The effects of clonidine on arterial baroreflex sensitivity and cardiopulmonary baroreflex control of sympathetic nerve activity in patients with left ventricular dysfunction

Background: Clonidine is a potent sympatholytic drug with central neural effects. The aim of this study was to evaluate the effects of clonidine on arterial baroreflex sensitivity (BRS) and cardiopulmonary (CP) baroreflex control of muscle sympathetic nerve activity (MSNA) in patients with left ventricular (LV) dysfunction. Method: Twenty patients were randomly assigned to either clonidine or placebo groups (10 in each group). BRS (by phenylephrine method) and CP baroreflex (by lower body negative pressure) effects on sympathetic nerve activity (circulating norepinephrine and MSNA recordings) were measured before and after a 4‐week treatment period. Results: Clonidine lowered blood pressure and heart rate. Clonidine was accompanied not only by a decrease in plasma noradrenaline (from 444 ± 196 to 260 ± 144 pg ml^?1) but also by a reduction in directly measured MSNA (from 47 ± 16 to 36 ± 16 bursts min^?1). BRS increased significantly from 3·01 ± 1·19 to 6·86 ± 2·84 ms mmHg^?1 after clonidine. When expressed as per cent change in MSNA during CP baroreceptor stimulation, CP baroreflex control of MSNA was significantly increased from 9·26 ± 8·93% to 28·83 ± 11·96% after clonidine. However, there were no significant changes in the measured variables in the control group. Conclusion: Clonidine enhanced BRS and CP baroreflex control of MSNA while reducing baseline sympathetic activity in patients with LV dysfunction.     

Increased sympathetic tone in forearm subcutaneous tissue in primary hypothyroidism

Summary. Sympathetic reflex regulation of subcutaneous blood flow (SBF) in the forearm was studied in eight patients with primary hypothyroidism. Diastolic arterial pressure was ≥95 mmHg in five patients. SBF was determined by local clearance of Na^99mTcO₄. Sympathetic vasoconstriction normally seen after lowering the forearm 40 cm below heart level was absent since SBF only decreased by 4% (± 7%, P > 0·1) during these conditions. In head-up vertical position we noticed a diminished baroreceptor response as SBF at heart level was reduced by 11% (±7%, P < 0·1) compared to supine position. After proximal local anaesthesia SBF increased by 351% (±81%, P < 0·01) and disclosed a normal vasoconstrictor response as SBF was reduced by 53% (±5%, P < 0·01) during arm lowering. Five of the treated patients were restudied in the euthyroid state. Mean arterial pressure was reduced in mean by 20 mmHg (± 6 mmHg, P < 0·02) during treatment and a significant vasoconstriction was observed both during arm lowering (SBF =-52% (±6%, P<0·02)) and in head-up vertical position (SBF= -45% (± 11%, P<0·02)). In conclusion sympathetic vasoconstrictor activity in adipose tissue is markedly increased in primary hypothyroidism. Sympathetic tone and arterial pressure are reduced during treatment.     

运动与脑血流量

人体进行随意运动时,支配前调节运动的大脑皮质的局部电运动增强,该区细胞代谢水平改变,从而局部脑血流量（rCBF）也发生变化。不同的rCBF的改变表示了相应运动涉及运动皮质的范围,其研究对认识脑的基本活动规律和特性有重要意义。本文简略介绍了rCBF的测量方法,并描述了受试者进行不同类型随意运动时皮质各个区域rCBF的变化和分布情况。     

动态动脉硬化指数与血压变异性的关系

目的 研究原发性高血压患者的动态动脉硬化指数(Ambulatory arterial stiffness index,AASI)与血压变异性(blood pressure variability,BPV)的关系.方法 随机选择120例原发性高血压患者进行动态血压监测,测定BPV、AASI.结果 AASI与24小时平均收缩压(r=0.231,P＜0.001)、24小时舒张压标准差(r=-0.132,P＜0.01)、24小时收缩压变异性(r=-0.13,P＜0.01)、24小时舒张压变异性(r=-0.21,P＜0.01)及勺型血压(r=-0.13,P＜0.01)有明显的相关性.AASI与24小时平均收缩压(β=0.018,P＜0.001)、24小时舒张压标准差(β=-0.011,P＜0.01)、24小时收缩压变异性(β=0.036,P＜0.01)、24小时舒张压变异性(β=-0.01,P＜0.01)、勺型血压(β=-0.15,P＜0.01)、及左心室质量指数(β=0.022,P=0.034)之间有线性回归关系.结论 AASI与BPV之间有明显的相关性.     

