Effects of a transfusion with a blood substitute (Fluosol-DA, 20%) on cerebral circulation in the monkey

Effects of partial blood replacement with pyridoxalated hemoglobin polyoxyethylene conjugate solution on transient cerebral ischemia in gerbil

Blood components were reported to be aggravating factors of ischemic cerebral injury. We previously reported that a partial blood replacement with Fluosol DA reduced ischemic neuronal injury. The purpose of this study is to elucidate whether pyridoxalated hemoglobin polyoxyethylene conjugate solution (PHP) exerts neuro-projective effects against cerebral ischemia.

METHODS

38 adult male gerbils were divided into 4 groups, such as normal group without ischemia or treatment, PHP group undergoing an exchanging blood transfusion with 5.0 ml PHP, ischemia group undergoing 5-min forebrain ischemia, and PHP-ischemia group with 5.0 ml PHP partial blood replacement prior to 5-min forebrain ischemia. Cerebral injury was assessed 7 days after treatment. In another group, effects of PHP on blood nitric oxide (NO) and cerebral blood flow (CBF) were studied.

RESULTS

CA1 cell density was 140-2/mm in normal group and 142-5/mm in PHP group. The cell density was markedly reduced to 38-13 in ischemia group. The cell density was further reduced 27-10/mm in PHP-ischemia group. PHP was found to have a potent NO scavenger action and reduce CBF.

CONCLUSION

Partial blood replacement with PHP prior to ischemia may cause cerebral vasoconstriction due to NO scavenger action and may worsen ischemic injury.

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.

The in-situ absorption of antipyrine as a measure of intestinal blood flow in Fluosol-DA haemodiluted rats

The effect of moderate Fluosol-DA haemodilution on intestinal blood flow has been investigated in the rat. Antipyrine in-situ intestinal absorption is blood flow limited, and did not alter 0.5, 24, 48, or 72 h after haemodilution with 40 mL kg-1 Fluosol. Thus the intestinal blood flow rate is maintained as part of the physiological response to ensure adequate perfusion of the vital organ.

Local hydrogen clearance as a method for the measurement of capillary blood flow

A hydrogen clearance technique for the measurement of capillary blood flow in skeletal muscle (both resting and working) and the beating heart in experimental animals is described. Various methods for introducing the hydrogen into the region of measurement are compared, together with the appropriate methods for evaluating the resultant curves. All methods yielded results which were proportional to each other signifying that this is a reliable method for measuring changes in capillary blood flow. Reproducible results were obtained, and physiological changes in flow could be easily detected. An approach towards obtaining absolute flow values is proposed by simultaneous measurement of the arterial input function together with the independent use of other indicators.

Effect of moderate haemodilution with Fluosol-DA or normal saline on low-dose phenytoin and (+/-)-5-(4-hydroxyphenyl)-5-phenylhydantoin kinetics

Phenytoin kinetics were determined in the rat following moderate (50%) blood exchange with either Fluosol-DA or normal saline. Rats received an intravenous phenytoin dose (10 mg kg-1) 0.5, 24, 48, or 72 h after exchange and were compared with non-exchanged controls. Phenytoin t 1/2 was not altered by exchange with either fluid. Its Cl and Vd were decreased and AUC increased 24, 48, and 72 h after saline exchange and 24 h after Fluosol-DA exchange. (+/-)-5-(4-Hydroxyphenyl)-5-phenylhydantoin (HPPH), a major metabolite of phenytoin, showed a decreased t1/2 and VHPPH 24, 48, and 72 h after exchange with either fluid; t1/2 was also reduced 0.5 h after Fluosol-DA exchange. The decreased Vd and VHPPH may result from changes in cardiac output secondary to haemodilution, or may represent a redistribution in the microcirculation. Fluosol-DA appears to enhance phenytoin and HPPH metabolism 48 and 72 h after exchange.

Effect of carotid artery ligation and infusion of fluosol FC-43 emulsion on brain surface oxygen tensions

In eight rabbits, the common carotid artery was ligated and multiple estimations of brain surface oxygen tension performed using a seven barrelled mini-electrode. In five rabbits ligation of the carotid artery resulted in impairment of cortical oxygenation. The remaining three rabbits showed no impairment in the supply of oxygen to the cerebral cortex after carotid occlusion. In the five rabbits who displayed a reduction in oxygen supply after carotid ligation, ventilation with 33% oxygen after the infusion of 15 ml/kg of Fluosol FC-43 produced an improvement in cortical oxygenation in only three of the five rabbits. When these animals were ventilated with 100% oxygen after carotid ligation and Fluosol infusion, oxygen supply in all five was commensurate with or greater than that during control conditions.

