Rachel Matthews, MSc, RN.
Ward Sister, Princess Alexandra Ward, Royal Brompton Hospital, London
Surgery for coronary heart disease (CHD) is now a common procedure but is not performed sufficiently quickly or frequently (Department of Health, 2000). This paper is intended to give an overview of coronary artery bypass grafting (CABG), including the implications of the National Service Framework for Coronary Heart Disease (NSF) (DoH, 2000). It will discuss why surgery is chosen, the purpose of surgical revascularisation, the surgical procedure and the principles of pre- and postoperative nursing care.
Reducing premature deaths
Revascularisation by surgical and non-surgical techniques is one of 12 standards identified in the NSF (DoH, 2000). This ambitious document describes a 10-year plan to reduce premature deaths from CHD and to improve the services currently available to those suffering from this condition. The NSF acknowledges that there has been chronic under-investment in this procedure in comparison to other European countries and patients in England experience long waiting times for both diagnosis and treatment. Key stages in the implementation of the NSF will see progress towards a goal where patients can expect to have their operation within three months of the decision to operate.
Implementation of the NSF is likely to increase public expectation of cardiac services and will lead to the review of the current infrastructure and manpower capability in this area.
The purpose of surgical revascularisation is to improve the blood supply to the myocardium, relieve symptoms of angina and to prolong the life expectancy of the patient diagnosed with CHD (Haworth and Wahrman, 2000). Importantly, surgery does not cure CHD. It is essentially palliative.
Patients for whom CABG is considered a suitable treatment option are likely to describe a variety of signs and symptoms that led to such a decision being made. Experiences tend to be common but some patients may have relatively few warning signs that indicate CHD (Ormerod, 1999). Patients usually, but not always, fall into three main groups: those with stable angina pectoris, those with unstable angina pectoris and those who experience an acute myocardial infarction (MI) (Abrahamov et al, 2000).
Surgery is not always the first treatment option and alternatives may be used in isolation or in combination before the decision to operate is taken. These include modification of risk factors, treatment with medication and percutaneous transluminal coronary angioplasty (PTCA) with or without stenting. Surgery will be considered only when a full history and key investigations have been obtained. Coronary angiography is likely to provide the evidence that surgical intervention is necessary. According to Abrahamov et al (2000): ‘Left main coronary artery disease and three-vessel coronary artery disease with moderately impaired left ventricular function are the clearest indications for CABG.’
Surgery for coronary artery disease is not without risk. The overall operative morbidity is around 2-3 %, the main complications being cerebrovascular accident (2%), MI (3%) and mediastinitis (1%). Increased mortality is associated with age (over 70), left ventricular dysfunction, female gender, previous CABG surgery, diabetes, peripheral vascular disease and chronic renal failure. (Abrahamov et al, 2000).
PTCA may be suitable for those patients with single, double or triple vessel disease, provided they do not have lesions in the left main stem, the proximal region of the left anterior descending coronary artery (LAD) or at a bifurcation of the coronary arteries. Those with diffuse disease throughout the coronary arteries, which is more frequent in patients with diabetes, are also unlikely to be suitable for PTCA. Randomised studies investigating both PTCA and CABG have maintained that surgery should be offered to those with triple-vessel disease, left main stem disease and impaired left ventricular function. These include the Coronary Artery Surgery Study (CASS), the Veterans Administration Study and the European Cardiac Society Study (ECSS), (Abrahamov et al, 2000; Pillai and Wright, 1999).
Preparation for surgery
Preparation for surgery should take into account individual circumstances. Although experiences may be similar, it is important to acknowledge that some patients will have been living with angina for a number of years and others may have recently suffered an MI or severe unstable angina.
The heart is an emotive organ and the prospect of major surgery will increase anxiety for the patient, family and friends. It is vital that the patient and family understand the purpose of surgery, the risks and benefits of the operation and the impact surgery may have in the immediate recovery period and in the long term.