Renal Gluconeogenesis and Blood Flow during Endotoxic Shock

Objectives: To determine whether endotoxic shock decreases the renal gluconeogenic capacity and the renal artery blood flow.
Methods: An in-vivo, murine, nonrecirculating kidney perfusion model was studied in a trauma research laboratory. Each of 12 fasted, male Holtzman rats (shock n = 6, control n = 6) was injected with 1 mL of normal saline or endotoxin (20 mg/kg). Five hours after the injection, all the rats were anesthetized and blood samples were obtained for the determination of the plasma glucose. Right renal artery blood flow was measured by an ultrasonic small-animal flow meter. The kidney was then perfused via the renal artery with 37°C, oxygenated, glucose-free Krebs-Henseleit solution in the presence of 100 μmol of phloridzin to inhibit the cellular uptake of glucose. Renal glucose production was determined by measuring glucose in both renal vein effluent and urine. After 30 minutes of equilibration, 5 mmol of lactate and 0.5 mmol of pyruvate were added to the perfusate as a gluconeogenic substrate. Renal vein and ureteral effluent samples were collected after 5, 10, and 15 minutes.
Results: The endotoxic shock group showed hypoglycemia (p < 0.05) as well as a decrease in renal artery blood flow (p < 0.05). Gluconeogenic stimulation was demonstrable in both the control and the endotoxic shock groups after 15 minutes of perfusion with substrate (p < 0.05). However, renal gluconeogenesis was significantly attenuated in the endotoxic shock group compared with the control.
Conclusions: Renal glucose production in response to a gluconeogenic substrate is significantly attenuated during the hypoglycemic phase of endotoxic shock. Endotoxic shock also causes a significant decrease of renal artery blood flow     

Complete Recovery From Intractable Complex Regional Pain Syndrome, CRPS-Type I, Following Anesthetic Ketamine and Midazolam

Objective: To describe the treatment of an intractable complex regional pain syndrome I (CRPS-I) patient with anesthetic doses of ketamine supplemented with midazolam.
Methods: A patient presented with a rapidly progressing contiguous spread of CRPS from a severe ligamentous wrist injury. Standard pharmacological and interventional therapy successively failed to halt the spread of CRPS from the wrist to the entire right arm. Her pain was unmanageable with all standard therapy. As a last treatment option, the patient was transferred to the intensive care unit and treated on a compassionate care basis with anesthetic doses of ketamine in gradually increasing (3–5 mg/kg/h) doses in conjunction with midazolam over a period of 5 days.
Results: On the second day of the ketamine and midazolam infusion, edema, and discoloration began to resolve and increased spontaneous movement was noted. On day 6, symptoms completely resolved and infusions were tapered. The patient emerged from anesthesia completely free of pain and associated CRPS signs and symptoms. The patient has maintained this complete remission from CRPS for 8 years now.
Conclusions: In a patient with severe spreading and refractory CRPS, a complete and long-term remission from CRPS has been obtained utilizing ketamine and midazolam in anesthetic doses. This intensive care procedure has very serious risks but no severe complications occurred. The psychiatric side effects of ketamine were successfully managed with the concomitant use of midazolam and resolved within 1 month of treatment.
This case report illustrates the effectiveness and safety of high-dose ketamine in a patient with generalized, refractory CRPS.     

