Coronary Artery Bypass Grafting
Coronary Artery Bypass Grafting
"Surgery and the Nurses Role"
2. CAD, Angina, MI The disease process and diagnosis
3. Pre-operative therapy and medications
4. Nurses pre-operative role: Assessment, Diagnostic studies, Medications, Education
5. Operation: Coronary Artery Bypass Grafting
6. Post-operative management
CABG: The nurses role and the surgical procedure
The nurse plays a major role in the success of a cardiac surgery patient. They evaluate the patient pre-operatively, post-operatively, during surgery, and in cardiac rehab afterwards. This paper discusses the different diagnosis and treatments for patients undergoing (CABG) Coronary Artery Bypass Grafting.
Underlying causes that make a need for CABG surgery
The major cause of CAD (coronary artery disease) is atherosclerosis. This is a pathologic process that causes thickening of artery walls. The thickening usually starts in individuals after age 20. These fibrous plaques or lesions usually produce localized narrowing in the proximal portions of the major coronary arteries. The blood supply to the myocardium can be impeded by several mechanisms: the lesion creates a fixed obstruction so that blood flow through the artery cannot increase in response to demands, the vessel lumen becomes completely occluded, or portions of clot or plaque embolize. The growth of obstructive lesions in the coronary arteries cause other blood vessels to provide alternative routes for blood flow to the myocardium. If the blood vessel becomes completely occluded, myocardial infarction is likely to occur. There are three major risk factors in CAD: hypertension, hypercholesterolemia, and cigarette smoking. Elimination or control of these factors offers hope of preventing disease and slowing its progression. Higher cholesterol levels, usually above 240 mg/dL increases risk for CAD. The risk factors for CAD that cannot be modified include: heredity, older age, and male sex. The individuals who are 30% over ideal body weight and who smoke are 10 times are likely to have cardiovascular events in their lives that non-obese smokers. The diagnosis of CAD is usually never seen until a MI or angina occurs. This preventive therapy is so important for individuals in the risk groups and it is usually determined by exercise stress testing, cardiac catherization, and sometimes radionuclide imaging techniques. A stress test is a noninvasive screening method. The procedure exercises the patient in a controlled setting while monitoring EKG, blood pressure, and heart rate. Cardiac catherization is the definitive diagnostic study for CAD. They use angiography, which a dye is injected into the right and left coronary arteries. The coronary anatomy is outlined and areas of narrowing are identified. A contrast injection of the left ventricle is performed to demonstrate the contractile status of the left ventricle and to obtain an estimation of the left ventricular ejection fraction. These are useful in diagnostic evaluation of selected patients with CAD.
The recurring symptom of CAD is angina and is typically precipitated by exercise. Most angina is caused by exercise, stressful situations, overeating, or exposure to cold. The easiest way to remember these factors are the 4 E’s: exercise, emotion, eating, and exposure. Angina usually lasts several minutes and is relieved by rest or nitroglycerin. The terms angina and chest pain are used interchangeably. Although angina, or myocardial ischemia is usually manifested as chest pain, it can alternatively cause a variety of other sensations. It’s very important to diagnose angina effectively. Chest pain can occur with conditions other than myocardial ischemia, such as gastroesophageal reflux or pleuritis. Anginal chest pain is usually described as substernal, squeezing chest discomfort or pressure. It is frequently mistaken for heartburn because of its substernal location. Angina also occurs as an abnormal sensation in the chest, epigastric region, neck, back, or arms. Some patients will deny chest pain, but describe a long history of tightness, fullness, numbness, or heaviness. Because of the wide variance in presentation, it is quite common for angina to continue unrecognized or ignored for long periods before its cardiac etiology is diagnosed.
A myocardial infarction is distinguished from angina by its ECG manifestations and its effect on cardiac isoenzyme levels. Changes in these levels produce specific changes in the ECG tracing. The effects of an MI occur within minutes on the ECG. As myocardial injury evolves into necrosis, the ECG readings change drastically. The measurement of blood enzymes also contributes to diagnosis of MI. When myocardial cells are irreversibly damaged, intracellular enzymes leak through the cell membranes and are detectable in the blood. The most sensitive indicator of myocardial damage is a CK isoenzyme, CK-MB. The elevation of the CK-MB enzyme is an early detector of an MI. This enzyme rises in 4-8 hours after an MI, and returns to normal 2-3 days after that.
