DOES MY PATIENT NEED

FLUID?

Value of mean systemic filling

pressure

Antoine Vieillard-Baron, Boulogne, France

Disclosures

• Baxter

• GSK

I

Physiology

Am J Physiol 1957

SVR = MSFP – RAP/RVR

Am J Physiol 1954

Dogs

Ventricular fibrillation

MSFP is defined as the pressure generated by the elastic

recoil in the overall systemic circulation during a no-flow state

MSFP (the forward pressure)

Guyton, Am J Physiol 1957

2 determinants

- Vasomotor tone (the “container”)

- Blood volume (the “contents”)

THE “STRESSED”

VOLUME

Epinephrine Fluid expansion

Clinical death and the measurement of stressed vascular volume.Magder S

Critical Care Medicine 1998

The average stressed volume was 1290 +/- 296

mL or 20.2 +/- 1.0 mL/kg. If one assumes a

normal blood volume of 65 mL/kg for women

and 69 mL/kg for men, this estimate gives an

average of 30 +/- 17% of the total predicted

blood volume.

7 surgical patients requiring cardiopulmonary bypass

“Bathtub” model

RAP (the backward pressure)

Am J Physiol 2017

Fessler HE Am Rev Respir Dis 1991

Nanas and Magder 1992

RESISTANCE TO VR

Am J Physiol 2016

Intensive Care Med 2004

II

Limitations in the ICU

(i)

Accurate measurement of MSFP

in heart-beating patients

Crit Care Med 2012

3 assumptions

• 1- Resistance to VR is constant during

mechanical ventilation

• 2- CO and SVR are similar, which means

that cardiac function does not change during

mechanical ventilation

J Appl Physiol 1999

3 assumptions

• 1- Resistance to VR is constant during

mechanical ventilation

• 2- CO and SVR are similar, which means

that cardiac function does not change during

mechanical ventilation

• 3- MSFP is not sensitive to change in intra-

thoracic pressure

Berger, Takala, Am J Physiol 2016

Jellinek H, JAP 2000

J Appl Physiol 2017

(ii)

Application of the concept in

critically-ill patients

Am J Physiol 2015

202 patients

MSFP 12.8 ± 5.6 mmHg

III

Published studies in fluid

“guiding”

Guérin, Crit Care 2015

Conclusion

• Too many limitations for using MSFP and the

driving pressure for venous return in clinical

practice

• Probably more suitable to train residents and

fellows to cardiopulmonary physiology which is

key for well-manage fluids requirement

• Look at the SVC to have an evaluation of the

resistance to venous return which is probably the

most important parameter with CVP