Measurement of cerebral venous oxyhemoglobin saturation in children by near-infrared spectroscopy and partial jugular venous occlusion

Surgery of the anterior cruciate ligament causes severe postoperative pain. This study aimed to compare efficacy and side effects of two postoperative analgesia methods, during 24 hours. Twenty healthy patients were assigned to two groups (n = 10): the patients of the first group were given by an epidural catheter 3 mg of morphine hydrochloride, every twelve hours. The patients of the second group received 2 mg h-1 of intravenous nalbuphine. The degree of pain was studied with a visual analogue scale. After the third postoperative hour, it was significantly higher in the second group, but the nalbuphine dose was low. The incidence of respiratory depression, nausea, pruritus was not statistically different between the groups, but 7/10 patients in the first group suffered of urinary retention (the first micturition was obtained 10.5 hours after the end of surgery in the first group and 5.3 h in the second one). Two patients needed an uretral catheter. These results might tend to show a greater efficactly of epidural morphine, with a higher incidence of urinary side effects.     

Continuous noninvasive measurement of cerebral arterial and venous oxygen saturation at the bedside in mechanically ventilated neonates

OBJECTIVES: To test the practicablity of a new spectrophotometric method using pulse oximetric techniques in combination with special filters for the noninvasive determination of cerebral arterial and venous oxygen saturation and oxygen extraction in neonatal intensive care unit patients. The spectrophotometer used three different wavelengths at a sampling rate of 100 Hz. DESIGN: Clinical evaluation of a new method and comparison with previously published data. SETTING: Design and construction of the special spectrophotometer at the Biomedical Engineering Laboratory of the Swiss Federal Institute of Technology. Measurements in the neonatal intensive care unit of the University Hospital, Zurich, Switzerland. PATIENTS: Convenience sample of 15 clinically stable newborn infants, who were mechanically ventilated and receiving supplemental oxygen. Median gestational age was 29 5/7 wks (range 26 3/ 7 to 36 0/7), median birth weight was 1555 g (720 to 2500), median postnatal age was 4 days (1 to 10). INTERVENTIONS: The emitter and receiver were placed on the forehead near the sagittal sinus, between 2 and 2.8 cm apart, and the pulsating light attenuations (arterial and venous pulse waves) were recorded. MEASUREMENTS AND MAIN RESULTS: Arterial and venous pulse waves were satisfactory in 10 of 15 infants. Mean cerebral arterial oxygen saturation was 89.9 +/- 5.4% (SD), mean cerebral venous oxygen saturation was 73.0 +/- 8.9%, and mean cerebral oxygen extraction was 16.9 +/- 11.7%. A linear regression analysis demonstrated a significant correlation between mean PCO2 and venous oxygen saturation (slope 1.0%/torr, p < .05) and between mean PCO2 and cerebral oxygen extraction (slope -1.3%/torr, p < .05). CONCLUSION: This new method has the potential for monitoring continuously, noninvasively, and simultaneously cerebral arterial and venous oxygen saturation and oxygen extraction in mechanically ventilated preterm infants.     

Effect of ketamine anaesthesia on the content of monoamines and their metabolites in the rat brain

The effects of ketamine anaesthesia (100 mg/kg i.p.) on the content of brain 5-hydroxytryptamine (5HT), 5-hydroxyindoleacetic acid (5HIAA), noradrenaline (NA), dopamine (DA) and homovanillic acid (HVA) were studied in male Wistar rats. Fifteen min after ketamine injection, when the rats were deeply anaesthetized, the 5HT content in many brain regions tended to be increased. An opposite tendency was found in the brain 5HIAA content. In rats treated with probenecid, which markedly lengthened ketamine anaesthesia, the accumulation of 5HIAA was significantly reduced by ketamine. In addition to ketamine anaesthesia, probenecid was found to lengthen thiopental anaesthesia. One hour after the ketamine administration, when the rats were no longer anaesthetized but were excited, the brain NA concentration was increased by 17% (P less than 0.02). The brain DA content was unchanged, but at 15 min and 1 hour after ketamine administration the striatal HVA content was increased by about 55% (P less than 0.05), suggesting an increased turnover of DA. The results suggest that during recovery from ketamine anaesthesia the increased NA content and the increased DA turnover may be associated with the postanaesthetic excitement of the rat, whereas the decreasamine anaesthesia.     

