An observational assessment of the sublingual microcirculation of pregnant and non-pregnant women

BackgroundThe microcirculation is responsible for distribution of blood within tissues, delivery of oxygen and other nutrients, and regulation of blood pressure. The objective of this study was to compare the sublingual microcirculation of pregnant participants to that of comparable non-pregnant volunteers.MethodsTwo groups of participants were recruited: a group of pregnant, non-laboring women with singleton pregnancies at term gestation and a control group of age-comparable non-pregnant volunteers. A sidestream dark field imaging device was applied to the sublingual mucosal surface obtaining a steady image for at least 20 s duration, in five visual fields. The resultant five video clips per participant were analyzed blindly and at random to prevent coupling between images. The mean microvascular flow index values for each group were compared using a paired t-test.ResultsThirty-seven participants were recruited (19 pregnant, 18 non-pregnant); a single pregnant participant was withdrawn because of technical issues. Baseline characteristics were similar with the exception of weight and body mass index. The mean microvascular flow index was significantly higher in the pregnant group 2.7 ± 0.2 compared to the non-pregnant group 2.5 ± 0.3 (P = 0.021), while the perfused vessel density and proportion of perfused vessels were not significantly different (P = 0.707 and 0.403, respectively).ConclusionThe microvascular flow index of pregnant women is higher than a comparable non-pregnant group, which appears to correlate with the physiological changes of pregnancy.     

异丙酚和硫喷妥钠对颅脑手术患者脑血流的影响

应用经颅超声多普勒（ＴＣＤ）监测仪观察异丙酚、硫喷妥钠对颅脑手术患者大脑中动脉血流速度的影响。选择２２例择期手术患者，ＡＳＡＩ～ Ⅱ级，年龄 ２０～５８岁，随机分为二组：异丙酚组（２. ０ｍｇ／ｋｇ，ｎ＝１２例）和硫喷妥钠组（４ｍｇ／ｋｇ，ｎ＝１０例）。监测指标包括大脑中动脉血流速度（ＣＢＦＶ）、心率（ＨＲ）、平均动脉压（ＭＡＰ）和呼气末ＣＯ２分压。测定程序为给药前５分钟和给药后ＩＱ分钟，通过控制呼吸维持ＰｅｔＣＯ２相对恒定。结果表明，异丙酚组ＭＡＰ、搏动指数，峰值和平均大脑中动脉血流速度分别下降１３％、２９％、３１％和２０％，而硫喷妥钠组则分别下降９．７％、１４％、２２％和１３％。除给药后血管阻力指数异丙酚组明显低于硫喷妥钠组外，其余各指标两组间无显著差异。异而酚对脑循环的影响和硫喷妥钠相似，对颅脑手术患者麻醉诱导是有益的。     

妇科腹腔镜手术中Trendelenburg体位时脑血流动力学的变化

目的应用经颅多普勒超声监测Trendelenburg体位(简称T位)时脑血流动力学的变化。方法择期腹腔镜下妇科手术患者40例,常规全身麻醉后行颈内静脉球部置管,监测麻醉诱导前(T1)、麻醉诱导后(T2)、气腹后(T3)、T位即刻(T4)、T位后30min(T5)、体位恢复后(T6)大脑中动脉平均血流速度(Vm)、搏动指数(PI)、阻力指数(RI),计算脑灌注压(CPP)。同时测量颈内静脉压,并于T2、T5采颈内静脉球部、桡动脉血进行血气分析。计算动-颈内静脉氧分压差(Da-jvO2)、二氧化碳分压差(Da-jvCO2)、血乳酸浓度差(Da-jvLac)和血糖浓度差(Da-jvGlu)。结果与T1时比较,T2时患者Vm、CPP明显降低(P0.05);与T2时比较,T4~T6时Vm明显升高(P0.05),T4、T5时PI、CVP和T5时RI、CPP明显升高(P0.05);T5时Da-jvO2明显降低(P0.05),Da-jvCO2、SjvO2明显升高(P0.05)。结论 Trendelenburg体位30min存在大脑过度灌注和脑氧摄取量减少,但未造成明显脑组织代谢障碍。     

