Dynamic pressure measurement for detection of blood access stenosis

A novel method for detection of access failure has been developed. It is based on the continuous evaluation of pre-pump arterial and venous pressure in the extracorporeal circuit. Knowing the flow resistance properties of the arterial and venous branches of the extracorporeal circuit from in-vitro measurements and the height differences, calculating the fistula pressure dynamically is possible. The fistula pressure allows identification of access failure as has been shown by other authors. The dynamic measurement however allows identification of bad needle placement. Dynamic measurement at different flow rates and comparison with static measurements allow for the identification of intra-access stenosis. The mathematical algorithm is described and pressure-flow curves for two sets of extracorporeal circuits are shown. In-vivo examples show a "normal" fistula and a fistula with intra-access stenosis.     

自体动静脉内瘘在血液透析中的应用

目的分析慢性肾功能不全尿毒症期患者自体动静脉内瘘在血液透析中的应用,并探讨其使用时间、初期成熟影响因素、并发症及透析充分性.方法回顾分析182人188例次自体内瘘手术的慢性肾功能不全尿毒症期患者的临床资料,探讨性别、年龄、原发病、术前血白蛋白、血色素、血肌酐、尿素氮、血脂、术后抗凝剂用量与内瘘初期成熟相关性以及1年内并发症和透析充分性.结果 182例慢性透析患者中男性93例,女性89例, 平均年龄52.4岁±8.52岁(18～89)岁,原发病为糖尿病肾病31例(17%).172例内瘘成熟,10例患者16例次失败;Logistic回归分析显示血压低于100/60mmHg患者与内瘘初期成熟成负相关(P<0.001),术后应用抗凝治疗与内瘘初期成熟成正相关(P<0.02);内瘘成熟后1年,通畅率为97.6%(168/172例次),栓塞率为2.3%(4/172例次),感染率为0.每例内瘘平均透析次数为(140.2±10.6)次,平均透析时间为(560.8±42.4)小时, 透析血流量200～250ml/min,KT/V为1.2～1.5, 再循环率R为3.2～3.4%.结论自体内瘘为1种永久性血液透析通路,其并发症主要为栓塞;血压低于100/60mmHg的患者内瘘初期成熟机率较低,术后应用抗凝治疗可减少内瘘阻塞的发生机率;自体内瘘作为血液透析通路,透析充分性好.     

Detection of vascular access stenosis by measurement of access blood flow from ionic dialysance

BACKGROUND/AIM: The measurement of the vascular access blood flow rate (Q(a)) in chronic hemodialyzed patients was proposed to predict access thrombosis. We have recently presented a new method based on the measurements of ionic dialysance at normal and reversed positions of the blood lines. We evaluate the reliability of the measurement of Q(a) by this method in detecting significant access stenoses. METHODS: Twenty-five patients on chronic hemodialysis and having a vascular access cannulated with two needles were studied. The Q(a) was evaluated by the Diascan ionic dialysance (Q(a-id)) method and by the ultrasound dilution technique (Q(a-us); Transonic) during the same dialysis session. The measurements were available for 23 patients. In addition, the patients had ultrasonography of their fistula followed by angiography, if a stenosis was detected. RESULTS: Q(a-id) and Q(a-us) were not significantly different, showing a difference in Q(a) at 32 +/- 469 ml/min. Q(a-id) was significantly different between patients with or without stenosis (508 +/- 241 vs. 1,125 +/- 652 ml/min, p < 0.05). Among patients with a Q(a) <500 ml/min by Q(a-id), 5 had a stenosis detected by ultrasonography (sensitivity 83%), and 3 had no stenosis (false-positive rate 18%). Of these 3 patients, 2 had a thrombotic event at 1 and 3 months, suggesting that a more sensitive detection of stenosis for this range of Q(a) is needed and that a Q(a) <500 ml/min has a higher power to predict thromboses than a stenosis by ultrasonography. CONCLUSIONS: The measurement of the access flow rate by the Q(a-id) method has a clinical relevance to the detection of vascular access stenosis. An intervention program based on the Q(a-id) has to be evaluated.     

