Sedation Agents Differentially Modulate Cortical and Subcortical Blood Oxygenation: Evidence from Ultra-High Field MRI at 17.2 T

Background

Sedation agents affect brain hemodynamic and metabolism leading to specific modifications of the cerebral blood oxygenation level. We previously demonstrated that ultra-high field (UHF) MRI detects changes in cortical blood oxygenation following the administration of sedation drugs commonly used in animal research. Here we applied the UHF-MRI method to study clinically relevant sedation drugs for their effects on cortical and subcortical (thalamus, striatum) oxygenation levels.

Methods

We acquired T2*-weighted images of Sprague-Dawley rat brains at 17.2T in vivo. During each MRI session, rats were first anesthetized with isoflurane, then with a second sedative agent (sevoflurane, propofol, midazolam, medetomidine or ketamine-xylazine) after stopping isoflurane. We computed a T2*-oxygenation-ratio that aimed at estimating cerebral blood oxygenation level for each sedative agent in each region of interest: cortex, hippocampus, thalamus and striatum.

Results

The T2*-oxygenation-ratio was consistent across scan sessions. This ratio was higher with inhalational agents than with intravenous agents. Under sevoflurane and medetomidine, T2*-oxygenation-ratio was homogenous across the brain regions. Intravenous agents (except medetomidine) induced a T2*-oxygenation-ratio imbalance between cortex and subcortical regions: T2*-oxygenation-ratio was higher in the cortex than the subcortical areas under ketamine-xylazine; T2*-oxygenation-ratio was higher in subcortical regions than in the cortex under propofol or midazolam.

Conclusion

Preclinical UHF MRI is a powerful method to monitor the changes in cerebral blood oxygenation level induced by sedative agents across brain structures. This approach also allows for a classification of sedative agents based on their differential effects on cerebral blood oxygenation level.     

Forebrain ischemia-reperfusion simulating cardiac arrest in mice induces edema and DNA fragmentation in the brain

Brain injury affects one-third of persons who survive after heart attack, even with restoration of spontaneous circulation by cardiopulmonary resuscitation. We studied brain injury resulting from transient bilateral carotid artery occlusion (BCAO) and reperfusion by simulating heart attack and restoration of circulation, respectively, in live C57Black6 mice. This model is known to induce neuronal death in the hippocampus, striatum, and cortex. We report the appearance of edema after transient BCAO of 60 minutes and 1 day of reperfusion. Hyperintensity in diffusion-weighted magnetic resonance imaging (MRI) was detectable in the striatum, thalamus, and cortex but not in the hippocampus. To determine whether damage to the hippocampus can be detected in live animals, we infused a T(2) susceptibility magnetic resonance contrast agent (superparamagnetic iron oxide nanoparticles [SPIONs]) that was linked to single-stranded deoxyribonucleic acid (DNA) complementary in sequence to c-fos messenger ribonucleic acid (SPION-cfos); we acquired in vivo T(2)*-weighted MRI 3 days later. SPION retention was measured as T(2)* (milliseconds) signal reduction or R(2)* value (s(-1)) elevation. We found that animals treated with 60-minute BCAO and 7-day reperfusion exhibited significantly less SPION retention in the hippocampus and cortex than sham-operated animals. These findings suggest that brain injury induced by cardiac arrest can be detected in live animals.     

Do inhalation general anesthetic drugs induce the neuronal release of endogenous opioid peptides?

The antagonism of some effects of inhalation general anesthetic agents by naloxone suggests that there may be an opioid component to anesthetic action. There is evidence that this opioid action component is due to neuronal release of endogenous opioid peptides. The strongest evidence is provided by studies that monitor changes in the concentration of opioid peptides in the perfused brain following inhalation of the anesthetic. Indirect or circumstantial evidence also comes from studies of anesthetic effects on regional brain levels of opioid peptides, antagonism of selected anesthetic effects by antisera to opioid peptides and anesthetic-induced changes radioligand binding to opioid receptors. It is likely that some inhalation general anesthetics (e.g., nitrous oxide) can induce neuronal release of opioid peptides and that this may contribute to certain components of general anesthesia (e.g., analgesia). More definitive studies utilizing in vivo microdialysis or autoradiography in selected areas of the brain during induction and successive states of general anesthesia have yet to be conducted.     

