Comparison of the effect of fluosol DA and dextran 40 on regional cerebral blood flow, infarction size, and mortality in cats with temporary occlusion of the middle cerebral artery

Administration of a second generation perfluorochemical in combination with hyperbaric oxygenation does not provide additional benefit in a model of permanent middle cerebral artery occlusion in rats

Objective

Both, second generation perfluorochemicals (Oxycyte®) and hyperbaric oxygen (HBO) have been shown to reduce necrotic tissue volume if administered early after experimental cerebral ischemia. With the idea of exponentiation of oxygen delivery to ischemic tissue, this study was conducted to investigate the combined effect of both treatment modalities on the extent of ischemic brain damage.

Methods

Permanent focal cerebral ischemia was induced in rats by middle cerebral artery occlusion (MCAO). Animals were assigned randomly to one of the following treatment groups: Control (0.9% NaCl, 1 ml/100 g i.v.), Oxycyte® (1 ml/100 g i.v.), HBO (1 bar hyperbaric oxygenation for 1 h) and HBO + Oxycyte® (1 ml/100 g i.v. combined with 1 bar hyperbaric oxygenation for 1 h). Injection of NaCl or Oxycyte® was performed following MCAO. After injection, breathing was changed to 100% oxygen in Oxycyte®-, HBO- and HBO + Oxycyte®-groups. After eight hours the necrotic volume was calculated from serial coronal sections stained with silver-nitrate and corrected for the extent of swelling.

Results

Hemodynamic and metabolic parameters were not affected by infusion of Oxycyte®. Total necrosis volume was significantly reduced in HBO-treated animals (223 ± 70 mm³), when compared to control animals (335 ± 36 mm³). In animals after Oxycyte®-treatment alone (299 ± 33 mm³) or combined HBO + Oxycyte®-treatment (364 ± 50 mm³) did not show a significantly smaller necrosis volume compared to control animals (necrosis volumes are given as mean ± SD).

Discussion

These results suggest that combination of hyperbaric oxygenation and Oxycyte® administered immediately after onset of vascular occlusion does not provide an additional neuroprotective effect in the early phase of brain ischemia.

Early administration of a second-generation perfluorochemical decreases ischemic brain damage in a model of permanent middle cerebral artery occlusion in the rat

OBJECTIVES

Perfluorochemicals (PFCs) may exert a neuroprotective function in the early phase of ischemia by improving the oxygen supply to the endangered tissue. We have, therefore, investigated the effect of Oxycyte, a second-generation perfluorocarbon solution, on the extent of early ischemic brain damage in a model of permanent focal cerebral ischemia.

METHODS

Eight hours of permanent focal cerebral ischemia was induced in isoflurane anesthetized male Sprague-Dawley rats by unilateral middle cerebral artery (MCA) thread occlusion under the control of laser Doppler flowmetry (LDF). Animals were assigned to one of the following treatment groups: nO2-NaCl and hO2-NaCl-NaCl (0.9%, 1 ml/100 g i.v.) and nO2-Oxycyte and hO2-Oxycyte-Oxycyte (1 ml/100 g i.v.). The injection of NaCl or Oxycyte was performed immediately after MCA occlusion. After injection, breathing was changed to pure oxygen in groups hO2-NaCl and hO2-Oxycyte while animals in groups nO2-NaCl and nO2-Oxycyte were allowed to breathe air. The necrotic volume was calculated from serial coronal sections stained with silver-nitrate. In addition, nitrotyrosine production was studied by immunohistochemistry.

RESULTS

Upon MCA occlusion, animals showed a reduction of cerebral blood flow of approximately 80% of the LDF signal in all groups. Hemodynamic and metabolic parameters were not affected by the infusion of Oxycyte. The total infarct volume was reduced in hO2-Oxycyte animals [group nO2-NaCl: 341+/-31 mm3 (mean+/-SD), group hO2-NaCl: 351+/-33 mm3, group nO2-Oxycyte: 354+/-24 mm3, and group hO2-Oxycyte: 300+/-29 mm3, p < 0.05 versus all other groups]. Moreover, hO2-Oxycyte animals showed lesser intensity of nitrotyrosine staining when compared with hO2-NaCl animals.

DISCUSSION

These results suggest that Oxycyte administered immediately after the onset of vascular occlusion may exert neuroprotective effects in the early phase of brain ischemia.

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.

Perfluorocarbon emulsions improve cognitive recovery after lateral fluid percussion brain injury in rats

OBJECTIVE

Perfluorocarbon emulsions have been shown to improve outcomes in stroke models. This study examined the effect of Oxycyte, a third-generation perfluorocarbon emulsion (04RD33; Synthetic Blood International, Inc., Costa Mesa, CA) treatment on cognitive recovery and mitochondrial oxygen consumption after a moderate lateral fluid percussion injury (LFPI).