A full clinical assessment will be conducted before surgery. This will secure the diagnosis and give some indication of individual prognosis. Pre-operative preparation will include a range of investigations depending on the signs and symptoms reported by the patient.
Pre-operative information and support can be given to patients and their families before coming into hospital and on the day of admission. Several studies have investigated the timing, format and content of pre-operative patient education but there is little consensus on optimal time frames or desired outcomes (Cupples, 1991; Devine, 1992; McHugh et al, 2000; Nelson, 1996; Shuldham, 2001).
Despite this lack of consensus, pre-admission clinics are valuable as they allow investigations to be performed and medical and nursing assessments can be completed. Importantly, people with physical, psychological and social problems may be identified early, such as those with previously undiagnosed diabetes and those with special needs - for example, people who have a visual impairment or those who lack social support on discharge. The multidisciplinary team, including hospital and community services, can be informed at an early stage and can plan care more effectively. Cancellations can also be prevented, with more efficient use of hospital beds (Emery and Pearson, 1998).
Patients for elective surgery are usually admitted the day before their operation. They will have been advised to discontinue aspirin or warfarin therapy up to seven days before admission to reduce the risk of peri-operative bleeding. Those who are smokers will have been advised to stop or cut down. Patients will be oriented to the ward environment and introduced to the nursing, surgical and anaesthetic teams.
Preparation and education at this stage will focus on the anticipation of events during the hospital stay. This will include pre-operative fasting, shaving, the journey to the operating theatre, the length of surgery and hospitalisation, time spent in intensive care or recovery unit, the presence of invasive monitoring and ventilation, pain management, location of surgical wounds, early mobilisation and common experiences after surgery, for example loss of appetite. Patients and their families should be encouraged to ask questions. They should be prepared for a relatively short hospital stay and be helped to anticipate their role in the period of convalescence, which can last two to three months.
The majority of CABG operations are performed by making a midline incision vertically down the chest (sternotomy) to expose the heart. The vessels (conduits) that are to be used as grafts are harvested from elsewhere in the body. The most commonly used conduits are the internal thoracic arteries, usually the left internal mammary artery (LIMA), saphenous vein and radial artery. Less commonly used are the ulnar artery, gastroepiploic artery and the inferior epigastric artery. The choice of donor sites will depend on the number of grafts to be performed, and whether saphenous veins are available and suitable. There may be visible varicosities, or they may have been stripped or used in previous surgery. Where possible arterial grafts, specifically the internal mammary artery (IMA), are used because they have a better patency rate. Arterial grafts may last longer than 10 years and numerous studies have compared physiological changes in arterial and venous grafts (Treasure and Batrick, 1999). However, the IMA requires skilled handling at the time of surgery and therefore the use of the saphenous vein is still recommended (Allen and Bonser, 1999).
Once cardiopulmonary bypass (CPB) has been established, grafting can proceed. In the case of a LIMA graft, the vessel has to be carefully dissected and mobilised from the chest wall before it can be sutured at its distal end below the stenosis on the diseased coronary artery. The IMA is usually used to revascularise the left anterior descending artery. Vein grafts will be sutured proximally to the ascending aorta and distally below the stenosis on the native coronary arteries. The duration of surgery will be determined in part by the number and type of grafts. Surgery can last between two and five hours.
While single and multiple grafting via a midline sternotomy with CPB accounts for the majority of CABG operations, there are alternative approaches that can be used for specific reasons and in carefully chosen cases. Revascularisation can be performed without CPB. This may be called ‘beating-heart’ or ‘off-pump’ surgery. There has been renewed interest in this technique as a way of avoiding the physiological effects of CPB, which can give rise to complications, particularly in high-risk patients. Elderly patients and those with renal, respiratory or cerebrovascular disease may benefit from this approach (Tsui and Dunning, 1999).
