Regional brain blood flow and cerebral cortical O2 consumption during sevoflurane anesthesia in healthy isocapnic swine

Regional distribution of brain blood flow was examined in seven previously catheterized healthy isocapnic swine while awake (control), and during 1.0 and 1.5 minimum alveolar concentration (MAC--2.66 and 3.99% end-tidal, respectively) sevoflurane anesthesia using radionuclide-labeled 15-micron diameter microspheres that were injected into the left atrium. In six additional pigs, the superior sagittal sinus was also catheterized so that cerebral cortical O2 consumption could be ascertained during these conditions. Control values of blood flow in the cerebral cortical gray matter, white matter, and caudate nuclei were 117 +/- 9, 38 +/- 2 and 105 +/- 8 ml X min-1 X 100 g-1, respectively. At 1.0 MAC sevoflurane, blood flow in these regions decreased to 66, 76, and 75% of respective control values, and these values were not different from those recorded at 1.5 MAC anesthesia. Cerebral cortical O2 consumption decreased by 50 and 52% at 1.0 and 1.5 MAC sevoflurane anesthesia, but the hemoglobin-O2 saturation in the cerebral cortical venous drainage (57 +/- 3% and 69 +/- 3% at 1.0 and 1.5 MAC) consistently exceeded control value (42 +/- 1%), suggesting that cortical O2 supply during both levels of sevoflurane anesthesia remained adequate. In cerebellum, blood flow decreased from 86 +/- 5 (control) to 68 +/- 4 ml X min-1 X 100 g-1 with 1.0 MAC sevoflurane, but returned toward control value at 1.5 MAC anesthesia. The thalamohypothalamic perfusion decreased to 59 and 75% of the control value with 1.0 and 1.5 MAC sevoflurane anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)     

安氟醚麻醉下牵拉胆囊对心肌ATP酶、ET、NOS的影响

目的 研究安氟醚麻醉下牵拉胆囊对心肌ATP酶、ET、NOS的影响。方法 健康家兔24只，随机分为A、B、C三组，A组对照组，B组吸入安氟醚达0．65MAC，C组吸入安氟醚达1．3MAC。暴露胆囊，坠以100g重物牵引10分钟。迅速开胸，取心肌组织测定ATP酶、内皮素(ET)、一氟化氯合成酶(NOS)。结果 三组心肌细胞的Na^2 —K^ ATPase、Mg^2 -ATPase差异元显著性，C组的Ca^2 -ATPase明显低于A组(P＜0．05)，B组、C组的ET明显低于A组(P＜0．05)。结论 安氟醚麻醉下牵拉胆囊可抑制了心肌细胞Ca^2 -ATPase和ET的释放。     

腰椎脊髓减压内固定手术160例的麻醉体会

目的探讨维持老龄脊柱手术中生命体征平稳的麻醉管理方式。方法对120例腰椎脊髓减压内固定的手术患者麻醉均采用气管插管静吸复合麻醉方式。将患者随机分为治疗组60例;对照组60例:治疗组麻醉诱导用咪唑安定0.15mg/kg,维库溴铵0.1mg/kg,芬太尼3μg/kg;对照组麻醉诱导用得普利麻1.5mg/kg,维库溴铵0.1mg/kg,芬太尼3μg/kg。治疗组术中麻醉维持用(1.0±0.5)MAC安氟醚吸入,芬太尼1μg/(kg.h),咪唑安定0.05mg/(kg.h);对照组麻醉维持用(1.0±0.5)MAC安氟醚吸入,芬太尼1μg/(kg.h),得普利麻0.5mg/(kg.h);术中监测HR,MAP。结果治疗组在插管后5min HR,MAP(较诱导前下降<20%,较诱导前下降20%～30%,较诱导前下降>30%)下降的例数及HR,MAP的数值均小于对照组(P<0.05)。结论咪唑安定全麻诱导平稳,有利于保持老龄患者全麻诱导时血液动力学的稳定,适用于老龄龄手术患者麻醉。     

