Question

1-Show the Two equations for determining stroke volume. Spell it out

2- What is the equation for the relationship between Total Peripheral Resistance (or SVR) affects mean arterial pressure?

3- What are the 4 ways the sympathetic nervous system increases blood pressure?

4- Define “hematocrit”.

5- A woman with a hematocrit of 40 and 5 L of blood loses 1 L of blood when shot.   The EMT stops the bleed & pumps 1 L of plasma into him to return her to original blood volume. What is her new hematocrit?

Answer 1

Ans 1:

Equations for determining stroke volume are:

(i) Stroke Volume (SV) = Cardiac Output (CO) / Heart Rate (HR)

(ii) Stroke Volume (SV) = End Diastolic Volume (EDV) - End Systolic Volume (ESV)

Ans 2:

Equation for relationship between Total Peripheral Resistance (TPR) or Systemic Vascular Resistance (SVR) affecting the Mean Arterial Pressure (MAP) is:

Mean Arterial Pressure (MAP) = [Cardiac Output (CO) x Systemic Vascular Resistance (SVR)] + Central Venous Pressure (CVP)

Ans 3:

Sympathetic nervous system increases blood pressure by the following ways:

(i) By increasing the cardiac output via increasing the rate of conduction of heart.

(ii) By increasing the heart rate (HR) via release of catecholamines - epinephrine and norepinephrine.

(iii) By increasing Endothelin-I derived vasoconstrictor tone leading to essential hypertension.

(iv) By increasing total peripheral resistance (TPR) by constricting the blood vessels.

Ans 4:

Hematocrit (Hct) is one of the hematological parameter, also known as packed cell volume (PCV). It is the ratio of the volume occupied by red blood cells to the total volume of blood after centrifugation. Its normal range in percent or fraction of 1 is: 42% - 52% or 0.42 -0.52 for men and 37% - 47% or 0.37 - 0.47 for women. Low Hct indicates anemia, blood loss or overhydration; while low Hct indicates polycythemia or dehydration.