Assessment of long-term vasoplegia induced by brachial plexus block: a favorable effect for hemodialysis angioaccess surgery?

PURPOSE: Loco-regional anesthesia, along with the neurosensitive inhibition causes arterial and venous vasodilatation, that could be of interest for vascular access surgery. We evaluated the long term vasoplegia persistence after brachial plexic block. METHODS: Five patients submitted to brachial plexus block for an orthopedic procedure have been observed. Both radial arteries, that of the blocked arm and the opposite as a control, were analyzed by ultrasound examination, at time 0 and 360 minutes after anesthesia induction. All patients were treated with the same anesthesiologic protocol: axillary approach, use of an electroneurostimulator, injection 10 ml of ropivacain 7.5% + 10 ml of mepivacain 2%. The parameters evaluated from the arterial ultrasound flowmetry were: peak systolic velocity (PSV), end diastolic velocity (EDV) and resistance index (RI). RESULTS: No modification of the arterial flow were observed in the control arm at 0 and 360'after block induction. The blocked arm instead showed a significant decrease of the resistive index, stable at 360 minutes. CONCLUSIONS: The vasoplegia accompaning plexic block lasted 6 hours after anesthesia induction. Whereas this longstanding haemodynamic effect is beneficial for early patency of vascular access for hemodialysis, needs to be ascertained by further investigations.

Lead contributes to arterial intimal hyperplasia through nuclear factor erythroid 2-related factor-mediated endothelial interleukin 8 synthesis and subsequent invasion of smooth muscle cells.

OBJECTIVE: To validate the hypothesis that the toxic heavy metal lead (Pb) may be linked to cardiovascular diseases via the initiation of atherosclerosis, in vivo and in vitro studies were conducted. METHODS AND RESULTS: During the human study part of this project, serum Pb levels of healthy young women were correlated to carotid intima-media thickness. Multivariate logistic regression analyses showed that increased serum Pb levels were significantly associated with an increased intima-media thickness (P=0.01; odds ratio per SD unit, 1.6 [95% CI, 1.1 to 2.4]). In vitro, Pb induced an increase in interleukin 8 production and secretion by vascular endothelial cells. Nuclear factor erythroid 2-related factor-2 is the crucial transcription factor involved in Pb-induced upregulation of interleukin 8. Endothelial cell-secreted interleukin 8 triggered intimal invasion of smooth muscle cells and enhanced intimal thickening in an arterial organ culture model. This phenomenon was further enhanced by Pb-increased elastin synthesis of smooth muscle cells. CONCLUSIONS: Our data support the hypothesis that Pb is a novel, independent, and significant risk factor for intimal hyperplasia.

Nonequivalence of inhaled and nebulized salbutamol in the assessment of endothelial dysfunction.

A noninvasive measure of global endothelial dysfunction may be obtained by pulse wave analysis (PWA) before and after administration of inhaled salbutamol. As some subjects may have difficulty using an inhaler, we determined whether equivalent doses of inhaled and nebulized salbutamol produced similar effects on a key measure obtained from PWA-the augmentation index (AIx). Twenty volunteers (11 with vascular risk factors and 9 healthy controls) underwent PWA at the right radial artery using SphygmoCor. Subjects were randomized to receive either 400 microg inhaled salbutamol via spacer device or 2.5 mg nebulized salbutamol. PWA was performed until there was no further drop in AIx. After AIx returned to baseline, salbutamol was administered via the alternative route and measurements were repeated. The primary outcome was the intraclass correlation coefficient of agreement (ICC) between maximum change in AIx following inhaled and nebulized salbutamol. The ICC was 0.32 (95% CI -0.07 to 0.64) and 0.39 (95% CI -0.04 to 0.70) with and without correction for heart rate. The median maximum decrease in AIx after inhaler was 4.8% (IQR 1.8-7.1), and after nebulizer was 8.5% (IQR 7.5-11.4) (p = < .001). When corrected for heart rate, the median maximum fall in AIx after inhaler was 4.0% (IQR 2.0-7.9) and after nebulized salbutamol was 5.0% (IQR 3.8-9.6) (p = 0.24). Although inhaled and nebulized salbutamol produced similar median reductions in AIx, the correlation between the two methods of salbutamol delivery was weak. Further research is required to validate the fall in AIx after nebulized salbutamol as a measure of endothelial dysfunction.