Lower limb vascular conductance and resting popliteal blood flow during head‐up and head‐down postural challenges

This study hypothesized that central and local reflex mechanisms affecting vascular conductance (VC) through the popliteal artery compensated for the reduction in muscle perfusion pressure (MPP) to maintain popliteal blood flow (PBF) during head‐down tilt (35? HDT), but not in head‐up tilt (45? HUT). Resting measurements were made on 15 healthy men in prone position to facilitate the access to the popliteal artery, on two separate days in random order during horizontal (HOR), HDT or HUT. In each body position, the body was supported, and the ankles were maintained in relaxed state so that there was no muscle tension, as with normal standing. Popliteal blood flow velocity and popliteal arterial diameter were measured by ultrasound, and PBF was calculated. MPP was corrected to mid‐calf from measured finger cuff pressure, and VC was estimated by dividing PBF by MPP. The MPP in HDT (48 ± 2 mmHg) was ~100mmHg less than in HUT (145 ± 2 mmHg). PBF was similar between HOR (51 ± 18 ml min^?1) and HDT (47 ± 13 ml min^?1), but was lower in HUT (30 ± 9 ml min^?1). VC was different between HDT (1·0 ± 0·3 ml min^?1 mmHg^?1), HOR (0·6 ± 0·2 ml min^?1 mmHg^?1) and HUT (0·2 ± 0·1 ml min^?1 mmHg^?1). In conclusion, the interactions of central and local regulatory mechanisms resulted in a disproportionate reduction of VC during HUT lowering PBF even though MPP was higher, while in HDT, increased VC contributed to maintain PBF at the same level as the HOR control condition.     

Sympathetic activation during the cold pressor test: influence of stimulus area

Summary. The purpose of this study was to determine the effect of the size of the stimulus area on the muscle sympathetic nerve activity (MSNA), systolic arterial blood pressure (SAP), and heart rate responses to the cold pressor test. To accomplish this, these variables were measured before (control), during, and after 1·5 min of ice water immersion of either one or both hands in nine healthy subjects (aged 19–27 years). The cold stimulus elicited significant increases above control levels in all three variables under both conditions (P<0·05). Immersion of both hands produced a much greater increase in total MSNA (+366%) than immersion of a single hand (+187%) (P<0·05). However, the magnitudes of the increases in SAP and heart rate during two-hand immersion (29±6 mmHg and 10±2 beats min^-1) were not significantly different from the responses during the one-hand trials (24±5 mmHg and 6±2 beats min^-1, P>0·05). There was a strong, direct relationship between total MSNA and SAP responses during one-hand immersion (r= 0·93, P<0·001) but not during immersion of both hands (r= 0·66, P= 0·08). These findings indicate that during the cold pressor test the magnitude of the increase in sympathetic discharge to skeletal muscle, but not the systolic blood pressure response, is influenced by the size of the tissue area exposed to the stimulus.     

Laser Doppler measurements of skin blood flow before,during, and after lumbar sympathetic blockade in children and young adults with reflex sympathetic dystrophy syndrome

Changes in the skin capillary blood flow (SBF) and temperature before, during, and 1 hour after unilateral lumbar paravertebral sympathetic blockade (LSB) were studied simultaneously with laser Doppler flowmetry and thermometry in patients with reflex sympathetic dystrophy syndrome. The baseline flow measurements in the toes on the affected limb were significantly lower than in the contralateral limb (p<0.01). During LSB, a 10-fold increase in SBF was detected within 4 minutes after injection of a local anesthetic agent when the sympathetic blockade was effective; an increase of more than 1°C in the skin temperature occurred within 11 minutes. Measurements 1 hour after blockade showed an 18-fold (mean) increase in SBF in the toes (p<0.0001) and a 2-fold (mean) increase in SBF in the thighs (p<0.001). There was a significant decrease in the skin blood flow in the contralateral toes after the sympathetic blockade (p<0.01). We conclude that laser Doppler flow measurements can be used to detect immediate onset of sympathetic blockade in patients under general anesthetic or conscious sedation.     

