Use of a proactive duplex ultrasound protocol for hemodialysis access.

OBJECTIVE: Arteriovenous fistula (AVF) creation is the preferred approach for hemodialysis access; however, the maturation of AVFs is known to be poor. We established a proactive early duplex ultrasound (DUS) surveillance protocol for evaluating AVFs before attempted access. This study determined the effect of this protocol related to improving AVF maturation. METHODS: From 2008 to 2013, 153 patients received new upper extremity AVFs and an early DUS surveillance protocol at a single academic institution. The protocol involved an early DUS evaluation before hemodialysis cannulation of the AVF at 4 to 8 weeks after AVF creation. A positive DUS result was identified as a peak systolic velocity of >375 cm/s or a >50% stenosis on gray scale imaging, along with decreased velocity in the outflow vein. Patients with positive DUS findings underwent prophylactic endovascular or open intervention to assist with AVF maturation. Nature of secondary interventions, as well as AVF patency and maturation, were assessed. Overall clinical outcomes and fistula patency were investigated. RESULTS: During the study period, 183 upper extremity AVFs were created in 153 patients, including 82 radiocephalic, 63 brachiocephalic, and 38 brachiobasilic AVFs. A mortality rate of 43% (n = 66) was observed in a median follow-up period of 34.5 months (interquartile range, 19.6-46.9). A total of 164 early DUS were performed at a median of 6 weeks (interquartile range, 3.4-9.6 weeks) after the initial creation. Early DUS showed nine AVFs were occluded and were excluded from further analysis. Hemodynamically significant lesions were found in 62 AVFs (40%); however, only 17 (11%) were associated with an abnormal physical examination. Positive DUS finding prompted a secondary intervention in 81% of the patients. Among those with positive early DUS findings, AVF maturation was 70% in those undergoing a secondary intervention compared with 25% in those not undergoing a prophylactic intervention (P = .011). Primary-assisted patency for AVFs with early positive and negative DUS findings were 83% and 96% at 6 months, 64% and 89% at 1 year, and 52% and 82% at 2 years, respectively (P < .001). CONCLUSIONS: Early DUS surveillance of AVFs before initial access is reasonable to identify problematic AVFs that may not be reliably detected on clinical examination. Although DUS criteria for AVFs have yet to be universally accepted, proactive early postoperative DUS interrogation assists in the early detection of dysfunctional AVFs and improvement of fistula maturation. Despite improved patency in those with positive DUS findings who undergo prophylactic secondary intervention, overall patency remains inferior to those without an abnormality detected on early DUS imaging.

National review of factors influencing disparities and types of major lower extremity amputations.

BACKGROUND: Despite advancements in the diagnosis and treatment of peripheral vascular disease, major lower extremity amputations are still performed at high rates with non-negligible economic burdens. Perioperative morbidity and mortality is greater for patients who receive an above-knee amputation (AKA) compared to patients who receive a below-knee amputation (BKA). We sought to further evaluate what variables affect whether a patient receives a BKA versus an AKA using the Nationwide Inpatient Sample (NIS). METHODS: From 2005-2008, all adult AKA and BKA procedures were identified in the NIS. Patients with trauma and oncologic diagnoses were excluded from the analysis. Rates of AKA and BKA were evaluated according to patient demographics, comorbidities, extent of preamputation vascular intervention, hospital setting/type, and geographic region. Multivariate logistic regression and 2-way analysis of variance were used to determine statistical significance. RESULTS: A total of 228,624 patients met inclusion criteria (126,076 BKAs; 102,548 AKAs). Patients who received an AKA were more likely to be female (P<0.0001), older (P<0.0001), have nonprivate insurance (P<0.0001), and have a higher Elixhauser Comorbidity Index score (P<0.0001). Patients who received a BKA were more likely to have hypertension, diabetes, and a spinal cord injury (P<0.0001). Fewer limb salvage vascular interventions were attempted in low-volume hospitals and in patients who subsequently received an AKA (P<0.0001), while more limb salvage vascular interventions were performed at high-volume centers where more BKA procedures were performed (P<0.0001). The majority of major amputations were performed in states in the southern United States (46.4%), and more BKA procedures were performed in urban and teaching hospitals (P<0.0001). CONCLUSION: Using the NIS database, we found important differences between patients who receive a BKA versus an AKA. These differences are broadly observed between patient demographics, race, comorbidities, insurance type, geographic region, and hospital type. Our findings highlight the need for more aggressive surveillance and preventative care of at-risk populations.

