Outcomes of Brachiocephalic Fistulas,Transposed Brachiobasilic Fistulas,and Upper Arm Grafts

Background and objectives: An upper arm vascular access is often placed in patients with a failed forearm fistula or with vessels unsuitable for a forearm fistula. The aim of this study was to compare the outcomes of three upper arm access types: brachiocephalic fistulas, transposed brachiobasilic fistulas, and grafts.Design, setting, participants, & measurements: A prospective, computerized access database was queried retrospectively to identify the clinical outcomes of upper arm accesses placed in 678 patients at a large dialysis center, including 322 brachiocephalic fistulas, 67 brachiobasilic fistulas, and 289 grafts.Results: Primary access failures were less common for brachiobasilic fistulas and grafts compared with brachiocephalic fistulas (18%, 15%, and 38%; hazard ratio of brachiocephalic fistulas versus brachiobasilic fistulas 2.76; 95% confidence interval 1.41 to 5.38; P < 0.003). For the subset of patients receiving a brachiocephalic fistula, a multiple variable logistic regression analysis including age, sex, race, diabetes, coronary artery disease, peripheral vascular disease, cerebrovascular disease, prior access, surgeon, arterial diameter, and venous diameter found that only vascular diameters predicted primary failure (P < 0.001). When primary failures were excluded, cumulative access survival was similar for brachiobasilic and brachiocephalic fistulas, but superior to that of grafts. Total access interventions per year were lower for brachiobasilic and brachiocephalic fistulas than for grafts (0.84, 0.82, and 1.87, respectively, P < 0.001).Conclusions: Transposed brachiobasilic fistulas may be preferred, due to (1) a lower primary failure rate (similar to grafts), and (2) a lower intervention rate (similar to brachiocephalic fistulas). However, this advantage must be balanced against the more complex surgery.An upper arm vascular access is typically placed in patients whose vessels are unsuitable for a forearm fistula or in those with a failed forearm fistula. There are two major considerations in selecting the type of vascular access to place. First, the new access must mature adequately to be suitable for dialysis. That is, it must be cannulated reproducibly and achieve a dialysis blood flow sufficient to provide adequate dialysis. Second, once maturation has been achieved, the access should maintain long-term patency with a minimum of percutaneous or surgical interventions (1). The two major types of upper arm access placed are the brachiocephalic fistula and the upper arm graft. Once suitability for dialysis has been attained, the brachiocephalic fistula is superior to an upper arm graft, because it requires substantially fewer interventions to maintain long-term patency (2). This advantage of fistulas is counterbalanced by their higher suitability failure, which occurs in 20% to 60% of new fistulas in recent series, as compared with 10% to 20% of new grafts (1,3).A third type of upper arm access is the transposed brachiobasilic fistula. This fistula is placed less commonly than the brachiocephalic fistula, as it is more technically challenging and time-consuming to create. Four series reporting on the outcomes of 34 to 59 brachiobasilic fistulas observed a primary failure (nonmaturation) rate ranging from 0% to 21% (4–7). Only two of these publications provided a direct comparison of the outcomes of brachiobasilic and brachiocephalic fistulas. These studies observed a lower suitability failure rate of brachiobasilic fistulas as compared with brachiocephalic fistulas, but a similar cumulative access survival (5,7). In both series, the access outcomes were ascertained retrospectively, and the fistulas were placed without the benefit of preoperative vascular mapping, an important factor that could affect vascular access outcomes.The goal of the present study was to evaluate the relative advantages and disadvantages of brachiocephalic fistulas, transposed brachiobasilic fistulas, and upper arm grafts when routine preoperative vascular mapping is used to plan the access surgery. We retrospectively analyzed a prospective, computerized access database to evaluate the outcomes of a large cohort of patients receiving an upper arm access at a single large dialysis center. The primary clinical outcomes analyzed were: (1) failure to achieve suitability for dialysis (primary failure) and (2) cumulative access survival (i.e. the time from access creation to its permanent failure, regardless of number of salvage procedures). Major secondary outcomes were the frequency of interventions required to maintain access patency and the duration of catheter dependence.     