Regional vascular changes during hypotensive anesthesia

The regional vascular effects of three different hypotensive drug treatments were compared in enflurane anesthetized rats. Controlled hypotension was induced with sodium nitroprusside (SNP), nitroglycerin (NTG),and deep enflurane anesthesia. Regional blood flow was measured during each hypotensive treatment using radioactive microspheres. All hypotensive treatments were compared with control rats, anesthetized with 2% inspired enflurane anesthesia. Results indicate that when the mean blood pressure was decreased from 124 to 70 torr with all three hypotensive treatments regionally specific blood flow changes occurred. These ranged from approximately 50% decreases seen in skin blood flow with all hypotensive drugs to 50-90% increases in flow in muscle and spleen tissues. When regional vascular resistance changes were compared between hypotensive drug treatments, SNP produced significantly less cerebrovasodilation than either NTG or deep enflurane. Deep enflurane induced hypotension resulted in significantly greater decreases in intestinal vascular resistance than either SNP or NTG. These results indicate that hypotensive anesthesia with SNP, NTG, or deep enflurane shift blood flow away from skin and toward skeletal muscle and spleen tissues. Blood flow in other tissues is relatively well maintained.     

Impact of 70% nitrous oxide administration on regional distribution of brain blood flow in unmedicated healthy swine

Regional distribution of brain blood flow was examined in 11 healthy, spontaneously breathing swine using 15 micron in diameter radionuclide-labeled microspheres that were injected into the left atrium. Measurements were made during inhalation of 30% O2/70% nitrogen (control) and at 15, 45, 75, and 120 min of 30% O2/70% nitrous oxide breathing. The animals were surgically prepared 10-12 days before the hemodynamic study. Arterial blood-gas tensions, arterial pH, mean aortic pressure, and cardiac output remained near their respective control values during exposure to 70% nitrous oxide. Control values of blood flow in the cerebrum, cerebellum, and the brain stem were 68.5 +/- 4.7, 75.6 +/- 4.2, and 54.2 +/- 4.0 ml . min-1 X 100 g-1, respectively. At 15 min of exposure to nitrous oxide, blood flow in the cerebrum, cerebellum, and the brain stem was 169, 127, and 145% of the control values, respectively. For the caudate nuclei and the corpus callosum, the corresponding figures were 141 and 131% of control, while that for remainder of the cerebrum was 178% of the control value. In the medulla, pons, and thalamus-midbrain, blood flow was 151, 157, and 141% of the respective control values. In all regions of the porcine brain, elevated levels of blood flow persisted throughout the 2 h of exposure to 70% nitrous oxide and no marked fluctuations occurred. It is concluded that administration of 70% nitrous oxide to healthy pigs caused pronounced cerebrovascular vasodilatation in all regions of the brain. This persisted throughout the 2 h of its administration.     

(S)-emopamil, a novel calcium and serotonin antagonist for the treatment of cerebrovascular disorders. 3rd communication: effect on postischemic cerebral blood flow and metabolism, and ischemic neuronal cell death

The effect of (S)-emopamil ((2S)-2-isopropyl-5-(methylphenethylamino)-2-phenylvaleronitril e hydrochloride) treatment on postischemic cerebral blood flow and metabolism was investigated in nitrous oxide anesthetized, artificially ventilated rats. Forebrain ischemia was induced and maintained for 20 min by lowering arterial blood pressure to approximately 40 mmHg and clamping both carotid arteries. Local cerebral blood flow and glucose utilization were evaluated autoradiographically in 34 cerebral regions. In the cerebral blood flow studies intravenous infusion of 0.1 mg/(kg min) (S)-emopamil was begun 5 min after the end of ischemia. Local cerebral blood flow was determined 60 min later using [14C]iodoantipyrine. When the animals were treated with saline only, postischemic blood flow of 22 affected forebrain areas fell on average to 42 +/- 13% of nonischemic control. Treatment with (S)-emopamil increased perfusion of the same areas in a region-dependent fashion by an average of 54 +/- 19%, resulting in 63 +/- 17% of control values. The rise of blood flow in structures not directly affected by ischemia amounted to 52 +/- 27% (134 +/- 23% of control). In the studies on cerebral metabolism, the experimental animals received a total of 6 mg/kg (S)-emopamil by slow intravenous infusion before and during the ischemic episode. Determination of local cerebral glucose utilization was initiated after 50 min of postischemic recirculation using [14C]deoxyglucose. In the placebo-treated experimental group average glucose utilization of 14 forebrain areas was significantly lower (74 +/- 9% of control) than in the nonischemic control group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diffusion-limited, but not perfusion-limited, compartmental models describe cerebral nitrous oxide kinetics at high and low cerebral blood flows.