A light and electron microscopic analysis of the mossy fibers of the rat dentate gyrus

The axon collaterals of dentate granule cells have been analyzed with the aid of a computerized microscope, following intracellular injections of horseradish peroxidase in hippocampal slice preparations. The axon of each granule cell gives rise to approximately seven primary collaterals; these collaterals usually divide into secondary and tertiary branches, which form an extensive plexus within the hilar region of the dentate gyrus. Individual axon collaterals vary greatly in length, but most have been found to be between 100 and 300 microns long. On average, the summed lengths of the collaterals (exclusive of the parent mossy fiber) are approximately 2,300 microns. Except for an occasional collateral that is given off by a mossy fiber in the proximal part of field CA3 of the hippocampus, the collaterals of the granule cell axons are confined to the hilar region; they are rarely seen in the granule cell layer itself and have never been observed in the molecular layer. In the longitudinal dimension of the dentate gyrus, most of the collaterals are contained within a zone about 400 microns wide. The distribution of the collaterals within the hilar region is correlated with the location of the granule cell body. Those that arise from cells near the tip of the suprapyramidal blade tend to be confined to the region above field CA3; those from cells nearer the crest and from the infrapyramidal blade ramify widely throughout the hilus. Two types of varicosities are present on the collaterals. Numerous small (approximately 2 microns), round varicosities are distributed unevenly along the collaterals; in electron micrographs these varicosities can be seen to make asymmetric synaptic contacts with dendritic shafts. On average, each granule cell collateral plexus has about 160 of these varicosities. The second type of varicosity is irregular in shape and ranges from 2 to 4 microns in diameter; there is usually only one such varicosity per collateral. In all respects except size, these varicosities resemble the expansions found on the parent mossy fibers. Mossy fiber trajectories in the proximal part of field CA3 were studied after extracellular injections of HRP into localized regions of the granule cell layer. Granule cells at different locations around the blade send their mossy fibers to different depths within the pyramidal cell layer in the proximal part of field CA3. However, further distally, mossy fibers from all parts of the granule cell layer contribute to the suprapyramidal bundle that occupies the stratum lucidum.

Hemodynamic, metabolic, and morphological effects of cardiopulmonary bypass with a fluorocarbon priming solution

Systemic perfusion, myocardial contractility, and morphological changes during and after cardiopulmonary bypass (CPB) were investigated in 22 greyhounds; Fluosol-DA 20% (FDA) and normal saline (NaCl) were compared as priming solutions for hypothermic (25 degrees C) CPB. Hemodynamic and oxygenation indices were similar in all groups. Animals with fluorocarbon primes had higher serum lactate concentrations (mean +/- standard error of the mean [SEM]) during CPB (NaCl 1.64 +/- 0.2, FDA 2.39 +/- 0.3, p less than 0.01), representing an increase over the control of 12% and 319% in the NaCl and FDA groups, respectively. After CPB, serum lactate concentration remained elevated in the FDA group, but it returned to the level of the control in the NaCl group (NaCl 1.49 +/- 0.5, FDA 2.29 +/- 1.1, p less than 0.01); increases over the control level were 7% and 302% in the NaCl and FDA groups, respectively. Myocardial contractility after CPB, expressed as dP/dt[40], was similar in the two experimental groups. Three weeks after CPB, a histological examination by light microscopy of multiple organs obtained from a separate group of 12 animals treated similarly was performed, demonstrating no significant morphological differences between animals primed with fluorocarbon or with saline. The results suggest that FDA is a satisfactory priming agent for hypothermic CPB. It adequately preserves myocardial function and causes no adverse morphological changes, but a persistent, as yet unexplained, elevation in serum lactate concentration occurs.

The effect of Fluosol-DA on oxygen availability in focal cerebral ischemia

The effects of Fluosol-DA 35% (15 ml/Kg, IV) on cortical oxygen availability (O2a), a relative measurement of cortical oxygen tension, were examined in 16 cats subjected to temporary middle cerebral artery (MCA) occlusion. The cats were divided equally into control and treatment groups and half of each group underwent MCA occlusion at room air ventilation and the other half at 100% O2 ventilation. Prior to occlusion, Fluosol had no effect on arterial PO2 or cortical O2a at normoxia, however, there was a significant increase in both arterial PO2 and O2a following 100% O2 ventilation (pre vs post Fluosol). In an additional 5 cats, Fluosol resulted in a transient decrease in blood oxygen content due to hemodilution. Concurrent to this decrease, cerebral blood flow increased substantially resulting in a net increase in oxygen delivery. Within ipsilateral hemispheres, MCA occlusion resulted in decreased O2a to levels below the pre-occlusion normoxic values in all animals except those treated with Fluosol and ventilated with 100% O2. During reperfusion, O2a immediately recovered to hyperoxic levels in the Fluosol 100% O2 animals, whereas in the other three groups, O2a returned more gradually towards the pre-occlusion value. Since neither 100% O2 alone nor Fluosol plus room air ventilation significantly improved O2a in the ischemic cortex, we conclude that increased delivery of plasma plus Fluosol bound oxygen was responsible for the observed improvements in O2a following MCA occlusion.