrombus, resulting in distal ischaemia of the cardiac tissue (Martinez & Bucher, 2007). An ST-segment elevation myocardial infarction (STEMI) is diagnosed when ischaemia results in changes to the ST-segment of the cardiac cycle, which may be visualized using an electrocardiogram (ECG) (Martinez & Bucher, 2007). Myocardial infarction generally, and STEMI specifically, are a significant problem in the United Kingdom (UK); indeed, statistics from the British Heart Foundation (2015) suggest that, in 2014, 88300 men and 52600 women presented to emergency care settings in the UK with a myocardial infarct. Despite a decreasing incidence, STEMI in particular remains "a significant contributor to morbidity and mortality" in the UK (Choudhury et al., 2016: p. 277).

It is essential that nurses working in emergency care settings in the UK are able to manage a patient who presents with a myocardial infarct by rapidly administering, or assisting with the administration of, appropriate interventions. Although myocardial infarction generally, and STEMI specifically, place a patient at significant risk of disability and death, rapid and appropriate intervention can significantly improve outcomes (National Institute for Health and Clinical Excellence, 2013). With reference to the relevant National Institute for Health and Clinical Excellence (NICE) guideline, Myocardial Infarction with ST-Segment Elevation: Acute Management, and the current literature, this paper identifies and critically discusses the key interventions to be used in the emergency care of a patient who is experiencing a STEMI, such as the one in the case study on which this discussion is based.

The Myocardial Infarction with ST-Segment Elevation: Acute Management guideline recommends that patients presenting to emergency care settings with STEMI be immediately assessed for their eligibility for coronary reperfusion therapy (NICE, 2013). Coronary reperfusion therapy is intended to restore the flow of blood to the ischaemic area of cardiac tissue, either by bypassing or removing the occlusion in the vessel (Howard & Steinmann, 2010). In emergency care settings in the UK, coronary perfusion therapy generally takes one of two forms: (1) percutaneous coronary intervention (PCI - designed to bypass the occlusion), or (2) fibrinolysis (designed to remove the occlusion) (NICE, 2013). The following sections of this paper will critically analyse each of these coronary perfusion therapies.

PCI is "the preferred coronary reperfusion strategy for people with acute STEMI" (NICE, 2013: p. 10). Although the techniques involved in PCI continue to develop rapidly, fundamentally it involves the use of an angiography-guided catheter to insert a stent into the occluded vessel; the stent acts to open the vessel and permits the revascularisation of the distal ischaemic tissue (Banning et al., 2015). Whilst it is primarily a medical intervention, nurses play an important role in PCI in terms of the concurrent administration of medications and the prevention of complications (Zughaft & Harnek, 2014) - which, as described in a later section of this paper, may be significant. UK research suggests that if PCI is administered rapidly in emergency care settings, outcomes - particularly in terms of morbidity and mortality - for patients experiencing a myocardial infarction are generally good (Garg et al., 2015). However, it is important to highlight that a patient is only eligible for PCI if: (1) they present to an emergency care setting within 12 hours of the onset of their infarct symptoms, and (2) PCI can be delivered within the first 120 minutes of the patient's presentation (NICE, 2013).

Although highly effective, it is important for nurses working in emergency care settings to bear in mind that PCI is not without risks. Indeed, reperfusion injury, where the rapid return of blood supply to the cardiac tissue post-PCI results in tissue damage or arterial dissection, is a known complication of PCI, even when protective strategies are used (Binder et al., 2015). In particular, arterial rupture as a result of reperfusion may result in haemorrhage, cardiac tamponade, ischaemia, re-infarction and rapid death (Martinez & Bucher, 2007). Uncontrolled reperfusion may also result in cardiogenic shock and cardiac arrest (Zughaft & Harnek, 2014). The spontaneous re-stenosis of a vessel in the post-PCI period has also been observed (Martinez & Bucher, 2007). Furthermore, the inappropriate use of PCI - that is, its use in patients who do not meet the eligibility criteria described earlier in this paper - remains a problem (Desari et al., 2015), though the physiological effects of the inappropriate use of PCI in a patient, if any, are unclear. 

