Fluorocarbon Solution Research Articles

Fluorocarbons: A Potential Treatment of Cerebral Air Embolism in Open-Heart Surgery

This study was designed to assess whether an oxygenated fluorocarbon solution could reduce ischemic brain damage related to arterial air embolism. Air embolism was produced by injecting air bubbles into the carotid artery of barbiturate-anesthetized rats breathing 100% oxygen. Results were assessed on electrocorticogram. In an additional set of experiments, mass spectrometry was used to provide continuous monitoring of intracerebral tissue oxygen (P o 2) and carbon dioxide (P co 2) tensions and intermittent measurement of cerebral blood flow (CBF). Fluorocarbon or saline solution (containing the emulsifying agent of fluorocarbons) was given intravenously after the initial air embolism (0.2 ml), and injections of air (0.1 ml) were repeated thereafter every five minutes. The maximal amount of air required to achieve complete and irreversible flattening of the electrocorticogram was 1.60 ± 0.06 ml (mean ± standard error of the mean) in the saline-treated rats and 5.20 ± 0.44 ml in the fluorocarbon-treated group ( p < 10 -7). In the second experiment, air embolism caused CBF to rise in both groups, the average percent of increase being higher in treated (41.6%) than in control animals (38.3%) ( p < 0.02). However, in the control group, the increase in CBF did not prevent intracerebral tissue P o 2 from decreasing by 7.4 ± 7.0% over the same period; conversely, in the fluorocarbon group, P o 2 levels fell by only 2.5 ± 3.7% ( p < 0.001 versus controls), but this time-averaged percentage was calculated over a longer period of cumulative ischemia because of the greater number of air emboli tolerated by treated animals. We conclude that fluorocarbons seem to be effective in extending the tolerance of the brain to ischemic damage secondary to air embolism. Their protective mechanism most likely involves increased availability of oxygen for ischemic tissues and possibly indirect reduction of the size of air bubbles through enhanced denitrogenation of blood.

Enhanced cardioplegic protection by a fluorocarbon-oxygenated reperfusate: A phosphorus-31 nuclear magnetic resonance study

Prolonged global ischemia results in a defect in oxygen extraction during early reperfusion. This study was thus undertaken to assess the effects of maintaining cardioplegia at the onset of reoxygenation in view of channeling available energy toward reparative cell processes rather than mechanical activity. Twenty-four isolated perfused rat hearts were subjected to 120 min of 15°C ischemia. Group I (control) was reperfused with the standard Krebs perfusion medium whereas in groups II and III the initial reperfusate consisted of an oxygenated alkaline cardioplegic solution prior to the resumption of Krebs perfusion. Oxygenation of the cardioplegic reperfusate was ensured by Fluorocarbons at a concentration of 10% (O 2 content: 5.5 vol %; group II) or 20% (O 2 content: 9 vol %; group III). In addition to hemodynamical determinations, high-energy phosphates and intracellular pH were monitored serially by phosphorus-31 nuclear magnetic resonance spectroscopy. After 30 min of reperfusion postischemic recovery of aortic flow was better in group II (74.0 ± 5.9% of control) than in group I (59.1 ± 5.4% of control, P < 0.05). This functional improvement correlated with a higher postischemic increase in phosphocreatine levels (103.21 ± 11.21% vs 74.12 ± 3.59%, at 3 min of reperfusion, P < 0.05) without significant differences in total ATP content. Group III hearts exhibited a slow recovery as evidenced by a severe depression in aortic flow, coronary arteriovenous difference, and total phosphate content during the 15 initial minutes of reperfusion. These results show that the protection provided by cardioplegia can be improved by a fluorocarbon-oxygenated cardioplegic reperfusate. The observation that the 10% fluorocarbon solution yielded a better recovery than the 20% solution tends to support the concept of an optimal amount of oxygen to be delivered during the early postischemic period to help minimizing reperfusion injury.

Retinal vascular occlusion: possibilities of a direct oxygen supply to the hypoxic areas

Treatment of a retinal vascular occlusion consists in restoration of normal oxygenation to the affected area. An experimentally induced increase in arterial CO2 provokes an increase in preretinal CO2 in a hypoxic retinal area which has developed after venous obstruction, but it is ineffective in anoxic areas of an arterial occlusion. However, clinical application of this treatment offers no benefit for the patient. Hyperoxia caused by respiration of a gas mixture of 5% CO2 and 95% O2 is also ineffective. On the other hand, the results of recent studies in which blood is replaced with fluorocarbon solutions are promising. Finally, it is pointed out that in cases of venous occlusion laser coagulation leads to reoxygenation of the inner hypoxic retina.

