Cardiac Output Monitoring

blood pressure cardiac output fluid therapy heart rate hemodynamics monitoring oxygen Sep 23, 2024

💡 Decoding Cardiac Output Monitoring: Optimising Treatment One Beat at a Time

To the untrained eye, cardiac output (CO) monitoring can seem overwhelming. So what exactly are you looking at?

❤️ CO is the measure of blood (in Litres) ejected from the ventricles per minute and is sensitive to changes in heart rate, preload, contractility, and afterload.

🔄 Recap:
👉 Preload - Tension in a full ventricle just before contraction (end diastole)
👉 Contractility - The heart’s ability to contract and expel blood
👉 Afterload - The force the heart muscles must work against to eject blood (during systole)

So why do we monitor CO?
👉 Indicates overall blood flow and oxygen delivery
👉 Used in high-risk surgical patients to prevent organ failure and reduce mortality
👉 Informs fluid therapy requirements to optimise oxygen delivery and prevent overload
👉 Determines the need for vasoactive agent administration and titration

🔢 CO Calculation:
Stroke Volume (SV) x Heart Rate (HR) = CO

CO Monitoring types:

👉 Non-Invasive: Transthoracic Oesophageal Echocardiography (TOE), advanced pulse oximeters

👉 Minimally Invasive: Arterial pulse contour analysis & oesophageal doppler

👉 Invasive: Pulmonary Artery Catheter, Specialised Arterial Lines and Central Venous Catheters

⚠️ Limitations:
🔺 Individual organ oxygen delivery cannot be measured; organ function must still be assessed
🔺 Not a complete solution for hemodynamic monitoring; it’s part of the bigger clinical picture
🔺 Invasiveness varies by monitoring type; may require arterial lines, central lines, or pulmonary artery catheters
🔺 Minimally invasive/non-invasive methods often require sedation or intubation and can be inaccurate or affected by interference

Build Knowledge
Improve Safety

Ref: 

Kobe J, Mishra N, Arya VK, Al-Moustadi W, Nates W, Kumar B. Cardiac output monitoring: Technology and choice. Ann Card Anaesth. 2019 Jan-Mar;22(1):6-17. doi: 10.4103/aca.ACA_41_18.

 

Lawson, T., Hutton, A. (2010) Cardiac Output Monitoring - Update in Anaesthesia. World Federation of Societies of Anaesthesiologists. https://resources.wfsahq.org/wp-content/uploads/uia28-Cardiac-output-monitoring.pdf



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