A MI is worse than CAD and angina because of the death that occurs to the tissue as a direct result of the lack of oxygen. CAD and angina are the predetermining factors for problems leading up to an MI.
Pre-operative medical therapy
There are many approaches that you can choose to slow down the progression of atherosclerosis. Pharmacological treatment to lower high blood pressure is a major component of risk reduction in susceptible individuals. Beta-adrenergic blocking and calcium channel-blocking agents are used to maintain normal blood pressure in patients with hypertension. Other antihypertensive agents, including diuretics, vasodilators, and angiotensin-converting enzyme inhibitors may be used. Dietary changes are encouraged to lower elevated cholesterol levels. The cessation of smoking is imperative because of the horrible effects of cigarettes. Smoking cessation decreases the risk of ischemia due to reduction of nicotine and carbon monoxide, increases HDL levels, and results in improved long-term survival. Three major categories of medications are used to reduce frequency of angina and improve exercise tolerance: nitrates, beta-adrenergic blocking agents, and calcium-channel blocking agents. Nitrates cause venous vasodilatation, arterial dilation, and relaxation of smooth muscle in epicardial vessels. Examples of nitrates are nitroglycerin and isosorbide dinitrate. Beta-blocking medications decrease heart rate and contractility. This lowers the myocardial oxygen demand so it doesn’t exceed the demand through the obstructed coronary arteries. They also have been shown to decrease the risk of cardiovascular mortality in patients who have had an MI. Calcium channel blocking medication cause vasodilatation that increases coronary blood flow. Different blocking agents decrease myocardial oxygen consumption by reducing blood pressure, afterload, and contractility. These interventions can all be used to try and prevent the need for invasive therapy. The need for invasive therapy may be necessary to restore blood supply to cardiac muscle.
The nurse plays a major role as the detector of cardiac problems. The nurse is the one who does the initial exam of a patient in the hospital setting. They draw the blood to test serum levels. They respond to an emergency in the Emergency room setting. The nurse uses their judgement in applying information for the doctor to use in his initial assessment. They administer the medication that manages chest pain and allows proper blood flow. The nurse is a vital organ in the process of medical care. They arouse suspicion and bring awareness to the physician of the underlying condition. One of the major functions of the nurse is their role in the pre-operative management of the patient. This includes interviewing, physical assessment, diagnostic studies, and pre-operative regimen.
The pre-operative period provides surgical, anesthesia, and nursing personnel with an opportunity to assess, distribute medication, review, and prepare the patient for the procedure. Patients are often admitted to the hospital on the day of a planned cardiac operation. Same-day admission is appropriate for patients with a low pre-operative risk. For patients with greater pre-operative risk, one or more preoperative days may be necessary. A primary nursing intervention in the pre-operative period is a thorough assessment with documentation of significant findings. This assessment complements the doctors admitting history and physical examination. It compares baseline information for comparison during the pre-op period. This allows the nurse to establish a relationship with the patient and identify problems that will require special interventions. The assessment is performed in a consistent and organized manner, beginning with an overall evaluation of general status and proceeding to a more detailed evaluation of cardiovascular function. The diagnostic tests that are performed pre-operatively tell about a patient’s current health status. The nurse tests for CBC (complete blood count), PT, PTT (partial prothrombin time), blood chemistry survey, urinalysis, ECG (electrocardiogram), and chest roentgenogram. These baseline studies are important to detect any abnormalities that may increase risk of the operation. Many patients, especially those with CAD have arterial occlusive disease. A noninvasive carotid ultrasound study is obtained if the patient had a history of carotid bruit or CVA (Cerebral Vascular Accident). Sometimes cardiac surgery is delayed because of diagnostic studies. Occasionally the patient becomes febrile between the time of admission and the planned operation. A temperature greater than 38.5 C is suggestive of infection. The planned operation is usually postponed because of increased risk of wound contamination from a preexisting infection. Most medications are continued during the pre-operative period, particularly those used to control hypertension, angina, or arrhythmias. Diuretics and digoxin are usually discontinued for several pre-operative days. Medications that affect hemostasis are also discontinued. Coumadin is withheld 4-5 days before the operation so the prothrombin time decreases to a normal level. Oral hypoglycemic agents are withheld from diabetic patients on the day of surgery. Patients who undergo cardiac operation almost always receive antibiotic prophylaxis. Wound contamination is most likely during the operation itself. Potential sources of pathogenic microorganisms include a pre-existing infection within the patient’s body, skin, and operating room personnel. Infection of the sternal wound causes significant morbidity when associated with sternal dehiscence, mediastinitis, and osteomyelitis of the sternum. With antibiotics, the pre-operative dose is administered before being transferred or in the operating room.
