In patients with severe heart failure, the use of mechanical circulation assistive systems must be considered if drug treatment is ineffective. Mechanical circulation assist devices include aortic balloon pump (IABP), extracorporeal circulation support system (ECMO), ventricular assist device (VAD), and total artificial heart (TAH).
I. Aortic balloon pump (IABP):
Can increase coronary blood flow, reduce left ventricular afterload, has the advantage of low invasiveness, so it is the first choice of mechanical circulation aids, but aortic balloon pump can not provide sufficient circulation in severe heart failure, especially When the heart rhythm is irregular. It only supports left heart failure and does not help right heart failure, so sometimes more effective assistive devices such as extracorporeal circulation support systems or ventricular assist devices are needed.
Second, extracorporeal circulation maintenance system (ECMO):
It can be set up quickly, providing right heart, left heart, and lung assistance, without the need for thoracotomy, and is the first choice for short-term use of the circulation aid. However, the extracorporeal circulation system is not suitable for long-term use unless the heart can recover or accept a heart transplant quickly. Consideration should be given to switching to a ventricular assist device (VAD).
Third, the total artificial heart (Total artificial heart):
Remove the heart and implant it into an artificial heart pump. The total artificial heart is only suitable for some patients who are not suitable for ventricular assist devices, such as aortic reflux, ventricular condyle defect, acute myocardial infarction within one week, and intracardiac thrombosis. Generally speaking, if it is used as a helper of excessive circulation before heart transplantation, it is sufficient to select a ventricular helper. At present, the artificial heart is still expected to be improved mechanically and electronically.
Fourth, the ventricular assist device:
Ventricular assist devices have been widely used in Europe, America, and Japan, and can effectively improve the survival rate of patients, successfully extend the waiting time for heart transplantation, and improve the quality of life. The catheter is implanted into the heart by thoracotomy, and the blood is drained out. The blood is then pumped into the artery through the pump to replace the ventricular function. Provides sufficient circulation support. Ventricular assist devices in patients with severe psychogenic shock give hopeless end-stage heart disease patients another chance to survive. Enable patients waiting for a heart transplant to survive the crisis and wait for a suitable heart transplant.
Ventricular assist devices can provide patients with heart failure, dying patients with long-term and sufficient cardiac support functions, enable patients to prolong life, improve organ functions such as liver, ** and successfully receive heart transplantation. According to function points, it can be divided into left ventricular assist, right ventricular assist, and dual ventricular assist.
According to the brand, the National Taiwan University Hospital currently has Thoractec VAS, HeartMate LVAS, Biopump or Roller pump VAD.
(1) HeartMate Left Ventricular Assist:
It can effectively and long-term assist the heart function. It has a unique blood interface that can reduce the risk of thrombosis. There are two driving modes: pneumatic and electric. HeartMate is purely a left ventricular assist device. The operation needs to be performed in the operating room and under artificial cardiopulmonary bypass. Blood is drained from the left ventricle tip and passes through a "chamber" composed of polyurethane and titanium. Body ", and then the blood is returned to the artery through the aortic prosthesis. The HeartMate chamber body is generally buried in the patient's abdominal wall. The volume of HeartMate's blood chamber is 83ml, and its huge chamber volume is not suitable for the physique of the Oriental. In addition, the abdominal surgery range is wide, the difficulty is high, and the complications More symptoms, such as bleeding. Because its interface is highly blood compatible, long-term use of anticoagulants may not be required. Heparin is usually used for a short period of time, and then only a low dose of aspirin is required.
(2) Thoratec (biventricular assist device):
Used in a ventricle or a patient with left and right ventricular failure. This machine replaces the ventricular function. The blood pump of the ventricular assist (VAD) is placed on the abdomen, and its connecting tube passes through the chest and the heart. Circulatory system connection, in the left heart: Cannula is mainly used to drain blood from the left ventricle or the left atrium to the Blood Pump, and then hit the blood to the aorta for delivery to the whole body. On the right heart side, the connection tube (Cannula) is mainly used to drain the blood from the right atrium to the blood pump, and then the blood is hit to the pulmonary artery to replace the function of the right ventricle. Pumps use pulse pressure (Vacum) to evacuate and fill blood. The blood pump is a pulsating type, which is in accordance with physiological conditions. Its blood chamber volume is only 65ml. The blood interface is a special Silicone medical polyurethane, and there is little thrombosis in long-term use. Anticoagulants must be used for a long time after surgery to maintain the clotting time at 1.5 to 2 times.
(3) Centrifugal ventricular assist device (Bio-pump VAD) or roller ventricular assist device (Roller pump VAD):
The blood is mainly drawn out of the left atrium by using a connecting tube. After passing through a pump or a roller-type roller, the blood is beaten back to the artery to serve as a left ventricular assist device. The blood is drained out of the right atrium through a connecting tube, passes through a pump or a roller-type roller, and then beats the blood back to the pulmonary artery as a right ventricular assist. Such a centrifugal chamber or a roller-type ventricular assist device has continuous blood flow in hemodynamics, which is relatively incompatible with physiological blood circulation, but is simple, economical, and money-saving. Bio-pump is external and transparent, and it is easy to observe the presence or absence of thrombosis. In order to prevent thrombosis, continuous use of anticoagulant (Heparin) is necessary, because there will be thrombosis and severe hemolysis, so the ventricular assist pump needs to be replaced every 5 to 7 days.