This study aimed to evaluate the relative importance of diffusion-limited vs. perfusion-limited mechanisms in compartmental models of blood-tissue inert gas exchange in the brain. Nitrous oxide concentrations in arterial and brain efferent blood were determined using gas chromatographic analysis during and after 15 min of nitrous oxide inhalation, at separate low and high steady states of cerebral blood flow (CBF) in five sheep under halothane anesthesia. Parameters and model selection criteria of various perfusion- or diffusion-limited structural models of the brain were estimated by simultaneous fitting of the models to the mean observed brain effluent nitrous oxide concentration for both blood flow states. Perfusion-limited models returned precise, credible estimates of apparent brain volume but fit the low CBF data poorly. Diffusion-limited models provided better overall fit of the data, which was best described by exchange of nitrous oxide between a perfusion-limited brain compartment and an unperfused compartment. In individual animals, during the low CBF state, nitrous oxide kinetics displayed either fast, perfusion-limited behavior or slow, diffusion-limited behavior. This variability was exemplified in the different parameter estimates of the diffusion limited models fitted to the individual animal data sets. Results suggest that a diffusion limitation contributes to cerebral nitrous oxide kinetics.     

Cerebrovascular effects of central depressants: a study of nitrous oxide, halothane, pentobarbital and ethanol during normocapnia and hypercapnia in the rat

The effect of the central depressants nitrous oxide, halothane, pentobarbital and ethanol upon cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2) and cerebral vascular reactivity to carbon dioxide were measured using the rapid and repetitive intraarterial 133Xenon injection technique modified for rat studies. The cerebrovascular resistance (CVR) during normocapnia in the pentobarbital group was significantly higher (P less than 0.01) than in the nitrous oxide group thus indicating a vasoconstrictor effect of pentobarbital that may be clinically important, because the ability of barbiturates to contract vessels in healthy brain regions may partly explain the protective properties of these drugs against cerebral ischemia. The results indicated that pentobarbital and ethanol may act synergistically with carbon dioxide in depressing CMRO2 and cerebral vascular reactivity. Finally, it is concluded that nitrous oxide anaesthesia (70% N2O: 30% O2) is suitable as a reference situation in rat studies of the effect of pharmocological agents on CBF, CMRO2 and cerebrovascular reactivity.     

Diffusion-Limited, but Not Perfusion-Limited, Compartmental Models Describe Cerebral Nitrous Oxide Kinetics at High and Low Cerebral Blood Flows

This study aimed to evaluate the relative importance of diffusion-limited vs. perfusion-limited mechanisms in compartmental models of blood–tissue inert gas exchange in the brain. Nitrous oxide concentrations in arterial and brain efferent blood were determined using gas chromatographic analysis during and after 15 min of nitrous oxide inhalation, at separate low and high steady states of cerebral blood flow (CBF) in five sheep under halothane anesthesia. Parameters and model selection criteria of various perfusion- or diffusion-limited structural models of the brain were estimated by simultaneous fitting of the models to the mean observed brain effluent nitrous oxide concentration for both blood flow states. Perfusion-limited models returned precise, credible estimates of apparent brain volume but fit the low CBF data poorly. Diffusion-limited models provided better overall fit of the data, which was best described by exchange of nitrous oxide between a perfusion-limited brain compartment and an unperfused compartment. In individual animals, during the low CBF state, nitrous oxide kinetics displayed either fast, perfusion-limited behavior or slow, diffusion-limited behavior. This variability was exemplified in the different parameter estimates of the diffusion limited models fitted to the individual animal data sets. Results suggest that a diffusion limitation contributes to cerebral nitrous oxide kinetics.     