结直肠癌根治术患者丙泊酚静脉麻醉期血液流变学及血流动力学变化及意义

目的:探讨结直肠癌根治术中丙泊酚静脉麻醉期患者血液流变学及血流动力学的变化及意义。方法:选择2014年3月-2015年3月我院择期行结直肠癌根治术的90例患者,按照随机数字表法分为实验组(n=45)和对照组(n=45),实验组采用丙泊酚静脉麻醉,对照组采用七氟烷(喜保福宁)吸入麻醉。记录麻醉前(T0)、诱导后90 min(T1)、诱导后150 min(T2)和进麻醉后监测治疗室(PACU)30 min(T3)4个时间点患者血液流变学及血流动力学指标,并进行比较分析。结果:实验组高切变率全血黏度、中切变率全血黏度、低切变率全血黏度在T1、T2和T3时较对照组下降显著(P0.05)。实验组心率(HR)、收缩压(SPB)在T2时均较T0显著下降(P0.05),但T3时又恢复到T0水平(P0.05),实验组和对照组舒张压(DBP)在T1、T2、T3时与T0时比较无显著性差异(P0.05)。结论:丙泊酚静脉麻醉可以降低结直肠癌患者的血液黏度,对患者血液动力学影响较小,是结直肠癌患者手术的理想麻醉药选择。     

三种不同麻醉方式对产妇血流动力学及新生儿的影响

目的;探讨硬膜外麻醉、蛛网膜下腔-硬膜外麻、气管插管全麻三种不同麻醉方式对剖宫产产妇血流动力学及胎儿的影响。方法:纳入行择期剖宫产产妇152例,采用随机表法将其分为硬膜外组(48例)、腰硬联合麻醉组(52例)、气管内插管全麻组(52例)。观察麻醉前正常状态时(T1)、麻醉成功后5 min(T2)、胎儿娩出时(T3)三个时间点产妇SBP、DBP、HR、SV、CO、SVR及胎儿相关指标,包括出生后1 min、5 min Apgar评分、脐动脉血pH、PCO_2、PO_2。结果:硬膜外麻、腰麻-硬膜外联合麻醉、全麻三组间麻醉起效时间有明显统计学差异(P0.05),气管内插管全麻组起效时间最快。三组间在T1时间点SBP、DBP、HR、SV、CO、SVR差异无统计学意义(P0.05)。在T2时间点,硬膜外麻、联合麻醉、全麻三组SBP、DBP、HR、SVR水平均较T1时间点明显降低,差异有统计学意义(P0.05)。T2时间点,全麻组SBP、DBP、HR、SVR水平高于硬膜外、联合麻醉组(P0.05)。T3时间点三组SBP、DBP、HR、SV、CO水平均较T2时间相比差异有统计学意义(P0.05)。T3时间点,全麻组SBP、DBP、SVR高于其他两组,心率低于其他两组,差异有统计学意义(P0.05)。三组间新生儿出生后1 min Apagr、5 min Apgar评分、脐动脉血学pH、PCO_2无统计学差异(P0.05)。三组间脐动脉血PO_2有明显统计学差异(P0.05),气管内插管全麻组脐动脉血PO_2最高。结论:三种麻醉均可以用于剖宫产术,全麻剖宫产术对产妇血流动力学影响最小,起效快,但对胎儿脐动脉血氧浓度有一定的影响。     

Mass-spectrometry analysis of disflurane,propofol, and fentanyl in plasma and cerebrospinal fluid

Concentrations of anesthetic agents were measured in blood plasma and cerebrospinal fluid using mass spectrometry with a membrane interface. Sampling of biological fluids was performed during balanced inhalational (disflurane and fentanyl) anesthesia and total intravenous (propofol and fentanyl) anesthesia. A rapid test method for the concentration measurement of organic molecules in biological fluids is described. This method does not require long-term sample processing before injecting the sample into the mass spectrometer interface. The pervaporation properties (uptake, diffusion, and evaporation) of anesthetic agents from biological fluids in a silicone membrane were used in the mass spectrometry interface. We report on the possibility of using a mass spectrometer with a membrane interface for the measurement of the absolute concentration of anesthetic agents in blood plasma for study of the properties of the blood–brain barrier.     