Payer status is associated with the use of prophylactic inferior vena cava filter in high-risk trauma patients.

BACKGROUND: It is controversial whether patients at high risk for pulmonary embolism (PE) should receive prophylactic inferior vena cava filters (IVC) filters. This lack of clarity creates the potential for variability and disparities in care. We hypothesized there would be differential use of prophylactic IVC filters for patients at high risk for PE on the basis of insurance status. METHODS: We performed a retrospective analysis using the National Trauma Databank (2002-2007). We included adult patients at high risk for PE (traumatic brain injury or spinal cord injury) and excluded patients with a diagnosis of deep venous thrombosis (DVT) or PE. Logistic regression was performed to control for confounders and a hierarchical mixed effects model was used to control for center. RESULTS: A prophylactic filter was placed in 3,331 (4.3%) patients in the study cohort. Patients without insurance had an IVC filter placed less often compared with those with any form of insurance (2.7% vs 4.9%, respectively). After adjusting for confounders, we found that patients without insurance were less likely to receive a prophylactic IVC filter, even when we controlled for center (OR 5.3, P < .001). CONCLUSION: When guidelines lack clarity, unconscious bias has the potential to create a system with different levels of care based on socioeconomic disparities.

Predictors of emergency department death for patients presenting with ruptured abdominal aortic aneurysms.

OBJECTIVE: Ruptured abdominal aortic aneurysm (rAAA) is a critically time-sensitive condition with outcomes dependent on rapid diagnosis and definitive treatment. Emergency department (ED) death reflects the hemodynamic stability of the patient upon arrival and the ability to mobilize resources before hemodynamic stability is lost. The goals of this study were to determine the incidence and predictors of ED death for patients presenting to EDs with rAAAs. METHODS: Data for patients presenting with International Classification of Disease, 9th Revision, Clinical Modification codes for rAAA from 2006 to 2008 were extracted from discharge data using the Nationwide Emergency Department Sample (NEDS), Healthcare Cost and Utilization Project, and Agency for Healthcare Research and Quality. The NEDS is the largest stratified weighted sample of US hospital-based ED visits with links to inpatient files. We compared those transferred to those admitted and treated. Sample weights were applied to produce nationally representative estimates. Patient and hospital factors associated with transfer were identified using multivariate logistic regression. These factors were then analyzed for a relationship with ED deaths. RESULTS: A total of 18,363 patients were evaluated for rAAAs. Of these, 7% (1201) died in the ED, 6% (1160) were admitted and died without a procedure, 42% (7731) were admitted and died after repair, and 41% (7479) were admitted, treated, and survived. Transfers accounted for 4% (793) of all ED visits for rAAAs. ED death was more likely for patients seen in nonmetropolitan hospitals (12.7%) vs metropolitan nonteaching (7.0%) or metropolitan teaching hospitals (4.5%; P < .0001). Compared with other regions, the West had a higher ED mortality rate (9.6% vs 5.1%-6.9%; P = .0038). On multivariate analysis, ED death was associated with hospital groups exhibiting both high and low transfer rates. CONCLUSIONS: ED death remains a significant cause for mortality for rAAAs and varies by hospital type, rural/urban location, and geographic region. Both delays in ED arrival and delays in providing definitive care may contribute to increased ED death rates, suggesting that improved regional systems of care may improve survival after rAAA.

Determinants of adverse events in vascular surgery.