There will be particular challenges at the time of surgery, not least of which is performing anastamoses on a beating heart and special stabilisers are used to reduce movement (Hart et al, 1999). A reduced dose of heparin is used during surgery and postoperatively subcutaneous dalteparin will be administered as thromboembolic prophylaxis. Postoperatively, the principles of nursing care are the same. Alternative approaches also include minimal access incisions, for example via a mini-sternotomy or with the use of a video-assisted thorascope, minimal-access vein harvesting and alternative methods for CPB for example femoro-femoral cannulation (Tsui and Dunning, 1999).
It is impossible to discuss cardiac surgery without briefly describing cardiopulmonary bypass (CPB). Very simply, CPB, or the heart-lung machine, allows temporary disruption of the circulatory system so the surgeon can operate on a still heart. The heart is stopped after the aorta is cross-clamped and cardioplegia solution containing potassium is infused into the heart (Pepper, 1999; D’Ancona, 2000). The machine maintains circulatory function, with oxygen demand during surgery reduced by lowering body temperature.
CPB is established by cannulating the venae cavae (via the right atrium) and the ascending thoracic aorta. Blood is diverted from the right side of the heart into the machine, where it is filtered to prevent clotting, oxygenated, diluted and warmed before it is returned to the patient via the ascending thoracic aorta. The patient will be heparinised while on CPB, the effects of which will be reversed when surgery is complete (Haworth and Wahrman, 2000; Young and Dai, 2000).
CPB allows surgery to be performed but it can cause major physiological disruption not only in the cardiovascular system but also in the renal, central nervous, respiratory and gastrointestinal systems (Dunning, 1999). Postoperative nursing care will need to be alert to such disruption.
Immediate postoperative care
When surgery is complete, the patient will be transferred, sedated and ventilated, to the intensive care or recovery unit. Most patients will be kept sedated generally between 6 and 12 hours after their operation while their condition is stabilised. Some centres will ‘fast track’ certain patients who are likely to have an uncomplicated recovery. They will be extubated earlier, have invasive monitoring discontinued sooner and are likely to make a more rapid recovery (Chong, 1992; Howard, 1995). Principles of care in the immediate postoperative period will focus on identifying and correcting common abnormalities. Ensuring effective pain management and providing psychological support for the patient and family are also vital components in cardiac surgical nursing.
Postoperative care in the ward
The patient usually returns to the ward, via a high-dependency unit, the day after surgery. A detailed account of postoperative nursing management is described by Emery and Pearson (1998). Nursing care focuses on haemodynamic monitoring, respiratory support, fluid management, effective pain control, chest clearance, early mobilisation, wound care, psychological support and education in preparation for discharge and convalescence.
Most patients can expect to be sitting out of bed in a chair the day after their operation. Invasive monitoring and urinary catheter will be removed on day 2 and they will usually be walking by this stage. Patients can shower or bathe by day 3 and most will be eating and drinking normally in the first few days. Recovery is often rapid and the nurse plays an important role in helping the patient to regain physical independence and confidence. Care will be individualised and some patients, particularly those who are older or have pre-existing conditions such as diabetes, may need additional support in preparation for discharge.
Discharge and convalescence
Most patients will be ready for discharge one week after surgery. Education is vital for patient and family to help them cope at home during the recovery period. Written and visual materials should reinforce verbal instruction. They will need to understand what activities they can perform, what should be avoided, what medication they are taking, how to care for their wounds and how to distinguish between normal recovery experiences and those where medical advice should be sought. Patients should understand that they might take about two to three months to recover. They should also be encouraged to attend cardiac rehabilitation programmes (DoH, 2000).
Surgery for CHD is now a common procedure. However, too many people are waiting for this operation, which not only increases life expectancy but may dramatically improve quality of life for those affected by this condition. Surgery should always be seen within the context of risk-factor management. Cardiac surgical nursing combines technical skill with a high degree of psychological and educational support.
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