Functional brain mapping by blood oxygenation level-dependent contrast magnetic resonance imaging. A comparison of signal characteristics with a biophysical model.

It recently has been demonstrated that magnetic resonance imaging can be used to map changes in brain hemodynamics produced by human mental operations. One method under development relies on blood oxygenation level-dependent (BOLD) contrast: a change in the signal strength of brain water protons produced by the paramagnetic effects of venous blood deoxyhemoglobin. Here we discuss the basic quantitative features of the observed BOLD-based signal changes, including the signal amplitude and its magnetic field dependence and dynamic effects such as a pronounced oscillatory pattern that is induced in the signal from primary visual cortex during photic stimulation experiments. The observed features are compared with the results of Monte Carlo simulations of water proton intravoxel phase dispersion produced by local field gradients generated by paramagnetic deoxyhemoglobin in nearby venous blood vessels. The simulations suggest that the effect of water molecule diffusion is strong for the case of blood capillaries, but, for larger venous blood vessels, water diffusion is not an important determinant of deoxyhemoglobin-induced signal dephasing. We provide an expression for the apparent in-plane relaxation rate constant (R2*) in terms of the main magnetic field strength, the degree of the oxygenation of the venous blood, the venous blood volume fraction in the tissue, and the size of the blood vessel.     

Endotracheal intubation with airtraq? versus storz? videolaryngoscope in children younger than two years - a randomized pilot-study

Background

Beach chair positioning during general anesthesia is associated with a high incidence of cerebral desaturation; poor neurological outcome is a growing concern. There are no published data pertaining to changes in cerebral oxygenation seen with increases in the inspired oxygen fraction or end-tidal carbon dioxide in patients anesthetized in the beach chair position. Furthermore, the effect anesthetic agents have has not been thoroughly investigated in this context. We plan to test the hypothesis that changes in inspired oxygen fraction or end-tidal carbon dioxide correlate to a significant change in regional cerebral oxygenation in anesthetized patients in beach chair position. We will also compare the effects that inhaled and intravenous anesthetics have on this process.

Methods/design

This is a prospective within-group study of patients undergoing shoulder arthroscopy in the beach chair position which incorporates a randomized comparison between two anesthetics, approved by the Institutional Review Board of the University of Michigan, Ann Arbor. The primary outcome measure is the change in regional cerebral oxygenation due to sequential changes in oxygenation and ventilation. A sample size of 48 will have greater than 80% power to detect an absolute 4-5% difference in regional cerebral oxygenation caused by changes in ventilation strategy. The secondary outcome is the effect of anesthetic choice on cerebral desaturation in the beach chair position or response to changes in ventilation strategy. Fifty-four patients will be recruited, allowing for drop out, targeting 24 patients in each group randomized to an anesthetic. Regional cerebral oxygenation will be measured using the INVOS 5100C monitor (Covidien, Boulder, CO). Following induction of anesthesia, intubation and positioning, inspired oxygen fraction and minute ventilation will be sequentially adjusted. At each set point, regional cerebral oxygenation will be recorded and venous blood gas analysis performed. The overall statistical analysis will use a repeated measures analysis of variance with Tukey??s HSD procedure for post hoc contrasts.

Discussion

If simple maneuvers of ventilation or anesthetic technique can prevent cerebral hypoxia, patient outcome may be improved. This is the first study to investigate the effects of ventilation strategies on cerebral oxygenation in patients anesthetized in beach chair position.

