Reduction In Peak Systolic Velocity Research Articles

Ocular blood flow in normal tension glaucoma and primary open angle glaucoma

Objectives: The purpose of the study was to study the ocular blood flow (OBF) in primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG) by color Doppler imaging (CDI) in the ophthalmic artery (OA), central retinal artery (CRA), and posterior ciliary artery (PCA) and to correlate this with structural and functional damage in glaucoma. Materials and Methods: This was a cross-sectional and observational study. This was a cross-sectional study, in which 30 eyes of each group and controls were studied, CDI was done by a single observer for all cases. Peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistive index (RI) were calculated for OA, CRA, and PCA. Visual fields and retinal nerve fiber layer (RNFL) analysis were done. Results: PSVs and EDVs were lower and RIs were higher for CRA and PCA of NTG and POAG compared to those of controls. The severity of glaucoma (visual field defect) increased when RI of OA was increased in NTG. No such relationship was established between RNFL thinning and OBF. Conclusion: Reduction in PSV and EDV leads to increased RI which is one of the contributory factors in the functional damage in NTG.

Blood flow effects of percutaneous peripheral nerve stimulation. A blinded, randomized clinical trial.

The vasculature function is mainly regulated by the autonomic nervous system. Importantly, the sensory-motor nervous system also innervates peripheral vessels and has the capacity to modulate vascular tone. Here we investigated the effects of electrical stimulation of a mixed nerve trunk on blood flow in deep arteries and muscle perfusion. Our hypothesis is that stimulation of a mixed nerve can modify blood flow. Twenty-nine healthy participants were included into a randomized-crossover and blinded clinical trial. Each subject received a placebo and two percutaneous peripheral nerve stimulation (pPNS) protocols on the median nerve: Pain Threshold continuous Low Frequency (PT-cLF) and Sensory Threshold burst High Frequency (ST-bHF). Blood flow was then assessed bilaterally using Power Doppler Ultrasonography at the main arteries of the arm, and blood perfusion at the forearm muscles. Afterwards, blood flow was quantified using a semi-automatized software, freely shared here. Placebo, consisting in needle insertion, produced an immediate and generalized reduction on peak systolic velocity in all arteries. Although nerve stimulation produced mainly no effects, some significant differences were found: both protocols increased the relative perfusion area of the forearm muscles, the ST-bHF protocol prevented the reduction in peak systolic velocity and TAMEAN of the radial artery produced by the control protocol and PT-cLF produced a TAMEAN reduction of the ulnar artery. Therefore, the arterial blood flow in the arm is mainly impervious to the electrical stimulation of the median nerve, composed by autonomic and sensory-motor axons, although it produces mild modifications in the forearm muscles perfusion.

Continuous monitoring of cerebral blood flow during general anaesthesia in infants

BackgroundGeneral anaesthesia is associated with neurocognitive deficits in infants after noncardiac surgery. Disturbances in cerebral perfusion as a result of systemic hypotension and impaired autoregulation may be a potential cause. Our aim was to study cerebral blood flow (CBF) velocity continuously during general anaesthesia in infants undergoing noncardiac surgery and compare variations in CBF velocity with simultaneously measured near-infrared spectroscopy (NIRS), blood pressure, and heart rate. MethodsNeoDoppler, a recently developed ultrasound system, was used to monitor CBF velocity via the anterior fontanelle during induction and maintenance of general anaesthesia until the start of surgery, and during recovery. NIRS, blood pressure, and heart rate were monitored simultaneously and synchronised with the NeoDoppler measurements. ResultsThirty infants, with a median postmenstrual age at surgery of 37.6 weeks (range 28.6–60.0) were included. Compared with baseline, the trend curves showed a decrease in CBF velocity during induction and maintenance of anaesthesia and returned to baseline values during recovery. End-diastolic velocity decreased in all infants during anaesthesia, on average by 59%, whereas peak systolic- and time-averaged velocities decreased by 26% and 45%, respectively. In comparison, the reduction in mean arterial pressure was only 20%. NIRS values were high and remained stable. When adjusting for mean arterial pressure, the significant decrease in end-diastolic velocity persisted, whereas there was only a small reduction in peak systolic velocity. ConclusionsContinuous monitoring of CBF velocity using NeoDoppler during anaesthesia is feasible and may provide valuable information about cerebral perfusion contributing to a more targeted haemodynamic management in anaesthetised infants.