The effect of dopamine depletion on the H2O2 production in the rat striatum following transient middle cerebral artery occlusion

The changes in the extracellular concentrations of rat striatal H2O2, dopamine (DA) and its metabolites during middle cerebral artery (MCA) occlusion and reperfusion were simultaneously examined by microdialysis, and the relationship between the ischemia-induced release of DA and the generation of H2O2 was estimated by assessing the effect of the lesion of the substantia nigra (SN). In the rats without SN lesions, a significant increase in the striatal H2O2 level was observed during the ischemia and reperfusion phases. In the rats with SN lesions, the ischemia-induced H2O2 production was not attenuated. These results suggest that DA is not an important source of H2O2 in cerebral ischemia and reperfusion.     

Experimental hypoxemic hypoxia: changes in R2* of brain parenchyma accurately reflect the combined effects of changes in arterial and cerebral venous oxygen saturation

PURPOSE: The objective of this study was to develop and evaluate a pulsatile drug delivery system based on an impermeable capsule body filled with drug and an erodible plug placed in the opening of the capsule body. METHODS: The erodible plugs were either prepared by direct compression followed by placing the tablets in the capsule opening or by congealing a meltable plug material directly within the capsule opening. The disintegration/erosion properties of these plugs were determined and optimized for the final delivery system. In order to assure rapid drug release of the capsule content after erosion of the plug, various excipients (fillers, effervescent agents) and drugs with different solubilities were evaluated. The lag time prior to drug release and the subsequent drug release were investigated as function of capsule content, plug composition, plug preparation technique, plug hardness, weight, and thickness. RESULTS: The erosion time of the compressed plugs increased with increasing molecular weight of the hydrophilic polymer (e.g. hydroxypropyl methylcellulose, polyethylene oxide), decreasing filler (lactose) content and decreased with congealable lipidic plugs with increasing HLB-value and inclusion on surfactants. For complete and rapid release of the drug from the capsule body, effervescent agents had to be included in the capsule content. The drug delivery system showed typical pulsatile release profiles with a lag time followed by a rapid release phase. The lag time prior to the pulsatile drug release correlated well with the erosion properties of the plugs and, besides the composition of the plug, could be controlled by the thickness (weight) of the plug. CONCLUSIONS: A single-unit, capsular-shaped pulsatile drug delivery system was developed wherein the pulsatile release was controlled by the erosion properties of a compressed or congealed plug placed within the opening of the capsule opening.     

Evaluation of early graft function by hepatic venous hemoglobin oxygen saturation following orthotopic liver transplantation in the rat

This study was designed to evaluate the use of hepatic venous oxygen saturation (Shvo2) as a predictor of early graft function after liver transplantation. We examined the levels of Shvo2 and serum ALT after transplantation using the isogeneic rat orthotopic liver transplant model. Shvo2 levels 2 hr after reperfusion in the 6-hr cold ischemia (nonviable allograft) group were significantly lower than those in the 1-hr and 3-hr cold ischemia (viable allograft) groups. However, there was no significant difference in ALT levels among these groups. These results suggest that decreased hepatic blood flow due to microcirculatory disturbances may occur in the nonviable allograft even in the early phase of reperfusion and may be responsible for ischemic damage to parenchymal cells. Therefore, Shvo2 could provide a simple index of the initial graft status and be useful for a rapid etiological diagnosis of early postoperative graft dysfunction and for estimating the graft outcome after liver transplantation.     