Disparities in Fistula Maturation Persist Despite Preoperative Vascular Mapping

Background and objectives: Failure to mature (primary failure) of new fistulas remains a major obstacle to increasing the proportion of dialysis patients with fistulas. This failure rate is higher in women than in men, higher in older than in younger patients, and higher in forearm than in upper arm fistulas. These disparities in the frequency of failure to mature may be due in part to marginal vessels in the high-risk groups and should be reduced by routine preoperative vascular mapping.Design, setting, participants, & measurements: A prospective, computerized database was queried retrospectively to evaluate the frequency of primary fistula failure in 205 hemodialysis patients for whom preoperative mapping was obtained. The association between clinical characteristics and risk for primary fistula failure was analyzed by univariate and multiple variable regression analysis.Results: The overall primary fistula failure rate was 40% (82 of 205 patients). On multiple variable logistic regression, three clinical factors were associated with an increased risk for failure to mature among patients who underwent preoperative vascular mapping: Female gender, age ≥65 yr, and forearm location. The primary fistula failure rate varied from 22% in younger men with an upper arm fistula to 78% in older women with a forearm fistula. Dynamic preoperative vascular measurements (change in peak systolic velocity and resistive index after tight fist clenching) did not differ between patients with mature and immature forearm fistulas.Conclusion: Disparities in fistula maturation persist despite the use of routine preoperative vascular mapping.The major hurdle to increasing arteriovenous fistula use in hemodialysis patients is the high frequency of fistulas that fail to mature. These fistulas are never usable for dialysis (primary failures) (1–3). The failure rate is not uniform, varying greatly among different patient subsets. A higher risk for failure to mature has been observed in older patients, women, nonwhite patients, and patients with cardiovascular disease (4,5). These differences are reflected in the prevalence rates of fistulas in US hemodialysis patients, which are lower in women, black patients, and older patients (6). Moreover, forearm fistulas are more likely than upper arm fistulas to fail to mature (5).Fistula maturation requires adequate arterial inflow, adequate venous outflow, and the ability of the vein to dilate and increase blood flow sufficiently to permit reproducible cannulation for dialysis and deliver an adequate dosage of dialysis (1). One plausible explanation for the disparities in fistula success among dialysis patients is that the high-risk groups are more likely to have marginal vessels. If so, then one might expect that careful selection of arteries and veins that are most suitable for fistula creation would reduce the primary failure rate of new fistulas and minimize the disparities among patient subgroups in the likelihood of failure to mature. The desire to increase fistula use in the United States has driven widespread implementation of preoperative vascular mapping to assist the surgeons in optimizing fistula success. Certainly, this approach has dramatically increased fistula placement at several medical centers (7–10); however, there has been little systematic effort to determine whether the introduction of routine preoperative mapping reduces the primary failure rate of new fistulas, particularly in patient subsets that are known to be at high risk for this complication.To evaluate this question, we evaluated the fistula maturation rate in hemodialysis patients at our medical center who received a new fistula after preoperative vascular mapping. A prospective, computerized access database was queried retrospectively to derive a comprehensive list of all fistulas placed, as well as their clinical outcomes.     

Retrospective analysis of arteriovenous fistula patency and failure in patients on dialysis for end-stage kidney disease in the Gaza strip

Background

The preservation of patent, well-functioning arteriovenous fistulas is one of the most difficult clinical problems in the long-term management of patients undergoing renal dialysis. This study aimed to define the patency and failure rates of fistulas in patients with end-stage kidney disease on dialysis and to examine how fistula failure is managed.

老年血液透析病人动静脉内瘘血流量对心功能及炎症反应的影响

目的 探讨老年血液透析病人动静脉内瘘血流量(AVFB)对心功能及炎症反应的影响.方法 选取2017年2月至2018年3月我院利用动静脉内瘘进行血液透析治疗的老年病人124例为研究对象,根据病人动静脉内瘘吻合术后1个月AVFB的流量大小,将病人分为高流量组(>600 mL/min,n=38)、中流量组(400～600 m...     

