The heart is the pump that moves blood through the lungs and the rest of the body. The blood carries oxygen and nutrients the body’s cells need to work and takes away waste products. The heart has four chambers: The right side of the heart takes care of blood going to the lungs. The left side of the heart delivers blood to the rest of the body.
The circulatory system is made up of arteries that carry blood away from the heart, veins that bring blood back to the heart. People admitted to the MSICU have their hearts and circulation closely monitored.
A person is in cardiac arrest when their heart has stopped beating for any length of time. In the hospital, this is called a Code Blue. Everyone in the MSICU is hooked up to a heart monitor, or ECG machine. The heart monitor sounds an alarm if there is no heartbeat, or if the beat is too fast, too slow, or irregular. A team of health care providers come quickly and begin chest compressions (CPR) if the heart is not beating. They look at the pattern of the heart’s electrical signals on the monitor and use this information to decide what to do next. Different medications will be given depending on what the source of the problem is. They may try to shock the heart back into a normal rhythm by running electricity across it with a defibrillator. The shock causes the heart to stop completely and gives it a chance to restart at a normal rhythm.
Also called a myocardial infarction (MI), a heart attack happens when the blood supply to part of the heart muscle gets cut off. If part of the heart muscle is without oxygen carried by the blood that part of the heart muscle can die. The heart may continue to beat but may not work as effectively.
An arrhythmia is an abnormal electrical rhythm in the heart. If the electrical signal does not travel along the regular route, the heart does not beat as effectively. Most healthy people have occasional arrhythmias. When they happen too often, they can cause problems with the output from the heart. Arrhythmias are treated with medications, a pacemaker or other treatments.
If the blood vessels of the body are diseased, they can become hard and less flexible over time. Deposits of fat form and harden onto the walls of the arteries. A clot can form over the fatty deposit. If the clot breaks off, it can travel through the body and become lodged in a narrower vessel. If a clot goes to the brain, it can cause a stroke. A clot can block an artery to the heart muscle, causing a heart attack. Atherosclerosis is a very common health problem in Canada.
Aneurysms are arteries with weak walls. Arteries carry blood at high pressure. Aneurysms are most common in the brain or in the aorta, the largest artery in the body. They can come in many shapes but are often found at the point when one artery branches off into two.
Deep Vein Thrombosis (DVT)
DVT is a complication of immobility. They form in the veins of the legs or groin. If a person is up and moving around normally, the action of the muscles in the legs helps to keep blood moving back towards the heart. When a person is too sick to move, the blood can pool and form clots that may break off. DVTs are a major cause of pulmonary embolisms. Patients are often given a low dose of blood thinners to help keep the blood from clotting. The team may also use compression stockings or Sequential Compression Devices that help squeeze the blood back towards the heart and help prevent clots.
Prevention and Therapies:
Cardioversion and Defibrillation
- Cardioversion is the use of a defibrillator when a person is not in cardiac arrest but has an abnormal heart rhythm. Sometimes the team will try to ‘shock’ a heart back into a normal rhythm. The patient will be given sedatives and pain relief before undergoing cardioversion.
- Defibrillation is the term used to describe this treatment when the heart is not pumping effectively at all. The heart may have stopped, or it could be ‘fibrillating’ or quivering, without pumping any blood. The shock of defibrillation can stop the heart and allow it to restart at a normal rhythm.
- A large volume of fluid (i.e., 500 mL) given all at once increases the volume in the blood circulation and can raise the blood pressure.
Intra-aortic balloon pump (IABP)
- If a person’s heart is not pumping well enough to get oxygen and nutrients to the body, they may be given the support of an IABP. The IABP sits in the aorta, the major artery from the heart. It is placed in the aorta through a large artery in the leg and threaded into place. The pressure settings on the pump are watched very closely to make sure they are effective.
Swan Ganz Catheter
- Also called a Pulmonary Artery Catheter. A Swan Ganz catheter is a catheter inserted into the right side of the heart via a large central vein. This catheter is used when the team requires detailed information about heart function. The tip of the catheter sits in the artery just before the lungs. A Swan-Ganz catheter looks at different blood pressures and is used to guide the medical staff to choose certain treatments for those critically ill patients.
Sequential Compression Devices
- The legs are a common place for clots called DVTs to form. Compression stockings and Sequential Compression Devices can help prevent DVTs by helping blood return from the legs to the heart.
- Also called an arterial line, or art line. This is usually inserted in an artery at the wrist. Blood gases need to be measured frequently in the MSICU. An arterial line provides a point of access for blood tests. The catheter is used to closely monitor blood pressure.
- The blood in arteries is under high pressure, so the arterial line is hooked up to a pressurized box that runs a small amount of fluid into the line to prevent clotting. The line is flushed after every use to keep it free of clots as well.
Intravenous Catheter (IV)
- A line inserted into a vein, usually on the hand or arm. IVs are used to give medication and fluids without having to stick a patient with any more needles than necessary.