METHODS

Adult male Sprague-Dawley rats (Harlan Bioproducts for Science, Indianapolis, IN) were allocated to 4 groups: 1) LFPI treated with a lower dose of Oxycyte (4.5 mL/kg); 2) LFPI with a higher dose of Oxycyte (9.0 mL/kg); 3) LFPI with saline infusion; and 4) sham animals treated with saline. Fifteen minutes after receiving moderate LFPI or sham surgery, animals were infused intravenously with Oxycyte or saline within 30 minutes while breathing 100% O2. Animals breathed 100% O2 continuously for a total of 4 hours after injury. At 11 to 15 days after LFPI, animals were assessed for cognitive deficits using the Morris water maze test. They were sacrificed at Day 15 after injury for histology to assess hippocampal neuronal cell loss. In a parallel study, mitochondrial oxygen consumption values were measured by the Cartesian diver microrespirometer method.

RESULTS

We found that injured animals treated with a lower or higher dose of Oxycyte had significant improvement in cognitive function when compared with injured saline-control animals (P < 0.05). Moreover, injured animals that received either dose of Oxycyte had significantly less neuronal cell loss in the hippocampal CA3 region compared with saline-treated animals (P < 0.05). Furthermore, a lower dose of Oxycyte significantly improved mitochondrial oxygen consumption levels (P < 0.05).

CONCLUSION

The current study demonstrates that Oxycyte can improve cognitive recovery and reduce CA3 neuronal cell loss after traumatic brain injury in rats.

The perfluorocarbon fluoromethyloadamantane offers cerebral protection in a model of isovolemic hemodilution in rabbits

BACKGROUND AND PURPOSE

Perfluorocarbons (PFCs) are considered promising cerebral protection agents because they could combine the beneficial effects of decreased blood viscosity with enhanced oxygen-carrying capacity and oxygen tissue delivery, but trials of PFCs as hemodilutants have been very limited. We evaluated fluoromethyloadamantane (FMA), a new perfluorocarbon compound, as an isovolemic hemodilutant and compared it with low-molecular-weight dextran 40 (D40) and a control group.

METHODS

Through a transorbital craniectomy, the internal carotid, anterior, and middle cerebral arteries were coagulated to create a cerebral infarction in anesthetized, mechanically ventilated rabbits. No other experimental procedure was performed in control animals. In the two other groups, hemodilution was commenced 30 minutes after the arterial occlusion with either D40 or FMA. Hemodynamic parameters and brain and systemic temperature were monitored throughout the experiments. All animals were killed 6 hours after the arterial occlusion.

RESULTS

Hemodynamic and metabolic parameters and blood oxygen content were not affected by the infusion of either FMA or D40. Brain and systemic temperature remained constant. The ratio of infarct volume to the hemispheric volume was 19.6 +/- 3.7% in the FMA group (n = 17), 19.9 +/- 4.6% in the D40 group (n = 16), and 40.3 +/- 5.7% in the control group (n = 17). The difference in infarct volume of both FMA and D40 animals compared with controls was statistically significant (P < .01) when tested with Student's t test. There was no significant difference between FMA and D40 groups.

CONCLUSIONS

These results suggest that FMA has cerebral protective properties and should be purified, optimized, and further tested experimentally to develop a stable, efficient, and safe oxygen carrier, potentially suitable for clinical trials.

"Brain attack": the rationale for treating stroke as a medical emergency

Stroke is the third leading cause of death in the United States, behind only heart disease and cancer. With an estimated three million survivors of stroke in the United States, the cost to society, both directly in health care and indirectly in lost income, is staggering. Despite recent advances in basic and clinical neurosciences, which have the potential to improve the treatment of acute stroke, the general approach to the acute stroke patient remains one of therapeutic nihilism. Most basic science studies show that to be effective, acute intervention to reperfuse ischemic tissue must take place within the first several hours, as is the case with ischemic myocardium. In addition, most neuroprotective agents must also be administered within a short time frame to be effective at salvaging at-risk tissue. Recent studies have suggested that the outcome after intracerebral and subarachnoid hemorrhage is improved with early intervention. However, most stroke patients fail to present to medical attention within this short "window of opportunity." The public's knowledge about stroke is woefully inadequate. However, clinicians who deal with stroke can use the dramatic changes in the treatment of acute myocardial infarction over the last 2 decades as a guide for shaping changes in the management of acute stroke. Comprehensive educational efforts aimed at clinicians and the public at large have dramatically reduced the time from symptom onset to presentation and treatment for acute myocardial infarction, enabling treatment methods such as thrombolysis to be effective. The Decade of the Brain offers a unique opportunity to all concerned with the treatment of the patient with acute stroke to engage in a concerted effort to bring patients with a "brain attack" to specialized neurological attention within the same timeframe that the "heart attack" patient is handled. Such an effort is justified because, although at the present time there are few therapeutic interventions of "proven" value in the treatment of acute stroke, there is more than sufficient suggestive evidence that a number of approaches may be beneficial within the first few hours after the onset of the stroke.

Fluosol and experimental spinal cord ischemia

Spinal cord ischemia was produced by temporary aortic occlusion for 12.5 min in 27 rabbits. Animals were divided into three groups: Group A received Fluosol DA 20% and 100% oxygen; Group B Fluosol and room air only, and Group C Dextran 40 and 100% oxygen. There was no difference in neurological outcome or in the extent and severity of histologically documented infarction of the spinal cord in the three groups. There was also no difference between these groups and untreated controls previously studied by us.