Cardiac effects of persistent hemodialysis arteriovenous access in recipients of renal allograft

In hemodialysis patients, large arteriovenous (AV) fistulas for vascular access may cause ventricular hypertrophy and high-output cardiac failure. The long-term cardiac consequences of functional AV fistulas in renal transplant patients are unclear. A precise knowledge of these consequences is important to decide if and when such fistulas should be closed in successfully transplanted patients. In this retrospective study including 61 stable renal transplant patients with adequate renal function (serum creatinine <2.0 mg/100 ml), echocardiography was performed in 39 patients with a functional AV fistula (group 1) and in 22 whose fistulas had been closed, for esthetic reasons, within 2 months postoperatively (group 2). The volume flow of the fistulas, measured in 22 randomly selected individuals of group 1, was 900 +/- 350 ml/min (range 500-1,600). Patients of group 1 were older (40 +/- 12 vs. 33 +/- 12 years, p < 0.05), had longer duration of the fistula (62 +/- 31 vs. 36 +/- 30 months, p < 0.05), higher body mass index (24 +/- 4 vs. 22 +/- 3 kg/m2, p < 0.05), systolic (154 +/- 24 vs. 138 +/- 18 mm Hg, p < 0.05) and diastolic (96 +/- 12 vs. 89 +/- 11 mm Hg, p < 0.05) blood pressure and increased left ventricular (LV) end-diastolic dimension (53 +/- 5 vs. 49 +/- 5 mm, p < 0.01). LV mass, cardiac index, ejection fraction and the proportion of patients with LV hypertrophy were comparable in the two groups. LV end-diastolic dimension was positively and independently influenced only by the presence of the AV fistula (p < 0.01) after adjusting for age, duration of the fistula, body mass index, systolic and diastolic blood pressure and the nature of the antihypertensive drugs used. In conclusion, the persistence of large, high-flow AV fistulas for prolonged periods of time had little impact on cardiac morphology and function of stable renal transplant patients with adequate renal function. The data do not support routine closure of these fistulas in all renal transplant patients.     

Hemodynamic and hormonal effects of atrial natriuretic factor in patients with essential hypertension

Hemodynamic and hormonal effects of two graded infusions of alpha-human-(1-28)-atrial natriuretic factor (0.5 microgram/kg prime followed by 0.05 microgram/kg per min for 20 minutes and by 0.1 microgram/kg per min for 20 minutes) were evaluated in 13 patients with mild to moderate essential hypertension. The lower dose of atrial natriuretic factor did not change significantly any of the considered variables, although it tended to reduce aortic mean blood pressure (from 132.6 +/- 5.3 to 125.5 +/- 4.6 mm Hg), cardiac index (from 3.67 +/- 0.2 to 3.54 +/- 0.18 liters/min per m2) and forearm vascular resistance (from 178.6 +/- 15 to 148.3 +/- 10 mm Hg/ml per s). The higher dose of atrial natriuretic factor significantly reduced mean aortic pressure (118.6 +/- 5 mm Hg), cardiac index (3.29 +/- 0.16 liters/min per m2) and stroke volume index (from 45.9 +/- 2.6 to 38.9 +/- 3 ml/m2) and slightly decreased pulmonary wedge pressure, whereas both total peripheral resistance and forearm vascular resistance were not modified. With this latter dose a reduction in aortic pressure was observed in all patients at the steady state, and this was associated with a fall in stroke volume index in 10 of the 13 patients and with a reduction in total peripheral resistance in only 6 patients. Heart rate and right atrial and pulmonary pressures did not change during infusion of atrial natriuretic factor. Plasma renin activity was only slightly reduced by atrial natriuretic factor, whereas plasma norepinephrine rose significantly (from 233 +/- 34 to 330 +/- 58 pg/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dobutamine on ischemic vasodilation of the forearm in patients with severe congestive heart failure

