Prognostic value of intraoperative blood flow measurements in vascular access surgery

Intraoperative Transit Time Flow Measurement Predicts Maturation of Radiocephalic Arteriovenous Fistulas

OBJECTIVE

The arteriovenous fistula (AVF) is the first choice for gaining vascular access for hemodialysis. However, 20-50% of AVFs fail within 4 months after creation. Although demographic risk factors have been described, there is little evidence on the intraoperative predictors of AVF maturation failure. The aim of this study was to assess the predictive value of intraoperative transit time flow measurements (TTFM) on AVF maturation failure.

METHODS

In this retrospective cohort study, the intraoperative blood flow, measured using TTFM, was compared to AVF maturation after 6 weeks in 55 patients. Due to its significantly higher prevalence and risk of non-maturation, the radiocephalic AVF (RCAVF) was the main focus of this study. A recommended cut-off point for high versus low intraoperative blood flow was determined for RCAVFs, using an ROC curve.

RESULTS

The average intraoperative blood flow in RCAVFs was 156 mL/min. Patients with an intraoperative blood flow equal or lower than the determined cut-off point of 160 mL/min, showed a 3.03 times increased risk of AVF maturation failure after 6 weeks, compared to patients with a higher intraoperative blood flow (P < .001).

CONCLUSION

The intraoperative blood flow in RCAVFs measured by TTFM provides an adequate means of predicting AVF non-maturation 6 weeks after surgery. For RCAVFs, a cut-off point for intraoperative blood flow of 160 mL/min is recommended for maximum sensitivity and specificity to predict AVF maturation failure after 6 weeks.

Brachiocephalic arteriovenous fistula maturity in end stage renal disease: The role of intraoperative brachial artery blood flow rate and peak systolic velocity

Introduction

Arteriovenous fistula (AVF) is the preferred vascular access option due to its lower risk of complications and better long-term outcomes. However, AVF maturation failure is still quite high. Achieving an adequate blood flow rate (BFR) through the AVF is essential for maintaining hemodialysis adequacy. This study aims to investigate brachial artery intraoperative BFR and peak systolic velocity (PSV) increase as a predictor of brachiocephalic AVF maturation.

Methods

A multicenter retrospective cohort study was conducted on patients with end stage renal disease undergoing brachiocephalic AVF creation from July 2019 to February 2022 from five hospitals. Doppler ultrasound examinations of BFR and PSV were collected. BFR and PSV increases were calculated by comparing pre-operative and intraoperative results. Maturity was determined at 6 weeks postoperatively.

Results

This study included 83 patients, with 50 patients (60.24%) achieving maturity at 6 weeks. Brachial artery BFR difference has an excellent diagnostic value to predict brachiocephalic AVF maturation with an area under the curve (AUC) of 97%. BFR increase of 184.58 ml/min predicts brachiocephalic AVF maturity with a sensitivity of 100%, specificity of 84.8%, and accuracy of 93.98%. Meanwhile, brachial artery PSV increase has a low diagnostic value to predict brachiocephalic AVF with an AUC of 71.2%. PSV increase of 8.97 cm/s predicts brachiocephalic AVF maturity with a sensitivity of 82%, specificity of 51.5%, and accuracy of 69.9%.

Conclusion

The increase in intraoperative brachial artery BFR and PSV in brachiocephalic AVF can be used as a useful parameter to predict AVF maturation.

Efficacy of blood flow measurement using intraoperative color flow Doppler ultrasound as a predictor of autologous arteriovenous fistula maturation

INTRODUCTION

Hemodialysis vascular access parameters of intraoperative Color flow Doppler ultrasound remain controversial. This study aimed to evaluate the optimal cut-off value and efficacy of intraoperative arteriovenous fistula parameters identified by Color flow Doppler ultrasound for arteriovenous fistula maturation success.

METHODS

This retrospective study consisted of a review of the medical records of 137 consecutive patients who underwent their first autologous arteriovenous fistula formation under local anesthesia for end-stage renal disease from April 9, 2020 to March 19, 2021.

RESULTS

The receiver operating characteristic curve analysis revealed that the optimal cut-off for intraoperative cephalic vein flow volume for brachiocephalic arteriovenous fistula maturation at the 4-week follow-up was 349.53 ml/min (area under the curve, 0.792; p, 0.036; Youden index, 0.514).