血管炎:ANCA诊断Wegener肉芽肿可靠吗

抗中性粒细胞胞浆抗体 (ＡＮＣＡ)是针对中性粒细胞和单核细胞胞浆组分的自身抗体。从 2 0世纪80年代早期被发现以来 ,常被用来帮助诊断原发性系统性血管炎和监测此类疾病的活动性。应用较多的血管炎性疾病有Ｗｅｇｅｎｅｒ肉芽肿 (ＷＧ) ,显微镜多血管炎 (ｍｉｃｒｏｓｃｏｐｉｃ ｐｏｌｙａｎｇｉｉｔｉｓ ,ｍＰＡＮ或ＭＰＡ) ,微弱免疫性节段性坏死性肾小球肾炎 ( ｐａｕｃｉｉｍｍｕｎｅｓｅｇｍｅｎｔａｌｎｅｃｒｏｔｉｚｉｎｇｇｌｏｍｅｒｕｌｏｎｅｐｈｒｉｔｉｓ)和Ｃｈｕｒｇ -Ａｔｓａｕｓｓ(Ｃ -Ｓ)综合征等。尤其是ＡＮＣＡ对…     

Planimetry of aortic valve area using multiplane transoesophageal echocardiography is not a reliable method for assessing severity of aortic stenosis.

OBJECTIVE: To assess the reliability of aortic valve area planimetry by multiplane transoesophageal echocardiography (TOE) in aortic stenosis. DESIGN: Study of the diagnostic value of aortic valve area planimetry using multiplane TOE, compared with catheterisation and the continuity equation, both being considered as criterion standards. SETTING: University hospital. PATIENTS: 49 consecutive patients (29 male, 20 female, aged 44 to 82 years, average 66.6 (SD 8.5)), referred for haemodynamic evaluation of an aortic stenosis, were enrolled in a prospective study. From this sample, 37 patients were eligible for the final analysis. METHODS: Transthoracic and multiplane transoesophageal echocardiograms were performed within 24 hours before catheterisation. At transthoracic echo, aortic valve area was calculated by the continuity equation. At TOE, the image of the aortic valve opening was obtained with a 30-65 degrees rotation of the transducer. Numerical dynamic images were stored on optical discs for off-line analysis and were reviewed by two blinded observers. Catheterisation was performed in all cases and aortic valve area was calculated by the Gorlin formula. RESULTS: Feasibility of the method was 92% (48/52). The agreement between aortic valve area measured at TOE (mean 0.88 (SD 0.35) cm2) and at catheterisation (0.79 (0.24) cm2) was very poor. The same discrepancies were found between TOE and the continuity equation (0.72 (0.26) cm2). TOE planimetry overestimated aortic valve area determined by the two other methods. Predictive positive and negative values of planimetry to detect aortic valve area < 0.75 cm2 were 62% (10/16) and 43% (9/21) respectively. CONCLUSIONS: Planimetry of aortic valve area by TOE is difficult and less accurate than the continuity equation for assessing the severity of aortic stenosis.     

Superiority of ambulatory to physician blood pressure is not an artifact of differential measurement reliability

BACKGROUND: Ambulatory blood pressure is a better predictor of target organ damage and the risk of adverse cardiovascular events than office measurements. Whether this is due to the greater reliability owing to the larger number of measurements that are usually taken using ambulatory monitoring, or the greater validity of these measurements independent of the number, remains controversial. METHODS: We addressed this issue by comparing physician readings and ambulatory measurements as predictors of left ventricular mass index. The number of readings was controlled by using the average of three physician readings and randomly selecting three awake readings from a 24-h ambulatory recording. RESULTS: In a multiple regression analysis that included both the ambulatory and physician blood pressure measurements, only the ambulatory systolic measurements significantly predicted left ventricular mass index (B=0.37, t=3.11, P=0.002); the coefficient for physician's systolic measurements was essentially zero (B=-0.01, t=-0.26, NS). CONCLUSIONS: These findings suggest that the superiority of ambulatory blood pressure as a predictor of target organ damage, compared with physician measurements, cannot be adequately/fully explained by the impact of the larger number of measurements obtained with ambulatory monitoring.     

How reliable is measurement of the anorectal angle by videoproctography?

The anorectal angle can be determined either by constructing a straight line along the lower border of the rectum (Method A) or by using the central longitudinal axis of the lower rectum (Method B). We have used a computer program to derive the centroid of the rectum for Method B. The coefficients of variation for angles measured at rest, during maximum pelvic floor contraction, and during attempted defecation were 0.616, 0.351, and 0.358, respectively, compared with 0.993, 0.972, and 0.968 for Method B. The presence of a rectocele had no influence on the measurement of the anorectal angle in incontinence, but there was a significant difference in assessment of the angle between constipated patients (P <0.05) and controls (P <0.05). Posterior indentation of the rectum had no significant influence on measurement of the angle in any group. These data indicate that a computer-derived centroid is more reliable for measurement of angles, but a correction factor for anterior rectocele is needed in constipated patients and controls.Read at the meeting of The American Society of Colon and Rectal Surgeons, Toronto, Canada, June 11 to 16, 1989.     