BACKGROUND: The significant changes that occur in the peripheral circulatory system in heart failure are well known. Although the central hemodynamic effects of dobutamine have been well described, data on its effect on peripheral vascular function in patients with severe left ventricular dysfunction are limited. METHODS AND RESULTS: Resting and hyperemic forearm blood flow and resistance were measured using forearm venous occlusion plethysmography in patients with advanced congestive heart failure (CHF) before and during the infusion of increasing doses of dobutamine. Total hyperemia was also calculated. We studied eight patients with New York Heart Association classes III to IV CHF who had a mean age of 62 +/- 5 years and a mean ejection fraction of 17.4% +/- 2.9%. Resting forearm blood flow increased from 2.3 +/- 0.2 to 3.4 +/- 0.4 mL/min/100 mL during peak dobutamine infusion (P < .05). Resting forearm vascular resistance decreased from 39 +/- 3 to 29 +/- 4 units (P < .02). Peak hyperemic forearm blood flow increased from 25 +/- 3 to 34 +/- 6 mL/min/100 mL of tissue (P < .02) and peak hyperemic vascular resistance decreased from 3.7 +/- 0.4 to 2.9 +/- 0.3 units (P < .01). Total hyperemia increased from 14.3 +/- 1.9 to 19.4 +/- 2.4 mL/100 mL (P < .01). CONCLUSIONS: The data show that in patients with advanced CHF, intravenous dobutamine not only increases resting forearm blood flow and decreases resting forearm vascular resistance, but augments the reactive hyperemic flow and improves the vasodilatory response of the forearm vessels to transient ischemic occlusion. The underlying mechanism for this response and its clinical significance remain to be identified.     

Circulation in neonates with intracranial arteriovenous fistula and cardiac failure

Two newborn infants with severe cardiac failure caused by a large cerebral arteriovenous communication were studied with complete cardiac catheterization, indicator-dilution curves and angiography. In one infant, studied at age 10 hours, a large right to left shunt through the patent ductus was seen with retrograde aortic flow into the left carotid artery. The entire flow in the descending aorta was supplied from the ductus. The second infant, studied at age 5 days, had a 20 percent right to left shunt through the foramen ovale and the ductus was closed. Hypoxia was caused by inadequate oxygenation of pulmonary venous blood, atrial right to left shunting and possibly ductal right to left shunting. The hemodynamic findings in cases of cerebral arteriovenous fistula would seem to depend on the patient's age at the time the studies are carried out and the severity of the lesion. Cardiac output was more than twice the normal value and blood flow through the arteriovenous fistula was probably greater than 4 liters/min per m².     

Sympathetic vasoconstriction during exercise in ambulatory patients with left ventricular failure

In patients with heart failure, exercise is thought to increase sympathetic vasoconstrictor tone. To investigate the extent of this sympathetic activation, we studied the effect of maximal exercise on nonexercising vascular beds in 35 patients with left ventricular failure (ejection fraction, 21 +/- 8%; peak exercise oxygen uptake (VO2), 12.3 +/- 3.5 ml/min/kg). In 28 patients, cardiac output and leg blood flow were measured during maximal upright bicycle exercise. Total flow to nonexercising tissue was then calculated as cardiac output--(2 x leg flow). In seven patients and six normal subjects, forearm blood flow was measured during supine bicycle exercise before and after alpha-adrenergic blockade with intravenous phentolamine. Maximal upright exercise increased the vascular resistance of nonexercising tissue from 34 +/- 16 units at upright rest to 45 +/- 25 units (p less than 0.02) but did not affect total flow to nonexercising tissue (rest, 2.9 +/- 1.0; maximal exercise, 2.8 +/- 1.4 l/min; p = NS). Supine exercise had no significant effect on forearm blood flow or vascular resistance in the normal subjects. In the patients with heart failure, supine exercise increased forearm vascular resistance from 45 +/- 17 to 58 +/- 25 mm Hg/ml/min/100 ml (p less than 0.02), again with no change in tissue flow (rest, 2.4 +/- 0.1; maximal exercise, 2.4 +/- 0.9 ml/min/100 ml; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)     

Clinical pharmacology and therapeutic application of prazosin in acute and chronic refractory congestive heart failure: Balanced systemic venous and arterial dilation improving pulmonary congestion and cardiac output