Central Venous Catheter
- Most patients in the MSICU will have a central venous catheter. Central lines, or central IVs are similar to regular IVs, but they are placed in a larger vein close to the right side of the heart.
- Central lines can be used in the same way as regular IVs, and can also be used to give nutrition and medications that may harm smaller veins. There is a lot more blood flowing through a central vein, so anything that is given gets diluted or watered down quickly, reducing the chance of irritation. Central venous catheters can also be used to measure certain blood pressures. Samples can be drawn to measure the blood gases as well.
Peripherally Inserted Central Catheter (PICC line)
- Another type of Central Venous Catheter is a PICC line. A PICC line is a long, thin IV that is often inserted into the arm and advanced until the tip of the catheter is located in a large central vein. These catheters can be inserted at the bedside by specially trained nurses.
There are many drugs that can be used to manage blood pressure that is too high or too low. They are often used in combination to get just the right effect for the individual patient. These drugs are only used when absolutely necessary, and their effects are closely monitored.
The following are some general types of drugs for the heart and circulation.
Also called vasopressors, or just ‘pressors’ for short. This type of drug is used to raise blood pressure by making the arteries tighten up or constrict. The same amount of blood flows through the constricted arteries at a higher pressure.
A vasodilator relaxes the blood vessels and makes their diameter wider. Vasodilators can lower the blood pressure if it becomes too high. Relaxation of the blood vessels reduces the resistance in the blood vessels and makes it easier for blood to flow. This makes it easier for the heart to pump blood and can be used to increase the amount of blood the heart pumps out with each beat.
These drugs can be used if a patient has an unusual heartbeat that is affecting blood pressure or the strength of the heartbeat. Anti-arrhythmic drugs help normalize the electrical impulses that cause the heart to beat.
Anti-coagulants are used to reduce the body’s ability to make blood clots. Anticoagulants are used for patients at risk for clot formation such as ICU patients who are in bed and unable to resume their normal activities, and patients with irregular heart rhythms. Many people with heart disease take a low dose of an anti-coagulant every day to reduce the risk of a stroke or heart attack.
Inotropes are used to increase the strength of the heart’s contraction, allowing it to pump harder with each beat and push out a larger amount of blood. Inotropes are used when the amount of blood being pumped by the heart is too small, which can be a cause of low blood pressure. These drugs are given through an IV line. This allows their use to be tightly controlled. Staff can start, stop, reduce, or increase the dose as needed.
Diagnostic Tests and Monitoring:
- These machines monitor heart rate and rhythm, blood pressure, and how much oxygen is in the blood.
Blood pressure (BP)
- The higher number is the pressure of the blood when the heart is squeezing. The lower number is the pressure when the heart has relaxed so it can fill up with more blood. The ideal blood pressure is 120 over 80, but there is a lot of individual variation.
Blood oxygen saturation (‘Sats’)
- This number, as a percentage, is an indication of the saturation of the blood with oxygen. This is a value we look at to see how well as patient is breathing. You can see this number on the bedside monitor. Ask the bedside nurse what this number should be for your loved one.
- The cardiac output measures how much blood the heart pumps out in litres per minute. It can be measured directly using a Swan Ganz catheter. This number determine the appropriate dosing of drugs. A low cardiac output can reduce the delivery of oxygen and nutrients and can lead to failure of other organs.
- A regular bedside monitor measures the heart’s electrical impulses from one or two points of view. The 12-lead ECG takes measurements from twelve different angles at the same time. This provides a detailed view of how each part of the heart is working and whether or not it is getting enough oxygen.
- An echocardiogram is a test that is done to look at the pumping action of the heart. It can be performed at the bedside by an echocardiogram technologist. It is useful at identifying damage to the heart wall or heart valves.
- The echocardiogram shows the four chambers of the heart, the right and left ventricles, and the right and left atria.
- Nuclear medicine involves using mildly radioactive substances, called isotopes, to identify injury or disease. Certain radioactive substances will find and attach themselves to particular cell types or proteins. The person is then scanned with a special camera. The isotopes ‘light up’, telling the physicians where the cell or protein they are looking for has collected. This can be very helpful to identify areas of the heart that have been damaged.
- Ultrasound tests use the measurement of sound waves sent into the body and reflected back to identify masses or fluid. It is painless and can be performed at the bedside. Ultrasounds can help a physician tell where to place a chest tube to drain fluid.
- Angiograms can be used to look at arteries anywhere in the body, such as the brain (cerebral angiogram) or heart (cardiac angiogram). Once the problem has been located, the physician may take steps to correct it all in one procedure if possible.
- The angiogram at left shows how blood vessels can be visualized using contrast.
There are a wide variety of blood tests or labs that need to be done in critical care. If a person is on a respirator, the levels of blood gases will be measured frequently. Blood gases can be drawn from an arterial line or tested from a capillary sample from the ear.
Other tests include blood sugar, blood chemistry (i.e., sodium), Complete Blood Count (CBC), and tests for infection. There are also specific chemical markers that show up in the blood if certain tissues have died or been damaged.