CONCLUSION

Intraoperative color Doppler ultrasound outflow cephalic vein flow volume is a useful factor in predicting arteriovenous fistula maturation. Intraoperative Color flow Doppler ultrasound should be performed.

Clinical Value of Intraoperative Flow Measurements of Brachiocephalic Arteriovenous Fistulas for Hemodialysis

Background

The aim of this study was to analyze the clinical outcomes of autogenous brachiocephalic arteriovenous fistulas and to investigate the factors associated with 1-year patency after initiation of hemodialysis.

Methods

We retrospectively reviewed the medical records of 41 patients who underwent surgery to create an autogenous brachiocephalic arteriovenous fistula between January 2015 and December 2017, received hemodialysis at the same hospital for longer than 1 year, and were monitored for their vascular access status. Intraoperative flow was measured using transit-time ultrasonography.

Results

The 1-year primary and secondary patency rates were 61% (n=25) and 87.8% (n=36), respectively. The functional group (subjects who required no intervention to maintain patency within the first year after hemodialysis initiation) displayed a significantly higher median intraoperative flow rate (450 mL/min) than the non-functional group (subjects who required intervention at least once regardless of 1-year patency) (275 mL/min) (p=0.038). Based on a receiver operating characteristic curve analysis, all patients were additionally subdivided into a high-flow group (>240 mL/min) and a low-flow group (≤240 mL/min). The high-flow group included a significantly greater number of functional brachiocephalic arteriovenous fistulas than the low-flow group (74.2% vs. 20%, respectively; p=0.007).

Conclusion

Transit-time flow, as measured with intraoperative transit-time ultrasonography, was associated with patency without the need for intervention at 1 year after initiation of hemodialysis.

Intraoperative use of transit time flow measurement improves patency of newly created radiocephalic arteriovenous fistulas in patients requiring hemodialysis

BACKGROUND

The autologous arteriovenous fistula is the primary choice to establish hemodialysis access without high failure rates. Intraoperative ultrasound flow measurements of newly created autologous arteriovenous fistulas represent a possibility of quality control and may therefore be a tool to assess their functionality. The aim of our study was to correlate intraoperative blood flow with access patency.

METHODS

Between March 2012 and March 2015, intraoperative transit time flow measurements were collected on 89 patients. Measurements were performed 5-10 min after the creation of a standardized anastomosis using 3-6 mm flow probes. To examine the correlation between intraoperative blood flow and access patency, groups of patients with high (> 200 mL/min) versus low flow (< 200 mL/min) were enrolled. Patients were assessed clinically and with ultrasound every 3 months. Data were analyzed retrospectively.

RESULTS

In the current short-term follow-up, including 89 patients (age 62 ± 3 years), 61 (68.5%) of the autologous arteriovenous fistulas were currently being used in an observation period ranging from 3 months to 3 years (mean observation period 546 ± 95 days) postoperatively. The intraoperative blood flow in patients with functioning autologous arteriovenous fistula (78) was significantly higher than that of patients without functioning autologous arteriovenous fistulas (407 ± 25 vs 252 ± 42 mL/min, respectively; p < 0.005) (11).

CONCLUSION

The intraoperative measurement of blood flow is a useful tool to predict the outcome of maturation in autologous arteriovenous fistula. With this method, technical problems can be detected and corrected intraoperatively. Routine implementation of intraoperative flow measurements has to be examined by prospective controlled trials.

Determinants of successful arteriovenous fistulae creation including intraoperative transit time flow measurement

BACKGROUND

The prevalence of hemodialysis patients is increasing, and it is important to create the arteriovenous fistula as early as possible to avoid hemodialysis by central venous catheter. International guidelines recommend arteriovenous fistula as the vascular access of first choice. Arteriovenous fistulae are associated with a failure rate of 23%. The success of an arteriovenous fistula can be evaluated intraoperatively by physical examination and by measuring the blood flow.

OBJECTIVES

The aim of the study is to describe the predictive value of various factors for fistula maturation in the context to the current literature.

METHODS

We report on a prospective cohort study of 41 patients, undergoing a primary arteriovenous fistula at the upper extremity. The primary endpoint of the study was the successful fistula maturation after 6 weeks.

RESULTS

The intraoperative measurement of the blood flow in the outflow vein has been identified as the unique significant parameter for the fistula maturation.

