Quantitative assessment of brain microvascular and tissue oxygenation during cardiac arrest and resuscitation in pigs

Abstract

Summary Cardiac arrest is associated with a very high rate of mortality, in part due to inadequate tissue perfusion during attempts at resuscitation. Parameters such as mean arterial pressure and end‐tidal carbon dioxide may not accurately reflect adequacy of tissue perfusion during cardiac resuscitation. We hypothesised that quantitative measurements of tissue oxygen tension would more accurately reflect adequacy of tissue perfusion during experimental cardiac arrest. Using oxygen‐dependent quenching of phosphorescence, we made measurements of oxygen in the microcirculation and in the interstitial space of the brain and muscle in a porcine model of ventricular fibrillation and cardiopulmonary resuscitation. Measurements were performed at baseline, during untreated ventricular fibrillation, during resuscitation and after return of spontaneous circulation. After achieving stable baseline brain tissue oxygen tension, as measured using an Oxyphor G4‐based phosphorescent microsensor, ventricular fibrillation resulted in an immediate reduction in all measured parameters. During cardiopulmonary resuscitation, brain oxygen tension remained unchanged. After the return of spontaneous circulation, all measured parameters including brain oxygen tension recovered to baseline levels. Muscle tissue oxygen tension followed a similar trend as the brain, but with slower response times. We conclude that measurements of brain tissue oxygen tension, which more accurately reflect adequacy of tissue perfusion during cardiac arrest and resuscitation, may contribute to the development of new strategies to optimise perfusion during cardiac resuscitation and improve patient outcomes after cardiac arrest.

Functional and anatomical evidence of cerebral tissue hypoxia in young sickle cell anemia mice

“…The brain O 2 tension was measured at 10-13 weeks of age in 7 sickle cell mice and 10 control mice using Oxyphor G4 phosphorescence as described previously, 13,32 utilizing a novel oxygen microsensor. 33 Briefly, mice were anesthetized using isoflurane (3% induction and 2% maintenance) and temperature was maintained at 37 C using a heating pad and monitored using a rectal probe. A small hole (1-2 mm in diameter) was made in the skull and a microsensor filled with the oxyphor and connected to a fiber optic thread was threaded through a 20-gauge needle and inserted into the brain.…”

Sanguinate's effect on pial arterioles in healthy rats and cerebral oxygen tension after controlled cortical impact

“…Details of the phosphorescence quenching dependent oxygen measurement equations and technique have been described previously (Wilson et al, 2006). The PQM technique has been used to measure tissue oxygen tension utilizing diffusion of the water soluble molecular probe Oxyphor R2 into spino-trapezius muscle (Song et al, 2013) and brain (Yu et al, 2013). In the current study, a different water soluble molecular probe, Oxyphor G4 (PdG4 molecular probe, Oxygen Enterprises Ltd., Philadelphia, PA) (Esipova et al, 2011), was utilized to measure PbtO 2 as described elsewhere (Mullah et al, 2016).…”

Water-soluble cyclometalated platinum(ii) and iridium(iii) complexes: synthesis, tuning of the photophysical properties, and in vitro and in vivo phosphorescence lifetime imaging

“…The oxygenation mapping with phosphorescent probes has found diverse utilization in various medical research such as oncology (see above), determination of local O 2 concentration in bone marrow, 22 retina, 29 and live brain, 30,31 tomographic oxygen mapping at the macroscopic level 32 as well as monitoring of in situ oxygenation of respiring cells and their responses to metabolic stimulation. 33 However, for successful application of the probes, in particular, in in vivo experiments, it is highly desirable to use the compounds having specic properties, such as (i) solubility and stability in aqueous media accompanied with internalization into living cells, (ii) emission and excitation shied as close as possible to the "window of transparency" of biological tissues (650-900 nm), 34,35 and (iii) appreciable response of emission parameters to the changes in oxygen concentration.…”