Direct spectroscopic observation of 1.27 μm and 1.58 μm emission of singlet ( 1Δ g) molecular oxygen in chemically generated and dye-photosensitized liquid solutions at room temperature

Direct spectroscopic observation of (0,0) at 1.27 μm and (0, 1) at 1.58 μm of 1Δ g→ 3Σ g − transitions of molecular oxygen in H 2O 2-OCl − chemiluminescence reaction and in dye-sensitized fluorocarbon solutions at room temperature is reported. Observation of these weak and ultraweak emissions was accomplished by developing an extremely sensitive near IR spectrophotometer using a thermoelectrically cooled PbS detector, optimized optics, and a boxcar integrator, as a data processor.

Isolated cardiac muscle performance during fluorocarbon immersion and effects of metabolic blockade.

SummaryThe mechanical performance of isolated trabecular muscle preparations from the left ventricle of rats was evaluated while immersed in Krebs-Henseleit and fluorocar-bon solution under oxygenated conditions and during hypoxia and total metabolic blockade with combined hypoxia and iodoa-cetic acid 10-4M. Under oxygenated conditions, mechanical performance was relatively stable in both Krebs-Henseleit and fluorocar-bon solutions for 60 minutes. With glycolytic blockade, performance in both groups was relatively stable, although it was significantly increased in fluorocarbon solution in comparison to Krebs-Henseleit solution at 60 min (P < 0.01). With total metabolic blockade, mechanical performance fell to zero within 10 min in both Krebs-Henseleit and fluorocarbon solution. With hypoxia alone, mechanical performance declined more promptly and remained at lower levels in fluorocarbon solution than in Krebs-Henseleit solution (P < 0.001).

Dynamic Nuclear Polarization: Collision Mechanics in Fluorocarbon Solutions

Dynamic polarization measurements at three widely different magnetic field strengths are presented for an array of chemically different free radicals and fluorocarbons. Observed fluorine NMR signal enhancements ranged from − 225 to + 430. The scalar hyperfine correlation time, which is shown to be the major factor governing the enhancement, is systematically longer for systems showing higher positive enhancement at low field. A generalized pulse-transform collision model is applicable to all cases, and it is found that the slope of the scalar spectral cutoff becomes progressively less steep as low-field scalar coupling increases. In extreme cases, the spectrum may be interpreted as a superposition of at least two component spectra, each corresponding to a pulse from a stereospecific collision attitude. The observed behavior is consistent with molecular orbital calculations. The range of computed hyperfine coupling energies is also in good qualitative agreement with observed differences between fluorocarbons of diverse structure and chemical nature. Over all, the results demonstrate the usefulness of measurements of this sort for understanding the microscopic character of molecular collisions.

Dynamic Nuclear Polarization Experiments on 19F in Solutions and their Interpretation by the “Pulse Model” of Molecular Collisions

The dynamic fluorine polarization by the Overhauser effect has been studied at four different magnetic field values and at various temperatures in several fluorocarbon solutions. The importance of intermolecular contact couplings is very sensitively dependent on the chemical environment of the fluorine nuclei. The experimental data are interpreted in terms of the stochastic “pulse model” of molecular collisions derived in a preceding paper. The parameters of the model, such as the relative contribution of scalar couplings, the shape and the time scale of collision pulses and the correlation times of the molecular motion are given explicitly for six fluorocarbon solutions of free radicals.

The Anomalous Behavior of Fluorocarbon Solutions

Existing data on 64 fluorocarbon solutions (vapor pressures, solubilities, heats of mixing and volume changes) are summarized, and the free energies deduced are compared in a consistent way with the predictions of Hildebrand's solubility parameter theory. Many solutions, notably fluorocarbon-- hydrocarbon mixtures, show very much larger positive deviations from ideal behavior than can be accounted for by the difference of thermodynamic'' solubility parameters. However, other solutions (e.g., C7F16 with CCl4 and with I2) are entirely normal. Variou s explanations of this anomalous behavior are reviewed and criticized: (1) the interpenetration of hydrocarbon molecules, (2) an empirical shift in 6 for hydrocarbons, (3) volume changes, (4) corresponding states theories, (5) polarity of C-- F bonds, (6) differences in ionization potential, and (7) non-central force fields. Of these, only the last two appear promising and they do not account for the behavior of all of the anomalous systems. Additional experimental and theoretical studies are needed; some directions for future research are suggested.