This chapter is relevant to Section G7(iv) of the 2017 CICM Primary Syllabus, which asks the exam candidate to "describe the methods of measurement of cardiac output including calibration,
sources of errors and limitations".
There are three main variables to look at when one is using the PiCCO to guide the resuscitation of a shock state. It comes down to a simple question: do I give them more fluids, or do I crank up the noradrenaline infusion?
The three cardinal variables:
Cardiac Index (CI)
Intrathoracic blood volume index (ITBVI)
Extravascular lung water index (EVLWI)
Look at the cardiac index.
Is it high or low?
Low cardiac index: what is the ITBVI?
If there is not enough intrathoracic blood volume, you need to fill your patient.
Ask of your PiCCO: is there already too much EVLW? Can I give more fluids safely without flooding the patients lungs?
If there is enough ITBVI, you cant really expect a fluid bolus to improve cardiac output. You need inotropes.
High or normal cardiac index: what is the ITBVI?
If your patient is shocked with a high cardiac index, this looks more like a septic vasodilated picture.
Still, one ought to try filling them up before going to vasopressors.
If the ITBVI is low, give fluids.
If the ITBVI is high, start vasopressors – you patient is well filled.
If the ITBVI is low and the EVLWI is high, you have overdone it with the fluids.