Home blood pressure is as reliable as ambulatory blood pressure in predicting target-organ damage in hypertension

BACKGROUND: Our objective was to assess the value of home blood pressure (BP) monitoring in comparison to office BP measurements and ambulatory monitoring in predicting hypertension-induced target-organ damage. METHODS: Sixty-eight untreated patients with hypertension with at least two routine prestudy office visits were included (mean age, 48.6 +/- 9.1 [SD] years; 50 men). Office BP was measured in two study visits, home BP was measured for 6 workdays, and ambulatory BP was monitored for 24 h. All BP measurements were obtained using validated electronic devices. Target-organ damage was assessed by measuring the echocardiographic left-ventricular mass index (LVMI), urinary albumin excretion rate (AER) in two overnight urine collections, and carotid-femoral pulse-wave velocity (PWV) (Complior device; Colson, Garges-les-Gonesse, Paris, France). RESULTS: The correlation coefficients of LVMI with office BP were 0.24/0.15 (systolic/diastolic), with home BP 0.35/0.21 (systolic, P < .01), and with 24-h ambulatory BP 0.23/0.19, awake 0.21/0.16, and asleep 0.28/0.26 (asleep, both P < .05). The correlation coefficients of AER with office BP were 0.24/0.31 (diastolic, P < .05), with home BP 0.28/0.26 (both P < .05), and with 24-h ambulatory BP 0.25/0.24, awake 0.24/0.25 (diastolic, P < .05), and asleep 0.26/0.18 (systolic, P < .05). There was a trend for negative correlations between PWV and diastolic BP measurements (not significant). In multiple-regression models assessing independent predictors of each of the three indices of target-organ damage, systolic home BP and age were the only independent predictors of increased LVMI that reached borderline statistical significance. CONCLUSIONS: These data suggest that home BP is as reliable as ambulatory monitoring in predicting hypertension-induced target-organ damage, and is superior to carefully taken office measurements.     

Immunohistochemical microvessel count is not a reliable prognostic predictor in colorectal carcinoma

BACKGROUND/AIMS: Immunohistochemical microvessel count for angiogenesis is associated with the growth and metastasis of various solid tumors, but its role in colorectal carcinoma remains controversial. This study aimed to determine its role in predicting the relapse and survival of colorectal carcinomas after curative surgery. METHODOLOGY: Representative paraffin-embedded sections of invasive colorectal cancers from 104 patients were studied by immunohistochemical staining using polyclonal anti-factor VIII antibody. Two investigators examined the microvessel count in the hot spot area of tumor using a 400x field in a blind fashion. RESULTS: There was no correlation between microvessel count and tumor size, location of carcinoma, tumor cell differentiation and nodal status. The microvessel count appeared to be lower among advanced-stage cancers as compared with early-stage cancers (pN0 vs. pN1+ pN2: 56 +/- 25. vs. 50 +/- 20; Dukes A + B vs. C + D: 56 +/- 25 vs. 49 +/- 18). In node-negative patients, the value of microvessel count greater than or equal to 75 seemed to correlate with longer disease-free survival and overall survival. CONCLUSIONS: Based on these results, immunohistochemical microvessel count seemed to decrease as colorectal cancer progressed and was not a reliable prognostic predictor in colorectal carcinoma.     

Simple detection of severe coronary stenosis using transthoracic Doppler echocardiography at rest

