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Biomedical subjects

Michelle L Robbin

Publications and source records attributed to Michelle L Robbin.

16 recordsLinked to original sources
PubMed2006

Cephalic vein measurement before forearm fistula creation: does use of a tourniquet to meet the venous diameter threshold increase the number of usable fistulas?

OBJECTIVE: To optimize forearm radiocephalic fistula success, many programs recommend a minimal cephalic vein diameter of 0.25 cm or greater on preoperative sonographic mapping. It is not established, however, whether a vein diameter before or after application of a tourniquet should be used in determining suitability for creation of a forearm fistula. METHODS: Before forearm radiocephalic fistula placement, preoperative sonographic mapping measured the cephalic vein diameter before and after application of a tourniquet. The patients fell into 2 groups: those with a pretourniquet vein diameter of 0.25 cm or greater (group 1) and those with a pretourniquet vein diameter of less than 0.25 cm that increased to 0.25 cm or greater after application of the tourniquet (group 2). The adequacy of each fistula for dialysis was determined clinically. RESULTS: Among 73 radiocephalic fistulas with known clinical outcomes, 28 were in group 1, and 45 were in group 2, on the basis of sonography. Fistula success rates were similar in group 1 patients (11 [39%] of 28) and group 2 patients (15 [33%] of 45) (P=.624, Fisher exact test). Inclusion of group 2 patients increased the number of patients recommended for placement of forearm fistulas and increased the total number of usable forearm fistulas from 11 to 26. The overall success rate of forearm fistulas was lower in women (19% versus 50%; P=.015, Fisher exact test). CONCLUSIONS: The use of a venous tourniquet increases the number of patients eligible for forearm fistulas without decreasing the adequacy rate of these fistulas. Therefore, a tourniquet should routinely be used in patients with small cephalic veins on pretourniquet evaluation.

Arteriovenous Shunt, Surgical↗
PubMed2005

Sonographic assessment of the severity and progression of autosomal dominant polycystic kidney disease: the Consortium of Renal Imaging Studies in Polycystic Kidney Disease (CRISP).

BACKGROUND: The accuracy and precision of ultrasonography (US) in assessing the severity of autosomal dominant polycystic kidney disease (ADPKD) is unknown. METHODS: US and magnetic resonance imaging (MRI) were performed at baseline and 1 year on 230 subjects with ADPKD. Ellipsoid volume was calculated from US length, width, and depth, and sequential transverse images were used to measure total and cystic volume directly. These were compared with MRI measurements of kidney volume and cystic volume. RESULTS: Variability between different sonographers ranged from 18% to 42%. Correlations between US and MRI volume were 0.88 and 0.89. The SD of the discrepancy from MRI ranged from 21% to 33% and was unrelated to kidney size or body mass. Kidney length was the most reproducible measurement, and its correlation with MRI volume was 0.84. All patients with an US volume less than 700 cm3 had an MRI volume less than 1,000 cm3, and all patients with an US volume greater than 1,700 cm3 had an MRI volume greater than 1,000 cm3. Increases in volume after 1 year were 12% +/- 36% for the ellipsoid method, 6% +/- 29% for the direct method, and 4.2% +/- 7.2% for MRI. Correlation between US and MRI measurement of fractional cyst volume was 0.80. CONCLUSION: Sonographic measurement of kidney volume in patients with ADPKD is inaccurate and lacks the precision necessary to measure short-term disease progression. However, sonography can provide an estimate of kidney volume that reflects severity and prognosis in individual patients.

Adolescent↗
PubMed2005

Augmentation in lower extremity sonography for the detection of deep venous thrombosis.

OBJECTIVE: The purpose of our study was to evaluate the usefulness of venous flow augmentation with duplex sonography in the evaluation of deep venous thrombus of the lower extremities. CONCLUSION: The augmentation component of the lower extremity sonogram rarely provides additional information in the diagnosis of deep venous thrombus. In our large series, no deep venous thromboses were discovered with augmentation. Factors such as the lack of usefulness and patient discomfort may justify removal of augmentation from the routine study. However, augmentation should still be applied as a diagnostic tool in difficult or uncertain cases.

Adolescent↗
PubMed2004

Association of pelvic arterial calcification with arteriovenous thigh graft failure in haemodialysis patients.

