Load a patient

CVP stands in here for how full the ventricle is. At the bedside, CVP predicts fluid response poorly: use dynamic tests such as a passive leg raise. Indexed values assume an adult with a body surface area of 1.9 m².

Stroke volume—mL / beat
Cardiac output—L / min
Mean arterial pressure—mmHg
Stroke index—mL / m²
Cardiac index—L / min / m²
SVR—dyn·s·cm⁻⁵

Response to a little more filling (in this model):

Try this

Five experiments worth five minutes

1. Fill the septic patient

Load Septic shock, then raise filling by a few points. Pressure improves, but only by driving cardiac output far above normal, because resistance is still very low.

2. Then tighten the vessels

Still in septic shock, raise SVR towards 900. Pressure recovers. That is what a vasopressor is for, and in real septic shock it is often started early, alongside fluid.

3. Over-fill the failing heart

Load Cardiogenic shock and raise filling. The curve is flat: more fluid adds almost nothing.

4. Unload the high-pressure failing heart

Load Heart failure and lower SVR towards 1300. Stroke volume almost doubles while pressure holds: a weak heart gains more from less afterload than a healthy one. This only works when blood pressure allows it. In cardiogenic shock with a low MAP, vasodilators are not the answer.

5. Too fast to fill

In the healthy adult, push heart rate up. Output gains less and less, then levels off and falls: the ventricle runs out of filling time.

What the model leaves out

Real patients have valves, rhythms, lungs and reflexes. Here SVR and heart rate stay where you put them, so resuscitating the hypovolemic patient overshoots into high pressure; in a real patient, compensation unwinds as flow returns. Learn directions here, then confirm with the real monitor.