During a CABG operation the surgeon uses the patient's own blood vessels to create a new pathway for blood to flow through the coronary arteries.
What does the cardiovascular system do?
The cardiovascular system (CVS) consists of the heart, lungs and blood vessels. It is responsible for transportation of vital nutrients, gases and hormones throughout the body. The heart functions as the central pump with the blood vessels the pipes of the body. The CVS is controlled by a number of internal and external systems, which keep the CVS in balance with the needs of the body.
The heart is a pear shaped organ positioned centrally within the chest cavity with the apex extending over to the left nipple. The heart is a divided into a right and left side, each side has an atrium and ventricle. Heart valves and the contraction of the heart muscle control blood flow through the heart. The right side receives de-oxygenated blood from the major veins of the body and pumps this blood into the lungs. The left side of the heart then receives oxygen rich blood from the lungs and pumps this blood into the Aorta and arteries of the body. This pumping action is a complex well-coordinated activity that cannot be fully explained here. The heart receives its blood supply via the left and right coronary arteries.
Poor or abnormal function of the cardiovascular system
May be a result of:
- Insufficient blood supply due to dehydration, bleeding or swelling;
- A poor blood supply to the heart, where there is not enough oxygen and other nutrients for its work;
- Poor lung function or obstruction to blood flow in the lungs, which places a strain on the heart muscle;
- Too many or too few electrolytes (eg. potassium, magnesium) that cause irregular heartbeats or dangerous rhythms in the heart.
- Weakness of blood vessel walls.
- Heart muscle weakness
What are coronary arteries & coronary artery disease?
Coronary arteries are blood vessels that carry blood, oxygen and other nutrients to the heart tissue to help it work effectively. As we get older our coronary arteries may become hardened and fatty deposits can build up on the inner lining of the vessel. This process (atherosclerosis) is what causes narrowing of the coronary arteries, where blood supply to heart muscle is reduced and symptoms of coronary artery disease usually begin. According to the National Heart Foundation in 2004 36% of all deaths in Australia were attributable to cardiovascular disease (CVD). Some symptoms of CVD include:
- Chest pain/heaviness
- Pain in the shoulders, arms, neck or jaw
- Shortness of breath.
- Excessive tiredness
Management with medication may reduce these symptoms but the arteries will remain diseased. A thrombus (blood clot) can form in an artery that is already narrowed thus resulting in the complete blockage of that vessel. The heart muscle previously supplied by that artery will die (= heart attack / myocardial infarct) without immediate medical treatment. Coronary artery bypass grafting aims to restore the blood supply to the heart muscle ideally at the stage when the artery is narrowed, and before the infarct occurs.
What is a coronary arteray bypass graft?
In a CABG operation the surgeon grafts other blood vessels onto the patient’s coronary artery and bypasses the diseased portion. This creates a new pathway for blood flow that ensures the delivery of oxygen and nutrients to the heart muscle. In the picture below two areas of blockage in coronary arteries have been bypassed in order to restore blood flow to the heart. Two commonly used vessels have been chosen, one from the leg and one from the chest area.
|This picture was sourced from MedicineNet
Following a general anaesthetic and insertion of a breathing tube (endotracheal tube) into the windpipe, the patient is connected to a breathing machine (ventilator). Monitoring lines and intravenous access lines are inserted.
An incision is made down the length of the sternum (breast bone) to access the heart. The patient’s blood is diverted from the heart to a heart-lung machine (cardiopulmonary bypass machine). This machine oxygenates, filters and cools or warms the blood as necessary. Oxygen rich blood is then returned to the body via the aorta, (a large artery exiting the heart), to maintain a continuous blood supply to the brain, kidneys and other organs. The body is cooled to protect these organs. A special fluid is then given which stops the heart. This provides the surgeon with a blood-free heart to work with.
The surgeon then uses some of the patients own “non essential” blood vessels to bypass the diseased coronary artery. These can be veins from the legs or arteries from the chest or arms. Multiple coronary arteries bypasses are carried out if the patient has several affected vessels. Smaller branches of the main arteries may also need to be bypassed.
In recent years the operation can in some cases be carried out without the patient going onto the bypass machine. A stabiliser is applied to the area of the heart being operated on and then the coronary artery is grafted in the same way as above except that the body is not cooled. This operation is called “off- pump” or “beating-heart” surgery.