Conduit artery constriction mediated by low flow a novel noninvasive method for the assessment of vascular function.

OBJECTIVES: We describe and validate a novel noninvasive method that complements the data from "traditional" flow-mediated dilation (FMD) studies. BACKGROUND: The study of peripheral vascular reactivity provides important diagnostic and prognostic information in patients with (or at risk for) cardiovascular disease. METHODS: High-resolution ultrasound and automatic computerized analysis were used to measure the diameter of the radial artery at rest and in conditions of locally decreased and increased shear stress (respectively, low-flow-mediated constriction [L-FMC] and flow-mediated dilation [FMD]). A composite end point (L-FMC + FMD) was also calculated. A total of 196 studies were performed. RESULTS: When the repeatability of the method was tested, the range of variation across measurements was 1.1% for L-FMC and 1.7% for FMD; the intraclass correlation coefficient was 0.80 and 0.68, respectively. Low-flow-mediated constriction, FMD, and their composite end point were significantly blunted after acute smoking, in coronary artery disease patients, and in hypertensive patients as compared with that seen in healthy age-matched volunteers (p < 0.01, analysis of variance). Low-flow-mediated constriction, but not FMD, was blunted (p < 0.05) after administration of fluconazole (an inhibitor of a cytochrome P450-derived endothelium-derived hyperpolarization factor) and aspirin (an inhibitor of cyclooxygenase). Flow-mediated dilation, but not L-FMC, was blunted (p < 0.05) by nitric oxide synthase inhibition. CONCLUSIONS: Low-flow-mediated constriction is a simple, rapid, and accurate measure of resting arterial tone that does not require further procedures as compared with "traditional" FMD measurements. While FMD measures endothelial responses to sudden increases in shear stress, L-FMC is a measure of the response to resting shear stress levels, and, therefore, it provides additional information that is complementary to FMD.

Assessment of endothelial function in the radial artery using inhaled albuterol.

Endothelial dysfunction is an early indicator of developing atherosclerosis and is a strong predictor of future heart attack and stroke. At present, evaluation of endothelial function (EF) (specifically, EF mediated by nitric oxide, NO) is too technically difficult to form part of a routine clinical examination. Non-invasive methods that measure NO-dependent EF in arteries make use of a 4-5 minute blood pressure cuff occlusion of the arm in order to induce reactive hyperemia (RH) upon cuff release. The increased blood flow that results from the RH stimulates the endothelial cells to release NO and relax the surrounding vascular smooth muscle. The magnitude of the change in arterial caliber or stiffness provides a measure of EF. The cuff occlusion is uncomfortable and inflation and release inevitably move the arm, increasing the technical difficulty of obtaining reliable measurements. In beta2-adrengergic agonist albuterol induces NO-mediated vasorelaxation in resistance vessels of humans. We examine, for the first time, the effect of albuterol on conduit vessels (radial artery) by measuring changes in the transit times of artificial pulses observed after inhalation of albuterol. We conclude that albuterol is able to relax the radial artery and that this correlates with the effects of RH (r=0.62, p=0.04). However, the response to a dose of 360 micro-g is smaller and more variable when compared to the response to RH-based stimulus.

Endoscopic versus conventional radial artery harvest for coronary artery bypass grafting: functional and histologic assessment of the conduit.

BACKGROUND: The radial artery's propensity for vasospasm and vulnerability to surgical trauma are well known. A less invasive endoscopic method to harvest the radial artery was recently introduced, but its effect on radial artery integrity is unknown. METHODS: To compare the effects of harvest method on radial artery function, we prospectively randomized 54 patients undergoing coronary artery bypass grafting with the radial artery into 3 groups on the basis of harvest techniques: endoscopic, conventional with cautery, and conventional with harmonic scalpel. We assessed endothelium-dependent and endothelium-independent relaxation of radial artery segments to sequential doses of acetylcholine and nitroglycerin, respectively, using standard organ-chamber methodology. Vasospasm was assessed as the vasoconstrictor response to the thromboxane analog U46619. We assessed endothelial integrity using light and electron microscopy and by rating intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and P-selectin expression by means of immunohistochemistry on a semiquantitative 0- to 3-point scale. Harvest procedures were performed by a single surgeon, and data analyses were blinded to the harvesting method. RESULTS: Maximal relaxation-contraction responses to acetylcholine, nitroglycerin, and U46619 and effective drug concentration yielding 50% response were similar in the 3 groups. Adhesion molecule expression and histologic changes, as assessed by means of light and electron microscopy, were similar in the 3 groups. CONCLUSIONS: Endoscopic harvest does not alter radial artery vasoreactivity or endothelial integrity compared with conventional harvest techniques. Because the endoscopic technique is less invasive, it might prove to be the technique of choice to harvest the radial artery.

