Haemodynamic monitoring
Haemodynamic monitoring is the study of how blood flows through the cardiovascular system (i.e. the heart and blood vessels). The purpose of the cardiovascular system is to deliver blood carrying oxygen and other vital nutrients to the cells and tissues the body.
The results of haemodynamic monitoring allow the healthcare team to check whether a person has:
- enough blood, to decide whether more or less is needed
- a suitable blood pressure
- structural problems with their heart that stops it from working properly
- a good heart rate, to decide the heart needs more support.
A steady blood pressure is needed so that blood and important nutrients are delivered to the organs. In serious illness, either high or low blood pressure can mean that a person’s condition is worsening and maybe serious. Blood pressure can be measured using a sphygmomanometer (a device with an inflatable rubber cuff that’s wrapped around the bicep and is connected via a tube to a blood pressure meter) or using an arterial catheter.
An arterial line or arterial catheter is a small thin plastic tube, similar to an intravenous (IV) catheter, that is inserted into an artery. An arterial catheter allows the healthcare staff to constantly check a person’s blood pressure. An arterial catheter also makes it easy to regularly take blood for sampling, rather than taking samples the usual way. Usually, arterial catheters are needed for a short time only.
How does it work?
Arterial catheters are inserted into arteries in the wrist, groin or foot, and are stitched and covered with a sterile plastic dressing to help keep it in place.
Once inserted, an arterial catheter is connected to a monitoring system and the patient’s blood pressure is shown on the bedside monitor. This monitoring assembly also flushes the catheter with fluid to stop it from blocking.
When the catheter is no longer needed, the nursing staff will remove it. The nurse will need to firmly press on the area for 3–5 minutes to stop any bleeding. A small dressing will be placed over the site, which can be removed the next day.
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Several tests are used to check whether the heart is pumping properly. These tests include electrocardiography (ECG), echocardiography and specialised catheters. The benefit of using a specialised catheter along with ECG and/or echocardiography is that it gives ongoing information. This makes it easy to regularly check a person’s response to treatment and pick up any potential problems early.
ECG monitoring is used to check the electrical activity of the heart. In the intensive care unit, this is done by placing sticky circular patches (electrodes) on a person’s chest. These electrodes are attached via leads to a device that shows the electrical pattern of the heart, including how fast and regular the heartbeat is.
This is slight different to an electrocardiogram (ECG), which is a formal test performed with 10 leads. An electrocardiogram can look for things like a heart attack or the size of the heart muscle, while ECG monitoring monitors only the rate and rhythm of the heartbeat.
Echocardiography is an ultrasound of the heart. It uses sound waves to create an image of the beating heart so that doctors can see the heart in action in real time.
An echocardiography is able to show:
- structural defects in the heart, including the heart muscle and valves
- blood flow problems
- the amount of blood pumped out by the heart, which is known as cardiac output
- the volume of blood in the heart.
How does it work?
A person can have the echocardiography in their beds or in a special unit set up for this purpose. When undergoing a transthoracic echocardiography (TTE), a person will be positioned lying down on their left side. A sonographer, a person specialising in performing the ultrasound, will then gently rub a small probe on the chest wall in several places around the heart. This probe releases high frequency sound waves and records the changes to these sound waves as they return to the probe. The echocardiography machine converts these sound waves into a digital image of the moving heart. A TTE usually takes around 20 minutes.
A more invasive echocardiography is a transoesophageal echocardiography (TOE). With a TOE, the ultrasound probe is in a long, flexible tube that is passed through the mouth, down the oesophagus (wind pipe). This gives much better pictures of the heart because the probe is closer to the heart. A sedative or light anaesthetic may be given to the person to make them more comfortable during this procedure.
A pulmonary artery catheter (also known as a Swan-Ganz catheter) is a long, specialised catheter that is inserted into a large vein. The pulmonary artery catheter is usually used in seriously ill people with heart and/or lung problems, or who have had high-risk surgery, such as some heart surgeries.
Pulmonary artery catheters help to diagnose and monitor conditions, which helps the healthcare team to decide on the best treatment for the person.
How does it work?
A pulmonary artery catheter is inserted into a large vein and then carefully threaded through the heart until the tip ends in the large blood vessels of the lungs. A chest x-ray is used to check that the catheter is in the right position.
The catheter is connected to the bedside monitor. This gives the healthcare team ongoing information on how well the heart is working and responding to treatment. It also helps to pick up any problems early on. The catheter is usually needed for a few days only.
PiCCO uses a specialised catheter to give ongoing information about how well the heart is working.
How does it work?
The healthcare team inserts a special central venous catheter to give a full picture of a person’s blood flow, including whether the person has enough blood and how well their heart is working.