The effect of blood glucose concentration on postasphyxia cerebral hemodynamics in newborn lambs

The effect of preasphyxia blood glucose concentration on postasphyxia (PA) cerebral hemodynamics was examined in 21 newborn lambs. Glucose was unregulated in one group (n = 7), and controlled throughout the study by glucose clamp in hyperglycemic (n = 7) and hypoglycemic (n = 7) groups. Cerebral blood flow, determined using radiolabelled microspheres, and arterial and sagittal sinus O2 contents were measured at control, 5 min, 1, 2, and 4 h after resuscitation from an asphyxial insult. Preasphyxia blood glucoses were 6.48 +/- 0.55 mM (mean +/- SEM), 12.08 +/- 0.80, and 2.66 +/- 0.14 in the three study groups. In all three groups, 5 min PA cerebral blood flow was significantly increased from control. In the late period after asphyxia, the unregulated group had decreased cerebral blood flow compared with control, 53.2 +/- 3.8 mL.100 g-1.min-1, mean +/- SEM, p less than 0.01; 49.6 +/- 2.0, p less than 0.005; 53.4 +/- 3.0, p less than 0.01, at 1, 2, and 4 h PA, respectively, versus 85.7 +/- 6.9 at control, whereas both the hyper- and hypoglycemic groups did not differ significantly from control measurements. Cerebral oxygen consumption (CMRO2) was significantly decreased in all three groups 5 min PA and remained decreased in the late period after asphyxia in both the unregulated and hypoglycemic groups. In the unregulated group, CMRO2 was 191 +/- 14 microM.100 g-1.min-1, mean +/- SEM, p less than 0.05; 200 +/- 4; and 181 +/- 10, p less than 0.05 at 1, 2, and 4 h, respectively, PA versus 251 +/- 12 at control.(ABSTRACT TRUNCATED AT 250 WORDS)

[Mechanisms of the pulmonary congestion in ligature strangulation (IX)]

The authors summarized 10 our papers on the mechanisms of pulmonary congestion in ligature strangulation. Since old times, a hypothesis based on hypersecretion of adrenaline at agonal stage in asphyxia is well-known. From our investigations, this hypothesis seemed to be applicable to ligature strangulated guinea-pig's lungs at least.

Studies on asphyxia: lipids in the alveoli of rats in hypoxic state

Biochemical characterization in alveolar lavage fluids of rats which had inhaled 5% oxygen, carbon dioxide and carbon monoxide was studied in comparison with control rats. The protein content, consisting mainly of serum albumin, markedly increased in the hypoxic states. The phospholipid content also increased one and a half to two times as much as in the control rats. The phospholipids which increased in the alveoli were mainly pulmonary surfactant phospholipids, i.e. phosphatidylcholine and phosphatidylglycerol. The phospholipid profiles did not appear to be affected by the leakage of plasma lipids. These findings indicate that pulmonary surfactant phospholipids accumulate in the alveoli of rats in the hypoxic states examined here.

[Mechanisms of the pulmonary congestion in ligature strangulation (V)]

The authors measured the iron contents and 3H-water contents of the lung et al.'s tissues of the guinea-pigs sacrificed by ligature strangulation. Congestion of the heart, lung, liver and kidney and anemia of the spleen were clearly recognized. And, the increase of hematocrit value of the heart blood was observed.

Novel pharmacologic approaches to brain resuscitation after cardiorespiratory arrest in the pediatric patient

Although no specific pharmacologic therapy for clinical application to cerebral resuscitation after ischemia exists, biochemically guided mechanistic studies are under way to unravel what appears to be an extremely complex process. The evolution of the primary parenchymal insult after ischemia in the brain appears to be coupled to a multifactorial interaction between blood and damaged brain tissue that is initiated very rapidly during reperfusion and leads to further tissue injury (Fig. 8). Current studies implicate calcium, oxyradicals, phospholipid-derived metabolites, and blood elements as possible mediators of tissue injury during reperfusion. However, the optimal conditions for repair and ongoing metabolism after ischemia remain to be defined. In this regard, studies to investigate postischemic communication failure, optimal active and basal metabolic rate in the postischemic brain, and optimal pressure and flow patterns during reperfusion are needed to guide future therapies. Future therapies based on these alternative approaches could supplement refined versions of the regimens presented in this article--those that attempt to minimize reperfusion injury. Meaningful progress in the mitigation of postischemic encephalopathy is almost certain to require novel, specific therapies used in multimodal regimens with a significant fraction of the agents administered as near as possible to the onset of reperfusion. To develop these regimens to treat the pediatric arrest, studies in pediatric models or at least models of asphyxial arrest are essential.

