Effects of hyperventilation on conjunctival oxygen tension in humans

A polarographic conjunctival oxygen sensor was used to measure oxygen tension in a tissue bed supplied by the internal carotid artery. The shared vascular source of the conjunctiva and brain suggests that conjunctival PO2 monitoring may provide an index of cerebral perfusion. We studied the effects of hyperventilation, a known stimulus of cerebral vasoconstriction, on conjunctival oxygen tension (PcjO2) in six normal, healthy adults; arterial blood gases were simultaneously measured in four of these subjects. A 5-min period of hyperventilation to a PaCO2 near 20 torr resulted in a rapid and significant (p less than .01) increase in systemic oxygen tension as measured by arterial blood gases and a transcutaneous oxygen monitor. These values gradually returned to baseline upon cessation of hyperventilation. PcjO2, however, decreased significantly (p less than .01) during hyperventilation, suggesting vasoconstriction of the conjunctival vascular supply. Because these changes temporally correlate with the cerebral vasoconstriction during hyperventilation, the conjunctival index of tissue oxygen tension may correlate with cerebral perfusion.     

Different Cerebral Hemodynamic Responses Between Sexes and Various Vessels in Orthostatic Stress Tests

Objective. The argument about why the head‐up tilt table test (HUT) does not include the posterior cerebral circulation, which is mainly responsible for syncope, as a monitor target has not been resolved. It is also unclear whether there is a sex difference in cerebral blood flow (CBF) changes. We hypothesized that orthostatic CBF changes more in the posterior circulation than in the anterior circulation and is different between sexes. Methods. Thirty healthy volunteers (13 female and 17 male) were recruited for the HUT. The blood pressure (BP), middle cerebral artery flow velocity (MCAFV), and posterior cerebral artery flow velocity (PCAFV) were monitored simultaneously. Static cerebral autoregulation (CA) was calculated. Results. The female volunteers had a lower BP, but there was no difference in orthostatic BP changes (female versus male: 1.29% ± 5.26% versus 4.22% ± 12.65%; P = .65). The female volunteers had a significantly greater orthostatic drop in the PCAFV than in the MCAFV (23.8% ± 9.1% versus 18.2% ± 7.3%; P = .008). The static CA in the middle cerebral artery was better than in the posterior cerebral artery, although not significantly (13.6% ± 34.8% versus ? 2.8% ± 12.2%; P = .15). Conclusions. Our study showed the different cerebral hemodynamic responses between anterior and posterior circulations and between sexes during the HUT. We conclude that HUT studies for syncope should include the posterior cerebral circulation, especially for female patients.     

Investigation of cerebral haemodynamics by near-infrared spectroscopy in young healthy volunteers reveals posture-dependent spontaneous oscillations

Autonomic reflexes enable the cardiovascular system to respond to gravitational displacement of blood during changes in posture. Spontaneous oscillations present in the cerebral and systemic circulation of healthy subjects have demonstrated a regulatory role. This study assessed the dynamic responses of the cerebral and systemic circulation upon standing up and the posture dependence of spontaneous oscillations. In ten young healthy volunteers, blood pressure and cerebral haemodynamics were continuously monitored non-invasively using the Portapres and near-infrared spectroscopy (NIRS), respectively. Oscillatory changes in the cerebral NIRS signals and the diastolic blood pressure (DBP) signal have been identified by the fast Fourier analysis. Blood pressure increased during standing and returned to basal level when volunteers sat on a chair. The mean value of cerebral tissue oxygen index (TOI) as measured by NIRS did not demonstrate any significant changes. Oscillatory changes in DBP, oxyhaemoglobin concentration [O2Hb] and TOI showed a significant increase when subjects were standing. Investigation of the low frequency component (approximately 0.1 Hz) of these fluctuations revealed posture dependence associated with activation of autonomic reflexes. Systemic and cerebral changes appeared to preserve adequate blood flow and cerebral perfusion during standing in healthy volunteers. Oscillatory changes in [O2Hb] and TOI, which may be related to the degree of cerebral sympathetic stimulation, are posture dependent in healthy subjects.     