If a patient experiencing a STEMI is ineligible for PCI based on the criteria described earlier in this paper, the Myocardial Infarction with ST-Segment Elevation: Acute Management guideline recommends that they be offered fibrinolysis (NICE, 2013). The two fibrinolytic therapies most commonly offered in emergency care settings in the UK are Ticagrelor and Bivalirudin, in combination with aspirin, clopidogrel and / or unfractionated or low molecular weight heparin (NICE, 2013). These medications, administered intravenously for maximum effect, act to lyse the thrombus in the cardiac vessel, allowing the revascularisation of the distal ischaemic tissue (Martinez & Bucher, 2007). It is important to note that although fibrinolytic therapy rapidly administered in emergency care settings results in improved outcomes for patients experiencing a myocardial infarct, the outcomes may not be as good as those for PCI (Rahman et al., 2016).

As with PCI, fibrinolytic therapy is associated with a number of significant complications. Fibrinolytic medications may not only lyse the clot occluding the cardiac vessel, but also other clots - including those at healing surgical sites (Martinez & Bucher, 2007), potentially resulting in major wound breakdown. Bleeding - particularly covert internal bleeding, including intracranial bleeding, resulting in haemorrhagic stroke - is a major complication associated with fibrinolytic therapy, and is a strong predictor for adverse prognosis in a patient experiencing a myocardial infarct (Oldgren et al., 2010; Bundhun et al., 2016). Furthermore, if the clot in the cardiac vessel is particularly large and unstable, it may rapidly reform following fibrinolysis, resulting in reoccurrence of STEMI; in this case, emergency 'rescue' PCI is usually administered (Ko et al., 2011). It is also relatively likely that fibrinolytic therapy will fail in patients with uncontrolled hyperglycaemia, a complication of diabetes - which is a common comorbidity in patients who experience a myocardial infarct (Kocas et al., 2015) - although the exact mechanisms of this are poorly understood.

As highlighted throughout this paper, the Myocardial Infarction with ST-Segment Elevation: Acute Management guideline recommends PCI and fibrinolysis as frontline interventions for the management of STEMI (NICE, 2013). However, there are a number of other interventions which may be administered in the management of a patient with STEMI, and these are a particularly important aspect of the nurse's role in managing patients presenting to emergency care settings with STEMI. Whilst waiting for PCI or fibrinolysis, a patient may be given sublingual glyceryl trinitrate (GTN); this medication has the effect of rapidly dilating the cardiac vessels, potentially providing short-term relief of tissue ischaemia distal to the blockage (Martinez & Bucher, 2007). Intravenous morphine sulfate, a fast-acting narcotic analgesic, may also be administered if a patient's severe chest pain is not relieved by GTN (Martinez & Bucher, 2007). High-flow oxygen, delivered via nasal prongs or a breathing mask, is also an important consideration for patients experiencing a myocardial infarct (Martinez & Bucher, 2007), as it may help to prevent progressive hypoxia which results from cardiac dysfunction. Β-adrenergic blockers may also be administered to reduce the patient's heart rate, thereby decreasing the oxygen demand of the cardiac tissue (Martinez & Bucher, 2007). Because these interventions are not described in the NICE (2013) Myocardial Infarction with ST-Segment Elevation: Acute Management guideline, nurses should be guided by their local hospital policies and procedures in their use.

It is important to highlight that, occasionally, the management of STEMI using both PCI and fibrinolysis will fail. In this situation, the Myocardial Infarction with ST-Segment Elevation: Acute Management guideline recommends "immediate specialist cardiological advice" should be sought to determine the ongoing management of the patient (NICE, 2013: 12). Often, a coronary artery bypass graft (CABG) will be required; this is a major surgical procedure, involving cardiopulmonary bypass, where vessels - often harvested form the patient's legs - are connected to divert blood around the occlusion to revascularise the distal tissue (Martinez & Bucher, 2007). Other surgical procedures to revascularise the cardiac tissue, including mechanical thrombus extraction, may also be considered; however, due to their invasiveness and the significant associated risks, these are not recommended as frontline interventions, even for patients with major STEMI (NICE, 2013).

This paper has identified and critically discussed the key interventions to be used in the emergency care of a patient who is experiencing a STEMI, with reference to the relevant National Institute for Health and Clinical Excellence (NICE) guideline, Myocardial Infarction with ST-Segment Elevation: Acute Management, and the current literature. In particular, this paper has discussed coronary reperfusion therapy - including PCI and fibrinolysis - as frontline interventions for the management of STEMI. This paper has demonstrated that the rapid provision of these interventions by nurses, as part of multidisciplinary teams, can significantly improve outcomes for patients, such as the one in the case study on which this discussion is based, who present to emergency care settings with myocardial infarct or STEMI.

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