The influence of body position on cerebrospinal fluid circulation

Background. Cerebrospinal fluid (CSF) circulation consists of two components, a net flow and a pulsatile flow. CSF is generally believed to be produced through the ventricular choroid plexuses and absorbed in sites such as the subarachnoid granulations and nerve roots, contributing to the net flow. The pulsatile driving forces include cardiac vascular pulsation, respiration and muscular contraction.1 Measuring CSF flow in the upright posture is important because we spend most of our lifetime upright.
 Methods. Thirty asymptomatic volunteers (age: 22-72; 9 males, 21 females) were scanned in the upright seated and supine position on a 0.6 T multi-position MRI scanner (Fonar, New York, USA). CSF flow and spinal cord pulsation were imaged and quantified at the axial mid-C2 level with cine phase-contrast MRI.
 Results. In the upright posture, heart rate increased by 10%, and peak CSF diastolic flow decreased by 43% compared to the supine posture.2 In addition, the oscillatory volume of CSF exchanged between the spine and cranium decreased by 37% when going from supine to upright posture, consistent with a previous study.3 This could mean that the amount of time spent in different postures as we age may affect the efficiency of glymphatic brain waste clearance and development of neurodegenerative diseases. A less studied but diagnostically important aspect of CSF flow is the concomitant pulsation of spinal cord and central nervous system (CNS) tissue. For example, it is found that in Alzheimer’s Disease patients, the spinal cord at mid-C2 is pulsating much more in the mid to high frequency range (4 to 8 Hz) compared to normal older people in the supine posture. In the normal population, the mid-C2 spinal cord pulsates much less in the upright posture, with a 40% reduction of peak systolic velocity compared to the supine posture. Other postural differences include the more prominent appearance of nerve roots in the supine posture, shift of venous outflow from jugular veins to epidural/smaller veins, and the slimming of the neck when upright. It is also found that CSF flow is much more sensitive to aging in the upright than in the supine position. More specifically, as we age, heart rate change between postures diminishes and the upright peak systolic/peak-to-peak pressure gradient decreases. Since studies have shown that meditation can slow down brain aging, it would be beneficial to study its effect on CSF flow and the process of brain waste production and clearance.
 Conclusions. Besides delineating the many significant postural differences in CSF circulation, multi-position CSF imaging is also valuable in diagnosing various diseases such as Chiari malformation,4 Ehlers-Danlos syndrome and tethered cord syndrome in the lumbar spine. Often pathology that is not evident in the traditional supine imaging position can be visualized in other patient positions. Finally, a seminal study5 in rodents found that glymphatic transport is most efficient in the lateral recumbent position compared to supine or prone position, which concluded that posture must be considered in future diagnostic imaging procedures to assess CSF – interstitial fluid (ISF) transport in humans.

Hemodynamic alterations with large spontaneous splenorenal shunt ligation during adult deceased donor liver transplantation.

A large spontaneous splenorenal shunt (SRS) will greatly impact portal inflow to the graft during liver transplantation (LT). Direct ligation of a large SRS is an uncommon surgical procedure and the hemodynamic consequences of this procedure are unknown. In this retrospective study, we described our technique for direct ligation of a large SRS and the consequent hemodynamic changes during LT. 3-Dimensional computed tomography and Doppler ultrasonography were used to evaluate SRS and portal vein blood flow volume (PFV). A total of 22 recipients had large SRS including 13 with PFV <85 ml/min/100 g (ligation group) and 9 with PFV ≥85 ml/min/100 g (no ligation group). The diameter of SRS was significantly larger in the ligation group than in the non-ligation group (22.92 ± 4.18 vs. 16.24 ± 3.60 mm; p = 0.0009). In all ligation patients, the SRS was easily identified and isolated, it was located just below the distal pancreas and beside the inferior mesenteric vein. PV flow increased significantly from 68.74 ± 8.77 to 116.80 ± 16.50 ml/min/100 g (p < 0.0001) after ligation; this was followed by a reduction in peak systolic velocity of the hepatic artery from 58.17 ± 14.87 to 46.67 ± 13.28 cm/s (p = 0.0013). Direct ligation of large SRS was an effective and safe surgical procedure to overcome the problem of portal hypoperfusion during LT.