高压氧治疗脑梗死疗效观察

Background:Hypoxia and ischemia resulting from cerebral infarction can further cause a series of pathological changes such as hydrocephallus.Drug therapy can improve cerebral blood circulation and enhance flow volume and decrease infarction area.If hyperbaric oxygen is added,pathophysiological changes such as ischemia and hypoxia can be improved and normal metabolism of brain cells be restored.     

Changes in cerebral oxygenation and haemodynamics during postural blood pressure changes in patients with autonomic failure

Patients with autonomic failure suffer severe postural hypotension that may be associated with symptoms of cerebral hypoperfusion. This study utilized near-infrared spectroscopy (NIRS) to measure changes in cerebral oxygenation and haemodynamics during the head-up tilt table test in 18 patients with autonomic failure and 10 healthy age-matched volunteers. Heart rate, blood pressure (MAP), oxygen saturation, cerebral tissue oxygen index (TOI) and total cerebral haemoglobin concentration [HbT] were measured continuously. In patients with autonomic failure there was a mean (SD) reduction in MAP of 46.7 (26.5) mmHg (p < 0.005) associated with a reduction in TOI of 8.6 (6.2)% (p < 0.005) during the head-up tilt table test. In healthy volunteers mean (SD) MAP rose by 12.3 (8.0) mmHg (p < 0.005) and TOI fell by 2.6 (3.2)% (p < 0.05). There was a mean (SD) reduction in [HbT] of 3.09 (2.82) micromol l(-1) (p < 0.005) in patients, equivalent to a decrease in cerebral blood volume of 0.2 (0.18) ml/100 g. There were no changes in [HbT] in the healthy volunteers. Postural hypotension in patients with autonomic failure is associated with a substantial decrease in absolute cerebral oxygenation measured by NIRS and this might reflect a critical reduction in cerebral oxygen delivery.     

超声造影评价正常成人脑血流循环时间

目的 应用超声造影检测正常人的脑循环时间(cerebral circulation time,CCT).方法 选择47例无心脑血管病史的志愿者,应用高频超声检测颈内动脉及椎动脉的血流量,选取同时显示颈内动脉及颈内静脉的切面,由肘正中静脉团注超声造影剂SonoVue后存储图像,应用分析软件根据时间峰值曲线准确测量CCT并进行分析.根据剂量不同将受检者分为三组.当血流信号恢复到基线信号强度后,在对侧重复测定一次.根据CCT计算脑血容量,并进行统计分析.结果 47例受检者中颈部血管图像均可清晰获得,计算脑血流量为603～990 ml/min,平均(778±171)ml/min;双侧CCT均可成功检测,CCT为4.1～10.2 s,平均(6.22±1.47)s.左右两侧CCT差异无统计学意义(P＞0.05).不同注射剂量组CCT差异无统计学意义(P＞0.05).根据脑血流量及CCT计算脑血容量为54～96 ml,平均(76±27)ml.结论 结合颈部血管超声,超声造影检测CCT可以准确、便捷地估测脑血容量.     

非霍奇金淋巴瘤患者行外周血单个核细胞采集前后血细胞的变化及影响因素分析

目的 探索拟行CAR-T治疗的非霍奇金淋巴瘤患者以及健康供者使用血细胞分离机采集单个核细胞后血细胞的变化,探讨影响终产品单个核细胞数量的因素以更好的提高采集效率.方法 使用COM.TEC血细胞分离机采集23例非霍奇金淋巴瘤患者以及22例健康供者的单个核细胞,分别于采集前,采集后即刻抽取血样,检测红细胞(RBC)、白细胞...     