CONCLUSION

The predictive value of intraoperative flow measurement is superior to intraoperative physical examination and could help reduce the fistula dysmaturation rate. Intraoperative transit time flow measurement is an easy method and can be used to predict successful fistula maturation in a high percentage rate.

Predicting Arteriovenous Fistula Maturation with Intraoperative Blood Flow Measurements

Objective

To establish the criteria for intraoperative blood flow measurements taken at the time of autologous arteriovenous fistula (AVF) construction to predict future access maturation and thereby avoid waiting periods for futile fistulas to declare themselves.

Methods

From April 2006 through to March 2007 consecutive patients undergoing native AVF construction at one institution underwent intraoperative measurements of blood flow using transit-time ultrasound technology. No action was taken based upon the flow measurement at the time of surgery. Patients were followed and data collected comprising demographics and AVF maturation. A fistula was considered mature when it was successfully accessed for hemodialysis (HD) at least three times. Statistical analysis was performed including receiver operating characteristics (ROC), ANOVA, and Chi square using the JMP software package.

Results

During the 12-month period, 70 autologous AVFs were created including 41 antecubital brachiocephalic, 21 radiocephalic, and 8 basilic vein transpositions in 35 females and 33 males with a mean age of 58 ± 1.7 (mean ± SEM). The group included 37 Hispanic, 17 Native American, 10 Caucasian, 3 African American and 1 Asian patient. The etiology of renal failure comprised 53 diabetics, 13 hypertensives, 1 polycystic kidney disease and 1 congenital abnormality. Complete follow-up was available in 69/70 AVFs in 67 patients. Patients were excluded from analysis if they had not yet started dialysis (n=12), stopped or died (n=4) before their fistula was accessed. Patients whose AVFs were patent, but required a secondary procedure to achieve a functional access were considered non-functional. There was a significant difference between the maximal intraoperative flow rates between functional and non-functional AVFs (573.6 ± 103 mL/min vs. 216.8 ± 35.8 mL/min; p<0.05). There was no difference between groups in regard to age, gender, race or etiology of renal failure. ROC analysis suggested a threshold value of 140 mL/min for radiocephalic and 308 mL/min for brachiocephalic AVFs to predict maturation to a functional access.

Conclusion

Intraoperative blood flow measurements obtained at the time of autologous AVF construction can identify fistulas that are unlikely to mature; and therefore, that require immediate revision or abandonment which will ultimately expedite the establishment of a useful access in the HD patient. This is the first study to establish the minimal flow values uniquely needed for both radial artery and brachial artery AVFs to expect primary maturation to a functional access.

Haemodynamics of Brachial Arteriovenous Fistula Development

This study observes the development of brachial arteriovenous fistulae, and assesses methods of predicting potential usefulness for haemodialysis. Creation of an adequate brachial fistula causes significant changes in blood flow to the forearm and hand.

A prospective study of fifteen consecutive patients undergoing brachial arteriovenous fistula formation for haemodialysis was undertaken. Clinical measurements and coloured flow Doppler measurements were performed pre operatively, immediately post operatively and at two and eight weeks after surgery. The morphology of the fistula was studied and the volume flow was measured. Digital pressure was measured pre and post exercise at each visit.

Fourteen fistulae worked well by eight weeks. There was an immediate large increase in brachial artery blood flow and by two weeks all fistulae that went on to develop well had a brachial artery flow of more than 700 mls/minute. The cephalic vein mean diameter pre operatively was 2.39 mm and increased to 5.4 mm by two weeks post operatively. Fistulae with flows over 400 mls/minute at two weeks had a good outcome. There were significant differences in digital pressure after fistula formation (P ≤ 0.05). Digital mean arterial pressure dropped from 118 mm Hg pre-operatively to 98 mm Hg post operatively, at rest, and 89 mm Hg after exercise. Four patients developed forearm/hand claudication on exercise or signs of distal ischaemia. Three of these were diabetic with calcified vessels.

All patients with a suitable cephalic vein should have attempted fistula formation rather than recourse to use of a synthetic graft. In diabetics creating a shunt in an already marginally competent vascular tree exposes the patient to risk of significant hand ischaemia.