Duplex-guided versus Conventional Percutaneous Transluminal Angioplasty of Iliac TASC II A and B Lesion: A Randomized Controlled Trial

Percutaneous transluminal angioplasty (PTA) requires the use of nephrotoxic contrast. Patients with chronic kidney disease are more prone to develop contrast-induced nephropathy after utilization of contrast. Doppler ultrasound (duplex)-guided PTA (DuPTA) is a novel technique and has recently proven to be a successful alternative to conventional PTA in the treatment of iliac stenotic disease, without the use of contrast. In this randomized controlled trial, we evaluated whether DuPTA is as effective as conventional PTA in the treatment of iliac arterial stenotic disease. From June 2013 till January 2017, 142 patients with symptomatic peripheral arterial disease (PAD), with significant (>70%) iliac stenotic lesions (both isolated and patients with multilevel disease without treatment of other lesions), were randomized to receive either conventional PTA or DuPTA of the iliac lesion, regardless of renal function. All patients received an ankle-brachial index, arterial mapping with duplex, and magnetic resonance angiography in the pre-operative work-up. Primary end point was procedural success, defined as passing the guidewire through the stenotic lesion and performing a PTA, with or without stenting. Reduction in peak systolic velocity (PSV) of ≥50% after successful PTA was required in the DuPTA group. Angiographic reduction of more than 50% was required in the interventional group. Decrease in PSV was evaluated in both groups 4weeks post-procedure. Passing of the guidewire through the stenotic lesion was achieved in 96.5% of the DuPTA group and 98.8% of the PTA group (P=0.34). Although PSV decreased significantly in both groups 4weeks post-operative, PSV reduction ≥50% was significantly higher in the DuPTA group, respectively 78% vs. 58% in the PTA group (P<0.01). The utilization of stents was significantly greater in the DuPTA group (52% vs. 18%, P<0.01). After correction of potential confounders, significant difference in ≥50% PSV reduction remained; technical success did not differ significantly. DuPTA is a feasible alternative to conventional PTA in the treatment of PAD on the iliac anatomic level. Duplex examination before removal of the guidewire is recommended to evaluate adequate decrease in PSV and identify potential recoil.

Effect of caffeine on superior mesenteric artery blood flow velocities in preterm neonates

Objective: To investigate the effect of caffeine infusion on superior mesenteric artery (SMA) blood flow velocities (BFV) in preterm infants.Methods: Prospective observational study on 38 preterm neonates 28–33+6 weeks gestation, who developed apnea on their first day of life, and caffeine citrate infusion was initiated at a loading dose of 20 mg/kg, followed by a maintenance dose of 5–10 mg/kg/day. Duplex ultrasound measurements of SMA BFV were recorded: peak systolic velocity (PSV), end diastolic velocity (EDV) and resistive index (RI), at 15 min before, 1-, 2- and 6-h after caffeine loading dose, and 2 h after two maintenance doses.Results: There was a significant reduction in PSV 1-h (p = .008), a significant decrease in EDV 1- and 2-h (p = .000 and p = .005, respectively) and a significant increase in RI 1- and 2-h (p = .003 and p = .005, respectively) following caffeine loading dose, as compared to values before caffeine infusion. No significant effect of caffeine maintenance doses on SMA BFV was observed (p > .05).Conclusion: Blood flow in SMA is significantly reduced after caffeine citrate infusion at a loading dose of 20 mg/kg. This effect continues for at least 2 h. Meanwhile, SMA BFV seems not affected by maintenance doses.

