Training
Advanced Cardiac Monitoring
Indications for Advanced Cardiac Monitoring
- Cardiovascular instability caused by but not limited to shock, pulmonary embolism, pulmonary oedeama, large blood loss, trauma and pre-eclampsia.
- High risk post-operative patients, particularly those with left ventricular dysfunction and/or ischaemic heart disease and those with large blood losses.
Why do we use Advanced Cardiac Monitoring?
- Monitor cardiac function.
- Monitor fluid status of patients.
- Monitor effectiveness of inotropes.
- Aid decision making in haemodynamic optimisation.
- Tighter control of patient parameters.
Types:
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How does it work |
Pros |
Cons |
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Oesophageal Doppler |
Uses an ultrasound probe that sits in the oesophagus to assess flow of blood in the decnding aorta. |
Non-invasive. Fewer potential complications than other methods. |
Can only be used in sedated patients. Cannot be used in patients at risk of perforation, abnormal physiology/ pathology of the upper GI tract, bleeding patients. Difficult to manipulate. |
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Transpulmonary lithium indicator dilution: LiDCO |
Dye is injected into a CVC and diluted concentrations of this are monitored in a downstream probe (often on a specialist femoral arterial line). |
Suitable for use in concious patients.
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Central line required. Cannot be used in patients receiving muscle relaxants due to the interaction with the lithium. Not recommended in patients who weight less than 40kg.
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Pulmonary Artery Catheterisation |
A four lumen, balloon flotation catheter is advanced into the pulmonary artery to monitor diastolic pressure. |
One of the first methods of advanced cardiac monitoring that provided reliable monitoring. Also can be used for cardiac pacing, pulmonary angiography and monitoring of mixed venous oxygen saturation. |
Potential complications include: pneumothorax, arrhythmias, endocarditis, valve trauma, thrombosis, artery rupture. |
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Thermodilution methods: Pulse-induced continuous cardiac output, PICCO |
Cannulae are placed in the femoaral artery and central vein. Cold fluid boluses are injected centrally then detected by a thermistor on the tip of the arterial line. |
Allows for measurement of lung water. Overcomes problems seen with dye injection menthods. |
Tendency to overestimate cardiac output. Accuracy depends on temperature of inject and 'smooth' injection. Multiple injections through out the ventilatory cycle are needed to improve accuracy. Requires injection of fluid that may be contary to the patients requirements and also cold boluses have been associated to bradycardia and supraventricular tachycardias. |
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Pulse Contour Analysis |
Calculations based entirely on arterial waveform characteristics in conjunction with patient demographic data. |
Continuous measurement. No need for additional measures so reduced nursing time required. Easy to use. |
Derived variables. |
Anatomy and Physiology
Cardiac output (CO) : The volume of blood, measured in litres, ejected each minute by the heart. For most adults normal resting CO is 4-8L/min.
CO is affected by:
- Changing tissue metabolic demands.
- Body composition.
- Changes in body position.
Cardiac index (CI): Cardiac index is a means of adjusting cardiac output for body size. Normal range is 2.4-4.5L/min/m.