Effects of sevoflurane and isoflurane on the ratio of cerebral blood flow/metabolic rate for oxygen in neurosurgery

Purpose. To examine the changes in cerebral blood flow (CBF) equivalent (CBF divided by cerebral metabolic rate for oxygen) during craniotomy under isoflurane and sevoflurane anesthesia in patients with intracranial disorders. Method. In 16 neurosurgical patients (8 anesthetized with isoflurane and 8 with sevoflurane), the CBF equivalent was measured while the end-tidal concentration of the selected volatile anesthetic was maintained at 0.5 and 1.0 minimum alveolar concentration (MAC) before surgery, and then 1.0 MAC during surgery, which lasted more than 4 h. Results. There was no significant difference in CBF equivalent at 0.5 MAC between the isoflurane (20 ± 4 ml blood/ml oxygen) and the sevoflurane (19 ± 4 ml blood/ml oxygen) groups. With increasing anesthetic depth from 0.5 to 1.0 MAC, the CBF equivalent significantly (P < 0.05) increased in both groups (22 ± 7 and 21 ± 5, respectively). At 1.0 MAC during operation, the CBF equivalent with both anesthetics was maintained with minimal fluctuation for 4 h. There were no significant differences in the average value of the CBF equivalent during a 4-h period at 1.0 MAC between the isoflurane (23 ± 5) and the sevoflurane (20 ± 4) groups. Conclusion. Deepening anesthesia from 0.5 to 1.0 MAC with isoflurane and sevoflurane produced a slight increase in the CBF equivalent. The CBF equivalent at 1.0 MAC was maintained with no difference between the two agents during 4 h of neurosurgery. Received: August 2, 1999 / Accepted: April 3, 2000     

猫脑缺血时脑不同部位脑血流与氨基酸的变化

目的 比较缺血时猫脑不同部位脑血流、氮基酸的变化并研究两者之间的关系。方法 利用激光多普勒血流计，持续监测猫脑不同部位（颞叶、枕叶）在脑缺血时脑皮层表面的血流变化；利用微透析技术，测定相同位置细胞间隙中的氨基酸变化。结果 在阻断猫大脑中动脉（MCA）后，颞叶和枕叶部位的脑血流迅速下降，分别为正常值的21．44％和23．61％，并在2h内缓慢下降；微透析液中谷氨酸浓度迅速增加，可达到正常值的80余倍。结论 缺血时猫颞叶和枕叶的脑血流与谷氨酸浓度变化相同，差异无统计学意义。     

Cerebral blood flow in minor cerebral contusion

Seventeen patients with minor cerebral contusion were selected from a series of patients with head injuries of various severity, who had undergone repeat evaluations of the regional cerebral blood flow. The mean global flow (expressed as mean global initial slope index) on early examination was found to be significantly lower, compared with that recorded in healthy volunteers. A tendency towards the recovery of higher flow values was apparent in repeat evaluations that were performed several weeks after the injury. Interhemispheric asymmetries of flow were a common occurrence, with lower perfusion and reduced attenuation values on computed tomography scans being, however, in good agreement only in approximately half of the cases.     

Pulsatile flow improves cerebral blood flow in pediatric cardiopulmonary bypass

The objective of this study was to evaluate the effect of pulsatile flow on cerebral blood flow (CBF) in infants with the use of a mild hypothermic cardiopulmonary bypass (CPB). Thirty infants scheduled for open heart surgery were randomized to the pulsatile group (Group P, n = 15) and nonpulsatile group (Group NP, n = 15). In Group P, pulsatile perfusion was applied during the aortic cross‐clamping period, whereas nonpulsatile perfusion was used in Group NP. The systolic peak velocity (Vs), the end of diastolic velocity (Vd), the mean velocity (Vm), and the pulsatility index (PI) and the resistance index (RI) of the middle cerebral artery were measured by a transcranial Doppler (TCD) ultrasound after anesthesia (T1; baseline), at the beginning of CPB (T2), 10 min after aortic cross‐clamping (T3), 3 min after declamping (T4), at the cessation of CPB (T5), and at the end of the operation (T6). During T3 and T4, the Vs in Group P was significantly higher than in Group NP. However, there were no statistically significant differences between Vd and Vm. The PI and RI in Group P were also higher than those in Group NP (both P < 0.05). During T5, Vd and Vm were higher in Group P (P < 0.05), whereas there was no difference in Vs. Additionally, PI and RI in Group P were significantly lower than those in Group NP (P < 0.05). However, there was no difference during T6. Pulsatile perfusion may increase CBF and decrease cerebral vascular resistance in the early period after mild hypothermic CPB.     