BACKGROUND: Arterial calcification is a common problem in patients with chronic kidney disease, and has been associated with adverse clinical outcomes. The goal of the present study was to evaluate whether pelvic artery calcifications are associated with technical failure of arteriovenous thigh grafts in haemodialysis patients. METHODS: From 1 January 1999 to 30 June 2002, thigh grafts were placed in 54 haemodialysis patients who had exhausted all options for permanent vascular access in the upper extremities. Perioperative computed tomography (CT) of the abdomen and pelvis was obtained in 32 of the patients for diagnostic purposes unrelated to vascular access planning. Two radiologists, who were blinded to the graft outcomes, scored the vascular calcifications on CT of the distal aorta, common iliac, external iliac and common femoral arteries on a semi-quantitative 5-point scale. The association between technical graft failure (inability to complete the anastomosis) and the vascular calcification score was analysed. RESULTS: There was a high inter-observer agreement in scoring vascular calcification (kappa = 0.801). Among 26 patients with absent or mild pelvic arterial calcifications (grade 1-2) on CT, none (0%) experienced technical graft failure. In contrast, three of six patients (50%) with moderate to severe calcification (grade 3-5) had technical graft failures (P = 0.004 by Fisher's exact test). The cumulative 1 year graft patency was lower in the group with grade 3-5 calcification (33 vs 81%, P = 0.09). The two groups were similar in age, gender, race, diabetes, duration of dialysis, serum calcium, serum phosphorus and serum parathyroid hormone. CONCLUSION: There is a strong association between pelvic artery calcifications and technical failure of thigh grafts. The presence of moderate to severe vascular calcification is predictive of poor cumulative 1 year graft patency.

Arteries↗
PubMed2004

Emergency Doppler evaluation of the liver and kidneys.

Doppler ultrasound is useful in the emergent evaluation of the liver and kidney transplant patient. Arterial stenosis, pseudoaneurysm, and venous thrombosis are treatable causes of allograft failure that can be detected easily with color and spectral Doppler. Doppler has a limited but important role in the emergent evaluation of the native liver and kidneys, usually involving prior biopsy or instrumentation.

Emergencies↗
PubMed2004

Preoperative sonographic radial artery evaluation and correlation with subsequent radiocephalic fistula outcome.

OBJECTIVE: Primary failure of forearm radiocephalic dialysis fistulas is common even when preoperative vascular mapping is used. Previous studies have suggested that low peak systolic velocity of the radial artery predicts subsequent fistula failure. The study goal was to evaluate whether preoperative spectral Doppler assessment of radial artery inflow can improve forearm fistula outcome prediction. METHODS: Forearm fistulas were placed in 112 patients after preoperative sonographic mapping. Preoperative spectral Doppler sonography measured radial artery peak systolic velocity during tight fist clenching for 3 minutes and after fist relaxation. Vessel diameters and peak systolic velocity were assessed for predictive value based on subsequent fistula adequacy. Fistula flow rates were determined 6 to 12 weeks postoperatively in a subset of patients. RESULTS: Failed and successful fistulas were similar in their preoperative arterial and vein diameters, resistive index, and peak systolic velocity during fist clenching and after fist relaxation. Specifically, there was no difference in fistula success with radial artery peak systolic velocity lower than 50 cm/s versus peak systolic velocity of 50 cm/s or higher. The change in peak systolic velocity after fist relaxation was highly predictive of subsequent fistula outcome among female patients in ad hoc analysis. Fistula adequacy for dialysis in women was 11% when the change in peak systolic velocity was lower than 0 cm/s and 50% when the change was 0 cm/sec or higher (P = .02). The postoperative fistula flow rates were lower when the preoperative change in peak systolic velocity was lower than 0 cm/s than when it was 0 cm/s or higher (316 +/- 46 versus 781 +/- 150 mL/min; P = .003). CONCLUSIONS: There was no difference in the preoperative peak systolic velocity or the resistive index of successful and failed fistulas. Measurement of the radial artery peak systolic velocity change after release of fist clenching was not useful in predicting outcomes in male patients but identified a subset of female patients with a very low likelihood of success. This criterion may merit further investigation in future trials.

Arteriovenous Shunt, Surgical↗
PubMed2003

Renal imaging with ultrasound contrast: current status.

The application of UCAs to the kidney is still in its infancy; however, there are several areas of great promise. UCAs may replace CT in complex renal cyst evaluation and follow-up, eliminating the need for costly CT scans with their attendant potential contrast nephrotoxicity. This approach may decrease patient and physician uncertainty and improve diagnostic confidence. The use of UCAs is likely to be clinically useful in the evaluation of the indeterminate small renal mass on CT or MR imaging. Another probable useful application will be in renal artery stenosis. Routine application of UCAs may increase the percentage of diagnostic examinations, increase diagnostic confidence, and decrease examination times. It also will likely become the first line of evaluation in pyelonephritis, and be useful in immediate assessment of residual tumor after radiofrequency ablation. Of course, substantial additional work needs to be performed in large groups of patients to prove this currently optimistic outlook.

Contrast Media↗
PubMed2003

Renal structure in early autosomal-dominant polycystic kidney disease (ADPKD): The Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease (CRISP) cohort.