Hemodialysis Arteriovenous Fistulas: A Nineteenth Century View of a Twenty First Century Problem

This is a literature review which approaches the problem of successful use of arteriovenous fistulas for dialysis within the construct of Virchow's triad. By organizing the literature with regard to Virchow's concepts of blood flow, vascular injury, and thrombophilia an improved understanding arteriovenous fistula placement, maintenance and repair can be obtained. This process is designed to increase understanding and options for treatment by looking at this problem and using scientific knowledge gained in cardiology, oncology and vascular surgery medicine. Future approaches to fistulas will hopefully be a multifaceted and based in cellular pathophysiology as well as surgical and radiologic interventions and repairs.

Novel use of infrared thermal imaging to predict arteriovenous fistula patency and maturation

OBJECTIVE

The arteriovenous fistula (AVF) is the preferred method of long-term haemodialysis. However, it has been shown to have a substantial rate of maturation failure. The formation of an AVF creates haemodynamic changes to blood flow in the arm with diversion of blood away from the distal circulation into the low pressure venous system, in turn, leading to thermal changes distally. In this study, we aimed to assess the novel use of infrared thermal imaging as a predictor of arteriovenous maturation.

METHODS

A prospective cohort study was conducted on 100 consecutive patients who had AVF formation from December 2015 to June 2016. Infrared thermal imaging was undertaken pre- and post-operatively on the day of surgery to assess thermal changes to the arms and to assess them as predictors of clinical patency and functional maturation.

RESULTS

For clinical patency, infrared thermal imaging was found to have a positive predictive value of 88% and a negative predictive value of 86%. For functional maturation, it was found to have a positive predictive value of 84%, a negative predictive value of 95%. In addition, it was shown to have superiority to the commonly used intra-operative predictor of thrill as well as other independent pre-operative patient factors.

CONCLUSIONS

Infrared thermal imaging has been found to be a very useful tool in accurately predicting fistula patency and maturation.

Comparison of Intraoperative Completion Flowmeter Versus Duplex Ultrasonography and Contrast Arteriography for Carotid Endarterectomy

Intraoperative completion studies of the internal carotid artery following carotid endarterectomy are recommended to ensure technical perfection of the repair. Transit time ultrasound flowmeter does not require trained technicians, requires less time than other completion studies such as duplex ultrasonography and contrast arteriography, and is noninvasive. Flowmetry was compared with duplex ultrasonography and contrast arteriography to determine if the relatively simpler flowmetry could replace these two more widely accepted completion studies in the intraoperative assessment of carotid endarterectomy. Comparative intraoperative assessment was performed in 116 carotid endarterectomies using all three techniques between December 1, 2000 and November 30, 2003. Eversion endarterectomy was performed in 51 cases and standard endarterectomy with prosthetic patching in 65 cases. Patients underwent completion flowmetry, duplex ultrasonography, and contrast arteriography studies of the exposed arteries, which were performed by vascular fellows or senior surgical residents under direct supervision of board-certified vascular surgeons. Duplex ultrasonography surveillance was performed 1 and 6 months postoperatively and annually thereafter. Mean follow-up was 18 months (range, 6-42 months). The combined ipsilateral stroke and death rate was 0%. The mean internal carotid artery flow using flowmetry was 249 mL/min (range, 60-750 mL/min). Five (4.3%) patients had flow < 100 mL/min as measured with flowmetry, but completion contrast arteriography and duplex ultrasonography were normal and none of the arteries were re-explored. One carotid endarterectomy was re-explored based on completion duplex ultrasonography that showed markedly elevated internal carotid artery peak systolic velocity (>500 cm/sec); however, exploration was normal and completion flowmetry and contrast arteriography were normal. Duplex ultrasonography studies revealed internal carotid artery peak systolic velocities > 150 cm/sec in 15 patients, but flowmetry and contrast arteriography were normal in all 15 cases and none of the arteries were re-explored. There was no correlation between flow rates measured using flowmetry and peak systolic velocities measured using duplex ultrasonography. One abnormal contrast arteriogram showed an intimal flap that was revised, but duplex ultrasonography and flowmetry were normal. Severe recurrent internal carotid artery stenosis developed in 2 patients at 6 and 9 months, but all 3 completion intraoperative studies at the time of the original operation were normal. Based on these results, wide variability in flowmetry values limits its potential usefulness to detect non—flow-limiting lesions and replace contrast arteriography or duplex ultrasonography as an intraoperative carotid endarterectomy completion study. Duplex ultrasonography was also of limited to no value, whereas contrast arteriography rarely documented a lesion that required repair.