Assessment of the efficacy of phentolamine to prevent radial artery spasm during cardiac catheterization procedures: a randomized study comparing phentolamine vs. verapamil.

The objective of this study was to evaluate phentolamine as radial artery spasmolytic in transradial catheterization procedures. Radial artery spasm is a relatively frequent complication during transradial approach, causing patient discomfort or even making it impossible to continue the procedure. As radial artery spasm is mediated by the stimulation of alpha-adrenoreceptors, the use of the alpha-blocker phentolamine could make sense as spasmolytic. We designed a randomized double-blind study to compare phentolamine vs. verapamil, the standard spasmolytic agent. Five hundred patients (250 in each arm) submitted to a transradial cardiac catheterization were consecutively included and randomly assigned to receive 2.5 mg of verapamil or 2.5 mg of phentolamine after sheath insertion. Both vasodilator agents induced a significant radial artery diameter increase (from 2.22 +/- 0.53 to 2.48 +/- 0.57 mm, P < 0.001 for verapamil, and from 2.20 +/- 0.53 to 2.45 +/- 0.53 mm, P < 0.001 for phentolamine). However, verapamil was more efficacious to prevent radial artery spasm (13.2% compared with 23.2% in phentolamine-treated patients; P = 0.004). Follow-up (20 +/- 18 days) evaluation of the radial artery patency by plestismography and pulse oximetry showed no differences between the two groups in the rate of radial occlusion (3.0% vs. 3.2% in verapamil and phentolamine treated patients, respectively). Phentolamine was an effective radial vasodilator agent, although it showed less ability to prevent radial artery spasm than verapamil. Radial artery occlusion rate was almost identical for both vasodilators. Thus, phentolamine could be a valid alternative to verapamil as a radial artery spasmolytic agent.

Assessment of endothelial function using peripheral waveform analysis: a clinical application.

OBJECTIVES: The study was done to determine whether radial artery applanation tonometry can be used as a noninvasive method of assessing global endothelial function. BACKGROUND; It is known that beta(2)-receptor stimulation results in endothelial release of nitric oxide. Furthermore, for over a century glyceryl trinitrate (GTN) has been known to markedly affect the arterial pressure waveform, even in the absence of significant blood pressure (BP) changes. Therefore, it was hypothesized that the change in the peripheral pressure waveform, as measured using tonometry and quantified using the augmentation index (AIx) and in response to Salbutamol (Salb), would allow assessment of global endothelial function. METHODS: The study contained three parts. In the first study, Salb (400 microg) was administered to 11 healthy subjects via inhalation after either intravenous N-omega-nitro-monomethyl-L-arginine (L-NMMA) (3 mg/kg over 5 min) or control solution (normal saline) in the supine, rested, fasted condition. The BP, heart rate and waveform responses were recorded each 5 min following Salb for 20 min. Next, GTN was given and responses recorded 5 min later. In the second study, both the reproducibility of Salb and the GTN responses were assessed in 9 subjects studied twice on separate days. In the third study, the Salb and GTN responses of 12 subjects with angiographic coronary artery disease (CAD) were compared with 10 age-matched control subjects with no atherosclerotic risk factors. RESULTS: After control infusion, AIx decreased following Salb, from 50.8 +/- 4.3% to 44.8 +/- 4.2%, a change of -11.8 +/- 3.7%, p < 0.01. After L-NMMA, AIx did not significantly change following Salb (54.2 +/- 5.1% vs. 52.9 +/- 5.3%, -2.0 +/- 3.1%). The GTN-induced decreases in AIx were similar after either infusion (35.1 +/- 3.3% vs. 36.5 +/- 3.3%). Reproducibility of Salb-induced changes in AIx between studies performed on separate days was good (r = 0.80, p < 0.01). Salb-induced changes in AIx in CAD patients were significantly less compared to control subjects (-2.4 +/- 1.9% vs. -13.2 +/- 2.4%, respectively, p < 0.002). The GTN-induced changes were not significantly different (-27.6 +/- 4.2 vs. -38.9 +/- 4.4%, p = 0.07). CONCLUSIONS: The peripheral arterial pressure waveform is sensitive to beta(2)-stimulation. Changes are related to nitric oxide release, are reproducible and can distinguish between clinical subject groups. Arterial waveform changes following Salb may thus provide a noninvasive method of measuring "global" arterial endothelial function.