Bilirubin in cerebrospinal fluid: an indicator of blood-brain barrier disruption in asphyxiated rats

To evaluate the relationship of serum cerebrospinal fluid (CSF) and brain total bilirubin levels in asphyxia, an experiment was designed with 5 to 6-week-old Sprague-Dawley rats. The rats were randomized into control and experimental groups. All rats received intravenously 30 mg/kg of bilirubin. Four hours later the experimental group was asphyxiated. Forty-eight hours after asphyxiation, the bilirubin concentrations in blood, CSF, and brain were measured in both study groups. Mean CSF and brain bilirubin levels were significantly higher in the experimental compared to the control group; however, mean serum bilirubin levels were not different. Moreover, in the experimental group a significant correlation existed between CSF and brain bilirubin concentrations. In conclusion, an asphyxiatic insult resulted in disruption of both the blood-brain and the blood-CSF barriers.

Brain energy metabolism in two kinds of total asphyxia: an in vivo phosphorus nuclear magnetic resonance spectroscopic study

Brain energy metabolism was studied in vivo by means of 31P-NMR spectroscopy in newborn mice during and after 20-minutes exposure to either pure carbon dioxide gas or nitrogen gas. In the N2 group, the brain ATP concentration remained almost normal throughout the experiment, while it showed a 30% reduction in the CO2 group. The brain concentration of phosphocreatine dropped to about 20% of the control value during the asphyxia in both groups, and its recovery was significantly delayed in the CO2 group compared to in the N2 group. Tissue acidosis and Pi accumulation were more remarkable and prolonged in the CO2 group.

Extracellular overflow of glutamate, aspartate, GABA and taurine in the cortex and basal ganglia of fetal lambs during hypoxia-ischemia

Extracellular levels of excitatory and inhibitory amino acids were measured in the cortex and striatum of asphyxiated fetal lambs. The fetus was exteriorized from the anesthetized ewe and dialysis probes were placed in the parietal cortex and caudate nucleus. Cerebral blood flow was measured with Xe-clearance. Cortical somatosensory-evoked potentials and electroencephalogram (EEG) were continuously recorded. Asphyxia was induced by clamping the umbilical cord or by graded compression of the maternal aorta. Asphyxia accompanied by elevated cerebral blood flow resulted in a moderate rise in extracellular amino acid levels. During extreme asphyxia, i.e. abolished evoked potentials and reduced cerebral blood flow, marked extracellular elevations of glutamate (3- to 11-fold), aspartate (3- to 7-fold), gamma-aminobutyric acid (GABA) (3- to 5-fold) and taurine (3- to 18-fold) occurred, the higher values representing striatum. Excessive levels of excitatory amino acids may exert injurious effects on immature neurons during such hypoxic-ischemic states.

Changes in cell proliferation kinetics in the mouse cerebellum after total asphyxia

This study was undertaken to investigate the effects of neonatal asphyxia on brain development, with special reference to the kinetics of neuronal proliferation by using autoradiography. For 30 minutes, two-day-old suckling mice, Jcl:ICR strain, were put into a chamber which was constantly flushed with 100% CO2 gas. After the exposure to asphyxia, 29% of the mice survived. Cell cycle studies were carried out at two days and at seven days on the external matrix cells, the precursor of the granule cells, at the external granular layer of the cerebellum from CO2-exposed and control mice by 3H-thymidine autoradiography. At two days the generation time of the control mice was about 15 hours, whereas that of the asphyxiated mice was about 17 hours. The prolongation of the generation time in the asphyxiated mice was caused mainly by a delay in the G2 phase. This prolongation was apparent for about five days and thereafter growth caught up. These results suggest that neonatal asphyxia has an adverse effect on cerebellar neuronal proliferation that may revert to normal spontaneously in older animals.