The acute and chronic cardiocirculatory effects of the oral vasodilator, prazosin, were evaluated by cardiac catheterization, forearm plethysmography, echocardiography, treadmill exercise, and symptoms in nine patients with advanced long-standing congestive heart failure due to coronary disease. Oral prazsoin (2 to 7 mg) reduced forearm venous tone from 58.9 to 18.5 mm Hg/ml (p < 0.001 and decreased forearm vascular resistance from 88.9 to 47.9 mm Hg/ml/100 g/min (p < 0.001). Concomitantly, mean systemic arterial pressure declined from 99.7 to 77.7 mm Hg (p < 0.001), left ventricular filling pressure decreased from 32.0 to 17.6 mm Hg (p < 0.001) and cardiac index was raised from 1.95 to 2.89 liters/ min/m2 (p < 0.001). These effects of a single dose of prazosin on left ventricular function were rapid in onset, maximal at 1 hour and sustained for the entire 6 hour period of observation. After two weeks of outpatient therapy with 2 to 7 mg prazosin four times daily, echographic end-diastolic dimension decreased (5.7 to 5.4 cm, p < 0.001) whereas the duration of treadmill exercise increased (209 to 317 seconds, p < 0.001). Symptoms (dyspnea, fatigue, angina) were diminished throughout the course of prazosin therapy (mean 94 days), and New York Heart Association functional class improved from 3.7 to 2.2. Thus, prazosin possesses sustained nitropruside-like balanced dilator actions on the systemic arterial and venous beds, which are effectively translated into beneficial hemodynamics of augmenting lowered cardiac output and relieving excessive left ventricular end-diastolic pressure, thereby accounting for the drug's efficacy in the ambulatory management of patients with chronic severe congestive heart failure.     

Measurement of cardiac output and exercise factor by pulsed Doppler echocardiography during supine bicycle ergometry in normal young adolescent boys

The purposes of this study were to determine the ability of pulsed Doppler echocardiography to consistently and accurately measure cardiac output during exercise, and to measure the exercise factor by Doppler methodology when oxygen consumption was simultaneously measured. Thirty-four healthy young adolescent male volunteers (mean age 13 years) were recruited. Submaximal exercise was performed by supine bicycle ergometry. Cardiac output was calculated as mean velocity X cross-sectional area. Successful rest and exercise determinations of cardiac output were obtained in 81% (n = 52) of the studies. Mean cardiac output increased from 4.6 to 8.9 liters/min (p less than 0.001) during exercise and mean oxygen consumption increased from 212 to 899 ml/min (p less than 0.001). Doppler-estimated rest and exercise cardiac outputs correlated well with simultaneously measured oxygen consumption (r = 0.89, SEE = 1.2 liters/min; y = 0.006 X 3.2 liters/min). Mean exercise factor was 6.4 (1.2 SD). Twenty-six pairs of rest and exercise cardiac output determinations by Doppler technique and indirect Fick method were simultaneously compared in a subset population (r = 0.86, SEE = 1.4 liters/min; slope = 0.93, y intercept = 1.4 liters/min). Results of this study demonstrate that cardiac output and exercise factor can be estimated by pulsed Doppler echocardiography during exercise.     

Shunt, Dialyseeinleitung, Katheter

The elective start of dialysis therapy via a well planned dialysis access requires early presentation at a nephrologist. Native fistulas, with their numerous modifications, are considerably superior to polytetrafluoroethylene (PTFE) grafts, both in terms of patient survival as well as infection and occlusion rates. Native fistulas should be placed at least 3 months and PTFE grafts 4 weeks prior the start of dialysis. If fistulas or PTFE grafts are not possible, or there are other contraindications such as severe heart insufficiency, dialysis should be started with a tunnelled catheter for vascular access. In Germany, dialysis is currently started at a mean GFR of 7.8 ml/min. Starting at <6 ml/min should definitely be avoided. In case of multimorbid patients, an earlier start may be necessary, exceptionally at a GFR >15 ml/min.     

