Microvascular permeability after cardiopulmonary bypass. An experimental study

Area of Science:

• Physiology
• Vascular Biology
• Surgical Research

Background:

• Microvascular permeability is often presumed to increase during cardiopulmonary bypass (CPB).
• However, direct experimental evidence demonstrating this increase has been lacking.
• Understanding changes in vascular function during CPB is crucial for patient outcomes.

Purpose of the Study:

• To directly investigate and quantify the effect of CPB on microvascular permeability.
• To determine if CPB alters the intestinal microvascular barrier function.
• To assess the impact of CPB on the passage of different sized molecules across the microvasculature.

Main Methods:

• A controlled experimental study was conducted using dogs.
• The small intestinal microvasculature permeability ratio was determined after 120 minutes of CPB or a sham procedure.
• Superior mesenteric venous pressure was incrementally increased to stabilize lymph/plasma protein concentration.

Main Results:

• The permeability ratio for total proteins and five of six protein fractions was significantly higher in dogs that underwent CPB compared to controls (p=0.01).
• A variable increase in permeability was observed, with some CPB animals showing more than double the control group's maximum permeability ratio.
• The increase in permeability was more pronounced for larger molecules, indicating altered pore size.

Conclusions:

• Cardiopulmonary bypass leads to a variable increase in microvascular permeability.
• This increase is primarily attributed to an enlargement of pores within the microvascular barrier.
• The findings highlight a significant physiological consequence of CPB on vascular integrity.