腰硬联合麻醉与笑气吸入分娩镇痛的临床研究

目的：观察研究腰硬联合麻醉镇痛法和笑气吸入法的临床效果及对产妇和新生儿的影响。方法：回顾性分析330例产妇,每组110例;其中硬膜外组采用腰硬联合麻醉,笑气组采用吸入含50％笑气和50％氧气的混合气体,对照组未用任何镇痛方法。观察各组的镇痛效果。结果：硬膜外组与笑气组镇痛效果显著优于对照组,硬膜外组镇痛效果、宫口开全（T3）后宫缩强度明显高于笑气组,第一产程孕妇活跃期短;分娩方式硬膜外组与笑气组显著优于对照组;新生儿不良反应、产后出血量、新生儿Apgar评分比较3组无明显差异。结论：笑气吸入的镇痛效果次于腰硬联合麻醉,但操作简单、经济实惠,值得基层医院推广;腰硬联合麻醉镇痛起效迅速、效果最佳,可作为分娩镇痛的首选方法。     

Correlation between degree of inhibition of parasympathetic reflex vasodilation and MAC value for various inhalation anesthetics.

Parasympathetic reflex vasodilation was elicited in the lower lip by stimulation of the central cut end of the lingual nerve in urethane plus alpha-chloralose-anesthetized, vago-sympathectomized cats. A dose-related inhibition of this response was induced by the inhalation anesthetics isoflurane, halothane, sevoflurane, and enflurane, the ID50 values being 0.94%, 0.82%, 1.74%, and 2.0%, respectively. These results indicate that the ID50 value is approximately two-thirds of the published MAC (for isoflurane, halothane, sevoflurane, and enflurane, 1.6%, 1.2%, 2.6%, and 2.4%, respectively) value for such anesthetics, suggesting that parasympathetic reflex vasodilation is more susceptible than somato-somatic reflexes to inhibition by inhalation anesthetics.     

七氟醚麻醉对新生鼠学习与记忆的影响

目的 探索用七氟醚麻醉发育期小鼠是否会引起成长过程中学习记忆障碍。 方法 实验包括122只新生鼠(出生后7 d)。其中72只分别经七氟醚1.0或0.5最低肺泡有效浓度(minimum alveolar concentration,MAC)麻醉或吸入40% O₂ 2 h,4周或12周行水迷宫实验,记录训练各天潜伏期和游泳速度,以及探索期平台滞留时间和平台穿越次数。另外50只小鼠用于测定七氟醚麻醉(1.0或0.5 MAC)过程(0、1、2 h)中动脉血血气分析。 结果 新生鼠在整个麻醉过程中,pH值、PaCO₂、PaO₂和SaO₂均保持稳定,P>0.05。麻醉后4周,训练期后3 d,对照组小鼠潜伏期明显低于麻醉组,且后2 d,0.5 MAC组小鼠的潜伏期明显短于1.0 MAC组。探索期,对照组小鼠平台停留时间和平台穿越次数均明显高于2组麻醉组。麻醉后12周,1.0 MAC组小鼠在训练第5天潜伏期仍明显延长。探索期,对照组小鼠平台停留时间和(或)平台穿越次数均明显高于麻醉组。 结论 七氟醚麻醉引起新生鼠成长过程中学习与记忆障碍,其程度与药物浓度有关,且随时间推移减弱。     

(S)-emopamil, a novel calcium and serotonin antagonist for the treatment of cerebrovascular disorders. 2nd communication: brain penetration, cerebral vascular and metabolic effects

The cerebral availability of the phenylalkylamine calcium antagonist (S)-emopamil ((2S)-2-isopropyl-5-(methylphenethylamino)-2-phenylvaleronitril e hydrochloride), was investigated in the anesthetized rat by computing the quotient of brain activity and integrated plasma activity 75 min after intraperitoneal injection of the 14C-labeled substance. The relative cerebral concentration defined in this way amounted to 2.05 for emopamil, 0.11 for verapamil and 0.03 ml/g for gallopamil, corresponding to a ratio of 70:4:1. The cerebral uptake of the same substances during a single capillary passage following intracarotid injection was determined by using tritiated water as an internal standard. Relative to the water the following brain uptake indices were obtained: (S)-emopamil 110.3, gallopamil 45.3 and verapamil 40.6%. According to these figures, emopamil is clearly superior to verapamil and gallopamil both with regard to cerebral availability and blood-brain barrier permeability. The effect of emopamil enantiomers on local cerebral blood flow was studied autoradiographically in the artificially ventilated rat anesthetized with nitrous oxide. The test substances were infused intravenously over 30 min, the determination of local cerebral blood flow being carried out 10 min after the end of the infusion. The numerical evaluation included 40 brain structures. In the investigated regions the infusion of 3 and 6 mg/kg (S)-emopamil led to an average blood flow increase of 24 and 52%, respectively. In the latter experimental group the values for the 22 cerebral structures showing a statistically significant effect were between 128 and 208% of control. In contrast, the application of 6 mg/kg (R)-emopamil did not lead to a significant change in blood flow in any of the areas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Research on the pharmacokinetics of ftorotan and pemtrane in human blood using gas-liquid chromatography