Coronary flow velocity can be measured by transthoracic Doppler echocardiography (TTDE). The purpose of this study was to detect severe coronary stenosis using the diastolic-to-systolic flow velocity ratio (DSVR) determined by TTDE at rest. We prospectively examined 190 consecutive patients with angina pectoris for whom coronary angiography was planned. Doppler spectral tracings of flow velocity in the distal left anterior descending artery were recorded by TTDE at rest. The mean and peak DSVR values were computed using mean and peak coronary flow velocities. DSVR measurement by TTDE at rest was performed within 24 hours before angiography, and in patients who underwent coronary intervention it was performed again within 48 hours after the intervention. The success rate for DSVR measurement by TTDE was 83.7%. There were significant differences in peak DSVR and mean DSVR between the patients with severe stenosis (percent diameter stenosis >85%) and those without severe stenosis (1.3 +/- 0.4 vs 1.9 +/- 0.50 and 1.2 +/- 0.4 vs 1.8 +/- 0.5, respectively; p <0.0001). In the 17 patients with successful intervention, DSVR was significantly increased after the procedure (mean 1.2 +/- 0.1 vs 2.0 +/- 0.2; peak 1.2 +/- 0.2 vs 2.0 +/- 0.3, respectively; p <0.0001). For percent diameter stenosis >85%, the best cut-off points were 1.6 for peak DSVR (sensitivity 79.0%, specificity 75.7%) and 1.5 for mean DSVR (sensitivity 77.0%, specificity 77.9%). Thus, DSVR measurement by TTDE is a simple, noninvasive method for detection of severe coronary stenosis at rest.     

Chlamydia pneumoniae infection is not involved in carotid artery stenosis

Recent studies have suggested the existence of a close relationship between Chlamydia pneumoniae infection and atherosclerosis. However, it has been speculated that C. pneumoniae infection is not associated with early atherosclerosis but with advanced atherosclerosis. In the present study, we test this hypothesis. In 524 consecutive patients who underwent cerebral angiography were recruited for the study. From the films obtained during angiography, percent stenosis of neck internal carotid artery was calculated according to the method of the North American Symptomatic Carotid Endarterectomy Trial (NASCET). Serum C. pneumoniae IgG and IgA antibodies were measured by a commercial ELISA enzyme immunoassay kit. Cerebrovascular risk factors such as age, gender, hypertension, diabetes mellitus, hyperlipidemis and smoking were assessed by interview. Old age above 60 years and diabetes mellitus were found to be independent risk factors for carotid artery stenosis in this study after adjustment for cerebrovascular risk factors. When we defined carotid artery stenosis as the presence of greater than 30% stenosis of one artery, there was no association after adjustment for other risk factors between C. pneumoniae IgG and IgA seropositivity and the presence of carotid artery stenosis for any cut-off value of seropositivity. When we defined carotid artery stenosis as the presence of greater than 70%, there was also no association between C. pneumoniae IgG and IgA seropositivity and the presence of carotid artery stenosis for any cut-off value of seropositivity. These results suggest that C. pneumoniae infection is not associated with carotid artery atherosclerosis.     

Intrahepatic pressure measurement: not an accurate reflection of portal vein pressure

Previous studies have established the reliability of percutaneous portal venous pressure measurement using a Chiba needle, a procedure requiring fluoroscopic guidance. Intrahepatic pressure has been advocated by some as a simple and safe index of portal venous pressure. The aim of this study was to examine the reliability of intrahepatic pressure measurement and its relationship to portal venous pressure. Fifty patients requiring liver biopsy were included: 29 with cirrhosis (n = 20 micronodular, n = 9 macronodular) and 21 with various hepatic disorders but no cirrhosis. The procedure was performed under fluoroscopic guidance, using a Chiba needle connected to a manometer by a saline-filled catheter. Immediately prior to biopsy, each patient underwent measurement of: (i) 3 to 5 separate intrahepatic pressures, the intraparenchymal site being inferred by the lack of blood or bile return; and (ii) portal and hepatic venous pressures, the intravascular position of the needle being ascertained by the reflux of blood and the vessel identified with injection of contrast. Intrahepatic pressure measurements showed great intraindividual variability (variation coefficient up to 115%). Mean intrahepatic pressure (13.19 +/- 8.32 mm Hg) was similar to portal venous pressure (14.43 +/- 6.10 mm Hg) in the noncirrhotics but significantly lower in the cirrhotics (intrahepatic pressure = 18.34 +/- 8.82 mm Hg, portal venous pressure = 22.52 +/- 9.47 mm Hg; p less than 0.01). The difference between these two parameters exceeded 3 mm Hg in 50% of patients (mean = 9 mm Hg, range = 4 to 19 mm Hg), both in cirrhotics and noncirrhotics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Coronary pressure measurement for functional evaluation and treatment of intermediate angiographic stenosis

Accurate understanding of the physiopathology of a coronary stenosis is a major objective in management during diagnostic coronary angiography. Measurement of fractional flow reserve (FFR) by coronary pressure measurement is a reliable method for evaluating the functional consequences of a lesion of the myocardium. This retrospective monocentric study of 114 patients showed that routine coronary pressure measurement for assessing the functional consequences of intermediate (30 to 70% stenosis) lesions or those of ambiguous topography: was necessary in 4% of diagnostic coronary angiographies enabling an immediate management decision. Using this method, 34% of complementary investigations were not performed (stress test, myocardial scintigraphy, dobutamine stress echocardiography). Seventeen per cent of unnecessary angioplasties were also avoided so that acute coronary event were also avoided when lesions with a FFR >0.75 were not treated by angioplasty. A 10-14% reduction in cost was achieved compared with a strategy of systematic angioplasty in respectively mono- or multivessel disease patients and 39% compared with performing ambulatory myocardial scintigraphy in patients with multivessel disease.     