The aspect of patient teaching is an important part of pre-operative therapy. Patient teaching is known to have many positive effects, including increased knowledge retention, decreases length of hospitalization, and improved cooperation with the medical regimen. Pre-operative education is one type of patient teaching in which the patient is instructed about planned operative procedure and the projected post-operative course. The role of teacher is a main role for a nurse. Making sure the patient understands the procedure, consequences and benefits. This allows the patient to remain under less stress and have a larger knowledge base.
Coronary Artery Bypass Grafting
The nurse plays a role in the actual surgery of the patient. They could perform as a circulating nurse or as a nurse anesthetist. The role of the surgeon in CABG is the most important. The surgeon controls the outcome of the patient on the basis of his skill. The nurses around him provide him with tools and make sure the room is set up properly. The nurse anesthetist provides the right level of anesthesia and watches the vital signs of the individual undergoing surgery. The nurses’ role in this aspect of the patient is minimal to moderate. But, as always their presence is very important and beneficial to the patient.
Surgical revascularization of the heart has been a major component in the treatment of CAD (Coronary Artery Disease) for more than 20 years. It is one of the most common operative procedures performed in the US today. There are three main objectives of surgical revascularization: control of ischemic symptoms, prevention of MI, and prolongation of life. Coronary Artery Bypass Grafting (CABG) is the main method of surgical revascularization and may be combined with a coronary artery endartectomy. CABG consists of using autologous artery or vein as a conduit to bypass stenotic lesions in the coronary arterial circulation. Bypass grafting is good because atherosclerotic lesions usually develop in proximal portions of the major coronary artery branches. These branches move through epicardial tissue on the surface of the heart before becoming deeply embedded in the myocardium. Target vessels for bypassing are identified preoperatively on a coronary angiogram. An angiogram is a contrast x-ray that identifies which vessels are occluded or not. Any of the three major coronary arteries: left anterior descending (LAD), circumflex, or the right coronary may be grafted. CABG surgery is not a cure for CAD, angina, or MI. It is an operative therapy that needs to be accompanied by medical treatment, physical activity, and proper diet. By following these steps, this surgery can have a positive outcome if all the factors for success exist.
The surgery starts with a median sternotomy incision. After the skin is cut, the sternum is cut longitudinally with special saw to open it up. Then the pericardium is opened up and tacked on the retractors for the sternum. This is done very carefully to avoid damaging the phrenic nerve which lies medial and posterior to the incision. When these steps are done, the right atrium and ascending aorta re cannulated and cardiopulmonary bypass is initiated. The body’s core temperature is cooled to approximately 28.0 C. The cardioplegic solution is administered into the coronary circulation to produce cardiac arrest and provide myocardial protection. Once these steps are in place a probe is passed into the artery being bypassed onto. This checks the size and patency of the artery. The vein is then sewn to the coronary artery and the distal end attached on the descending aorta. The person managing the heart-lung machine repeats the doses of the cardioplegic solution every 15-20 minutes. The amount of grafting depends on the amount of grafting depends on the amount of blockage to the arteries. The heart can be bypassed many times to help increase blood flow. After the graft is complete the probe is inserted again to measure the blood flow. When this is complete the myocardium is warmed sufficiently to resume spontaneous electrical rhythm. This weans the patient form the cardiopulmonary bypass. The cannulas are removed and hemostasis is achieved. The sternum is reapproximated and fastened with heavy suture material or wire and the skin is closed.