A New Method of Measurement of Cerebral Circulation Time: Contrast-Enhanced Ultrasonography in Healthy Adults and Patients with Intracranial Shunts

Alterations in the cerebral circulation time (CCT) are observed in several cerebrovascular diseases. We designed a new method of global CCT measurement using gray-scale contrast-enhanced ultrasound and studied healthy Chinese adults and patients with intracranial shunts. Eighty-one healthy volunteers and eight patients with intracranial shunt disease were enrolled. The contrast agent Sonovue was used. Perfusion in the carotid artery and internal jugular vein bilaterally was recorded. Start and peak filling CCTs were calculated and analyzed. Imaging of carotid vessels was uncomplicated in all patients. The bilateral start CCT was 6.23 ± 1.39 s in healthy patients. There were no significant differences within subgroups and contrast-dosage groups. In the patient group, the mean start CCT was 3.0 ± 0.56 s. There was a significant difference between the control and patient groups (p < 0.001). This new method using gray-scale contrast imaging can measure CCT and cerebral blood volume accurately. It can be used to visualize blood flow differences in real time and is less dependent on the training of the operator.     

奥扎格雷钠对脑梗死血液流变学的影响

目的：探讨脑梗死与血液流变学异常之间的关系及奥扎格雷钠对异常血液流变学的影响。方法：奥扎格雷钠800mg加入5％葡萄糖或Ringer液500ml静脉滴注，每天2次，疗程2周。患者于治疗前后分别采用LBY-N6型旋转式粘度计，以温氏法检测血液流变性；采用国产MCAS-2011型微循环图像测量分析系统，根据“甲襞微循环综合定量评价方法“对微血管形态、微血流流态及袢周状态进行测量与评分。结果：56例脑梗死患者治疗前全血粘度、血浆粘度、红细胞压积及红细胞聚集指数明显增高，甲襞微循环障碍；治疗后上述指标不同程度得到明显改善，与治疗前比较，差异有显著性。结论：奥扎格雷钠具有改善血液流变性、改善微循环障碍及降低血液粘度的作用，而血液流变性不仅可用来阐述脑梗死的发病机理，而且是指导治疗、判定药物疗效及疾病预后的重要参数之一。     

Conjunctival oxygen tension monitoring during a controlled phlebotomy

A decrease in the conjunctival oxygen tension (Pcjo2) and conjunctival index (Pcjo2/Pao2) has been shown to be an early marker of acute blood loss. We sequentially measured Pcjo2, Pcjo2/Pao2, blood pressure, and pulse rate in five healthy adults after controlled phlebotomy of 450 mL and after intravenous fluid repletion. No significant changes occurred in either the Pcjo2 or Pcjo2/Pao2 after phlebotomy or after fluid replacement. We conclude that a blood loss of 450 mL in healthy, euvolemic adults is insufficient to perturb the conjunctival index. The lower limits of sensitivity of changes in Pcjo2 and Pcjo/Pao2 in response to acute blood loss remain to be established.     

血尿酸增高与急性脑梗死相关性研究

目的探讨血清尿酸增高与急性脑梗死的相关性。方法将54例急性脑梗死患者设为研究组,55例健康体检者设为对照组,检测两组血尿酸、血糖、甘油三酯、总胆固醇,对检测结果进行相关分析。结果研究组血尿酸、血糖、甘油三酯、总胆固醇检测结果均显著高于对照组（P〈0．05或0．01）;血尿酸增高及血糖、总胆固醇升高与急性脑梗死的发生均呈显著正相关（P〈0．05或0．01）。结论急性脑梗死患者血尿酸水平显著高于正常人群,且血尿酸增高与血糖、总胆固醇升高一样,均是急性脑梗死的独立危险因素,与急性脑梗死的发病有显著相关性。     

