8 Integrated Hemodynamics Practice Questions Free Online FlashCards

How is cardiac output calculated?

Cardiac output is heart rate multiplied by stroke volume: $\mathrm{CO}=\mathrm{HR}\times\mathrm{SV}$. Convert the result to liters per minute when needed.

How is cardiac index calculated, and what does it adjust for?

Cardiac index is cardiac output divided by body surface area: $\mathrm{CI}=\frac{\mathrm{CO}}{\mathrm{BSA}}$. It adjusts output for body size.

How do you calculate pulse pressure?

Pulse pressure is systolic blood pressure minus diastolic blood pressure: $\mathrm{PP}=\mathrm{SBP}-\mathrm{DBP}$.

What is a common estimate for mean arterial pressure?

A common estimate is $\mathrm{MAP}\approx\mathrm{DBP}+\frac{1}{3}(\mathrm{PP})$. It is an approximation, especially with a high heart rate or irregular rhythm.

A blood pressure is $86/50\,\mathrm{mm\,Hg}$, with worsening alertness and cool extremities. What is concerning?

The estimated $\mathrm{MAP}$ is $62\,\mathrm{mm\,Hg}$. With worsening alertness and cool extremities, this is concerning for inadequate perfusion and warrants prompt reassessment and escalation.

How is systemic vascular resistance estimated?

Systemic vascular resistance is estimated as $\mathrm{SVR}\approx80\times\frac{\mathrm{MAP}-\mathrm{CVP}}{\mathrm{CO}}$, using pressures in $\mathrm{mm\,Hg}$ and cardiac output in $\mathrm{L/min}$.

What pattern does $\mathrm{MAP}=58$, $\mathrm{CVP}=8$, and $\mathrm{CO}=7.2$ suggest?

The estimate is about $556\,\mathrm{dyn\cdot s/cm^5}$, a low-resistance pattern despite the relatively high output. Marked vasodilation is one possible explanation for hypotension.

What does preload describe?

Preload describes ventricular filling and myocardial stretch before contraction.

What is afterload?

Afterload is the load the ventricle must overcome to eject blood.

Does a low CVP alone establish that a patient will respond to more fluid?

No. CVP is a static filling-pressure measurement; by itself, it is a poor guide to fluid responsiveness and does not prove that output will rise with fluid.

How can a passive leg raise help assess fluid responsiveness?

When appropriate, measure stroke volume or cardiac output during a passive leg raise. An increase in flow with this reversible change in venous return can help assess fluid responsiveness.

How can intense systemic vasoconstriction reduce cardiac output?

Increased afterload raises the load the ventricle must overcome to eject. This can lower stroke volume and, consequently, cardiac output.