ОСОБЕННОСТИ ПОЧЕЧНОГО КРОВОТОКА У БОЛЬНЫХ МНОЖЕСТВЕННОЙ МИЕЛОМОЙ НА РАЗНЫХ ЭТАПАХ ОПУХОЛЕВОЙ ПРОГРЕССИИ

The features of renal hemodynamics in 90 patients with multiple myeloma (MM) at different stages of tumor progression have been studied. The signs of renal hemodynamics disorder by ultrasound Dopplermetry data are already revealed at the first stages of MM. In the I and IIA stages there were diagnosed the following changes: the increase in average blood flow velocity (Vave) at the level of the interlobular arteries (20%); the reduction of peak systolic velocity (Vmax) at the level of arteries arc (11.4%); the drop of Vmax (24.5%), of Vave (11%), of diastolic velocity (Vmin) by 26% on interlobular arteries; the decrease of Vmin (26%) on segmental and main renal arteries. There was also revealed an increase in the indices of vascular resistance index (IR by 11%, IP by 13%) and main renal arteries (IR by 12%, IP by 16%). Under disease progression in IIIA stage there was: the growth of Vmax (21.5%), Vave (24.9%), Vmin (42.7%) on interlobular arteries; the decrease of Vave (24.8%), Vmin (51.5%) on interlobular renal arteries. The decrease of IR on interlobular arteries (9%) and its increase at the level of segmental and main renal arteries (11%) were diagnosed. The biggest changes in the blood flow by Dopplermetry data were diagnosed in MM patients at chronic renal disease (IІ and IIIB stages): the reduction of speed indicators on interlobular arteries – Vmax (26%), Vave (42%), Vmin (44%); on arc arteries – Vmax (29%), Vave (21%), Vmin (38%); on interlobar arteries – Vmax (30%), Vave (39%), Vmin (46%); on segmental arteries – Vmax (17%), Vave (22%), Vmin (42%); on the main renal artery – Vmax (11%), Vmin (33%). An increase in the indices of vascular resistance was revealed: IR on interlobular arteries (11%), the arc arteries (12%), interlobular arteries (11%), segmental arteries (13%), the main renal arteries (11%); IP on interlobular arteries (13%), the arc arteries (12%), interlobular arteries (13%), segmental arteries (12%), the main renal arteries (12%). These parameters correspond to Doppler criteria of chronic renal insufficiency of compensated stage.

Percutaneous Transluminar Angioplasty and Stenting of Post Transplant Renal Artery Stenosis(TRAS): Monocentric Experience.

Introduction We retrospectively evaluated the occurrence of post transplant renal artery stenosis (TRAS) in 808 recipients of a cadaveric renal transplantation performed in our unit between 1991 and 2013 and the outcome after a percutaneous revascularization. Materials TRAS was diagnosed when a Peak systolic Velocity(PSV) > 2.5 m/sec was found in the graft renal artery by Doppler ultrasound. Subsequently an angiography and eventually a percutaneus transluminal angioplasty (PTA) with stenting was performed. We compared renal function, blood hypertension, PSV and Resistive index (RI) at the time of the diagnosis of TRAS with the values collected at the last follow up visit. Results We found 74 (8.9%) TRAS of whom 18 due to a kinking of the artery or a non hemodinamic stenosis (defined as PSV between 2.0 and 2.5 m/sec) that didn't require angiography. 56 patients underwent an angiography. In 4 cases the stenosis was not confirmed, 51 were treated with PTA with stenting and one only with PTA without stenting. The median of the time between the diagnosis of TRAS and the renal transplantation was 70 days (range 2-3347 days). TRAS occurred near the anastomosis in 60% of the cases. We observed 1 hemorragic complication during the procedure (1.9%) that required an urgent nephrectomy. A restenosis was found in 8 cases (17%) treated again with a PTA in 4 patients, PTA and stenting in 2, and with medical therapy in 2. With a mean follow up of 5±4 years we confirmed the reduction of PSV, blood pressure and serum creatinine and an increase of RI and GFR as show in table 1.Table: No Caption available.Conclusions TRAS was found in 8.9% of our cohort of transplanted patients. The angiography is useful to confirm the diagnosis made by doppler examination and eventually treat the lesion