Reduced arterial O2 saturation during supine exercise in highly trained cyclists

As part of a larger effort aimed at optimizing the properties of pellets produced by spheronization of extruded masses, the effect of the moisture content of wet masses on extrusion force and torque was studied. The wet masses were composed of either microcrystalline cellulose (MCC) or mixtures of MCC with lactose or dicalcium phosphate. Based on the force and torque data, a moisture content "window" was defined for consistent extrusion. Moisture exerts a lubricant effect, and a moisture level of 100-120% w/w dry solid seemed necessary for the extrusion of MCC into rod-shaped, discrete pieces. Screen force clearly depended on the moisture content but was relatively insensitive to extruder speed, especially at 80% and 100% moisture content. The physical properties of pellets as a function of spheronization time were studied by sampling the material at known intervals. The percent yield, tapped density, and a two-dimensional sphericity index of an 18/20 mesh fraction of pellets were measured. Maximum yield, tapped density, and sphericity were achieved within 60 sec in the spheronizer. With increasing residence time, the shape and density were unchanged while the yield was severely reduced. Among the formulations studied, pellets with equal amounts of lactose and MCC were superior to those of pure MCC in yield, density, and sphericity. Based on these results, an outline to optimize the endpoint of the spheronization process for formulations containing MCC is suggested.     

Effect of N-methyl-D-aspartate receptor blockade on the control of cerebral O2 supply/consumption balance during hypoxia in newborn pigs

Using dizocilpine (MK-801), we tested the hypothesis that N-methyl-D-aspartate (NMDA) receptors are important controllers of cerebral O2 supply/consumption balance in newborn piglets both during normoxia and hypoxia. Twenty-five 2 to 7-day-old piglets were anesthetized and divided into four groups: (1) Normoxia (n = 6), (2) Normoxia + MK-801 (n = 6), (3) Hypoxia (n = 6), and (4) Hypoxia + MK-801 (n = 7). Regional cerebral blood flow (rCBF) in ml/min/100 g was measured using 14C-iodoantipyrine, and we determined arterial and venous O2 saturations by microspectrophotometry, calculating cerebral O2 consumption (VO2) in ml O2/min/100 g in the cortex, hypothalamus and pons. MK-801 did not significantly affect regional VO2 or rCBF in normoxic piglets. Hypoxia resulted in an increase in local rCBF compared to controls: from 41 +/- 6 to 103 +/- 18 in the cortex; 34 +/- 7 to 101 +/- 20 in the hypothalamus; and 45 +/- 10 to 95 +/- 11 in the pons. Pretreatment with MK-801 abolished this hypoxic flow effect in the cortex (51 +/- 2) and hypothalamus (49 +/- 5), but not in the pons (91 +/- 17). Similar results were observed for VO2 with control values of 1.9 +/- 0.3, 1.6 +/- 0.2 and 2.1 +/- 0.3 for the cortex, hypothalamus and pons respectively. Hypoxia resulted in an increase in the VO2 to 3.9 +/- 0.4 (cortex), 3.8 +/- 0.6 (hypothalamus) and 3.9 +/- 0.8 (pons). Pretreatment with MK-801 prior to hypoxia abolished these effects in the cortex (2.1 +/- 0.2) and hypothalamus (2.1 +/- 0.2), but not in the pons (2.9 +/- 0.2). These findings suggest that NMDA receptors may play a role in the control of cerebral metabolism during hypoxia in this immature porcine model.     

Effects of ketamine on the peripheral autonomic nervous system of the rat

It has been demonstrated that activated C3 products might bind to lymphocyte C3 receptors and inhibit subsequent complement-dependent lymphocyte rosette formation. Sera from patients with various types of chronic glomerulonephritis (GN) have been tested in a complement-dependent rosette inhibition assay using normal donors' lymphocytes as reacting cells. Control subjects consisted of healthy donors and patients with miscellaneous renal and general diseases. Most sera of membranoproliferative GN and of systemic lupus erythematosus, and two-thirds sera of focal glomerolosclerosis patients, significantly inhibited rosette formation. Only 15-40 percent sera of patients with other types of GN were inhibitory. Serum inhibiting activity usually correlated with low serum C3 level (P less than 0.0005), although inhibition could be observed with normal serum C3. However, no correlation was found between a patient's own complement-dependent lymphocyte rosette count and his serum inhibitory activity. These results extend previous findings and suggest that the complement-dependent rosette inhibition assay can be used routinely to detect serum activated complement components either free or bound to immune complexes.     