BACKGROUND: Autosomal-dominant polycystic kidney disease (ADPKD) is characterized by gradual renal enlargement and cyst growth prior to loss of renal function. Standard radiographic imaging has not provided the resolution and accuracy necessary to detect small changes in renal volume or to reliably measure renal cyst volumes. The Consortium for Radiologic Imaging Studies in Polycystic Kidney Disease (CRISP) is longitudinally observing ADPKD individuals using high-resolution magnetic resonance (MR) imaging to determine if change in renal and cyst volumes can be detected over a short period of time, and if they correlate with decline in renal function early in disease. METHODS: Standardization studies were conducted in phantoms and four subjects at each participating clinical center. After, in the full-scale protocol, healthy ADPKD individuals 15 to 45 years old with creatinine clearance>70 mL/min underwent standardized MR renal imaging, renal iothalamate clearance, comprehensive clinical evaluation, and determination of 24-hour urinary albumin and electrolyte excretion. Stereology was used from T1-weighted images to quantify renal volume, and region-growing thresholding was used from T2-weighted images to determine cyst volume. Renal structures were evaluated in relation to demographic, clinical, and biochemical variables using means/medians, standard deviations, and Pearson correlations. RESULTS: Reliability coefficients for MR renal and cyst volume measurements in phantoms were 99.9% and 89.2%, respectively. In the full-scale protocol, 241 ADPKD individuals (145 women and 96 men) were enrolled. Total renal, cyst, and % cyst volume were significantly greater in each decade group. Hypertensive individuals demonstrated greater renal, cyst, and % cyst volume than normotensive subjects. Age-adjusted renal (r = -0.31, P < 0.0001), cyst (r = -0.36, P < 0.0001), and % cyst volume (r = -0.35, P < 0.0001) were inversely related to glomerular filtration rate (GFR). Age-adjusted renal volume (r = 0.42, P < 0.0001), cystic (r = 0.39, P < 0.0001, and % cyst volume (r = 0.41, P < 0.0001) were related with urinary albumin excretion. CONCLUSION: MR measures of renal and cyst volume are reliable and accurate in patients with ADPKD. ADPKD is characterized by significant cystic involvement that increases with age. Structure (renal and cyst volume) and function (GFR) are inversely related and directly related with the presence of hypertension and urinary albumin excretion in individuals with normal renal function.

Adolescent↗
PubMed2003

Gender differences in outcomes of arteriovenous fistulas in hemodialysis patients.

BACKGROUND: The prevalence of arteriovenous (A-V) fistula use is lower among female than male hemodialysis patients. This difference may be due, in part, to smaller vessel diameter in women. However, even when routine preoperative vascular mapping is used to select vessels with suitable diameters, fistulas are still less likely to mature in women than in men. METHODS: To explore the reasons for this gender discrepancy, we evaluated the outcomes of 230 A-V fistulas placed at our institution after preoperative mapping. Vessel diameters, radiologic and surgical interventions, and fistula adequacy for dialysis were assessed. RESULTS: Fistula adequacy for dialysis was lower in women than men (31 vs. 51%, P = 0.001). The inferior outcome of fistulas in women was observed for both forearm fistulas (18 vs. 43%, P = 0.02) and upper arm fistulas (39 vs. 60%, P = 0.04). Differences in vessel diameter did not explain the lower patency rate of fistulas among women. Among fistulas not lost due to technical failure or early thrombosis, 31% underwent one or more interventions (salvage procedures) due to failure to mature. These interventions included angioplasty, ligation of tributaries, superficialization, and surgical revision of the anastomosis. A salvage procedure was more likely in women than in men (42 vs. 23%, P = 0.04). The likelihood of fistula maturation after an intervention was similar among women and men (50 vs. 37%, P = 0.40). Salvage procedures increased the proportion of adequate fistulas to a greater degree in women than in men (relative increases of 68 and 15%, respectively). CONCLUSIONS: These data suggest that fistulas are less likely to be useable for dialysis in women than in men, despite routine preoperative mapping and frequent interventions undertaken to salvage immature fistulas.

Adolescent↗
PubMed2003

Comparison of arteriovenous grafts in the thigh and upper extremities in hemodialysis patients.