Duplex-guided Percutaneous Transluminal Angioplasty in Iliac Arterial Occlusive Disease

Chronic renal insufficiency (CRI) is a growing global problem. PTA can be performed without nephrotoxic contrast, utilizing Doppler-ultrasound (Duplex) guidance. Duplex-guided infra-inguinal interventions and access-related interventions have been reported. Duplex-guided iliac interventions have not been performed to any extent because of the anatomic location. In our study we evaluated the safety and efficacy of Duplex-guided percutaneous transluminal angioplasty (DuPTA) in iliac arteries. From June 2012 until February 2013, 31 patients (35 iliac lesions), underwent DuPTA. Indications ranged from Rutherford 3 to 5. Preoperative evaluation included Ankle Brachial Index (ABI), Duplex and MRA. Procedural success was defined as crossing the lesion with a guidewire and dilating or stenting the lesion. Clinical success was defined as 50% reduction in peak systolic velocity (PSV) or clinical improvement. PSV was evaluated after PTA, then at 2 weeks. Clinical results were assessed 2 weeks after the procedure. Procedural success was achieved in 94% of patients (33/35), all of whom also had clinical success. Post-procedural PSV reduction showed an average improvement of 63% (431 cm/s to 153 cm/s). Mean preoperative ABI was 0.72 and improved to 0.88 postoperatively. PTA using Duplex-guidance in significant iliac stenosis is a safe method with major advantages in patients at high risk for developing contrast-induced nephropathy.

Duplex-guided Percutaneous Transluminal Angioplasty in Iliac Arterial Occlusive Disease

Chronic renal insufficiency (CRI) is a growing global problem. PTA can be performed without nephrotoxic contrast, utilizing Doppler-ultrasound (Duplex) guidance. Duplex-guided infra-inguinal interventions and access-related interventions have been reported. Duplex-guided iliac interventions have not been performed to any extent because of the anatomic location. In our study we evaluated the safety and efficacy of Duplex-guided percutaneous transluminal angioplasty (DuPTA) in iliac arteries. From June 2012 until February 2013, 31 patients (35 iliac lesions), underwent DuPTA. Indications ranged from Rutherford 3 to 5. Preoperative evaluation included Ankle Brachial Index (ABI), Duplex and MRA. Procedural success was defined as crossing the lesion with a guidewire and dilating or stenting the lesion. Clinical success was defined as 50% reduction in peak systolic velocity (PSV) or clinical improvement. PSV was evaluated after PTA, then at 2 weeks. Clinical results were assessed 2 weeks after the procedure. Procedural success was achieved in 94% of patients (33/35), all of whom also had clinical success. Post-procedural PSV reduction showed an average improvement of 63% (431 cm/s to 153 cm/s). Mean preoperative ABI was 0.72 and improved to 0.88 postoperatively. PTA using Duplex-guidance in significant iliac stenosis is a safe method with major advantages in patients at high risk for developing contrast-induced nephropathy.

Invited commentary

Invited commentary

Does kidney transplantation onto the external iliac artery affect the haemodynamic parameters of the cavernosal arteries?