不同留置针在外周动脉血压监测中的安全性比较

目的比较直式留置针和带延长管留置针应用于外周动脉血压监测中的安全性。方法将2009年10月至2010年12月佛山市某三级甲等医院ICU行有创动脉血压监测的100例患者随机分为观察组和对照组各50例,观察组使用20 G带延长管留置针,对照组使用20 G直式静脉留置针。比较两组患者的置管意外(导管折叠、脱出和阻塞)发生率、穿刺点渗血情况和置管时间。结果观察组导管折叠和脱出的发生率、穿刺点渗血率低于对照组,而置管时间3 d以上者多于对照组,差异均有统计学意义(P<0.05)。结论有创动脉血压监测时使用带延长管的留置针,可减少导管折叠、脱出和穿刺点渗血的发生率,延长留置时间,在减轻患者痛苦和经济负担的同时,也减少了护理人员的工作量。     

女性高血压患者心肺运动试验中血压经时变化研究

目的 探讨女性高血压患者心肺运动试验中,随运动强度增加血压的经时变化及其临床意义。方法 选取本院2018年8月至2019年8月心肺运动试验排除心肌缺血,且未服用β受体阻滞剂及非二氢吡啶类钙离子拮抗剂的1级、2级高血压女性患者64例(高血压组),以及同期心肺运动试验排除心肌缺血的年龄匹配的健康女性86例(非高血压组),比较两组心肺运动试验中随运动强度增加血压的经时变化。结果 高血压组运动中静息3 min时血压、无氧阈值时血压和峰值血压均显著高于非高血压组(Z > 3.306,P<0.001)。两组峰值摄氧量无显著性差异(Z = 1.549, P > 0.05)。 结论 1级和2级高血压患者血压对运动的反应容易过度升高,在日常体育运动训练及运动康复中应关注血压的变化。     

Middle cerebral artery velocity during head-up tilt induced hypovolemic shock in humans

Summary. Middle cerebral artery mean velocity (V_mean) and pulsatility index (PI) were followed during head-up tilt induced hypovolaemic shock in nine subjects. Mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP) and thoracic (TI) electrical impedance were also recorded. V_mean, PI, and CVP did not change during head-up tilt to 50°, while MAP increased from 92 (81–106) (median and range) to 100 (97–112) mmHg, HR from 63 (53–74) to 84 (68–89) beats min^-1 and Tl_100kHz from 30 (27–36) to 32 (30–39) Ohm (P < 0.01) (n= 8). During maintained tilt, V_mean decreased from 52 (32–72) to 34 (16–59) cms^-1, whereas HR increased to 87 (52–108) beats min^-1 and Tl_100kHz to 33 (31–39) Ohm (P < 0.01). Presyncopal symptoms appeared after 33 (3–46) min and were associated with a MAP of 65 (32–84) mmHg (P < 0.01) and a HR of 58 (52–71) beats min^-1 (P < 0.05).V_mean decreased to 25 (16–36) cms^-1, and cerebral conductance index (V_mean/MAP_brain) and PI increased (P < 0.01). Arterial collapse was observed (diastolic velocity of zero) in one subject at a brain (diastolic) blood pressure of 21 mmHg and he developed tachycardia (131 beats min^-1) during presyncope. P_aCO₂ did not change. Maintained tilt resulted in central volume depletion reflected by changes in MAP, HR, and thoracic electrical impedance but not in CVP. Transcranial Doppler derived indices of cerebral perfusion demonstrated critically low values despite marked increase in conductance index.     