一站式CT血管造影+CT脑灌注成像可评估脑血管狭窄程度及侧支循环的开放程度

  目的  探究一站式CT血管造影术（CTA）+CT脑灌注成像（CTP）检查在急性脑梗死合并脑血管狭窄或闭塞诊断及脑血流灌注评估中的应用价值。  方法  选择2021年1月~2022年5月共86例急性脑梗死患者作为研究对象,均给予CTA+CTP检查。根据脑血管狭窄程度将其分为轻中度组（中度狭窄、轻度狭窄,n=60）及重度组（脑血管闭塞、重度狭窄,n=26）,分析脑血流灌注指标[脑血流量（CBF）、局部血容量（CBV）、平均通过时间（MTT）、达峰时间（TTP）]对脑血管狭窄程度的评估价值;根据侧支循环开放程度将患者分为侧支循环较好组（n=36）及侧支循环不良组（n=21）,分析脑血管灌注指标对侧支循环开放程度的评估价值。  结果  86例脑梗死患者脑血管闭塞、重度狭窄、中度狭窄及轻度狭窄发生率分别为10.47%（9/86）、19.77%（17/86）、36.05%（31/86）、33.72%（29/86）;轻中度组及重度组患者患侧CBV及CBF均小于健康侧,TTP、MTT长于健康侧（P < 0.05）;重度组健康侧的CBV、CBF小于轻中度组（P < 0.05）;重度组患侧相比于健康侧CBV、CBF下降值及TTP、MTT增大值大于轻中度组（P < 0.05）;CTP指标联合检测评估脑血管狭窄程度的AUC大于CBV、CBF等指标单独检测（P < 0.05）。侧支循环不良组的CBF高于侧支循环较好组,CBV低于侧支循环较好组,MTT、TTP短于侧支循环较好组（P < 0.05）;CTP指标联合检测评估侧支循环开放程度的AUC值大于各指标单独检测（P < 0.05）。  结论  CTA+CTP检查可急性脑梗死患者脑部血流灌注情况,可用于评估脑血管狭窄程度及侧支循环开放程度。      

Using 100% oxygen does not alter the cardiovascular autonomic regulation during non-invasively simulated haemorrhage in healthy volunteers

We tested the effect of 100% oxygen on heart rate (HR), arterial blood pressure (ABP), cardiac output (CO), stroke volume (SV), total peripheral resistance (TPR), HR variability (HRV), systolic blood pressure variability (SBPV) and baroreflex sensitivity (BRS) in 20 healthy volunteers during simulated haemorrhage induced by -40 mmHg lower body negative pressure (LBNP). HRV in the high frequency region (HRV HF), BRS, ABP and TPR were significantly increased, SBPV in the low frequency region (SBPV LF), CO and SV were unchanged, and HR was significantly decreased by 100% oxygen administration during normovolaemia. HRV HF, BRS, CO and SV were significantly decreased, SBPV LF and ABP were unchanged, and HR and TPR were significantly increased by LBNP during 21% or 100% oxygen administration. There were no significant differences in cardiovascular autonomic and haemodynamic responses to LBNP during 21% or 100% oxygen administration, suggesting that 100% oxygen does not alter normal cardiovascular autonomic responses during simulated haemorrhage.     

Skin hemodynamics during change from supine to lateral position.

The purpose of this study was to identify the skin hemodynamics during the position change from supine to lateral in patients with neurodegenerative diseases. The participants were 19 patients with neurodegenerative diseases and 12 healthy volunteers. The alteration in the total concentration of oxyhemoglobin and deoxyhemoglobin, indicative of change in blood volume, was measured in the skin of the left flank by using a portable noninvasive tissue oxygen monitor by near-infrared spectroscopy. The positions were changed from the left and right lateral with a return to the supine between each procedure. In healthy volunteers, total hemoglobin concentration (skin blood volume) increased when the position changed from supine to left lateral and decreased when changed from supine to right lateral. The decreased skin blood volume gradually recovered after a change from the supine to the right lateral position in healthy volunteers. However, it did not recover in three sporadic olivopontocerebellar atrophy (OPCA) patients with marked autonomic dysfunction and one Parkinsonian patient with severe orthostatic hypotension. Our study identified that the intracutaneous blood was changing dynamically during the position change from supine to lateral and was regulated by autonomic nerve function.     

