Methods for assessing hepatic distending pressure and changes in hepatic capacitance in pigs

Area of Science:

• Physiology
• Hepatology
• Hemodynamics

Background:

• Hepatic vascular distending pressure (P(hd)) is crucial for understanding liver hemodynamics.
• Accurate measurement of P(hd) is essential for assessing liver function and disease.
• Existing methods for measuring hepatic pressure and compliance can be time-consuming.

Purpose of the Study:

• To validate hepatic lobar vein pressure (P(hlv)) as a measure of hepatic vascular distending pressure (P(hd)).
• To compare dynamic pressure-volume (PV) curves with static PV curves for assessing hepatic vascular compliance and unstressed blood volume.
• To evaluate the effects of norepinephrine (NE) on hepatic pressures and blood volume.

Main Methods:

• Simultaneous occlusion of hepatic vascular inflow and outflow to determine P(hd).
• Measurement of hepatic lobar vein pressure (P(hlv)) using a micromanometer-tipped catheter.
• Construction of dynamic PV curves using sonomicrometry during brief vascular occlusions.
• Comparison of dynamic and static PV curves to estimate hepatic compliance and unstressed blood volume.

Main Results:

• P(hlv) closely resembled P(hd) at baseline and during norepinephrine infusion.
• Dynamic and static PV curve methods yielded comparable estimates for hepatic vascular compliance and unstressed blood volume.
• Norepinephrine infusion increased P(hd) and portal vein pressure (P(pv)) but not P(hlv) or P(hv).
• Norepinephrine infusion reduced unstressed blood volume but did not alter hepatic compliance.

Conclusions:

• Hepatic lobar vein pressure (P(hlv)) is a reliable indicator of hepatic vascular distending pressure (P(hd)).
• Dynamic pressure-volume (PV) curve analysis provides a fast and valid method for assessing hepatic compliance and unstressed blood volume.
• Norepinephrine influences hepatic vascular tone and blood volume distribution.