二维和多普勒超声心动图对动脉导管未闭肺循环量、肺动脉压及肺阻力的定量研究

本文联合应用二维、脉冲式和连续式多普勒技术测定了15例动脉导管未闭患儿的主动脉体积血流、动脉导管两侧收缩期最大压力阶差、舒张末期压力阶差和平均压力阶差,并同时用袖带法测量肱动脉压,由此分别计算肺循环量、肺动脉收缩压、舒张压和平均压及肺总阻力,与心导管术测值比较相关性良好(相关系数r=0.87～0.94)。提出并证实了应用二维/多普勒超声心动图可对动脉导管未闭的肺循环血流动力学改变作出系统的定量诊断。     

Middle cerebral artery blood flow velocity in response to lower body positive pressure

Lower body positive pressure (LBPP) has been used in the treatment of haemorrhagic shock and in offsetting g‐force induced fluid shifts. However, the middle cerebral artery blood flow velocity (MCAv) response to supine LBPP is unknown. Fifteen healthy volunteers (mean ± SD: age, 26 ± 5 year; body mass, 79 ± 10 kg; height, 174 ± 9 cm) completed 5 minutes of 20 and 40 mm Hg LBPP, in a randomized order, separated by 5 minutes rest (baseline). Beat‐to‐beat MCAv and blood pressure, partial pressure of end‐tidal carbon dioxide (P_ETCO₂) and heart rate were recorded and presented as the change from the preceding baseline. All measures were similar between baseline periods (all P>0·30). Mean arterial pressure (MAP) increased by 7 ± 6 (8 ± 7%) and 13 ± 7 mm Hg (19 ± 11%) from baseline during 20 and 40 mm Hg (P<0·01), respectively. The greater MAP increase at 40 mm Hg (P<0·01 versus 20 mm Hg) was mediated via a greater increase in total peripheral resistance (P<0·01), with heart rate, cardiac output (Model flow) and P_ETCO₂ remaining unchanged (all P>0·05) throughout. MCAv increased from baseline by 3 ± 4 cm s^?1 (5 ± 5%) during 20 mm Hg (P = 0·003), whilst no change (P = 0·18) was observed during 40 mm Hg. Our results indicate a divergent response, in that 20 mm Hg LBPP‐induced modest increases in both MCAv and MAP, yet no change in MCAv was observed at the higher LBPP of 40 mm Hg despite a further increase in MAP.     

The Vertebral Artery is Unlikely to be the Sole Source of Vascular Complications Occurring during Stellate Ganglion Block

Introduction:   Stellate ganglion block (SGB) is commonly performed for upper extremity complex regional pain syndrome and other conditions. Known complications of stellate block include Horner's syndrome, hoarseness, hematoma formation, airway compromise, immediate seizure (presumably from vertebral artery injection), and death. A previous arterial anatomy study demonstrated other vessels, eg, the ascending and deep cervical arteries, reinforcing the blood supply of the spinal cord and brain stem. The potential role of these vessels in the pathogenesis of seizures or hematoma during SGB has not been studied.
Methods:   The anatomical recording log from 10 cadaver dissections and photographic records of same were reviewed to ascertain the presence of the ascending or deep cervical arteries, or other branches emanating from the thyrocervical or costocervical trunk and their relationship to the medial anterior surface of the C6 and C7 transverse processes.
Results:   In 4 cases, as determined by the dissection log, and in 6 cases, determined by photographic images, the ascending cervical artery or a branch from the thyrocervical trunk passed over the anterior aspect of the transverse processes of C6 or C7.
Discussion:   Arterial vessels other than the vertebral artery that also supply the anterior spinal cord and brain stem pass directly anterior to the transverse processes at the most common sites of the SGB. It is anatomically possible, therefore, that accidental injection or induced spasm of these vessels and not the vertebral arteries is responsible for some cases of seizure, hematoma, or other vascular complications during SGB.     

Leg uptake of calcitonin gene‐related peptide during exercise in spinal cord injured humans