近红外光谱技术用于运动和运动想象时大脑皮质血氧反应监测的研究

目的:使用近红外光谱技术监测运动和运动想象时大脑血氧反应的变化以探讨运动和运动想象运用于脑卒中偏瘫患者康复治疗和评价的理论依据。方法:选取64名健康大学生,随机分为两组:运动组32名,运动想象组32名。运用近红外光谱技术监测运动组受试者安静时和运动时大脑皮质的血氧代谢相应变化情况,以及运动想象组受试者安静时和运动想象时大脑皮质的血氧代谢相应变化情况,并将监测结果进行统计学比较和分析。结果:①运动时,大脑氧合血红蛋白和总血红蛋白明显增加,而还原血红蛋白下降。②运动想象时,也呈现大脑氧合血红蛋白和总血红蛋白增加,而还原血红蛋白下降。与安静时进行比较,差异均有显著性意义。结论:运动想象与实际运动同样会提高大脑皮质血氧饱和度,改善相应区域大脑皮质血氧供应。     

Differences in vascular effects and removal of endothelin-1 in human lung,brain, and skeletal muscle,

Summary. To investigate the effects and elimination of endothelin-1 in humans, an intravenous infusion of endothelin-1 (ET-1) (4 pmol kg^-1 min^-1 for 20 min) was given to 10 healthy volunteers. Arterial plasma endothelin-1 like immunoreactivity (ET-1-LI) increased eleven-fold. The fractional extraction of ET-l-LI was 41% and 30% across the pulmonary and skeletal muscle vascular beds, respectively. The lung eliminated almost half of the administered ET-1. No fractional extraction was found in the cerebral circulation. The pulmonary oxygen uptake (VO₂)was increased slightly by endothelin-1. Across both the cerebral and skeletal muscle vascular beds the arterio-venous oxygen difference decreased (P < 0–05), suggesting vasodilation, the effect lasting up to 1 h after the end of endothelin-1 infusion in the cerebral circulation. Arterial-pulmonary artery oxygen difference increased by 20%. ET-1 infusion led to a decrease in heart rate (10%), cardiac output (14%) and stroke volume (8%) (all with P < 0'05) as well as a 7% increase in mean arterial blood pressure. Pulmonary and systemic vascular resistance increased by 67% and 25%, respectively (P < 0–05). These results demonstrate the regional differences in the removal of circulating endothelin-1, the lung being mainly responsible for the plasma elimination. Endothelin-1 seems to exert both vasoconstrictive and vasodi-latory actions in humans, probably depending on differences in receptor populations and endothelium configuration in various vascular beds.     

A comparative evaluation of "cerebral oximetry" during anesthesia with xenon and other anesthetics

The oxygen status dynamics during the general anesthesia is one of the most important issues of anesthetic monitoring. The set target was to study the cerebral oximetry (rSO2) in anesthesia with xenon as compared with other anesthetics. A total of 80 patients (class ASA I-II) were examined in the venectomy surgery. According to an anaesthetic used in induction and anesthesia management, the patients were divided into 3 groups. Group 1--40 patients with xenon mono-anesthesia; group 2--20 patients with propofol + N2O + neurolpangesia; and group 3--20 patients with N2O + ftorotan. At xenon induction, rSO2 went up by 6.4%. At propofol induction, there were no changes in rSO2. A biggest increase in the cerebral blood circulation was noted, at the anesthesia management stage, in the patients' group, who received ftorotan; a lesser increase was registered in xenon anesthesia. An increased rSO2 level was higher, during the wakening stage, in case of ftorotan administration than in the group, which received xenon; the process of recovering the initial parameters was slower in the former group. Xenon and ftorotan were shown to contribute to a higher oxygen status and an increased volume of the cerebral blood circulation. In case of xenon mono-anesthesia, there was a smaller increase in the cerebral blood circulation as compared to N2O + ftoratan anesthesia. Further special investigations are needed to give a final answer to the question on whether it is possible to use xenon in neuroanesthesiology and in intensive care of patients with a neuroresuscitation-type pathology of the brain.     