Trial registration

NCT01535274     

不同麻醉方法对腹腔镜子宫全切2型糖尿病患者血流动力学、血糖水平及补体C3、C4的影响

摘要 目的：探讨不同麻醉方法对行腹腔镜子宫全切2型糖尿病（T2DM）患者血流动力学、血糖水平及补体C3、C4的影响。方法：前瞻性选择2016年1月至2019年1月期间我院收治的120例拟行腹腔镜子宫全切术的T2DM患者,采用随机数字表法将患者分为两组,A组（60例）采用靶控输注丙泊酚、瑞芬太尼全麻,B组（60例）采用靶控输注丙泊酚、瑞芬太尼复合吸入七氟醚全麻。观察两组围手术期血流动力学、血糖、胰岛素、胰高血糖素、C肽及补体C3、C4水平变化和差异,对比两组麻醉效果。结果：B组苏醒时间、拔管时间短于A 组（P＜0.05）,苏醒后视觉模拟评分法（VAS）评分低于A组（P＜0.05）。B组建立气腹前（T1）、建立气腹后1.5 h（T2）、手术结束时(T3)、苏醒时(T4) 观测点平均动脉压（MAP）高于A组（P＜0.05）。建立气腹前（M1）、建立气腹后1.5 h（M2）、术后第1 d（M3）、术后第3 d（M4）观测点胰岛素、C肽水平低于A组（P＜0.05）。M1-M4观测点血糖高于A组（P＜0.05）,M2-M4观测点胰高血糖素水平高于A组（P＜0.05）。M1-M4观测点补体C3、C4水平高于A组（P＜0.05）。结论：靶控输注丙泊酚、瑞芬太尼复合七氟醚全麻麻醉效果更好,且有助于维持腹腔镜子宫全切T2DM患者血流动力学稳定,改善补体C3、C4水平,而靶控输注丙泊酚、瑞芬太尼全麻可维持血糖水平稳定,临床应根据患者情况选择合适的麻醉方案。     

The cardiorespiratory effects of diazepam-ketamine and xylazine-ketamine anesthetic combinations in sheep

The cardiorespiratory dynamics and anesthetic effects of intravenously administered diazepam-ketamine (0.375 mg kg-1/7.5 mg kg-1) and xylazine-ketamine (0.1 mg kg-1/7.5 mg kg-1) were investigated in six domestic sheep (Ovis aries). The depth of analgesia and sedation was evaluated and the effects of the anesthetic drug combinations on hemodynamics and pulmonary mechanics were monitored before, and up to 90 minutes after, drug administration. Diazepam-ketamine and xylazine-ketamine induced effective anesthesia for periods lasting 15 minutes and 25 minutes, respectively. Both drug combinations caused transient respiratory acidosis. However, no profound effects on respiration or pulmonary function were observed. Neither anesthetic regimen caused significant effects on heart rate or pulmonary hemodynamics, but they caused significant decreases in cardiac output. Xylazine-ketamine resulted in a significant decrease in mean systemic arterial blood pressure (Psa) with a concurrent decrease in systemic vascular resistance (SVR). Diazepam-ketamine caused a significant increase in SVR without affecting Psa. Xylazine-ketamine may be contraindicated in animals with compromised heart function because of its hypotensive effects. Otherwise, both drug combinations, in the doses used, can provide short-term anesthesia suitable for minor surgical procedures and painful experimental maneuvers.     

The effects of barbiturates upon the hemodynamic responses to intravenous methionine-enkephalin in dogs: modulation by the GABA complex

In conscious animals, the intravenous administration of enkephalins increases heart rate (HR) and mean systemic arterial blood pressure (MAP); however, when given during barbiturate anesthesia, enkephalins reduce HR and MAP. We have investigated the potential role of the gamma-aminobutyric acid (GABA) complex (consisting of chloride-ion channel and binding sites for GABA, benzodiazepine, and barbiturate/picrotoxin) as the site of modulation of enkephalin responses by certain anesthetic agents in our chronically instrumented dog model. In our model, methionine-enkephalin (Met5-ENK) (35 micrograms/kg intravenously) increased HR and MAP, but following induction of general anesthesia with barbiturate (pentobarbital) or of sedation with benzodiazepine (diazepam), Met5-ENK produced vasodepressor responses despite differing levels of consciousness in the treated animals. Subsequent administration of picrotoxin restored pressor responses to Met5-ENK in the barbiturate-treated dogs, but not in those treated with benzodiazepine; picrotoxin did not alter the level of consciousness. Picrotoxin had no effect upon Met5-ENK responses in the conscious state. In contrast, alpha-chloralose, a convulsive anesthetic agent which does not appear to alter GABA complex activity, blunted but did not reverse pressor responses to Met5-ENK, despite causing a level of anesthesia similar to that produced by barbiturate. The observed pressor response to Met5-ENK during alpha-chloralose anesthesia was totally inhibited by naloxone, indicating that this response was still mediated by opiate receptors. Our data are compatible with modulation of enkephalin responses by GABA complex activity. Systemic enkephalins may generate afferent signals which may subsequently undergo GABA complex processing; the state of activation of the GABA complex may then determine whether systemic enkephalin signals are translated as vasopressor or vasodepressor responses.     

