Tissue oxygenation and microvascular hemodynamics in experimental arterial gas embolism

Microvascular hemodynamic responses to arterial gas embolism (AGE) and local oxygen tensions (PO2) have never been evaluated in vivo using intravital microscopy. A system was implemented to study AGE in real time using brightfield and phosphorescence microscopy as well as laser-induced microvessel occlusion. Bubble dynamics, microhemodynamics and oxygenation were studied following AGE in 61 microvessels and 41 interstitial spaces from 19 anesthetized rats. AGE was induced by direct air injection into the femoral artery ipsilateral to the studied cremaster muscle. Bubble-induced vaso-occlusion was investigated, and microvascular blood flow redistribution were associated with changes in intravascular and interstitial PO2. Microvascular blood flow as well as intravascular and tissue PO2 decreased after microvascular occlusion following microembolism. However, certain areas did not become fully hypoxic since redistribution of blood allowed oxygen to be supplied by nearby microvessels with blood (or plasma) flow or tissue gas diffusion. A linear correlation between interstitial and intravascular PO2 was found during baseline and after AGE. Because some microvessels remain flowing even after AGE, our observations suggest that intravascular therapeutic agents administered during severe AGE may reach microvascular networks and provide additional oxygenation to tissue areas where blood flow is compromised due to occlusion of some microvessels.