What happens in the Intensive Care Unit?
After coronary artery bypass surgery the patient is admitted to the Intensive Care Unit. The patient is monitored to assess their progress. The patient is attached to a breathing machine (ventilator) as they will be under the effects of the anaesthetic and will not be awake enough to breathe independently. As the patient wakes up and is able to do more of their own breathing, the role of the ventilator is “weaned” until the patient is able to breathe well on their own. Once this happens the breathing tube can usually be removed. This process may take more time in patients with lung disease. In some cases the patient may need more sedation and support from the breathing machine if, for example, they are agitated or if bleeding from the chest is difficult to control. The effectiveness of the breathing machine is assessed regularly with a blood sample (ABG)looking at oxygen and carbon dioxide levels in the blood. An oxygen saturation probe attached to the patient’s finger monitors the oxygen level in the blood continuously. A nurse observes the patient continuously while he/she is on the breathing machine. As the patient wakes the nurse will explain to the patient what is happening.
The patient is attached to a bedside monitor that displays heart rhythm (ECG / electrocardiogram), blood pressure, and pressures around the heart and in chest. Several monitoring lines will have been inserted into the patient while in the operating theatre to enable this process. An arterial catheter monitors the blood pressure on a continuous basis.
Some monitoring lines can give the Intensive Care staff very detailed information about heart function. For example a pulmonary artery catheter calculates the amount of blood that the heart is pumping out each minute. This assessment is made regularly in the first 24 hours after surgery.
- Abnormalities in heart rhythm usually require treatment.
- Strict blood pressure control is achieved by medications infused via rate-controlled pumps. Fluid is also given intravenously at first to treat low blood pressure.
- Body temperature is monitored. A powered blanket filled with warm air may be used to bring the body temperature back to normal.
- A drainage bottle collects blood shed from around the chest and heart area. This is monitored for signs of excessive bleeding.
- A urinary catheter will be in position to allow for monitoring of kidney function.
If you are visiting a patient in the Intensive Care Unit at this stage you should expect to see many lines, tubes, and drains attached to the patient.
What are the possible complications following CABG?
All surgery carries risks of complications. Possible complications following cardiac surgery include:
- Arrhythmia – irregular heart beat
- Excessive bleeding – may require returning to the operating theatre and a blood transfusion may be necessary
- Stroke – debris from the inner lining of the aorta (major blood vessel) can break off and lodge in the brain
- Infection – may occur in leg, arm or chest wound or in the chest
A member of the surgical team will discuss complications with the patient prior to surgery. Any further questions you may have can be directed to the Intensive Care doctors and nurses.
What is the expected length of stay in the ICU ?
Most patients will stay one or two days in the Intensive Care Unit following coronary artery bypass graft surgery and can be discharged home five days later. However some patients with complications will stay in the Intensive Care Unit for weeks or months.
What is life like after CABG surgery?
Following transfer from ICU to the ward the patient will have the support of a multi disciplinary team to help get them back on their feet and ready for home. This team consists of doctors, nurses, physiotherapists, occupational therapists, dieticians, pharmacists, and social workers. The team gives advice on exercise guidelines and provides a program is for the patient to return to usual activities for the weeks after discharge from hospital.
The patient is encouraged to attend a cardiac rehabilitation program that offers education sessions and supervised exercise programs. It also provides a valuable opportunity to meet with other people who have recently had heart surgery. Some hospitals also run a “Carer/Spouse Support Group” to address the needs of this group.
Some patients find that they feel tired and have difficulty in concentrating after heart surgery. This is not unusual and should improve in approximately 4-8 weeks after surgery. Of course if you have any questions or issues, always discuss them with your doctor.
The information contained on this page is general in nature and therefore cannot reflect individual patient variation. In addition it reflects Australian intensive care practice which may differ from other countries. It is meant as a back up to specific information which will be discussed with you by the Doctors and Nurses caring for your loved one. ICCMU attests to the accuracy of the information contained here BUT takes no responsibility for how it may apply to an individual patient. Please refer to the full disclaimer.
CABGVersion 1 (Author Deirdre Moran CNS Royal North Shore Hospital, Sydney)
First Published July 2007
Correspondence: ICCMU CNC