Cervical spinal cord stimulation increases cerebral cortical blood flow in an experimental cerebral vasospasm model

Summary Background. Cerebral microcirculatory changes during cerebral vasospasm after aneurysmal subarachnoid haemorrhage (SAH) are still controversial and uncertain. The aim of our study is to demonstrate that spinal cord stimulation (SCS) augments cerebral cortical microcirculatory blood flow in an experimental cerebral vasospasm model by using Laser Doppler Flowmetry (LDF).Method. The experiments were carried out on 24 New Zealand rabbits. Three experimental groups were designed. In group 1, Cerebral cortical blood flow (CCoBF) was evaluated by LDF in 8 rabbits. In group 2, Intracisternal saline injection and cervical epidural electrode placement without SCS were performed in 8 animals before LDF. In group 3, LDF was performed before and after SCS on the 4^th day of SAH in 8 rabbits. CCoBF parameters obtained from LDF data were compared.Findings. The occurrence of vasospasm after SAH was demonstrated with significant changes in LDF values. In all SAH animals, SCS resulted in significant increase (30%) in CCoBF. This increase was observed to continue even after the cessation of the stimulation.Conclusions. These results indicate that SCS improves cortical ischemia due to vasospasm after induced SAH. The cervical SCS may constitute a new therapeutic modality in treating disturbed CCoBF due to vasospasm.     

Effect of ketanserin on cerebral blood flow autoregulation in healthy volunteers

Summary The effect of a clinically relevant dose of ketanserin (10 mg as a bolus followed by an infusion of 6mg/h) on cerebral blood flow (CBF) and CBF autoregulation was examined in 12 healthy volunteers. Changes in CBF were estimated by the cerebral arteriovenous-oxygen saturation difference method, while mean arterial blood pressure (MABP) was increased by norepinephrine and decreased by ganglionic blockade (trimethaphan camphosulphonate) combined with lower body negative pressure one hour after the infusion of ketanserin. During ketanserin infusion, MABP fell insignificantly by 2.5 mmHg (6 to –2), while CBF rose insignificantly by 5 ml/100 g/min. Autoregulation was preserved in all volunteers. CO₂-correction factors from 0 to 4.6% CBF/0.1 kPa were used. The lower limit of CBF autoregulation was 82 mmHg (80–86) with an SE of 3 mmHg (1–5) similar to a previous control group of healthy volunteers. Aside from a major decrease in MABP in one subject, no adverse side effects were observed.The present study shows that CBF autoregulation is maintained during ketanserin infusion.     

Precerebral arterial blood flow pattern in intracranial hypertension with cerebral blood flow arrest

Summary A pulsed echo Doppler flowmeter was used to confirm cerebral flow arrest in patients with intracranial hypertension resulting in a cerebral perfusion pressure of zero or close to zero. The cerebral angiograms showed non-filling. The term brain tamponade is used for this condition. The patients had a mean arterial blood pressure at the time or recording ranging from 70 to 160 mmHg. Under these conditions the transcutaneous recording of internal carotid artery flow velocity immediately distal to the carotid bifurcation showed a reverberating flow pattern with marked pulsations. The forward flow in systole was counterbalanced by the retrograde flow during diastole resulting in a net flow of zero. This flow pattern is basically caused by a combination of intracranial vascular obstruction, the arterial blood pressure at the site of measurement, and finally the compliance of the distal arterial segment as well as the intracranial compliance. This noninvasive method is of potential value in the determination of intracranial flow arrest.     