Regional hemodynamic responses to nicotine in conscious and anesthetized dogs: comparative effects of pentobarbital and chloralose

This study was conducted in 12 dogs to evaluate regional hemodynamic responses during intravenous infusion of nicotine (36 micrograms/kg/min) in the conscious state and compare them with those in the same dogs following either pentobarbital (n = 6) or chloralose anesthesia (n = 6). Values for regional blood flow were obtained with 15-microns radioactive microspheres and used to calculate regional vascular conductance. In the conscious state, nicotine increased aortic pressure (+70%) and caused hyperventilation that reduced arterial PCO2 (-44%). These systemic effects were associated with decreases in vascular conductance in the renal cortex (-48%), pancreas (-81%), duodenum (-58%), and cerebral cortex (-55%), whereas no significant change in vascular conductance was evident in spleen, liver, or myocardium. Pentobarbital anesthesia blunted the increases in aortic pressure and respiratory activity and the reductions in vascular conductance in the renal cortex, pancreas, duodenum, and cerebral cortex during nicotine infusion. In contrast, chloralose anesthesia accentuated the increase in aortic pressure and the decrease in vascular conductance in the renal cortex during nicotine infusion, while it converted no change in vascular conductance in the spleen into a decrease and no change in vascular conductance in the myocardium into an increase. Chloralose anesthesia blunted nicotine-induced hyperventilation. These findings demonstrate that general anesthetic agents may have markedly different effects on cardiovascular reflex pathways. They emphasize the importance of considering the particular characteristics of the anesthetic agent used in interpreting results from studies of cardiovascular pharmacology and physiology in anesthetized animals.     

Low dose isoflurane exerts opposing effects on neuronal network excitability in neocortex and hippocampus

The anesthetic excitement phase occurring during induction of anesthesia with volatile anesthetics is a well-known phenomenon in clinical practice. However, the physiological mechanisms underlying anesthetic-induced excitation are still unclear. Here we provide evidence from in vitro experiments performed on rat brain slices that the general anesthetic isoflurane at a concentration of about 0.1 mM can enhance neuronal network excitability in the hippocampus, while simultaneously reducing it in the neocortex. In contrast, isoflurane tissue concentrations above 0.3 mM expectedly caused a pronounced reduction in both brain regions. Neuronal network excitability was assessed by combining simultaneous multisite stimulation via a multielectrode array with recording intrinsic optical signals as a measure of neuronal population activity.     

右美托咪定联合去甲肾上腺素在全麻下腰椎手术中对患者围术期循环及术后恢复质量的影响

摘要 目的：探究右美托咪定联合去甲肾上腺素在全麻下腰椎手术中对患者围术期循环指标及术后恢复指标的影响。方法：选择2019年1月至2020年12月于我院接受治疗的68例行全麻下腰椎手术患者为研究对象,按照随机、双盲、对照的方式区分为研究组与对照组（每组各34例患者）,对照组患者术中应用右美托咪定,研究组患者在对照组基础上加用去甲肾上腺素,对比两组患者围术期血流动力学（血压、心率）变化、术中出血量、手术时间、麻醉时间、术后疼痛度、苏醒指标的影响。结果：比较显示术前（T0）、插管时（T1）两组患者的平均动脉压（Mean arterial pressure,MAP）与心率（heart rate,HR）组间差异不大（P>0.05）,但手术30 min（T2）、手术60 min（T3）、手术结束拔管（T4）时研究组MAP和HR均高于对照组（P<0.05）;研究组患者术中出血量与对照组比较无明显差异（P>0.05）,研究组患者麻醉时间低于对照组患者（P<0.05）;研究组患者苏醒躁动评分以及术后6 h疼痛度评分均低于对照组（P<0.05）。结论：全麻下腰椎手术患者联用右美托咪定与去甲肾上腺素能够显著稳定患者围术期血流动力学,缩短麻醉苏醒时间,且不增加术中出血量,不增加患者术后苏醒躁动及应激性疼痛现象,值得临床推广应用。     