Reduced cavernosal arterial inflow has been hypothesized to be the likely cause of erectile dysfunction after kidney transplants in recipients revascularized through end-to-end anastomosis to the internal iliac artery, suggesting that end-to-side anastomosis at the external iliac artery is preferable. The aim of this study was to prospectively evaluate the effect of the use of the external iliac artery on erectile function, hormone profiles and penile blood flow by evaluating changes in penile colour Doppler ultrasound parameters in a consecutive series of 22 recipients before and after end-to-side external iliac artery transplantation. The mean International Index of Erectile Function-Erectile Function (IIEF-EF) domain score decreased significantly 3 months after transplant (18.09±6.33 vs. 22.50±7.09, P=0.01). The reduction in peak systolic velocity (PSV) was significant for the cavernous artery homolateral to the side of transplant (42.60±18.77 vs. 52.01±19.91, P=0.01). The mean postoperative end diastolic velocity (EDV) did not differ significantly from the preoperative value (P=0.74). No statistical differences were found in the serum levels of testosterone or prolactin. Kidney grafts anastomosed at the external iliac artery produced significant (P=0.01) reductions in arterial inflow at the homolateral cavernosal artery that remained above the normal threshold. Whether these haemodynamic changes can explain the worsening of postoperative erectile function remains to be proven.

Spontaneous regression of initially elevated peak systolic velocity in renal transplant artery

There is limited knowledge about the incidence, clinical implication and spontaneous course of transplant renal artery stenosis detected early after renal transplantation. We performed Doppler ultrasound examination of the transplant artery(s) 2 months after transplantation in 98 consecutive patients and peak systolic velocity (PSV) was measured. All patients with an elevated PSV ≥1.8 m/s were reexamined 20 months later and clinical data were followed for 3 years. At the initial examination 2 months after transplantation 15 recipients had a PSV ≥1.8 m/s, mean value for PSV 2.5 (1.8-3.6) m/s, whereas 83 recipients had a normal PSV of 1.3 (0.7-1.7) m/s (P<0.01). At baseline there were no statistical significant differences in clinical parameters between the high PSV versus normal PSV recipients. Twenty (15-28) months after transplantation 14 patients with initial elevated PSV were re-examined. There was an overall mean reduction in PSV of 0.5 (-0.7 to 1.2) m/s from 2.4 (1.8-3.4) m/s to 1.9 (1.2-3.1) m/s (P=0.02). Detection of a high PSV early after transplantation did not affect graft function or blood pressure 3 years after engraftment. We conclude that a high PSV, at 2 months after engraftment, seems to be more of an 'incidental finding' that should be re-challenged and carefully interpreted.

Hotelling's test, multiple t‐tests, and uterine artery Doppler evaluation

I read with interest the paper by Lima et al. in the September 2009 edition of Ultrasound in Obstetrics and Gynecology1. The authors assessed pregnant women showing evidence of premature labor who were given oral nifedipine as a tocolytic agent, performing Doppler ultrasound evaluation before drug administration and after 5 and 24 h. Two Doppler ultrasound parameters, resistance index (RI) and peak systolic velocity (PSV), were recorded from three vessels: maternal uterine, fetal middle cerebral (MCA) and umbilical arteries. Significant changes were observed only in the fetal MCA; a reduction in PSV was observed 5 h after nifedipine (but not after 24 h) and a reduction in RI was observed after 24 h (but not after 5 h). The objective of this paper was to evaluate drug safety. Several issues in this paper arouse concern. Firstly the statistical analysis: the authors compared the ultrasound parameters among the three different times using Hotelling's test and performed pair-wise comparisons using multiple paired t-tests. Hotelling's test is usually used in multivariate analyses, but the authors evaluated Doppler parameters by a univariate approach where repeated measures ANOVA would usually be used. Additionally, two problems are expected when using multiple t-tests: the interpretation becomes cognitively more difficult as multiple results are obtained, and the probability of at least one type I error occurring somewhere in the analysis greatly increases. This increase in type I error resulted in findings of additional significant differences in the PSV of the umbilical and right uterine arteries in the pair-wise comparison that were not observed when the sets of measurements were assessed using Hotelling's test. These problems could be avoided by performing repeated measures ANOVA and a post-hoc test, such as Tukey's test. When describing how they determined their sample size, the authors made a small mistake. They reported an SD for MCA-RI of 0.005 without any reference, but the SD values for this parameter reported for their study population were 0.04 (evaluation before drug and after 5 h) and 0.06 (after 24 h) so I presume that the SD used by the authors to estimate sample size was 0.05 instead of 0.005. However, considering SD = 0.05, the estimated sample size to determine a difference of 0.03 would be 44 and not 33, as reported. Regarding Doppler evaluation, the authors reported use of the triplex system in all scans. When using triplex, spectral Doppler waves are interleaved with color Doppler and B-mode ultrasound waves, which results in noisy signals and limitation of the pulse repetition frequency that can be used. This should be avoided, especially when evaluating uterine arteries, when high velocities are expected. Moreover, the reported measurements of uterine artery PSV are far below the values expected; when evaluating these vessels I usually notice PSV between 100 cm/s and 200 cm/s, sometimes reaching 300 cm/s, whilst the reported means were below 70 cm/s in this paper. This difference was probably due to use of triplex or improper angle correction. Finally, in the discussion section the authors explained that the reduction in MCA-RI could be related to a decrease in PSV, which is a component of the numerator in the RI formula. However, this explanation does not fit with the observed results as the decrease in PSV was observed only 5 h after drug administration, when RI remained unchanged, and the decrease in MCA-RI was observed only 24 h after drug administration, when PSV had already increased. W. P. Martins*, * Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo, Departamento de Ginecologia e Obstetrícia and Escola de Ultra-sonografia e Reciclagem Médica de Ribeirão Preto (EURP), Rua Casemiro de Abreu, 660, Ribeirão Preto, São Paulo, Brasil CEP: 14020-060