Portapres and differential oscillometric finger blood pressure changes during deep breathing test in the assessment of BRS index

The aim of this study was to investigate changes in the finger blood pressure during a deep breathing test (DB) and to find out whether the mean blood pressure might be used as a substitute for the systolic pressure in calculations of baroreflex sensitivity from data derived from the DB test. Continuous beat-to-beat finger pressure was recorded by the volume clamp method (Portapres model 2 monitor). In addition, the mean arterial pressure was recorded by the modified oscillometric method (UT9201 beat-to-beat monitor, University of Tartu, Estonia). Fifteen healthy volunteers, aged 25-56 years, were studied. The amplitude of respiration-linked oscillations in the Portapres systolic (Psyst) and mean blood pressure (Pmean) was 22.2 +/- 8.8 and 16.6 +/- 5.8 mmHg, respectively. There was no significant difference between the amplitudes of induced changes in Pmean recorded by the two devices: the amplitude of oscillations in the mean blood pressure recorded by the differential oscillometric monitor was 16.0 +/- 5.9 mmHg. The amplitude of oscillations in Psyst correlated significantly with the amplitude of oscillations in Pmean recorded either by Portapres or by UT9201 (r=0.95 and 0.98, respectively). The high correlation between the amplitudes of oscillations in mean and systolic blood pressure allows to conclude that mean arterial pressure changes during a DB test might be used instead of systolic pressure changes in calculation of the ratio of changes in pulse interval to changes in blood pressure, which is considered to reflect baroreflex sensitivity.     

急性脑血管病患者外周血、脑脊液白细胞计数的动态研究

目的：探讨白细胞增多在急性脑血管病（ＡＣＶＤ）发病中的作用。方法：对１５０例ＡＣＶＤ患者外周血和脑脊液（ＣＳＦ）白细胞计数进行了动态观察。结果：ＡＣＶＤ患者急性期外周血和ＣＳＦ中白细胞计数均显著高于对照组（Ｐ均＜０．０１）；外周血和ＣＳＦ中白细胞计数在病后４８小时开始升高，７２小时达高峰；随着病情改善，白细胞计数逐渐恢复正常；且白细胞计数与ＡＣＶＤ患者的病情严重程度及预后存在一定相关性（ｒ＝０．３９５，Ｐ＜０．０１）；病变部位不同，白细胞计数的变化明显不同〔基底节出血（或梗死）＞脑叶出血（或梗死）＞其它部位出血，Ｐ＜０．０１或Ｐ＜０．０５〕。结论：外周血和ＣＳＦ中的白细胞计数可作为判断ＡＣＶＤ病情、病变部位及预后的辅助指标；白细胞参与了ＡＣＶＤ的病理生理过程，并在其发病和脑组织损伤中起重要作用。     

Oxymétrie cérébrale

Two main technologies have been proposed to monitor cerebral oxymetry. Near infrared spectroscopy (NIRS) is a non invasive device theoretically dedicated to measure cerebral blood oxygen saturation (ScO₂). The second device allows the invasive measurement of interstitial O₂ partial pressure in brain tissue (PtiO₂). Despite improvements in technologies, NIRS does not allow to measure exclusively cerebral blood saturation since NIRS signal is strongly affected by extracranial tissue blood saturation. In contrast, the invasive measurement of PtiO₂ is reliable and allowed to identify frequent episodic cerebral hypoxic injuries unrelated to known determinants of cerebral O₂ transport. Interestingly, integration of PtiO₂ measurement in multimodal monitoring allowed the identification of a new pathologic entity involved in secondary cerebral ischemic insults.