Pancreatic function testing: serum PABA measurement is a reliable and accurate measurement of exocrine function.

A comparison between the NBT-PABA/14C-PABA test (NBT-PABA, n-benzoyl-tyrosyl para-aminobenzoic acid) using the PABA excretion index (PEI) and serum PABA estimation at 90 minutes has been made in 42 consecutive subjects attending for investigation of possible pancreatic disease to a District General Hospital (DGH). The PEI was unobtainable or incorrect on 38% of occasions compared with 9% for the serum test. Sensitivity, specificity, and efficiency for the PEI (n = 33 valid results) were 71%, 88%, and 79% respectively and for the serum PABA (n = 41 valid results), 95%, 90%, and 93% respectively. These results confirm that measurement of serum PABA is a simpler, more reliable, and a more accurate method of assessing pancreatic function.     

Lability of arterial pressure after baroreceptor denervation is not pressure dependent

The mechanisms of increased arterial pressure lability after sinoaortic deafferentation remain unknown. We have shown previously in rats with chronic sinoaortic deafferentation (7-14 days after sinoaortic deafferentation) that ganglionic blockade significantly reduced mean arterial pressure and arterial pressure lability. The present study investigated the possibility that lability is related to the level of arterial pressure. Rats were instrumented chronically and heart rate and mean arterial pressure were sampled every 5 seconds in the conscious, freely moving state. Graded sustained increases in pressure (+10 to +82 mm Hg) produced by constant infusion of angiotensin II, phenylephrine, or vasopressin did not affect lability (standard deviation of 30-minute sampling period); whereas, graded hypotension (-10 to -70 mm Hg) produced by infusions of adenosine, nitroprusside, or nisoldipine appeared to reduce lability. Analysis of covariance and orthogonal polynomial curve fitting demonstrated a significant correlation between the decrease in mean arterial pressure and the decrease in lability produced by nisoldipine but not by adenosine or nitroprusside. Lability does not appear to be solely dependent on the level of arterial pressure because lability was reduced by adenosine when pressure was maintained at control levels by simultaneous infusion of phenylephrine. We conclude that 1) arterial pressure lability is not influenced by elevation of arterial pressure but can be reduced when pressure is lowered by certain vasodilators and 2) pressure alone does not appear to be the major determinant of lability because it can be attenuated by vascular smooth muscle relaxants even when pressure is maintained.     

Routine measurement of pleural fluid amylase is not indicated

BACKGROUND: The routine measurement of pleural fluid amylase is frequently recommended, but the cost-effectiveness of this procedure is unknown. METHODS: To assess the utility of routine measurement of pleural fluid amylase in evaluating pleural effusions, we measured amylase, glucose, lactate dehydrogenase, and protein levels and blood cell counts in 379 patients undergoing thoracentesis during a 22-month period from 1997 to 1999. Of these, 199 had effusions after cardiac surgery; 61, malignant; 48, transudative; 28, parapneumonic; 2, chylous; 2, rheumatoid; 1, tuberculous; and 1, from chronic pleuritis. There were 37 exudates of unknown origin. RESULTS: Measurement of pleural fluid amylase levels did not assist in determining the origin of the effusion in any of the patients. Amylase levels greater than 100 U/L (normal serum level in our laboratory is 30-110 U/L) were found in 5 (1.3%) of 379 patients: 1 patient with congestive heart failure (amylase, 173 U/L), 2 with post-cardiac surgery effusions (144 U/L and 130 U/L), 1 with pneumonia (109 U/L), and 1 with lung cancer (105 U/L). CONCLUSIONS: The routine measurement of pleural fluid amylase levels is neither clinically indicated nor cost-effective. We suggest that pleural fluid serum amylase levels be measured only if there is a pretest suspicion of acute pancreatitis, chronic pancreatic disease, or esophageal rupture.