应用SPECT研究地氟醚麻醉对人脑血流分布的影响

目的研究吸入不同浓度地氟醚麻醉下健康志愿者脑血流(CBF)分布的动态变化。方法选择9名志愿者,每位志愿者分别在清醒、吸入0.5和1.0MAC地氟醚后采用单光子发射计算机断层成像(SPECT)仪进行扫描,观察地氟醚麻醉下人局部脑血流(rCBF)的动态变化。结果全脑CBF计数在清醒时为127.5±23.1,吸入0.5MAC地氟醚麻醉后全脑CBF计数为130.8±25.4,吸入1.0MAC地氟醚后为128.8±22.9,三组间比较差异无显著意义;额叶、顶叶、颞叶、枕叶、中脑、小脑、丘脑、海马、基底核、扣带回和舌回等脑区rCBF计数差异也均无显著意义。结论在保持PETCO2和MAP稳定且在正常范围时,吸入地氟醚麻醉不影响人脑内血流量的分布。     

利多卡因对脑挫伤鼠局部脑血流量的作用

目的　探讨盐酸利多卡因对急性局部脑挫裂伤大鼠伤侧及对侧脑组织局部血流量(r CBF)的影响。方法　利用Feeney法制作大鼠急性局部脑挫伤模型 ,然后用 0 .2 %盐酸利多卡因进行试验性治疗 ,连续观察大鼠脑挫伤侧及挫伤对侧大脑皮层局部脑血流量的变化。同时对对照组大鼠用同样的方法进行治疗 ,观察利多卡因对正常大脑血流量的影响。结果　盐酸利多卡因使正常脑组织局部血流量自 3 5 .71ml/ 10 0g .min-1下降至 3 0 .93ml/ 10 0g .min-1(P <0 .0 5 ) ,但使挫伤脑组织局部脑血流量明显高于未用药组 (P <0 .0 1)。结论　利多卡因可阻止挫伤脑组织局部血流量的减少并改善其局部脑血流量。     

Brain oedema,intracranial pressure and cerebral blood flow

Brain oedema leads to pathological changes in intracranial pressure (ICP) and cerebral blood flow in a wide range of clinical scenarios, because the brain produces oedema in response to many diseases. Clinical management often focuses on minimizing elevations of ICP and maintaining adequate cerebral blood flow. A working knowledge of physiological principles linking brain oedema, ICP and blood flow is essential for clinicians facing these clinical problems. These principles are explained here, and also some insights are provided concerning the mechanisms of disease on the cellular level. This is then applied to the clinical problem of traumatic brain injury illustrating physiological principles in clinical practice.     

A review of the effects of external pressure on skin blood flow

The human foot is a complex mechanical structure consisting of bones, ligaments and joints. They act together to provide a robust system capable of absorbing and dissipating the intermitted pressure that is subjected to its plantar surface during walking to prevent soft tissue breakdown. Current studies suggest that plantar foot pressure may lead to soft tissue breakdown (e.g. neuropathic ulceration) and hence research has so far concentrated on investigating the mechanical effects of plantar foot pressure on the foot’s integrity. This has been possible through the widely available pressure and force platforms as well as in-shoe pressure systems. However, to understand how plantar foot pressure causes soft tissue breakdown it is vital to investigate both the physiological–mechanical interactions between the skin and plantar foot pressure. This review suggests that with the current advances in technology, the physiological response of skin blood flow to mechanical plantar foot pressure should be investigated and correlated further, both during static and dynamic loading, by developing a new system capable of either measuring both variables simultaneously or by synchronising two systems in real time.     