Gas liquid chromatography was used to study and compare the changes in pentrane and halothane concentrations in the blood of patients with general surgical diseases under the conditions of monopentrane and combined (pentrane plus nitrous oxide) anesthesia (19 children aged 1-14 years), monohalothane anesthesia with different types of premedication (18 children aged 6-12 years) and with different types of the general anesthesia maintenance (24 patients aged 20-52 years). The use of combined anesthesia and premedication with suppositories containing phentanyl, methacin and etaperazine under the conditions of monohalothane anesthesia makes it possible, upon the attainment of stage III1 anesthesia, to reduce the concentration of the fluorine-containing anesthetics in the venous blood of the children by 1.7-1.8 times on an average. The maintenance of the general anesthesia by subanesthetic concentrations of a mixture of halothane, pentrane, nitrous oxide and phentanyl provides for adequate general anesthesia with substantially reduced concentrations of the fluorine-containing anesthetics in the arterial and venous blood of patients at the main stage of surgical intervention: halothane concentration is reduced 1.6 and 1.7-fold, that of pentrane 2.6- and 3.6-fold, respectively.     

赛庚啶对心、脑、肾血流量的影响及对实验性脑血栓的影响

目的观察赛庚啶对大鼠脑血流量、心肌血流量及肾血流量的影响及其对以ADP、凝血酶、肾上腺素复合物为诱导剂的实验性脑血栓的影响。方法：放射性微球法。结果：赛庚啶iv2mg·kg(－1)可以使正常SD大鼠脑血流量增加28．6％，心肌血流量增加43．0％，肾皮质血流量增加45．6％，与对照组相比差异有显著性。ivlmg·kg(－1)可以抑制实验性脑血栓的形成。结论：赛庚啶可以改善心、脑、肾的血液循环。     

Effects of NG-nitro-L-arginine methyl ester on the cardiovascular system of the anaesthetized rabbit and on the cardiovascular response to thyrotropin-releasing hormone.

1. The effects of 300 mg kg-1 of the nitric oxide (NO) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) on the regional blood flow, on the flow response to 1 mg kg-1 of thyrotropin-releasing hormone (TRH) and on cerebral blood flow autoregulation were studied in urethane anesthetized rabbits subjected to unilateral sectioning of the cervical sympathetic claim. The blood flow measurements were performed by the tracer microspheres method. 2. The cerebral arteriovenous difference in oxygen saturation (CAVOD) was measured before and after the administration of L-NAME and TRH in order to ascertain whether the effects on cerebral blood flow that were observed were secondary to changes in cerebral metabolism. 3. L-NAME caused a significant decrease in blood flow in several cerebral regions; CBFtot decreased to 72 +/- 4% of control (P < 0.001). An increase in blood pressure and a concurrent decrease in heart rate and cardiac output were noted. 4. In the eye, L-NAME caused a reduction in uveal blood flow which was more pronounced on the sympathetically intact side; in the retina the blood flow decreased to 50% of control on both sides. 5. The administration of TRH in animals pretreated with L-NAME caused a significant increase in blood pressure and cerebral blood flow. 6. In L-NAME-treated animals the CBF was not affected when the mean arterial blood pressure was increased by ligation of the abdominal aorta. 7. The CAVOD increased from 56.0 +/- 5.2 to 73.6 +/- 3.5%, 20 min after the administration of L-NAME.(ABSTRACT TRUNCATED AT 250 WORDS)     

Agreement between ultrasonic Doppler venous outflow and Kety and Schmidt estimates of cerebral blood flow.