瑞芬太尼复合右美托咪定在心脏手术中的麻醉效果及对血流动力学的影响

目的:分析瑞芬太尼(REM)复合右美托咪定(DEX)在心脏手术中的麻醉效果及对患者血流动力学的影响。方法:选取我院2013年12月至2015年9月行心脏手术的100例患者,按随机数字表法分为两组麻醉Ⅰ组和麻醉Ⅱ组各50例。麻醉Ⅱ组患者以REM复合DEX进行麻醉;麻醉Ⅰ组患者以REM行麻醉。比较不同麻醉方式的麻醉效果及对血流动力学的影响。结果:麻醉Ⅱ组患者手术不同时间点动脉压、心率、血氧饱和度变化不明显,(P0.05)。麻醉Ⅰ组患者插管即刻动脉压、心率、血氧饱和度下降显著,经t检验对比后有统计学意义(P0.05)。麻醉Ⅱ组Ramsay评分明显高于麻醉Ⅰ组,经t检验对比后有统计学意义(P0.05)。两组患者拔管、苏醒、恢复呼吸时间相近,无显著差异(P0.05)。麻醉Ⅱ组麻醉优良率明显高于麻醉Ⅰ组,经x~2检验对比后有统计学意义(P0.05)。结论:REM复合DEX在心脏手术中的麻醉效果确切,可维持患者血流动力学的平稳,提高镇静效果。同时不影响其拔管、苏醒和呼吸恢复,值得推广。     

The baboon model under anesthesia for in vivo cerebral blood flow studies using single photon emission computed tomographic (SPECT) techniques.

Single photon emission computed tomography of the brain can be useful in animal experimentation directed toward cerebral conditions. A well established and understood baboon model, necessarily under anesthesia, could be especially valuable in such investigations. Six normal baboons were studied under various anesthetic agents and their combinations: ketamine, thiopentone, pentobarbitone, and halothane. Cerebral blood flow (CBF) studies were performed with 99mTc-HMPAO. CBF effects from various anesthesia were detected, requiring careful choice of the anesthesia for cerebral investigations.     

Experimental nerve imaging at 1.5-T

Experimental lesions of the peripheral nerve system can be visualized in vivo by magnetic resonance imaging (MRI). Many studies of the rat peripheral nervous systems were performed on dedicated animal MR scanners with a high magnetic field strength for good spatial resolution. Here, we present an MR protocol to study experimental lesions of the rat nervous system with clinical 1.5-T MR scanners and commercially available coils. Using a three-sequence approach (T1-weighted imaging, fat-saturated T2-weighted imaging and fat-saturated T1-weighted imaging with Gd-DTPA in the same plane), the relevant signal changes of the lesioned nerve can be visualized and separated from other structures, e.g., blood vessels. Furthermore, we give an overview on different types of contrast agents used for peripheral nerve MR imaging and MR findings in selected experimental models of rat peripheral nerve injury.     

Cardiovascular responses to V1-vasopressinergic antagonism in conscious versus anesthetized rats