Thermographic assessment of stellate ganglion block effectiveness during cardiosurgical procedures.

UNLABELLED: The study present thermographic assessment of the effectiveness of temporary stellate blockade performed during cardiosurgical procedures. The assumption behind this method was the increase in the temperature of upper extremity on the side of blockade, due to the broadening of arterial bed. MATERIAL AND METHOD: The study was conducted on a group of 30 patients (21 men and 9 women) operated due to coronary disease involving three vessels. Mean age of the patients was 53 years. After introduction of anaesthesia blockade were performed with 2 ml 2% lignocainum and 8 ml 0.5% bupivacaine solution using peratracheal approach. Blockade effectiveness was assessed on the basis of images obtained in thermovisual camera, comparing the temperatures of upper extremity before and within 15 minutes after performing the blockade. Free blood outflow from radial artery, its diameter and length were also evaluated. The results obtained were subject to statistical analysis. RESULTS: Twenty-three patients (76.6%) displayed the increase in the temperature of upper extremity by 1-3 degrees C. Free blood outflow from radial artery was greater in this group than in the remaining patients. CONCLUSIONS: Thermography is a useful method for the assessment of stellate blockade effectiveness. Effective blockade results in the increased blood flow in radial artery.

Comparison of non-invasive methods for the assessment of haemodynamic drug effects in healthy male and female volunteers: sex differences in cardiovascular responsiveness.

1. The study was performed to determine the sensitivity and short-term and day-to-day variability of a novel technique based on laser interferometry of ocular fundus pulsations and of non-invasive methods for the quantification of haemodynamic drug effects. An additional aim was to assess sex differences in haemodynamic responsiveness to cardiovascular drugs in male and female healthy volunteers. 2. Ten males and nine females (age range 20-33 years) were studied in a double-blind, randomized, cross-over trial. Simultaneous measurements from systemic haemodynamics, laser interferometry of ocular fundus pulsations, systolic time intervals from mechanocardiography, a/b ratio from oxymetric fingerplethysmography and Doppler sonography of the radial artery were used to describe the haemodynamic effects of cumulative, stepwise increasing intravenous doses of phenylephrine, isoprenaline, sodium nitroprusside and of placebo. 3. Laser interferometry detected the isoprenaline-effects at the lowest dose level of 0.1 micrograms min-1 with a high signal-to-noise ratio. The reproducibility of measurements under baseline was high, no changes were observed after systemically effective doses of phenylephrine or sodium nitroprusside. Systolic time intervals were sensitive and specific for isoprenaline-induced effects, PEP and QS2c-measurements had high reproducibility. Fingerplethysmography proved a sensitive measurement for the detection of the vasodilating effects of sodium nitroprusside, but was not specific, and showed low reproducibility. Measurements from Doppler sonography had lower reproducibility and sensitivity compared with the other applied methods. 4. There was a significant sex difference for several of the haemodynamic parameters under baseline conditions; however, the responsiveness to the drugs under study was not different, when drug effects were expressed as %-change from the baseline. 5. Laser interferometry is a valuable non-invasive, highly sensitive and specific approach for the detection of pulse pressure changes. A battery of non-invasive tests appears useful for the characterization of cardiovascular drugs. Gender differences may not pose a relevant problem for the study of acute haemodynamic effects of cardiovascular drugs.