Nitrate effects on cardiac output and left ventricular outflow resistance in chronic congestive heart failure

Nitrates have been used for long-term vasodilator therapy of left ventricular failure. Whereas left ventricular filling pressure (LVFP) consistently decreases, cardiac output does not always increase after nitrate administration, suggesting that preload reduction may be the predominant action of these agents in congestive heart failure. In 28 patients with chronic congestive heart failure due to cardlomyopathy, nitrate administration reduced mean systemic arterial pressure from 91.9 to 83.6 mm Hg, LVFP from 29.3 to 19.0 mm Hg and systemic vascular resistance from 33.2 to 24.0 U. Cardiac index increased from 1.70 to 2.09 liters/min/m². All changes were significant (p < 0.001). The change in cardiac index after nitrate administration correlated positively with the control LVFP (r = 0.52) and inversely with the control cardiac index (r = 0.52). In six patients, nitrate effects were compared to those of preload reduction with the application of tourniquets and outflow resistance reduction with the administration of nitroprusside. All three interventions reduced LVFP comparably and significantly, tourniquets by 6.3 mm Hg, nitroprusside by 9.3 mm Hg and nitrates by 8.7 mm Hg. The cardiac index decreased 0.16 liters/min/m² after tourniquets, but increased 0.50 liters/min/m² during nitroprusside therapy and 0.21 liters/min/m² after the administration of nitrates. The differences in cardiac index response between tourniquets and the two vasodilators were statistically significant, as was that between nitroprusside and nitrates. We conclude that the hemodynamic actions of nitrates in congestive heart failure are qualitatively similar to those of nitroprusside, but quantitatively less. Nitrates reduce outflow resistance as well as preload in congestive heart failure, and the magnitude of the former response is dependent upon the base line cardiac index and LVFP.     

Coronary artery fistulas in adults: Incidence,angiographic characteristics,natural history

The incidence, angiographic characteristics, and natural history of coronary artery fistulas in patients undergoing diagnostic cardiac catheterization have not been well defined. Of 33,600 patients who had diagnostic cardiac catheterization, 34 (0.1%) had coronary artery fistula. Nineteen fistulas originated from the right, 11 from the left anterior descending, and 4 from the circumflex coronary arteries, respectively. The mean ratio of pulmonary to systemic flow was 1.19 ± 0.33. Only one patient with coexistent atrial septal defect had a pulmonic to systemic flow ratio >1.5. Right and left heart pressures, with the exception of three patients in whom left ventricular end-diastolic pressure was >12 mm Hg, were within normal limits. During a mean follow-up period of 6.3 years (range 2–14 years), there were no complications related to coronary artery fistula. It was concluded that the incidence of coronary artery fistulas detected during diagnostic coronary angiography is very low. Coronary artery fistulas originate predominantly from the right coronary artery and are not associated with hemodynamic abnormalities or other congenital heart diseases. The prognosis of coronary artery fistulas in adults is good. © 1995 Wiley-Liss, Inc.     

Maintenance of forearm vasodilator action of atrial natriuretic factor in congestive heart failure secondary to ischemic or idiopathic dilated cardiomyopathy.

Infusions of atrial natriuretic factor (ANF) are frequently associated with attenuated natriuretic and diuretic responses in patients with congestive heart failure. However, ANF infusions result in systemic vasodilation, suggesting that end organ responsiveness to ANF may not be uniformly decreased. To determine if the vasodilator effects of ANF were altered in heart failure, strain-gauge plethysmography was utilized to measure forearm blood flow responses to the intraarterial infusion of ANF using a dose range that was low enough to avoid systemic effects. In 9 control subjects, ANF infusions of 0.5, 1.0, 2.0 and 4.0 micrograms/min/100 ml forearm volume significantly increased forearm blood flow from 3.21 +/- 1.71 to 5.69 +/- 3.14, 6.20 +/- 2.57, 6.64 +/- 2.53 and 6.97 +/- 2.49 ml/min/100 ml forearm volume, respectively (all p less than 0.01). In 7 patients with heart failure, ANF infusion significantly increased forearm blood flow from 2.19 +/- 0.98 to 3.18 +/- 1.70, 3.76 +/- 2.0 and 4.42 +/- 2.80 ml/min/100 ml forearm volume for the 0.5, 1.0 and 2.0 micrograms doses, respectively (all p less than 0.05). By analysis of variance, the forearm blood flow responses pooled over all doses were not significantly different between the 2 groups. At the 2.0 micrograms dose, the peak increase in forearm blood flow in normal subjects represented a 107% increase over baseline compared with a 102% increase in patients with heart failure. In summary, these data demonstrate that intraarterial administration of ANF in patients with heart failure resulted in dose-related increases in forearm blood flow. The responses were not significantly different from normal subjects expressed both as an absolute response and as a percent increase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prevention of thrombosis in arteriovenous fistulas