Experiments were performed to compare the possible effect of endogenous arginine vasopressin on renal hemodynamics between anesthetized, surgically stressed rats and conscious rats. Animals were instrumented with arterial and venous catheters as well as with a pulsed Doppler flow probe on the left renal artery. The rats were studied under the following conditions: (1) conscious and unrestrained; (2) anesthetized only; (3) anesthetized with minor surgical stress; and (4) anesthetized with major surgical stress. Two anesthetic agents were also compared, a mixture of ketamine (110 mg/kg i.m.) and acepromazine (1 mg/kg i.m.), and sodium pentobarbital (50 mg/kg i.p.). Baseline mean arterial blood pressure was significantly higher in pentobarbital-anesthetized rats following surgical stress compared with conscious animals, but blood pressure was not affected by ketamine-acepromazine anesthesia. After baseline measurements of blood pressure, heart rate, and renal blood flow, a specific V1-vasopressinergic antagonist (d(CH2)5Tyr(Me) arginine vasopressin, 10 mg/kg i.v.) was administered to each group. Mean arterial blood pressure, heart rate, and renal blood flow were monitored for an additional 15 min. Mean arterial blood pressure and renal blood flow decreased after V1 antagonism in ketamine-acepromazine-anesthetized rats with major surgical stress, but were not affected in pentobarbital-anesthetized animals. Heart rate and renal vascular resistance were not affected following V1 blockade with either anesthetic agent. These data suggest that arginine vasopressin plays a role in maintaining blood pressure and renal perfusion in ketamine-acepromazine-anesthetized rats following surgical stress, but does not have a significant effect on renal hemodynamics under pentobarbital anesthesia.     

Effects of anesthetics on systemic hemodynamics in mice

The aim of this study was to compare the systemic hemodynamic effects of four commonly used anesthetic regimens in mice that were chronically instrumented for direct and continuous measurements of cardiac output (CO). Mice (CD-1, Swiss, and C57BL6 strains) were instrumented with a transit-time flow probe placed around the ascending aorta for CO measurement. An arterial catheter was inserted into the aorta 4 or 5 days later for blood pressure measurements. After full recovery, hemodynamic parameters including stroke volume, heart rate, CO, mean arterial pressure (MAP), and total peripheral resistance were measured with animals in the conscious state. General anesthesia was then induced in these mice using isoflurane (Iso), urethane, pentobarbital sodium, or ketamine-xylazine (K-X). The doses and routes of administration of these agents were given as required for general surgical procedures in these animals. Compared with the values obtained for animals in the conscious resting state, MAP and CO decreased during all anesthetic interventions, and hemodynamic effects were smallest for Iso (MAP, -24 +/- 3%; CO, -5 +/- 7%; n = 15 mice) and greatest for K-X (MAP, -51 +/- 6%; CO, -37 +/- 9%; n = 8 mice), respectively. The hemodynamic effects of K-X were fully antagonized by administration of the alpha(2)-receptor antagonist atipamezole (n = 8 mice). These results indicate that the anesthetic Iso has fewer systemic hemodynamic effects in mice than the nonvolatile anesthetics.     

超声引导下外周神经阻滞麻醉对老年单膝关节置换术患者血流动力学和认知功能的影响

目的:探究超声引导下外周神经阻滞麻醉对老年单膝关节置换术患者血流动力学和认知功能的影响。方法:选取2017年3月-2019年3月在我院进行单膝关节置换术的老年患者82例,根据麻醉方式不同分为研究组和对照组,每组各41例。研究组采用超声引导下外周神经阻滞麻醉,对照组采用全身麻醉,对比两组的麻醉诱导时间、麻醉维持时间、手术时间等指标,两组入室麻醉前(T0)、气管插管时(T1)、切皮(T2)、止血带60 min(T3)、松止血带5 min(T4)、拔除气管导管时(T5)、术后6 h(T6)、术后24 h(T7)的收缩压(Systolic blood pressure,SBP)、舒张压(Diastolic blood pressure,DBP)、心率(Heart rate,HR)等指标,两组术前、术后6 h、术后12 h、术后24 h的认知功能评分及术后镇痛药物的使用量。结果:研究组的麻醉诱导时间明显长于对照组(P0.05);两组的麻醉维持时间、手术时间比较均无明显差异(P0.05);研究组T1、T3、T5时点HR显著低于对照组(P0.05),T2、T3时点SBP、DBP水平明显高于对照组,T3、T4、T5、T6时点SBP、DBP水平显著低于对照组(P0.05)。两组术前、术后24 h的认知功能评分对比均无统计学差异(P0.05);但研究组术后6 h、术后12 h的认知功能评分均明显高于对照组(P0.05),术后24 h、术后48 h、术后72 h的镇痛药物使用量均明显低于对照组(P0.05)。结论:在老年单膝关节置换术中,超声引导下外周神经阻滞麻醉对患者血流动力学和认知功能的影响较小,且术后镇痛药物使用量更少。