Exercise‐induced increases in cardiac output (CO) and oxygen uptake (VO₂) are tightly coupled, as also in absence of central motor activity and neural feedback from skeletal muscle. Neuromodulators of vascular tone and cardiac function – such as calcitonin gene related peptide (CGRP) – may be of importance. Spinal cord injured individuals (six tetraplegic and four paraplegic) performed electrically induced cycling (FES) with their paralyzed lower limbs for 29 ± 2 min to fatigue. Voluntary cycling performed both at VO₂ similar to FES and at maximal exercise in six healthy subjects served as control. In healthy subjects, CGRP in plasma increased only during maximal exercise (33·8 ± 3·1 pmol l^?1 (rest) to 39·5 ± 4·3 (14%, P<0·05)) with a mean extraction over the working leg of 10% (P<0·05). Spinal cord injured individuals had more pronounced increase in plasma CGRP (33·2 ± 3·8 to 46·9 ± 3·6 pmol l^?1, P<0·05), and paraplegic and tetraplegic individuals increased in average by 23% and 52%, respectively, with a 10% leg extraction in both groups (P<0·05). The exercise induced increase in leg blood flow was 10–12 fold in both spinal cord injured and controls at similar VO₂ (P<0·05), whereas CO increased more in the controls than in spinal man. Heart rate (HR) increased more in paraplegic subjects (67 ± 7 to 132 ± 15 bpm) compared with controls and tetraplegics (P<0·05). Mean arterial pressure (MAP) was unchanged during submaximal exercise and increased during maximal exercise in healthy subjects, but decreased during the last 15 min of exercise in the tetraplegics. It is concluded that plasma CGRP increases during exercise, and that it is taken up by contracting skeletal muscle. The study did not allow for a demonstration of the origin of the CGRP, but its release does not require activation of motor centres. Finally, the more marked increase in plasma CGRP and the decrease in blood pressure during exercise in tetraplegic humans may indicate a role of CGRP in regulation of vascular tone during exercise.     

Conjunctival oxygen tension is influenced by plasma and blood volume, and flow through the external carotid artery

An investigation of the feasibility and validity of measurement of the conjunctival oxygen tension as a monitor of peripheral circulation, blood and extracellular fluid volume and cerebral circulation was carried out in 7 healthy volunteers and 5 unconscious critical care patients with proven total cerebral infarction. The healthy volunteers were subjected to changes in hydration achieved by the administration of furosemide and subsequent rehydration by administration of normal saline. Conjunctival oxygen tension was found to be a sensitive indicator of changes in the degree of hydration presumably by its ability to detect changes in peripheral circulation depending upon circulating blood and extracellular fluid volume. A drawback is that other stimuli of the sympatho-adrenergic system such as temperature and pain, interfere with measurement in the conscious volunteer. In patients with presumed total brain infarction the conjunctival PO₂ cannot be used as a reliable monitor of cerebral blood flow because of varying perfusion of the palpebral conjunctiva from the external carotid artery in the occasional patient.     

Effect of propofol and thiopentone on regional blood flow in brain and peripheral tissues during normoxia and hypoxia in the dog

Summary. The effect of propofol and thiopentone on cerebral (CBF), myocardial (MBF), muscular, and arterial hepatic blood flow was assessed with radiolabeled microspheres in 12 chronically instrumented dogs, six given propofol and six thiopentone. Tissue blood flows were measured in the awake animal, after 30 min of normoxic anaesthesia (room air), and after 30 min of hypoxic anaesthesia using a mixture of 10% O₂ and 3% CO₂ in nitrogen. The decrease in CBF from awake to normoxic anaesthesia was similar with propofol and thiopentone (propofol: 77 ±8 to 38±3 ml min^-1 100 g^-1, P<0.01; thiopentone: 66±3 to 33±2 ml min^-1 100 g^-1, P<0.01). During hypoxia, CBF rose moderately in the two groups (respectively + 19% and +28%, P<0.05). The MBF increased in propofol and thiopentone groups after 30 min of anaesthesia with air (propofol: 97 ±23 to 137 ± 15 ml min^-1 100 g^-1; thiopentone: 82 ±7 to 141 ± 10 ml min^-1 100 g^-1) and increased still more during hypoxia. The increase in MBF was related to an increase in heart rate and blood pressure. The quadriceps blood flow decreased during anaesthesia in normoxia and in hypoxia. The diaphragmatic blood flow increased with thiopentone under hypoxia. The hepatic arterial blood flow was unchanged. It is concluded that the effects of propofol on regional blood flows are very similar to those of thiopentone.