To prevent thrombosis in arteriovenous fistulas it is necessary to obtain the knowledgeable cooperation not only of the whole health care team, but also of the patient. The first step is preservation of forearm veins by avoiding unnecessary venipunctures in patients with chronic renal failure. Fistulas should be constructed well in advance of need and use natural rather than prosthetic veins whenever possible. Major surgery elsewhere is a potential cause of fistula thrombosis. Fistula construction is often best delayed till major surgery is over and until the veins have recovered from the effects of systemic steroid therapy. Avoidance of premature fistula cannulation and correct needling techniques help to prevent vein wall damage. Alertness to the presence of high venous pressures on dialysis and observation of inefficient dialysis due to recirculation should lead to detection of narrowed segments which can be surgically corrected before thrombosis occurs. Antiplatelet drugs are of proven value in the prevention of recurrent thrombotic episodes.     

Comparative systemic and renal effects of dopamine and angiotensin-converting enzyme inhibition with enalaprilat in patients with heart failure

Renal and systemic hemodynamics were measured during titration of dopamine and serially after intravenous administration of enalaprilat in nine patients with chronic severe congestive heart failure. During titration of dopamine, renal blood flow increased by 99%, from 304 +/- 120 to 604 +/- 234 ml/min (p less than .01) at a dose of dopamine of 2.1 micrograms/kg/min, which produced only a 21% increase in cardiac index, from 1.96 +/- 0.36 to 2.38 +/- 0.35 liters/min/m2 (p less than .05). Cardiac index was increased maximally at a dose of 4.0 micrograms/kg/min dopamine; however, renal blood flow was not further augmented. In contrast, after intravenous administration of enalaprilat, peak improvement of renal blood flow and cardiac index occurred concomitantly. Renal blood flow increased by 35%, from 316 +/- 97 to 427 +/- 107 ml/min (p less than .05), and cardiac index increased by 18%, from 1.99 +/- 0.40 to 2.35 +/- 0.40 liters/min/m2 (p less than .05). At similar increases in cardiac index, dopamine produced a greater increase in renal blood flow than enalaprilat: 604 +/- 234 vs 427 +/- 107 ml/min (p less than .05). Mean systemic arterial pressure, however, was greater with dopamine than with enalaprilat (78.1 +/- 16.7 vs 70.2 +/- 17.2 mm Hg; p less than .05) at peak effect. Thus, although both drugs appear to be potent renal vasodilators in patients with severe congestive heart failure, dopamine may be more effective in augmenting renal blood flow.     

Attenuated forearm vasodilator response to atrial natriuretic factor in the elderly.