1. The present study compares the indirect Fick nitrous oxide equilibration method of Kety and Schmidt for cerebral blood flow (CBF) estimation with a direct ultrasonic Doppler index of venous outflow. 2. Cerebral blood flow was determined simultaneously by the direct measurement of sagittal sinus blood velocity and the indirect Kety and Schmidt method in five anaesthetized sheep during high and low steady states of CBF. High- and low-flow states were achieved by altering ventilation to produce hypercarbia and hypocarbia, respectively. 3. Four different sets of calculations were used to make the Kety and Schmidt estimations: arterial-venous nitrous oxide concentration differences during uptake or elution of the indicator and with or without extrapolation of arterial-venous differences to infinity. 4. During 15 min nitrous oxide administration, apparent blood:tissue equilibration of nitrous oxide was rapid in some data sets and slow in others. 5. There were no significant differences in CBF estimates between any of the four Kety and Schmidt calculations or the direct ultrasonic Doppler venous outflow method; however, CBF estimates based on nitrous oxide uptake correlated more strongly with the direct method than estimates based on nitrous oxide elution. 6. In the high-flow state, CBF estimates based on nitrous oxide uptake, but not those based on elution, distinguished between rapid and slow blood:tissue equilibration of nitrous oxide. 7. This provides validation of the Doppler sheep brain venous outflow method against the widely used Kety and Schmidt method.     

The effects of central injections of adenosine analogs on blood pressure and heart rate in the rat

Rats were implanted with chronic indwelling cannulae into the lateral cerebral ventricle. After recovery from surgery, acute experiments on blood pressure were conducted under methoxyflurane/nitrous oxide anesthesia. Rats were injected intracerebroventricularly with two adenosine analogs, 5'-N-ethylcarboxaminidoadenosine (NECA) and (-)-N-(1-methyl-2-phenylethyl)adenosine(L-phenylisopropyladenosine) (L-PIA), and the effects on blood pressure and heart rate recorded. Both analogs produced dose-related reductions in blood pressure and heart rate with L-PIA producing a more potent depression of heart rate than NECA. These effects on blood pressure and heart rate were antagonized by parenteral injections of caffeine. In separate experiments, the responses of blood pressure and heart rate to microinjection of NECA into the brainstem of rats anaesthetized with methoxyflurane/nitrous oxide were also examined. Microinjection of 2.7 nmol/kg into the fourth ventricle in the region of the area postrema produced a profound and long-lasting depression of blood pressure and heart rate. These results show that central injections of analogs of adenosine can influence the areas of the central nervous system involved in the control of cardiovascular function.     

Modelling the neural control of intrarenal blood flow

1. The aim of the present study was to produce a mathematical model that describes the way dynamic changes in renal sympathetic nerve activity affect renal, cortical and medullary blood flow. 2. Cortical blood flow (CBF) and medullary blood flow (MBF) were measured using laser-Doppler flowmetry and (total) renal blood flow (RBF) was measured by transit-time flowmetry in six pentobarbitone-anaesthetized rabbits. The renal nerves were stimulated with rectangular pulses of 2 msec width and constant voltage at frequencies of 0.5, 1, 1.5, 2 and 3 Hz. 3. An exponential function with two parameters was applied; steady state gain and a dynamic constant for the blood flow reduction with stimulation. The steady state gain coefficients were similar for RBF and CBF, but significantly less for MBF. The time taken to reach minimum flow was less for MBF than for RBF and CBF. 4. The model parameters indicate that there is differential neural control of CBF and MBF.     

笑气吸入+斯康杜尼局麻在口腔门诊无痛拔牙中的应用研究

目的观察笑气吸入配合斯康杜尼局麻在个各年龄阶段牙科焦虑症成年患者拔牙术中的效果及安全性。方法采用笑气吸入装置,患者先吸入50%笑气30~40s,待患者处于镇静状态,采用加压注射器行斯康杜尼局部浸润麻醉拔牙,记录不同牙位麻醉效果及比较患者拔牙术前、中、后的血压和心率。结果使用笑气吸入+斯康杜尼局麻的300例患者中,有效率达到98%以上,患者出现不良反应的情况较少。结论笑气吸入配合斯康杜尼局麻为牙科焦虑患者拔牙术提供了一种安全有效的麻醉方法。