Fick Principle & IOP

Question 1

True or false:

The Fick principle states that the amount of substance given off or taken up by an organ in a unit of time is equal to the product of blood flow through the organ, and the concentration difference of the substance across the organ

Answer 1

True. This is simply another way of expressing the principle that during any time interval, the quantity of a substance entering a compartment in the inflowing blood must equal the sum of the accumulation in the compartment, and the quantity leaving in the efferent blood.

Question 2

True or false:

The Fick principle allows us to determine cardiac output non-invasively

Answer 2

False. Whichever method we choose to employ, some invasive monitoring or sampling will be required.

Question 3

True or false:

Renal artery and renal vein sampling will be required to estimate creatinine clearance

Answer 3

False. We can determine the minute excretion of creatinine (M) by urinary collection over a timed period. If we measure plasma creatinine we can then determine creatinine clearance using the formula:

Creatinine Clearance = M / Plasma Creatinine

Question 4

True or false:

Using a dye dilution technique, cardiac output can be determined by dividing the area under the curve of a plasma dye concentration plot by the mass of dye injected

Answer 4

False. Area under curve (AUC) x Q = M

or

Q = M / AUC