Prospective Evaluation of Factors Associated with Early Failure of Arteriovenous Fistulae in Hemodialysis Patients

Recent guidelines have recommended performing native arteriovenous fistulae (AVF) in hemodialysis patients rather than synthetic grafts whenever possible. However, early failure of AVF may reach up to 50%. The purpose of this study was to assess the factors associated with early failure of such procedures in hemodialysis patients.

A prospective study was performed on all patients with end-stage renal disease who had an AVF between June 2003 and March 2005. Data including patient characteristics and the type of AVF were recorded. The internal diameter of the vein and artery and intraoperative blood flow were measured. Patients were followed up for 3 months.

One hundred twenty-six AVF were included in this study. Early failure was in 14 (9%) patients. The internal diameter of the vein and artery and intraoperative blood flow were significantly lower in the failure group than in the patent group. The failure rate was not significantly related to other parameters.

Our data showed that intraoperative blood flow is a reliable parameter that determines the early failure of an AVF. Careful selection of the vein and the artery may reduce the rate of failure.

First-week postoperative flow measurements are highly predictive of primary patency of radiocephalic arteriovenous fistulas

PURPOSE

This study was conducted to determine whether volume flow rate at the first postoperative visit could predict early failure of radiocephalic arteriovenous fistulas (RCAVFs).

METHODS

We retrospectively studied the records of 264 patients who received a RCAVF between 2007 and 2013 at our centers. Data collected included patient demographics, medical history, arterial and venous mapping, and volume flow rate intraoperatively after fistula creation but before closing the surgical incision. An intraoperative flow rate &gt;100 mL/minute was targeted. We measured volume flow at the first postoperative visit 1 week after surgery and thereafter as needed.

RESULTS

Intraoperative flow was not a significant predictor of primary patency (p = 0.44) but flow at the first postoperative visit was a statistically significant predictor of fistula primary patency (p = 0.002). No fistula with a blood flow &lt;200 mL/minute at the 1-week postoperative visit reached maturity without receiving a maturation procedure. The hazard ratio for the first follow-up flow (mL/min) was 0.9973 (95% CI 0.9956, 0 .9989), indicating that for every 100 mL increase in blood flow the primary patency increases by 10%.

CONCLUSIONS

Flow rate at the 1-week postoperative visit was the most important predictor of RCAVF patency. Thus, it should be possible to identify patients who would benefit from early intervention or closer follow-up as soon as the first postoperative visit. This should help reduce the use of bridging hemodialysis catheters and minimize the risks of catheter dependency.

U-vein compressor improves early haemodynamic outcomes in radiocephalic arterio-venous fistulae in under 2-mm superficial veins

AIM

In this study, we sought to determine the early postoperative results of arterio-venous fistulae (AVF) created by U-vein compressors with veins between 1.5 and 2 mm in size.

METHODS

Pre-operative venous mapping was done. The fistula tract was marked at 0-, 4-, 8- and 12-cm points; 0 cm was the estimated point where the anastomosis would be done. With Doppler ultrasonography, transverse diameters in the estimated fistula tract were measured at the 0-, 4-, 8- and 12-cm points. A superficial vein that would be used as the fistula tract was dilated using U-vein compressors. In the first postoperative hour, the flow in the anastomosis, and the transverse diameter of the fistula tract at the 0-, 4-, 8- and 12-cm points were measured by Doppler ultrasonography.

RESULTS

Forty patients were included in the study. U-vein compressors were used for 20 patients. Postoperative expansion of vein diameters and postoperative flow velocities were found to be statistically significantly different in patients where a U-vein compressor had been used (p < 0.001).

CONCLUSION

We present a technique to dilate veins that are between 1.5 and 2 mm in diameter, which are generally accepted as poor vessels to create radiocephalic arteriovenous fistulae.

Obesity-related decrease in intraoperative blood flow is associated with maturation failure of radiocephalic arteriovenous fistula

OBJECTIVE

Successful arteriovenous fistula (AVF) maturation is often challenging in obese patients. Optimal initial intraoperative blood flow (IOBF) is essential for adequate AVF maturation. This study was conducted to elucidate the effect of obesity on IOBF and radiocephalic AVF maturation.