Effect of acute hypoxia on ascorbate content of plasma, cerebral cortex, and adrenal gland

Levels of ascorbic acid (AA) in the plasma, brain, and adrenal gland of rats were determined after 15 min of hypoxia (PaO2 less than 25 mm Hg) and following asphyxia. In rabbits, AA plasma levels were followed up to 75 min of reoxygenation following 15 min of hypoxia of the same severity. A significant increase (approximately 70%) in AA levels was found in plasma of rats and rabbits after hypoxia and asphyxia. This increase was found to be transient, with a return to normal levels within 1 h after resumption of normal oxygenation. Pretreatment with dexamethasone reduced the increase in AA level in both rabbits and rats. Adrenalectomy in rats, performed 24 h before the experiment, abolished the response to hypoxia. Ascorbate levels in the cerebral cortex, hypothalamus, and adrenal gland of awake rats subjected to hypoxia or asphyxia were found to be the same as in normoxic rats. Our results suggest that the observed changes in plasma AA levels are probably mediated through adrenocorticotropic hormone and that the adrenal gland is the major source of ascorbate efflux into the circulation during oxygen deprivation.

Central monoamines and the death process time (antemortem time) during asphyxia. An experimental study in the mouse brain

The changes of the brain monoamines, norepinephrine (NE), dopamine (DA), and serotonin (5-HT), during acute asphyxia, caused by strangulation, anoxia, and drowning, were studied in the mouse. In several asphyxiated animal groups significant linear correlation was found between the level of monoamines, NE, DA, and 5-HT, and the death process times or antemortem times were r = 0.50, 0.98 (P less than 0.05), and 0.57, respectively. It is concluded that the level of brain NE and DA increased in the mouse that died of asphyxia, and the level of 5-HT showed only an apparent decrease in anoxia groups as compared with the control group and showed a twice as high increase in drowning groups. Especially, there was a tendency that the longer the death process times or antemortem times, the higher was the level of DA.

Physiologic and metabolic alterations associated with seizures in normoxic and asphyxiated neonatal dogs

The effect of asphyxia on seizures was determined in neonatal dogs. In normoxic (paralyzed and ventilated) neonatal dogs, bicuculline-induced seizures produced significant elevations of arterial blood pressure, PO2, glucose, lactate, and epinephrine. Cerebral blood flow increased severalfold; brain glucose, adenosine triphosphate (ATP), and phosphocreatine (PCr) did not decrease significantly. In contrast, seizures during asphyxia were associated with hypoxia, hypotension, hypercarbia, and acidosis. Significant cerebral ischemia developed. Brain glucose, ATP, and PCr were significantly depleted. Complete oxygen deprivation during neonatal seizures exhausts brain energy stores, which leads to cessation of seizure activity.

Brain lactate and alanine-glutamate ratios during and after asphyxia in rats

Recently, Conger, Garcia, Kauffman, Lust, Murakami and Passonneau, (1981) proposed the use of brain alanine-glutamate ratios (A:G) for the prediction of outcome after brain ischemia. This study evaluates this parameter and brain lactate concentration during and after asphyxial insults in rats. During the first 15 min of asphyxial death in rats (n = 37), lactate increased sharply from mean values of 1.48 to 18.06 mumol g-1 wet brain, and thereafter to 19.44 mumol g-1 wet brain at 180 min. During total body asphyxia (n = 38) and recovery after resuscitation, brain lactates increased to mean values of 15 and 17.5 mumol g-1 wet brain at 5 and 10 min, respectively, to recover after 30-60 min to baseline. The alanine-glutamate ratios did not rise during the insult; however, after restoration of circulation, the ratios rose to peak at about 15 min post-restoration of circulation and recovered slowly during the next 165 min to still slightly increased levels. During intermittent asphyxia (n = 15), lactate and alanine-glutamate ratios followed the same patterns as found before except at lower levels. The conclusions of this study are: (1) brain lactate concentrations had no value in predicting the potential of recovery; (2) increased lactate concentrations during recovery indicated secondary insult; (3) brain A:G's did not increase during asphyxiation; (4) brain alanine-glutamate ratios increased after restoration of circulation and may have reflected the quality of reflow; (5) increased ratios during recovery beyond 20 min indicated secondary insult. Brain alanine-glutamate ratios could not be used for prediction of outcome in asphyxial insults in rats.