Measurement of cerebral oxyhaemoglobin saturation and jugular blood flow in term healthy newborn infants by near-infrared spectroscopy and jugular venous occlusion

Data of cerebral haemodynamics and oxygenation are important for optimal treatment and prognosis in neonatal intensive care. Mostly premature and asphyxiated infants have been examined, but near-infrared spectroscopy (NIRS) allows estimations in healthy term newborns. In this study, cerebral venous saturation (CVsO2) and jugular blood flow (JBF) was estimated in 11 healthy term newborns. Mean CVsO2 was 64.12 +/- 4.6%, which conform with expectations. Mean JBF was only 6.1 ml/100 g/min, which is unacceptably low compared to earlier published data. We discuss physiological and methodological aspects and conclude that the combination of NIRS and venous occlusion appears to be a reliable method for estimation of CVsO2 in normally healthy newborns, whereas the reason for the failure of the method for estimation of JBF is unclear.     

Partial saturation of rat liver Cd-binding proteins by Cd2+ in vivo

Liver Cd-binding proteins (Cd-BP) were isolated from rats chronically treated with 109Cd-labeled CdCl2 for ten days. Fractions purified using Sephadex G-75 and DEAE-Sephadex were characterized and found to be similar to those isolated by other investigators. Cd-binding was not saturated in any of the preparations and significant amounts of Cu and Zn were also found bound to the proteins. The percentage of saturation of Cd-BP1, and Cd-BP2 was independently determined by atomic absorption spectrometry and spectroscopy at 254 nm. These results indicate that the fraction of binding sites unoccupied by Cd on Cd-BP approaches 20% in vivo.     

Effect of Na2O on the Reduction of Fe2O3 Compacts with CO/CO2

Compacts of Fe₂O₃ and Fe₂O₃ doped with varying amounts of Na₂O were isothermally reduced at several temperatures, using CO/CO₂ mixed gas in a vertical resistance furnace. To determine the effect of Na₂O on the reduction of Fe₂O₃ compacts, the mass loss due to oxygen removal was continuously recorded, from which the reduction rate and rate constant were obtained. Na₂O was found to retard the reduction of Fe₂O₃ compacts. The apparent activation energy (E _a) of reaction and the mathematical relationship for pore gas diffusion suggested that the reduction behavior at the initial stages was controlled by a combination of pore gas diffusion and interfacial chemical reaction. At the intermediate and late stages of reduction, pore gas diffusion was the sole contributing factor. Morphological examination of the reduced compacts showed the formation of a liquid phase during the reduction process, which appeared to lower the rate of reaction.     

The measurement of peripheral venous oxyhemoglobin saturation in newborn infants by near infrared spectroscopy with venous occlusion

A novel, noninvasive method for measuring peripheral venous oxygen saturation (Svo2) in newborn infants using near infrared spectroscopy (NIRS) with venous occlusion is described, along with a comparison with co-oximetry of peripheral venous blood. Peripheral Svo2 was measured in 16 newborn infants by NIRS with venous occlusion, and the results were compared with those obtained by co-oximetry of blood from a forearm vein. There was a significant correlation between the two measurements (r = 0.85, p < 0.0001) and close agreement between the two techniques (mean difference (co-oximeter-NIRS) 6%, limits of agreement-5.1% to 17.1%). Three different methods for analysis of the NIRS data were examined to determine which period during the venous occlusion provided the most accurate measurement. The agreement was the same for all methods of analysis.     