METHODS

Patients with a newly created radiocephalic AVF were included (N = 252). Obesity was defined as a baseline body mass index (BMI) ≥25 kg/m(2), and primary maturation failure was defined as failure to use the AVF successfully by 3 months after its creation. IOBF was measured immediately after construction of the AVF with a VeriQ system (MediStim, Oslo, Norway).

RESULTS

The mean BMI was 24.1 ± 3.9 kg/m(2), and the prevalence of obesity was 31.3%. Particularly, 8.3% (21 patients) had a BMI ≥30 kg/m(2). Primary maturation failure occurred in 100 patients (39.7%), and an IOBF <190 mL/min was closely associated with the risk of maturation failure (relative risk, 3.05; 95% confidence interval, 1.52-6.11). Compared with nonobese patients, obese subjects had a significantly higher prevalence of diabetes and elevated high-sensitivity C-reactive protein levels, whereas diameters of vessels were similar. When the patients were further divided into three groups as BMI <25, 25 to 29.9, and ≥30 kg/m(2), patients in the higher BMI group showed significantly lower IOBF and higher maturation failure rate. According to multivariate analysis, the statistically significant variables that determined maturation failure were obesity, previous vascular disease, increased high-sensitivity C-reactive protein levels, and IOBF <190 mL/min.

CONCLUSIONS

Obese patients had a significantly lower IOBF, and both obesity and low IOBF contributed to the primary maturation failure of AVF. Obesity-associated inflammation and atherosclerosis might play roles in this association.

Intraoperative assessment of vascular access

PURPOSE

The intraoperative quality assessment of the arteriovenous fistula for hemodialysis is an essential process to limit early failure due to technical problems or inadequate vascular quality. This step is not clearly defined in the literature with no recommendations.

METHODS

We selected published articles related to the topic of intraoperative quality control of the vascular access for hemodialysis.

RESULTS

The intraoperative blood flow measurement greater than 120 ml/min in autologous fistula and less than 320 ml/min in arteriovenous graft was described as predictive factors for early failure.

CONCLUSIONS

The blood flow measurement should be performed after the confection of the anastomosis. When blood flow is limited, fistulography is an essential step to assess patency.

Does preemptive stellate ganglion blockage increase the patency of radiocephalic arteriovenous fistula?

OBJECTIVE

Radio-cephalic arteriovenous fistulas (AVFs) have high early failure ratio. Increased sympathetic activity and spasm of radial artery during the surgery may responsible for early occlusion rate.

DESIGN

Fifty patients were randomized to two groups (each containing 25 patients). Stellate Ganglion Blockade (SGB) was performed in Group 1. Another group was considered as control group (Group 2) to make statistical comparisons. All AVFs were performed under local anesthesia in both groups.

RESULTS

Average fistula flow was 201.4+/-40.4 ml/min in Group 1 and 155.6+/-27.4 ml/min in Group 2 (p < 0.001). While average peak velocity of radial artery was 167.1+/-31.3 cm/sec in Group 1, it was 107.8+/-15.8 cm/sec in Group 2 (p < 0.001). Thrill was found in all Group 1 patients, but there was thrill only 13 of the Group 2 patients (p < 0.001). Mean maturation time was 41.4+/-6.8 days after surgery in Group 1 and 77.1+/-10.5 days in Group 2 (p < 0.001). Adequate vascular access was obtained 19 patients in Group 1 and 12 patients in Group 2 (p = 0.041).

CONCLUSION

AVF occlusion rate is much more common in early postoperative period. Diminished sympathetic tonus by preemptive SGB not only increases early patency rate but also increases fistula maturation rate.

Effect of lower extremity bypass surgery on inflammatory reaction and endothelial dysfunction in type 2 diabetic patients

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia and dyslipidemia. The abnormalities in nutrient metabolism and elevated inflammatory mediators resulting from DM lead to impairment of wound healing and vulnerability to infection and foot ulcers. Diabetic lower limb ischemia often leads to limb necrosis. Lower extremity bypass surgery (LEBS) is indicated to prevent limb loss in patients with critical leg ischemia. This study investigated the alteration of inflammatory and endothelium dysfunction markers before and after LEBS in DM patients. Twenty one type 2 DM patients with LEBS were included. Blood was drawn before and at 1 day and 7 days after surgery in the patients. Plasma soluble cellular adhesion molecule levels and blood leukocyte integrin expressions were measured. Also, plasma concentrations of endothelin-1 and nitric oxide were analyzed to evaluate the vascular endothelial function. The results showed that there were no significant differences in plasma cellular adhesion molecules, endothelin-1 and nitric oxide levels, nor did any differences in leukocyte integrin expressions before and after the operation. These results suggest that the efficacy of LEBS on alleviating inflammatory reaction and improving endothelial function in DM patients was not obvious.