[Activation of lipid peroxidation and its prevention with ionol during mechanical asphyxia followed by resuscitation]

It was shown in experiments on random-bred male rats that during mechanical asphyxia, lipid peroxidation in the brain, heart, lungs and skeletal muscles experiences activation. At the beginning of the resuscitation measures under elevated tissue oxygenation there is a further increase in the intensity of lipid peroxidation, whereas the content of lipid hydroperoxides and Schiff's bases approaches the initial values only after 3 months. It is assumed that excessive activation of lipid peroxidation plays the key role in the pathogenesis of the postresuscitation disease. Preliminary administration of the synthetic antioxidant ionol in a dose of 30 mg/kg reduces activation of lipid peroxidation in all the organs and tissues under study, improves energy supply of the brain and heart, and decreases 3-fold the lethality in the early postresuscitation period.

Cortical oxidative metabolism under conditions of ischemia, hypoxia, and asphyxia in the rabbit

The purpose of this investigation was to compare the effects of hypoxia, asphyxia, and ischemia on brain cortical oxidative metabolism. This study was carried out using 14 New Zealand White rabbits. The effects of episodic stress were measured simultaneously on brain functional metabolism by monitoring cortical oxygen tension (brain pO2), cortical cerebral blood flow (cCBF), cortical blood volume, and mitochondrial oxidative metabolism. During hypoxia (when the fraction of inspired O2 (FiO2) was reduced to 10%) and asphyxia (induced by turning the respirator off), there was a decrease of brain pO2 but an increase of cCBF and blood volume. Similarly, there was a reduction of cortical oxidative metabolism. In post-asphyxic conditions, an overshoot of brain pO2 and post-asphyxic oxidation of cytochrome (Cyt.) aa3 were usually shown. Under ischemic conditions (induced by sudden severe hypotension plus bilateral common carotid occlusion), cCBF and blood volume were decreased. There was also a decrease of brain pO2 and a reduction of Cyt. aa3 following ischemia. These techniques are applicable in intraoperative monitoring of patients.

Lactic acid concentrations in vitreous humor: their use in asphyxial deaths in children

Lactic acid concentrations in brain tissue of humans have been shown to increase with an extended agonal period. Infants and children dying from various causes are undergoing different stress conditions terminally and the postulate of this study is that natural death cases and traumatic asphyxia cases are characterized by varying agonal periods, the former being somewhat prolonged with the latter being rather brief. One-hundred-and-two cases of infants and children were examined for vitreous humor lactic acid concentrations. They were divided into two major categories, Sudden Infant Death Syndrome (SIDS) and non-SIDS cases. SIDS was further divided into SIDS without additional findings and SIDS with secondary findings which contributed to death. The non-SIDS category included traumatic asphyxia cases as well as those dying from blunt trauma, known respiratory diseases, and other causes. Categorical mean values and standard deviations were calculated. The vitreous humor lactic acid mean value for traumatic asphyxia was significantly lower than the mean value for SIDS. Also the mean value for known respiratory diseases was statistically lower than the mean value for SIDS with secondary findings. These findings are probably suggestive of agonal time differences and may be a reflection of the various mechanisms of death.

Cerebral arterio-venous difference for hypoxanthine and lactate during graded asphyxia in the fetal lamb

Hypoxanthine (HX) and lactate are degradation products from energy-rich intracellular substrates (ATP and glycogen), and their concentration will increase during anaerobic conditions, such as fetal asphyxia. In this study the accumulation of the two metabolites in blood during asphyxia was studied in 7 acutely exteriorized fetal lambs. The arterio-venous difference of HX and lactate over the brain was related to the function of the fetal brain as reflected by the somato-sensory evoked electroencephalogram potentials (SEP). Increased concentrations of HX in plasma and lactate in blood occurred simultaneously with deterioration of the SEP and the 3 variables correlate highly significantly. During normoxia, a net cerebral influx was found for HX, which in combination with severe asphyxia gradually changed to a net efflux. A linear correlation was found between the cerebral arterio-venous differences of HX and the impairment of the SEP. No such correlation existed for lactate. The results suggest, that the fetal brain has a high threshold for degrading its energy-rich intracellular purines.