The patient is transferred to the ICU as soon as the patient is hemodynamically stable. The OR team accompanies the patient to the ICU. The patient is reassessed by nurses and the many IV’s, chest tubes, and catheters are checked. A respirator should be set up and running to assist the patients breathing. Electrocardiographic leads are connected to the monitor and pulmonary artery catheter transducers are transferred. The chest tube suction is reestablished. The arterial catheter and all IV lines are assessed and checked for patency. The nasogastric tube is hooked up to suction and the pacing electrodes are covered up with finger cots. A baseline set of blood for potassium, hemoglobin, and hematcrit are drawn and sent to the lab STAT. The patient’s cardiac rhythm and hemodynamic parameters are observed continuously. The vital signs are documented every 15-20 minutes. The nurse is now a constant observer and participator in the care of this patient. The nurse is in direct care and the patient outcome relies indirectly on the nurse in charge. It is the nurse who reports any abnormalities that could complicate the patient’s outcome.
Most patients are ready for discharge from the hospital by the sixth or seventh post-operative day. Written instructions regarding the medications, activity level, restrictions, diet, and follow-up appointments are given. Most patients who undergo coronary artery revascularization procedures are discharged on anticoagulation therapy. Oral pain medication may be prescribed for a few weeks. Discharge instructions include goals to guide progression of activity. The patient will have to come back to the hospital for cardiac rehabilitation to ensure an excellent recovery. The nurse also provides the instructions, education, and information for the patient at this stage. The nurse provides a lot of moral support and is the one who decides what should be done to maximize the outcome.
I discovered many new things during this project. I saw many sides of nursing that you cannot see on the surface. The overall feelings and actions I was involved in were amazing. This experiment opened my eyes to the side of nursing care that I don’t usually see on the floor during my shift. I thought many actions that seemed confusing at first, made sense after it was thoroughly explained. The nurses that were involved in my experiment were very helpful. I saw many procedures that I was usually left out of. This was an excellent project to be involved in. I first started to gain experience with Open Heart Patients by passing out flyers to get feedback for this report. The nurses were very receptive to the fact that I was interested in the process of Open Heart Surgery. I purposely handed out the flyers with questions first because it would let me display my interest in this aspect of nursing care. This led into the other physical investigations that I was involved in. I individually talked to the nurses that were directly involved in the care of a heart patient. This led to more in-depth descriptions of the drugs involved in maintaining a patients hemodynamic factors. I listened in on the titrating of many vasopressors and vasodilating drugs. I thought that it was much more complicated than it really was. Then I had one nurse in particular who was really active in participation of describing certain aspects of care. She explained the step-by-step procedure of when a patient arrives back from open-heart surgery. The time a patient arrives back from Open Heart is the busiest for a nurse during their shift. This perspective was much more descriptive than just observing the process. It helped give me details that I didn’t get from standing around. Next, I used some books provided by the nurses to look up terminology and different procedural tasks. I got a great inside perspective of the whole nursing process. This look into the minds of the nursing staff was great. You can look, stand around, and gawk at what is going on during a procedure and never really get the whole picture. These nurses were very helpful and descriptive. I am glad that I put a lot of effort into this project. It opened my eyes into the side of nursing that I was very confused over. This project made me a better critical thinker and a better future nurse.
The role of the nurse in the hospital is very important. The nurse is a central figure in the care of a patient. The doctor does a lot of the initial tests, and he hypotheses a lot of ideas, but it is the nurse who finds out a lot the doctor cannot. The recent nursing shortage is only going to get worse for the future of the United States. When the amount of nurses is critically low, people will start to appreciate nurses for their role in the care of human beings. Nurses are unreplacable and will always be known for their caring, compassion, and effort. This is the role of a nurse.
American College of Cardiology/ American Heart Association Task Force on Assessment and Diagnosis "ACC/AHA Guidelines and indications for coronary artery bypass graft surgery" 1991
Spencer, F. "Bypass Grafting for coronary artery disease" 1990
Finkelmeier, Betsy "Cardiothoracic Surgical Nursing" 1995