Placement of a thigh graft is an option in hemodialysis patients who have exhausted all upper extremity sites for permanent vascular access. The outcome of thigh grafts has been reported only in retrospective studies. The outcomes of 409 grafts placed at a single institution during a 3.5-yr period were evaluated prospectively, including 63 thigh grafts (15% of the total). Information was recorded on surgical complications, dates of radiologic and surgical interventions, and date of graft failure. The technical failure rate was approximately twice as high for thigh grafts, as compared with upper extremity grafts (12.7 versus 5.8%; P = 0.046). Intervention-free survival was similar for thigh and upper extremity grafts (median, 3.9 versus 3.5 mo; P = 0.55). Thrombosis-free survival was also comparable for thigh and upper extremity grafts (median, 5.7 versus 5.5 mo; P = 0.94). Cumulative survival (time to permanent failure) was similar for thigh and upper extremity grafts (median, 14.8 versus 20.8 mo; P = 0.62). When technical failures were excluded, the median cumulative survival was 27.6 mo for thigh grafts and 22.5 mo for upper extremity grafts (P = 0.72). The frequency of angioplasty (0.28 versus 0.57 per year), thrombectomy (1.58 versus 0.94 per year), surgical revision (0.28 versus 0.18 per year), and total intervention rate (2.15 versus 1.70 per year) was similar between thigh and upper extremity grafts. Access loss as a result of infection tended to be higher for thigh grafts than for upper extremity grafts (11.1 versus 5.2%; P = 0.07). In conclusion, placement of thigh grafts should be considered a viable option among hemodialysis patients who have exhausted all options for a permanent vascular access in both upper extremities.

Aged↗
PubMed2003

Radial artery injury from a catfish sting.

We present a case of an isolated radial artery laceration injury secondary to a catfish sting. Six months after surgical removal of the cartilaginous spine and primary repair of the vessel wall, the patient had an uneventful follow-up with minimal symptoms of cold intolerance and maintained arterial patency as documented by Allen's test and ultrasound.

Adult↗
PubMed2002

Increasing arteriovenous fistulas in hemodialysis patients: problems and solutions.

National guidelines promote increasing the prevalence of fistula use among hemodialysis patients. The prevalence of fistulas among hemodialysis patients reflects both national, regional, and local practice differences as well as patient-specific demographic and clinical factors. Increasing fistula prevalence requires increasing fistula placement, improving maturation of new fistulas, and enhancing long-term patency of mature fistulas for dialysis. Whether a patient receives a fistula depends on several factors: timing of referral for dialysis and vascular access, type of fistula placed, patient demographics, preference of the nephrologist, surgeon, and dialysis nurses, and vascular anatomy of the patient. Whether the placed fistula is useable for dialysis depends on additional factors, including adequacy of vessels, surgeon's experience, patient demographics, nursing skills, minimal acceptable dialysis blood flow, and attempts to revise immature fistulas. Whether a mature fistula achieves long-term patency depends on the ability to prevent and correct thrombosis. An optimal outcome is likely when there is (1) a multidisciplinary team approach to vascular access; (2) consensus about the goals among all interested parties (nephrologists, surgeons, radiologists, dialysis nurses, and patients); (3) early referral for placement of vascular access; (4) restriction of vascular access procedures to surgeons with demonstrable interest and experience; (5) routine, preoperative mapping of the patient's arteries and veins; (6) close, ongoing communication among the involved parties; and (7) prospective tracking of outcomes with continuous quality assessment. Implementing these measures is likely to increase the prevalence of fistulas in any given dialysis unit. However, differences among dialysis units are likely to persist because of differences in gender, race, and co-morbidity mix of the patient population.

Arteriovenous Shunt, Surgical↗
PubMed2002

Hemodialysis arteriovenous fistula maturity: US evaluation.

PURPOSE: To compare various objective ultrasonographic (US) criteria for native arteriovenous fistula (AVF) maturation with subsequent fistula outcomes and clinical evaluation by experienced dialysis nurses. MATERIALS AND METHODS: US fistula evaluation results were analyzed retrospectively in 69 patients within 4 months after AVF placement; adequacy for dialysis was known in 54. Measurements included minimum venous diameter and blood flow rate. Experienced dialysis nurses examined 30 fistulas clinically. Predictors of fistula adequacy were analyzed with univariate and multivariate logistic regression. Mean fistula diameters and blood flow rates were compared by using analysis of variance or unpaired Student t tests. RESULTS: Fistula adequacy for dialysis doubled if the minimum venous diameter was 0.4 cm or greater (89% [24 of 27]) versus less than 0.4 cm (44% [12 of 27]; P <.001). Fistula adequacy for dialysis was nearly doubled if flow volume was 500 mL/min or greater (84% [26 of 31]) versus less than 500 mL/min (43% [nine of 21]; P =.002). Combining venous diameter and flow volume increased fistula adequacy predictive value: minimum venous diameter of 0.4 cm or greater and flow volume of 500 mL/min or greater (95% [19 of 20]) versus neither criterion met (33% [five of 15]; P =.002). Women were less likely to have an adequate fistula diameter of 0.4 cm or greater: 40% (12 of 30) of women versus 69% (27 of 39; P =.015) of men. No significant differences in blood flow or minimum venous diameter were found during 2-4 postoperative months. Experienced dialysis nurses' accuracy in predicting eventual fistula maturity was 80% (24 of 30). CONCLUSION: US measurements of AVF at 2-4 months in patients undergoing hemodialysis are highly predictive of fistula maturation and adequacy for dialysis.

Adult↗