Intraoperative Flow Measurements Are Helpful in the Treatment of High-Inflow Steal Syndrome on a Predialysis Patient with a Brachiocephalic Fistula: A Case Report

Distal revascularization and interval ligation (DRIL) is currently one of the mainstay treatments for severe steal syndrome. However, when high inflow is the underlying cause, this technique does not fully address the problem. Here, we describe the use of intraoperative flow measurements using transit time ultrasound technology to help identify the cause of steal syndrome in a predialysis patient (no transonic surveillance) with a brachiocephalic fistula, who then was treated successfully by inflow reduction surgery using a bovine ureter graft. We believe that inflow reduction might be superior to DRIL in treating steal syndrome caused by high inflow and that transit time ultrasound might be helpful when transonic treatment is not possible.

Blood flow volume changes in the maturing arteriovenous access for hemodialysis

In our center, we start hemodialysis using arteriovenous accesses empirically 1 mo after surgery in nearly all patients, when the vein diameter reaches 5 mm and blood flow is assumed to be adequate. We measured blood flow and vessel diameter in the maturing autogenous and prosthetic access to determine if this approach can be justified by quantitative physiological parameters. Of 66 consecutive autogenous and prosthetic arteriovenous accesses created over 3 mo in 2004, 62 were prospectively examined by duplex ultrasonography preoperatively, immediately after surgery in the recovery room, at 10 d postoperatively and 1 mo after surgery before first cannulation. In the 20 forearm accesses, the immediate postoperative mean blood flow was 549 +/- 189 mL/min, 885 +/- 227 mL/min at 10 d and 934 +/- 260 mL/min at 1 mo. In the 22 upper-arm accesses, the immediate postoperative mean access blood flow was 858 +/- 292 mL/min, 1060 +/- 326 mL/min at 10 d and 1116 +/- 427 mL/min at 1 mo. In 20 prosthetic accesses, near maximal flow was attained immediately after surgery (990 +/- 256 mL/min). Most of the increased flow in autogenous accesses occurred early in the maturation process. This suggests that 1 mo is adequate for autogenous access maturation before use for hemodialysis. The process of access maturation appears to be less relevant in prosthetic accesses, where blood flow is high from the day of surgery and tissue incorporation is, therefore, more important.

Resistance within hemodialysis shunts predicts patency

The authors examined the relationship between patency after thrombectomy of clotted dialysis grafts and intraoperative measurements of flow (Q), pressure gradient (PGR), and longitudinal resistance (RL). Eighteen thrombosed arteriovenous (AV) grafts underwent 21 thrombectomies. Pressures at arterial (P1) and venous (P2) ends of the AV grafts were determined with 22-gauge catheters and standard transducers; flow was measured with transit-time probes; arithmetic averaging of waveforms was used to compute mean Q, PGR, and RL. Kaplan-Meier patency curves were analyzed by using log rank methods. Mean patency for all grafts was 164 +/-152 days. For each variable, the 21 measurements were split and the patency curve for the grafts with the 11 lowest value grafts was compared to the curve representing the 10 highest value grafts. The difference between high RL versus low RL patency curves was significant with high-resistance grafts having a median patency of 55 days and low-resistance grafts having a median patency greater than 151 days (p = 0.0089). In contrast, the high Q group median patency was 151 days versus 174 days for the low Q group (p = 0.86). Median patency for the low PGR group was 115 days compared to 62 days for the high PGR group (p = 0.162). Longitudinal resistance within AV grafts, but not flow or pressure gradient, showed a significant correlation with patency after thrombectomy. Increased resistance to flow within AV grafts appears to be an important factor affecting the propensity of dialysis grafts to thrombose.