Application of ventricular assist:
1. Bridges before heart transplantation in end-stage heart failure
2. After acute myocardial infarction
3. Myocardial stunning after happy surgery
4. Heartbeat stops, during artificial cardiopulmonary resuscitation
Indications of ventricular assist devices:
1. Cardiac output is less than 1.8L / min / M2
2. Systolic pressure is less than 90mmHg
3. Left atrial pressure is less than 20 mmHg
4. Are end-stage heart failure ready to accept a heart change
5. When the patient has used high-dose cardiotonics and the aortic balloon pump is still unable to maintain proper blood circulation
The following conditions do not apply to ventricular assist devices:
1. ** Poor function: BUN ＞ 100 mg / dl, Cre ＞ 5.0 mg / dl, Anuria
2. Pulmonary dysfunction: emphysema, resent infarction, COPD
3. Poor liver function: Total bilirebin ＞ 10 mg / dl, cirrhosis or portal hypertension
4. Systemic infection
5. severe blood abnormalities
6. Severe peripheral or cerebrovascular disease
7. Malignant tumor
8. Acute myocardial infarction within 7 days
Complications of ventricular assist devices:
1. Bleeding: major bleeding after surgery, must be reopened
2. Infection: strict requirements for aseptic technique
3. Right ventricular failure with left ventricular assist
4. Thromboembolism: Oral Aspirin, Dipyridamole, Conmadin
5. Concurrent multiple organ failure
Ventricular assistive care:
The patient just returned to the intensive care unit after installing VAD. Usually under general anesthesia. When a patient wakes up from anesthesia, morphine, meperidine, fentanyl and other drugs can be used to reduce their pain. If the patient does not have a plan to remove the endotracheal tube, pancuronium (pavulon) can be used to prevent the patient from excessive restlessness and reduce the need for metabolism. Restricting the limbs throughout the treatment process is a necessary protective measure to prevent patients from accidentally removing the endotracheal tube.
Sedated and restrained patients need to use a respirator to provide adequate oxygen. When the respirator is normally set to ACMV, FiO2 is set based on the results of arterial blood gas analysis. Many patients need to use 100% FiO2 in the beginning. Because long-term use of high-concentration oxygen can cause oxygen toxicity, if the patient's condition permits, try not to use FiO2100% for a long time. Ideally, FiO2 given by continuous oxygen is maintained at or below 50%. In patients with atelectasis, the use of PEEP (end-expiratory positive pressure) can prevent alveolar collapse and can give lower concentrations of oxygen.
The use of downstream catheters can continuously monitor changes in hemodynamics. Pulmonary artery pressure (PAP) can be obtained from the downstream catheter to reflect the left atrial end-diastolic pressure (LVEDP), which is an indicator of myocardial function. This stress is usually higher when the patient has heart failure. Cardiac output (C.O) can also be measured using a downstream catheter.
The pump output of the ventricular assist device is controlled by the surgeon, perfusionist, or trained intensive care nurse to adjust the speed of blood flow. The left ventricular assist device (LVAD) usually measures blood flow to maintain cardiac output. Its blood flow is usually maintained at 1 to 5 L / min to maintain left ventricular pressure (LAP) between 4 and 12 mmHg. The maintenance of cardiac output when using the right ventricular assist device (RVAD) depends on the function of the left ventricle; therefore, the adjustment of blood flow rate is based on the value of left ventricular function.
In order to prevent blood from coagulating at the pump head, the use of anticoagulants is necessary. Blood coagulation at the pump head can cause blood flow to decrease or even occasionally form thrombi. Heparin-controlled activated clotting time (ACT) is typically maintained at 150 to 200 seconds. Closely monitor platelet or other hematological values, such as blood clotting tests and numbers, and treat them based on the results of the tests.
The volume in the blood vessel must be able to provide sufficient blood flow and cardiac output. The decrease in vascular volume may be caused by excessive use of anticoagulants or bleeding due to glial osmotic pressure and reduced plasma proteins, which causes water to run to third-space. Decreasing intravascular volume can also reduce pulmonary artery pressure (PAP), left ventricular pressure (LAP), or central venous pressure (CVP). Administration of blood products or colloidal solutions increases the volume in blood vessels.
Patients who use ventricular assist devices (VAD) will have many holes in the skin to enter the body. They have low self-defense capabilities and are prone to infection. Sometimes a ventricular assist device (VAD) catheter is placed in the chest cavity so the sternum cannot be sutured. All the factors described above are likely to cause infections in patients. For the above reasons, it is necessary to have complete hand washing technology and some anti-quarantine measures to prevent patients from being exposed to pathogenic bacteria brought by medical personnel.
Because patients with ventricular assist devices (VAD) have increased metabolic expenditure, it is necessary to increase calorie and nutrient intake. Nutrition can be supplied via nasogastric tube feeding or total intravenous hypertrophic therapy.
When the patient's myocardium has signs of recovery, it can begin to detach from the ventricular assist device (VAD). Cardiac output (C.O) and pulmonary arterial pressure (PAP) can be used as indicators of ventricular function recovery. Carefully monitor cardiac output (CO), pulmonary arterial pressure (PAP), and left atrial pressure (LAP) while gradually reducing blood flow. The ventricular assist device (VAD) can also be separated from the aortic balloon pump (IABP) at the same time, but the cardiac output (CO), left atrial pressure (LAP), and pulmonary artery pressure (PAP) must be used as indicators of ventricular function .
Caring for patients using atrial assist devices (VAD) is a big challenge. Knowledge of perfusion and technique is necessary to adjust the pump output of ventricular assist devices. The patient's condition must be continuously monitored to prevent potential problems.
Care planning is an important tool for nursing staff when caring for patients using ventricular assist devices (VAD).