尼莫地平、别嘌呤醇对完全性脑缺血后脑血流和氧耗影响的实验研究

２４只健康杂种犬随机平分为四组，单纯缺血组，尼莫地平组，别嘌呤醇组和复合治疗组。各治疗组在完全性脑缺血２０分钟后即刻，静注２０ｕｇ／ｋｇ尼莫地平或别嘌呤醇 ２０ｍｇ／ｋｇ，观察再灌注期间脑血流及氧耗的变化。研究结果显示，各治疗组脑血流量在再灌注期间明显增加，５～３０分钟时达最大值。随时间延长，脑血流量逐渐减少。再灌注初期，脑血管阻力明显降低。随后，脑血管阻力逐渐增加。脑组织可供氧量、矢状窦氧分压与脑血流量变化一致，脑组织氧耗变化不显著。本研究表明，尼莫地平。别嘌呤醇可以改善完全性脑缺血后微循环障碍，增加脑血流和可供氧量。两种药物可部分地发挥协同治疗作用。     

The effect of ketanserin on cerebral blood flow and oxygen metabolism in healthy volunteers

Summary The effect of the anti-hypertensive agent ketanserin on average global cerebral blood flow (CBF) and average global cerebral oxygen metabolism (CMRO₂) was examined in 8 healthy volunteers. CBF and CMRO₂ were measured with the Kety-Schmidt technique before ketanserin administration (baseline) and after administration of 2 different doses of ketanserin intravenously (dose I: 10 mg bolus and an infusion of 6 mg/h; dose II: 20 mg bolus and an ifusion of 20 mg/ h). Baseline CBF and CMRO₂ were 60 and 3.6 ml/100 g/min, respectively, and were not changed by administration of ketanserin dose I. During administration of dose II, however, CBF fell to 52 ml/ 100 g/min (p=0.05) and CMRO₂ was reduced to 3.2 ml/100 g/min (p < 0.05).We conclude that when administered in a high dose, ketanserin has the ability to depress cerebral oxygen metabolism, but when administered in a clinically relevant dose ketanserin does not influence average global CBF or average global CMRO₂. Ketanserin could be a safe antihypertensive drug in neuroanaesthesia or in the neuro-intesive care unit.     

机械通气对室间隔缺损患儿脑氧合和脑血流速度的影响

目的探讨麻醉诱导期间机械通气变化对室间隔缺损(ventricular septal defect, VSD)修补术患儿区域脑组织氧饱和度(regional cerebral oxygen saturation, rScO_2)和大脑中动脉血流速度(cerebral blood flow velocity, CBFV)的影响。方法选择VSD修补术患儿67例,男34例,女33例,年龄1岁,体重3.4～11.0 kg,ASAⅡ或Ⅲ级。入室麻醉诱导后气管插管,调整通气参数使P_(ET)CO_2初始值为30 mmHg(T_(30))。持续使用Fore-Sight实时监测右侧额部rScO_2,TCD间断测量CBFV_(收缩期)、CBFV_(舒张期)、CBFV_(平均值)。通过调整通气参数使P_(ET)CO_2逐渐上升至35 mmHg(T_(35))、40 mmHg(T_(40))、45 mmHg(T_(45)),记录对应的CBFV值以及rScO_2,计算每分钟通气量(MV)和T_(30)—T_(35)、T_(35)—T_(40)、T_(40)—T_(45)三个时段的脑血管CO_2反应性(CO_2R)。结果 T_(30)—T_(45)时rScO_2、CBFV_(收缩期)、CBFV_(舒张期)、CBFV_(平均值)均明显增大(P0.01),PI、RI均明显减小(P0.01)。T_(35)—T_(40)时CO_2R在最高值。结论室间隔缺损患儿在麻醉诱导阶段,机械通气对脑氧合和大脑中动脉脑血流速度有明显影响,正常低通气能明显增加脑氧合和脑血流速度。     

腹腔镜手术中对大脑中动脉血流的影响

目的：观察腹腔镜胆囊切除术对病人大脑中动脉血流的影响。方法：采用TCD检测19例全麻病人在气腹前、气腹时和气腹后的平均血流速度（ Vm）、脉动指数（PI）和无创伤动脉血压。结果：各时期Vm无明显变化；PI在气腹时期明显增高，气腹后恢复正常；动脉收缩压和舒张压在气腹时增高，舒张压在气腹后仍高于气腹前水平。结论：腹腔镜胆囊切除术中CO2气腹可通过CO2吸收入血而使脑血管阻力有一定程度的改变，但只要PaCO2维持在正常范围，CO2对脑血流的影响不大。