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Doppler velocimetry of the uterine, umbilical and fetal middle cerebral arteries in pregnant women undergoing tocolysis with oral nifedipine

To evaluate Doppler velocimetry (resistance index (RI) and peak systolic velocity (PSV)) in the maternal-fetal circulation before and 5 and 24 h after tocolysis with oral nifedipine. This was a prospective, observational, analytic cohort study performed in 47 pregnant women undergoing nifedipine tocolysis, each subject acting as her own control. Doppler assessment of uterine, umbilical and fetal middle cerebral (MCA) arteries was performed before and 5 and 24 h after an initial 20-mg sublingual dose, which was repeated twice at 20-min intervals if contractions failed to diminish. The maintenance dose consisted of 20 mg orally every 6 h for 24 h up to a total of 100-120 mg nifedipine. We analyzed whether there was a time effect and compared values at the different time-points. The MCA-RI had decreased significantly after 24 h of tocolysis (0 h = 0.85; 5 h = 0.85; 24 h = 0.81; P = 0.001), with no differences in uterine or umbilical arteries or in the MCA to umbilical artery ratio. The MCA-PSV had reduced significantly after 5 h (0 h = 41.5 cm/s; 5 h = 34.7 cm/s; P = 0.001), returning close to baseline levels between 5 and 24 h. The PSV increased significantly between 5 and 24 h in the right uterine artery (5 h = 55.1 cm/s; 24 h = 65.0 cm/s; P = 0.037) and in the umbilical artery (5 h = 28.4 cm/s; 24 h = 33.1 cm/s; P = 0.038). Nifedipine tocolysis is associated with a reduction in RI in the MCA but not in the uterine or umbilical arteries, a reduction in PSV in the MCA after 5 h but returning to baseline within 24 h, and an increase in PSV between 5 and 24 h in the umbilical and right uterine arteries.

Effect of sitting in ergonomic chairs on lower limb venous blood flow

The objective of the research was to assess the effect on lower limb venous blood flow of sitting in two ergonomic chairs. In a cross-over design 12 healthy subjects had popliteal vein blood flow measured by Doppler ultrasound in different sitting positions, in the Aeron and airCentric chairs. Measurements were made lying prone, sitting with the leg flexed 90° and sitting with the leg flexed 120° in one chair, followed by the same measurements in the second chair, the order determined randomly. The primary outcome measure was popliteal vein peak systolic velocity. Simple paired t-tests and a mixed linear model were used to compare blood flow between chairs and different sitting positions. For the Aeron chair, the prone to 90° position resulted in a reduction in peak systolic velocity from 27.8 to 3.5cm/s, adjusted difference 21.0 (95% CI 17.3 to 24.8), and for the airCentric chair from 21.4 to 3.7cm/s, adjusted difference 21.2 (95% CI 17.4 to 24.9). There was no statistically significant difference in peak systolic velocity between the two chairs, in the two sitting positions. There was a marked reduction in popliteal vein blood flow with sitting, but no significant difference in effect between the two ergonomic chairs.

