Effects of perfluorochemical evaporative properties on oxygenation during partial liquid ventilation

Platelet and White Cell Reactivity to Top-Load Intravenous Perfluorocarbon Infusion in Healthy Sheep

BACKGROUND

Perfluorocarbon emulsions (PFCs) are intravenous artificial oxygen carriers with enhanced gas solubility. As lipid micelle nanoparticle emulsions, PFCs may have a class effect that causes degrees of thrombocytopenia. Understanding the extent of the platelet effects, including mechanism and potential inflammation after PFC infusion, is important for safe human trials.

METHODS

Normal sheep (Dorper) were infused with 5 mL/kg of Oxygent (w/v 60% PFC) or Perftoran (w/v 20% PFC). Controls received 6% Hetastarch or were naive. Blood samples were analyzed from baseline, time 0 (the end of infusion), 3 and 24 hours, and 4 and 7 days. Platelet count, plateletcrit, mean platelet volume, platelet distribution width, and CD-62p (a platelet activation-dependent membrane protein) were measured. Neutrophils, monocytes, and total white blood cell counts were analyzed.

RESULTS

In these inflammatory cell lines, there were no consistent changes or cellular activation after PFC infusion. A decrease (<10% from baseline and naive controls) in platelet count was seen on day 4 after Oxygent infusion (3 g/kg), which recovered by day 7. No platelet effect was seen in Perftoran (1 g/kg). Plateletcrit, mean platelet volume, and platelet distribution width did not change significantly at any time point among the groups. CD-62p, ADP, and collagen aggregometry showed no significant change in platelet function.

CONCLUSION

There was no evidence of overall reduction in platelet number, or any correlation with the change in platelet activation or inhibition. Therefore, the risk of increased thrombosis/bleeding after PFC intravenous infusion is low in this non-trauma sheep model.

Animal models of smoke inhalation injury and related acute and chronic lung diseases

Smoke inhalation injury leads to various acute and chronic lung diseases and thus is the dominant cause of fire-related fatalities. In a search for an effective treatment and validation of therapies different classes of animal models have been developed, which include both small and large animals. These models have advanced our understanding of the mechanism of smoke inhalation injury, enabling a better understanding of pathogenesis and pathophysiology and development of new therapies. However, none of the animal models fully mirrors human lungs and their pathologies. All animal models have their limitations in replicating complex clinical conditions associated with smoke inhalation injury in humans. Therefore, for a correct interpretation of the results and to avoid bias, a precise understanding of similarities and differences of lungs between different animal species and humans is critical. We have reviewed and presented comprehensive comparison of different animal models and their clinical relevance. We presented an overview of methods utilized to induce smoke inhalation injuries, airway micro-/macrostructure, advantages and disadvantages of the most commonly used small and large animal models.

Oxygenated Static Preservation of Donation after Cardiac Death Liver Grafts Improves Hepatocyte Viability and Function

BACKGROUND

Cell therapy, such as hepatocyte transplantation (HTx), is promising for the treatment of metabolic liver diseases or as a bridge to orthotopic liver transplantation in patients with fulminant liver failure. However, one of the limitations of this therapy is the shortage of donors. The present study aims to investigate whether the two-layer method (TLM) of cold preservation with oxygenation improves the viability and activity of hepatocytes from rat donation after cardiac death (DCD) donors compared with results obtained with the University of Wisconsin (UW) solution. Moreover, we evaluated the hepatocyte function after culture or transplantation into the spleen.

MATERIALS AND METHODS

We used male Sprague-Dawley rats for this study. The DCD model was induced by phrenotomy after injecting heparin. We assigned rats based on warm ischemia times of 15 and 30 min to groups S and L, respectively. Each group (n = 5) was then subdivided as follows: (1) group S: not preserved (S/N), preserved by TLM for 3 h (S/TLM3) and 12 h (S/TLM12), and in the UW solution for 3 h (S/UW3) and 12 h (S/UW12), and (2) group L: not preserved (L/N), preserved by TLM for 3 h (L/TLM3) and 12 h (L/TLM12), and in the UW solution for 3 h (L/UW3) and 12 h (L/UW12). The cell viability and function of isolated DCD hepatocytes were analyzed for culture or HTx into the spleen.

RESULTS

The viability and ATP levels of DCD hepatocytes significantly improved after TLM compared with the values after preservation in cold UW solution in group S/N (p < 0.059). The levels of albumin production and urea synthesis by hepatocytes after culture were significantly higher in groups S/TLM3 and S/TLM12 than in groups S/UW3 and S/UW12 (p < 0.05), respectively. Further, serum albumin levels after HTx were also markedly higher in groups S/TLM3 and S/TLM12 than in groups S/UW3 and S/UW12. The morphological features revealed that cultured and transplanted hepatocytes remained clearly viable and maintained an expression for specific hepatic function, such as the production of albumin and glycogen.

CONCLUSION

This novel method of oxygenated cold preservation of DCD livers can expand the hepatocyte donor pool for HTx and establish a wider application of this developing technique.

Evaluation of lung recovery after static administration of three different perfluorocarbons in pigs

BACKGROUND

The respiratory properties of perfluorocarbons (PFC) have been widely studied for liquid ventilation in humans and animals. Several PFC were tested but their tolerance may depend on the species. Here, the effects of a single administration of liquid PFC into pig lungs were assessed and compared. Three different PFC having distinct evaporative and spreading coefficient properties were evaluated (Perfluorooctyl bromide [PFOB], perfluorodecalin [PFD] and perfluoro-N-octane [PFOC]).