Effect of surgical banding of a high-flow fistula on access flow and cardiac output: Intraoperative and long-term measurements

Creation of either a natural arteriovenous graft or a fistula as a vascular access to support long-term hemodialysis can lead to "high-output" cardiac failure. The authors describe a patient who underwent surgical banding of an upper arm arteriovenous fistula. Access flow and cardiac output were measured not only pre- and postoperatively but also intraoperatively using a modified Swan Ganz catheter, originally developed to measure access flows during radiologic procedures. Banding resulted in a significant decrease in access flow and cardiac output, which was sustained for up to 1 year postoperatively.

Early result of arteriovenous graft with deep forearm veins as an outflow in hemodialysis patients

The purpose of this study was to evaluate the result of arteriovenous (A-V) grafting with the deep forearm veins as an outflow system in hemodialysis patients. Between June 1999 and July 2001, 27 A-V grafts consisting of ePTFE and deep forearm veins were constructed in 26 patients. All patients followed up for assessment of all relevant values, and the median follow-up period was 17.3 months. Seven grafts (26%) failed during the follow-up. The patency rates were 93% and 80% at 3 months and 12 months, respectively. No difference in patency rate was found between males and females, or between diabetics and nondiabetics. Graft-related complications, excluding graft thrombosis, occurred in five patients. These included operative wound dehiscence in two cases, a graft infection, a seroma, and a mild hypoperfusion in the hand. We conclude that the early patency rate of A-V graft using the forearm deep veins as an outflow system is very good and that this technique may be a recommended surgical modality for vascular access in patients with exhausted superficial veins.

Intraoperative evaluation of blood flow in the internal mammary or thoracodorsal artery as a recipient vessel for a free TRAM flap

Although the free microvascular transverse rectus abdominis musculocutaneous (TRAM) flap is in routine use for breast reconstruction, little is known of its hemodynamics. The purpose of this study was to determine whether any differences exist when the free TRAM flap is anastomosed to the thoracodorsal or internal mammary vessels. The study comprised 25 patients receiving a free TRAM flap for breast reconstruction. The thoracodorsal vessels were used as recipients in 21 patients and the internal mammary vessels were used in 4 patients. Blood flow rate was measured directly in the donor and recipient arteries, and after anastomosis by a transit-time ultrasonic flowmeter (CardioMed). Two- and 3-mm probes were used. The blood flow rate in the donor artery (deep inferior epigastric) before flap dissection was 11 +/- 6 ml per minute (mean +/- standard deviation). The rate was significantly (p < 0.05) lower (5 +/- 3 ml per minute) in the recipient thoracodorsal artery than in the donor, but after transplantation it increased to 14 +/- 5 ml per minute (p < 0.05), attaining the same value as the donor artery. The blood flow rate in the intact internal mammary artery was significantly higher (25 +/- 10 ml per minute) than in the donor and thoracodorsal arteries, but after anastomosis it dropped to the same value (12 +/- 3 ml per minute; p < 0.05) as the donor artery. The intake of blood in TRAM flaps supplied by the intemal mammary artery seems to be no greater than that in free flaps anastomosed to thoracodorsal vessels, although the flow in the internal mammary artery was much higher. The authors concluded that the blood supply in a free TRAM flap is independent of the flow in the recipient artery and that thoracodorsal vessels, although often in a scarred bed and radiated, are as suitable for anastomosing a free TRAM flap as are internal mammary vessels.

Effects of intraoperative blood flow on the early patency of radiocephalic fistulas

The purpose of this study was to find the correlation between intraoperative blood flow and early patency of the radiocephalic fistula. Between March 1998 and March 1999, 50 radiocephalic arteriovenous fistulas were constructed in 41 patients. Intraoperative blood flow measurements were made 10 min after completion of the vascular anastomoses with 3-4 mm handheld flow probes. Patients were followed until failure of fistula or 3 months after the first hemodialysis with these fistulas. Intraoperative blood flow as well as age, gender, presence of diabetes, size of cephalic vein, thrill on the fistula, and flow of radial artery were correlated with early patency. The mean intraoperative blood flow was 174.7 +/- 13.2 mL/min and ranged from 50 to 500 mL/min; it was the only significant parameter that determined early patency of the radiocephalic fistula. Fistulas with flow <160 mL/min (10 of 25) had a higher failure rate than those with flow >160 mL/min (4 of 25), which was statistically significant (p < 0.01). All of the patients with flow <70 mL/min (5 of 5) failed to maintain patency within a month. However, the other variables were not correlated with early patency. We conclude that intraoperative blood flow is a reliable parameter that determines the early patency of radiocephalic fistulas.