Cardiac monitoring Flashcards
Define Cardiac Output? What is a normal value?
CO=SV x HR
SV norm about 60-75mls giving a normal CO of 5L
What is Cardiac Index? What is normal?
The correction of Cardiac output for body surface area
Norm is 2.5-4.2L/min/m2
What are the four determinants of Cardiac output?
Preload, contractility, afterload and heart rate
What two relationships involve the use of cardiac output?
BP = CO x SVR
And
Oxygen delivery (DO2) = CO x CaO2 (arterial oxygen content)
What is the Frank-Sterling Law?
The Frank-Starling law states that the greater the volume of blood entering the ventricle during diastole (end diastolic volume), the greater the volume of blood ejected during systolic contraction (stroke volume) and viceversa.
Describe the four main important reasons for sustaining an adequate cardiac output and how these can be measured?
hint - lung, heart, tissue, cell, SV
O2 Uptake from lungs -> O2 Delivery by the heart (Oxygen Delivary)-> O2 extraction by the tissues -> O2 utilization by the cells (Oxygen Consumption)
The effectiveness of O2 delivary and O2 consumption van be measured by Central Venous Oxygen Saturation (Scv02)
What is the difference between SCV02 and SV02?
Hint - IJ vs PA
Central venous oxygen saturation (ScvO2) is a useful surrogate for SvO2 and is measured in the superior vena cava through an ordinary central venous catheter. ScvO2 only measures venous blood returning from the upper half of the body, while SvO2 samples the true mixed venous blood leaving the right heart. Central (ScvO2) is normally slightly lower than mixed (SvO2)
Reported normal ranges for SvO2 vary from 60-80%; a normal SvO2 of 70% is frequently cited.
How can you measure the determinants of stroke volume and how can you optimise them?
Hint - P,A,C
Preload - measuring EDV andpresence of Pulmonary oedema. Enhance with volume
Afterload - Systemic Resistance measured by MAP. Enhance with Vasopressors.
Contractility - ECHO, enhanced by Inotropes