The vasodilator potency of human atrial natriuretic factor-(99-126) was investigated in the forearm vascular bed of 10 young and 10 elderly normotensive volunteers with venous occlusion strain gauge plethysmography. Atrial natriuretic factor was infused at six increasing dose steps into the brachial artery from 0.001 up to 0.3 microgram/min/100 ml of forearm volume. This induced a mean +/- SEM increase in blood flow from 1.4 +/- 0.2 up to 6.0 +/- 1.0 ml/min/100 ml in the young and from 1.4 +/- 0.2 up to 3.9 +/- 0.6 ml/min/100 ml in the elderly. The dose-response curves of forearm blood flow and of forearm vascular resistance after increasing infusion rates of atrial natriuretic factor were shifted to the right in the elderly when compared with the young subjects. The mean percent decrease in forearm vascular resistance, induced by atrial natriuretic factor, during this dose-response curve averaged -31 +/- 3% in the elderly versus -56 +/- 3% in the young subjects (p = 0.0002). The calculated forearm spillover of the second messenger of atrial natriuretic factor, cyclic guanosine monophosphate, significantly increased from baseline values of 1.2 +/- 1.1 and 0.7 +/- 0.5 pmol/min/100 ml in young and elderly subjects, respectively, up to 23.2 +/- 5.0 and 30.5 +/- 7.0 pmol/min/100 ml during the highest dose of atrial natriuretic factor (both p less than 0.01 versus baseline). There were no significant differences in the increments of the forearm spillover of this second messenger between both age groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Noninvasive measurement of cardiac output during surgery using a new continuous-wave Doppler esophageal probe

The ability of a new continuous-wave Doppler esophageal probe to measure cardiac output noninvasively during surgery under general anesthesia was tested and compared with simultaneously measured thermodilution cardiac output. A Doppler computer, calibrated for the aortic diameter and the transcutaneously measured cardiac output from the suprasternal notch, computed the Doppler cardiac output from the descending aortic blood flow velocity signal. A total of 246 paired Doppler cardiac output and thermodilution cardiac output measurements were made in 14 patients during surgery. The average thermodilution cardiac output was 5.90 +/- 3.27 (standard deviation) liters/min (range 1.20 to 19.18); the average Doppler cardiac output was 6.21 +/- 4.0 liters/min (range 2.30 to 28.20). The difference between the cardiac output measured by the 2 techniques was 1.38 +/- 2.2 liters/min (range 0.04 to 16.8). Two to 5 cardiac output measurements were averaged and arranged into "time periods." The average standard deviations for thermodilution and Doppler cardiac outputs within each time period were 0.64 and 0.47 liters/min, respectively. There was a correlation between the 2 measurements over a range of cardiac output values (r = 0.76, Doppler cardiac output = 0.93 x thermodilution cardiac output +0.7, standard error of the estimate = 1.76). Reproducible measurements of Doppler cardiac output were obtained during intraobserver (mean difference 0.64 +/- 0.52 liter/min) and interobserver (mean difference 0.41 +/- 0.36 liter/min) studies (n = 8). Cardiac output measurement by the Doppler esophageal probe could be used for hemodynamic monitoring during surgery in selected patients with cardiopulmonary disease.     

Coronary artery fistula in the heart transplant patient. A potential complication of endomyocardial biopsy

All follow-up annual cardiac catheterizations performed on recipients of orthotopic heart transplant were reviewed, and 14 patients with coronary artery fistula were identified. The prevalence (8.0%, 14 of 176 patients) was strikingly higher than that for patients without transplant (0.2%) who underwent routine cardiac catheterization. These 14 patients had 21 coronary artery fistulas: single in nine and multiple in five patients. Fifty-two percent arose from the right, 43% from the left anterior descending, and 5% from the circumflex coronary artery. All drained into the right ventricle. Four patients underwent oximetric evaluation, and left-to-right shunting was not detectable. No patient had symptoms attributable to the fistula. Hemodynamic measurements were similar to those of a control group of 28 age- and sex-matched recipients of heart transplant without coronary artery fistula; however, the cardiac index (p = 0.02) and pulmonary artery oxygen saturation (p = 0.03) were significantly higher, and the arteriovenous oxygen difference (p = 0.01) was significantly lower in the group with coronary artery fistula. The histologic features of rejection, large arterioles, or epicardial fat on any biopsy specimen predating coronary artery fistula diagnosis were not associated with the development of the fistula when the two groups were compared. Nine patients (11 coronary artery fistulas) had follow-up studies performed, and three fistulas were larger, three were unchanged, two were smaller, and three had resolved. No complications of coronary artery fistula developed during a mean follow-up of 28 months (range, 12-42 months).(ABSTRACT TRUNCATED AT 250 WORDS)