Carotid Ultrasound Criteria for Detecting Intracranial Carotid Stenosis

Background/Aims: This study attempted to establish carotid ultrasound criteria for identifying stenosis of the intracranial internal carotid artery (ICA) and middle cerebral artery (MCA). Methods: Two hundred and fifty-five patients were enrolled. Ultrasound measurements for common carotid artery (CCA) and ICA were as follows: flow volume (FV), peak systolic velocity (PSV), end-diastolic velocity (EDV), pulsatility index (PI) and resistance index (RI). The sensitivity and specificity of the ultrasound criteria for determining intracranial ICA or MCA ≧50% stenosis were calculated. Results: The criteria identified for detecting intracranial ICA ≧50% stenosis were ICA FV <159 ml/min, ICA PSV <33 cm/s and CCA PSV <42 cm/s. When ICA PSV <33 cm/s was combined with CCA PSV <42 cm/s, sensitivity increased to 82%, with 91% specificity. The criteria identified for detecting MCA ≧50% stenosis were CCA FV <285 ml/min, ICA FV <179 ml/min, ICA PSV <33 cm/s, >35% reduction in FV in the CCA, >40% reduction in FV in ICA, and >35% reduction in PSV in ICA. When these criteria were combined, sensitivity increased to 69%, with 85% specificity. Conclusion: This study demonstrated that ultrasound criteria are sensitive and specific for detecting intracranial ICA and MCA significant obstruction.

The effect of age on ocular blood supply determined by pulsatile ocular blood flow and color Doppler ultrasonography.

Pulsatile ocular blood flow (POBF) assessment measures the choroidal circulation and provides diagnostic value to certain ocular diseases such as glaucoma. This technique assumes a constant ocular rigidity and is influenced by axial length, diurnal variation, and age. This study investigated the effect of age on POBF, with consideration of the above factors. Ocular blood supply in the ophthalmic artery was also determined using color Doppler ultrasonography. A total of 118 healthy subjects aged 19 to 75 years were recruited. They were divided into five groups (below age 30, 30 to 39, 40 to 49, 50 to 59, and 60 or above) of at least 20 subjects each. Only one eye of each subject, with axial length <24.5 mm, was considered. The subject's supine POBF was determined followed by a measurement of the blood flow velocity in the ophthalmic artery using color Doppler ultrasonography. All the measurements were at around the same time of day to eliminate any effect from diurnal variation. The scleral rigidity was measured using a Schiotz tonometer with 5.5- and 7.5-g weights. Linear regression analysis demonstrated a significant increase of scleral rigidity with age (Pearson correlation coefficient r = 0.26, p < 0.01) and a significant decrease of POBF with age (r = -0.35, p < 0.01). The reduction in peak systolic velocity in the ophthalmic artery with age was significant (r = -0.28, p < 0.01). Both the systolic and diastolic brachial pressure showed significant increase with age (r = 0.55, p < 0.01; r = 0.40, p < 0.01, respectively). Using multiple regression analysis, POBF showed a significant correlation with age (partial correlation r = -0.36, p < 0.01), but not with scleral rigidity or systolic or diastolic brachial pressure. The peak systolic velocity in the ophthalmic artery also showed significant correlation with age (partial correlation r = -0.29, p < 0.01). The reduction in POBF with age was significant. Although aging affects scleral rigidity and systemic blood pressure, multiple regression analysis indicates that the most influential factor affecting POBF is aging. The peak systolic velocity in the ophthalmic artery also decreased with age, indicating reduced ocular blood supply.