METHODS

Pigs were anesthetized and submitted to mechanical ventilation. They randomly received an intra-tracheal administration of 15 ml/kg of either PFOB, PFD or PFOC with 12 h of mechanical ventilation before awakening and weaning from ventilation. A Control group was submitted to mechanical ventilation with no PFC administration. All animals were followed during 4 days after the initial PFC administration to investigate gas exchanges and clinical recovery. They were ultimately euthanized for histological analyses and assessment of PFC residual concentrations within the lungs using dual nuclei fluorine and hydrogen Magnetic Resonance Imaging (MRI). Sixteen animals were included (4/group).

RESULTS

In the PFD group, animals tended to be hypoxemic after awakening. In PFOB and PFOC groups, blood gases were not significantly different from the Control group after awakening. The poor tolerance of PFD was likely related to a large amount of residual PFC, as observed using MRI in all lung samples (≈10% of lung volume). This percentage was lower in the PFOB group (≈1%) but remained significantly greater than in the Control group. In the PFOC group, the percentage of residual PFC was not significantly different from that of the Control group (≈0.1%). Histologically, the most striking feature was an alveolar infiltration with foam macrophages, especially in the groups treated by PFD or PFOB.

CONCLUSIONS

Of the three tested perfluorocarbons, PFOC offered the best tolerance in terms of lung function, gas exchanges and residuum in the lung. PFOC was rapidly cleared from the lungs and virtually disappeared after 4 days whereas PFOB persisted at significant levels and led to foam macrophage infiltration. PFOC could be relevant for short term total liquid ventilation with a rapid weaning.

Efficacy of intratracheal instillation of a meropenem/perfluorochemical suspension in acute lung injury

Perfluorochemical (PFC) is theoretically a good vehicle for delivering biological agents to the lungs. This study was designed to investigate the efficacy of intratracheal (IT) instillation of meropenem using PFC liquid as a vehicle in a piglet model of acute lung injury (ALI). Eighteen piglets were injured with lung lavages to induce ALI, and randomly assigned to intravenous (IV) infusion or IT instillation groups, the latter using either PFC or normal saline (NS) as a delivery vehicle for meropenem. Blood samples were obtained at 0, 15, 30, and 60 min, and then hourly for 6 hr. Sera and extracts of lung tissues were assayed for meropenem content using high-performance liquid chromatography. We found that the IV group had significantly higher serum concentrations of meropenem during the first hour after dosing (P < 0.05). There was no significant difference between IT-PFC and IT-NS groups regarding changes in serum meropenem concentrations during the experimental period. Meropenem content in lung tissue was highest in the IT-PFC group, lower in the IT-NS group, and undetectable in the IV group (P < 0.05). The IT-NS group had the highest peak inspiratory pressure (P < 0.05), but there were no significant differences in other cardiopulmonary parameters among the three groups studied. In conclusion, meropenem can be safely administered to injured lungs by IT instillation in a meropenem/PFC suspension. Using PFC liquid as an IT vehicle to carry meropenem provides better pulmonary drug depositions than IV injection or IT instillation with NS in ALI.

Perfluorocarbon emulsions as a promising technology: a review of tissue and vascular gas dynamics

Perfluorocarbon (PFC) emulsions are halogen-substituted carbon nonpolar oils with resultant enhanced dissolved respiratory gas (O(2), N(2), CO(2), nitric oxide) capabilities. In the first demonstration of enhanced O(2) solubility, inhaled PFC could sustain rat metabolism. Intravenous emulsions were then trialed as "blood substitutes." In the last 10 yr, biocomputational modeling has enhanced our mechanistic understanding of PFCs. Contemporary research is now taking advantage of these physiological discoveries and applying PFCs as "oxygen therapeutics," as well as ways to enhance other gas movements. One particularly promising area of research is the treatment of gas embolism (arterial and venous emboli/decompression sickness). An expansive understanding of PFC-enhanced diffusive gas movements through tissue and vasculature may have analogous applications for O(2) or other respiratory gases and should provide a revolution in medicine. This review will stress the fundamental knowledge we now have regarding how respiratory gas movements are changed when intravenous PFC is present.

High vapor pressure perfluorocarbons cause vesicle fusion and changes in membrane packing

Perfluorocarbons (PFCs) hold great promise for biomedical applications. However, relatively little is known about the impact of these chemicals on membranes. We used unilamellar vesicles to explore the effects of PFCs on membrane packing and vesicle stability. Four clinically relevant PFCs with varying vapor pressures (PP1, 294 mbar; PP2, 141 mbar; PP4, 9.6 mbar; and PP9, 2.9 mbar) were examined. Microscopy imaging and spectroscopic measurements suggest that PFCs, especially those with high vapor pressures, lead to vesicle fusion within hours. Upon exposure to PP1 and PP2 for 72 h, vesicles retained a spherical shape, but the size changed from approximately 200 nm to approximately 20-40 mum. In addition, membrane packing underwent marked changes during this timeframe. A significant decrease in water content in the lipid polar headgroup regions occurred during the first 1-2-h exposure to PFCs, followed by a steady increase in water content over time. Possible mechanisms were proposed to explain these dramatic structural changes. The finding that chemically inert PFCs exhibited fusogenic activity and marked changes in membrane surface packing is novel, and should be considered when using PFCs for biomedical applications.