Li2O对CaO-SiO2-MgO-Fe2O3-MnO2-P2O5精炼渣系脱磷的影响

在Li2 O替代CaO SiO2 MgO Fe2 O3 MnO2 P2 O5精炼渣系中部分CaO的条件下 ,研究了Li2 O含量、碱度及氧化性对钢液磷含量的影响。结果表明 ,在Li2 O =15 % ,碱度 (CaO +Li2 O) /SiO2 为 2 .0～ 2 .5 ,(Fe2 O3 +MnO2 )为 7%的条件下 ,该渣系对钢液的脱磷率在 70 %以上 ,控制钢液磷含量在 0 .0 0 9%以下。     

The use of ketamine in an experimental model of generalized cerebral ischemia

Thus far, a sufficiently effective cerebroprotective substances has not been discovered. Glutamate overproduction plays a key role in ischemic brain lesion. Ketamine is assigned to the group of commonly used clinical anesthetics, being also familiar as NMDA antagonist. Sodium fluoride-induced cerebral ischemia in mice is used as a model of circulatory ischemic lesion. As shown by the experimental data, simultaneous administration of NaF + ketamine has no effect whatsoever on the survivorship of animals, as compared to that in the control group treated with NaF alone. Beforehand treatment of mice with 150 mg/kg ketamine brings about considerable prolongation of the survival term (15 per cent of the animals survive for more than 2 hours). The inference is reached that ketamine is endowed with cerebroprotective activity largely attributable to glutamate antagonism at the level of ischemia involved neurons.     

Effect of the production factors on the hydrogen saturation of steel

The available data on the influence of hydrogen on the steel quality and its main hydrogen-induced defects are analyzed. The factors that influence the hydrogen content in steel under conditions of the oxygen-converter plant of the Magnitogorsk metallurgical works have been revealed. The methods of decreasing the hydrogen content in steel are considered.     

CaF_2-MgF_2对钢中Al_2O_3夹杂物去除作用的研究

采用不同量的CaF_2、MgF_2、Na_3AlF6以及CaF_2与MgF_2的混合物对钢液中Al_2O_3夹杂物进行改性处理。结果表明:经过改性处理后的钢中全氧含量都有明显的降低,但其添加量需要在一个合适的范围,其中添加1.0%的CaF_2与MgF_2的混合改性剂的效果最好。另外经过改性剂处理后的钢中夹杂物呈现出MnS包裹Al_2O_3的复合分层形态,更加有利于夹杂物的上浮去除,而且MnS为塑性夹杂物,可降低残留在钢中Al_2O_3夹杂物对钢的危害。     

Cardiovascular effects of ketamine in the pithed rat, rabbit and cat

The effect of i.v. ketamine on arterial pressure and heart rate were examined in pithed rats, rabbits and cats. In all three species ketamine caused a brief decrease in arterial pressure and heart rate. In the rat, but not in the other two species, this initial decrease in arterial pressure was followed by a pressor response which was resistant to alpha-adrenoceptor blockade, depletion of tissue noradrenaline stores and adrenalectomy. It is concluded that the peripherally mediated pressor response found in the pithed rat is specific to this species, is not a result of liberation of peripheral catecholamines and does not explain the pressor effect of ketamine found in man and several animal species.     

Regional cerebral blood flow during and after 2 hours of middle cerebral artery occlusion in the rat

In this study we explored if the secondary bioenergetic failure, which occurs a few hours after recirculation, following transient middle cerebral artery occlusion (MCAO) in rats, is caused by a compromised reflow. We induced 2 hours of MCAO and measured CBF at the end of the ischemia, as well as 15 minutes, 1, 2, and 4 hours after the start of recirculation, using autoradiographic or tissue sampling 14C-iodoantipyrine techniques. After 2 hours of MCAO, the autoradiographically measured CBF in the ischemic core areas was reduced to 3 to 5% of contralateral values. The reduction in CBF was less in neighboring, penumbral areas. After recirculation, flow already normalized in core tissues after 15 minutes, and remained close to normal for the 4 hours recirculation period studied. However, in penumbral tissues, recovery CBF values were usually below normal. The results show that tissues that are heavily compromised by the 2-hour period of ischemia and are destined to incur infarction, show a "relative hyperemia" during recirculation. In fact, some areas of the previously densely ischemic tissue showed overt hyperperfusion. This finding raises the question whether the relative or absolute hyperemia reflects events that are pathogenetically important. Because drugs that clearly ameliorate the final damage incurred fail to alter the relative hyperperfusion of previously ischemic tissues, it is concluded that vascular events in the reperfusion period do not play a major role in causing the final damage.