BACKGROUND: Patient safety is a national priority. Patient Safety Indicators (PSIs) monitor potential adverse events during hospital stays. Surgical specialty PSI benchmarks do not exist, and are needed to account for differences in the range of procedures performed, reasons for the procedure, and differences in patient characteristics. A comprehensive profile of adverse events in vascular surgery was created. STUDY DESIGN: The Nationwide Inpatient Sample was queried for 8 vascular procedures using ICD-9-CM codes from 2005 to 2009. Factors associated with PSI development were evaluated in univariate and multivariate analyses. RESULTS: A total of 1,412,703 patients underwent a vascular procedure and a PSI developed in 5.2%. PSIs were more frequent in female, nonwhite patients with public payers (p < 0.01). Patients at mid and low-volume hospitals had greater odds of developing a PSI (odds ratio [OR] = 1.17; 95% CI, 1.10-1.23 and OR = 1.69; 95% CI, 1.53-1.87). Amputations had highest PSI risk-adjusted rate and carotid endarterectomy and endovascular abdominal aortic aneurysm repair had lower risk-adjusted rate (p < 0.0001). PSI risk-adjusted rate increased linearly by severity of patient indication: claudicants (OR = 0.40; 95% CI, 0.35-0.46), rest pain patients (OR = 0.78; 95% CI, 0.69-0.90), ulcer (OR = 1.20; 95% CI, 1.07-1.34), and gangrene patients (OR = 1.85; 95% CI, 1.66-2.06). CONCLUSIONS: Patient safety events in vascular surgery were high and varied by procedure, with amputations and open abdominal aortic aneurysm repair having considerably more potential adverse events. PSIs were associated with black race, public payer, and procedure indication. It is important to note the overall higher rates of PSIs occurring in vascular patients and to adjust benchmarks for this surgical specialty appropriately.

Validation of a power law model in upper extremity vessels: potential application in ultrasound bleed detection.

Vascular ultrasound can provide quick and reliable diagnosis of arterial bleeding but it requires trained and experienced personnel. Development of automated sonographic bleed detection methods would potentially be valuable for trauma management in the field. We propose a detection method that (1) measures blood flow in a trauma victim, (2) determines the victim's expected normal limb arterial flow using a power law biofluid model where flow is proportional to the vessel diameter taken to a power of k and (3) quantifies the difference between measured and expected flow with a novel metric, flow split deviation (FSD). FSD was devised to give a quantitative value for the likelihood of arterial bleeding and validated in human upper extremities. We used ultrasound to demonstrate that the power law with k = 2.75 appropriately described the normal brachial artery bifurcation geometry and adequately determined the expected normal flows. Our metric was then applied to three-dimensional (3-D) computational models of forearm bleeding and on dialysis patients undergoing surgical construction of wrist arteriovenous fistulas. Computational models showed that larger sized arterial defects produced larger flow deviations. FSD values were statistically higher (paired t-test) for arms with fistulas than those without, with average FSDs of 0.41 ± 0.12 and 0.047 ± 0.021 (mean ± SD), respectively. The average of the differences was 0.36 ± 0.12 (mean ± SD).

Intradialytic hypotension and vascular access thrombosis.

Identifying potential modifiable risk factors to reduce the incidence of vascular access thrombosis in hemodialysis could reduce considerable morbidity and health care costs. We analyzed data from a subset of 1426 HEMO study subjects to determine whether more frequent intradialytic hypotension and/or lower predialysis systolic BP were associated with higher rates of vascular access thrombosis. Our primary outcome measure was episodes of vascular access thrombosis occurring within a given 6-month period during HEMO study follow-up. There were 2005 total episodes of vascular access thrombosis during a median 3.1 years of follow-up. The relative rate of thrombosis of native arteriovenous fistulas for the highest quartile of intradialytic hypotension was approximately twice that of the lowest quartile, independent of predialysis systolic BP and other covariates. There was no significant association of intradialytic hypotension with prosthetic arteriovenous graft thrombosis after multivariable adjustment. Higher predialysis systolic BP was associated with a lower rate of fistula and graft thrombosis, independent of intradialytic hypotension and other covariates. In conclusion, more frequent episodes of intradialytic hypotension and lower predialysis systolic BP associate with increased rates of vascular access thrombosis. These results underscore the importance of including vascular access patency in future studies of BP management in hemodialysis.

Postoperative pneumonia-prevention program for the inpatient surgical ward.

BACKGROUND: Postoperative pneumonia can lead to increased morbidity, length of hospital stay, and costs. Pneumonia-prevention programs have been successfully implemented in ICU settings, but no program exists for surgical ward patients. STUDY DESIGN: A pilot prevention program was designed and implemented based on literature review. The program consisted of education of physicians and ward staff and a standardized postoperative electronic order set consisting of incentive spirometer, chlorhexidine oral hygiene, ambulation, and head-of-bed elevation. Quarterly staff meetings discussed the results of and compliance with the program. The intervention commenced in April 2007. Baseline incidence of inpatient ward pneumonia was calculated from the National Surgical Quality Improvement Program database for fiscal year (FY) 2006 and FY 2007. Postintervention incidence was calculated in the same manner from FY 2007 through FY 2008. Any patient who contracted pneumonia in the ICU was excluded from analysis. RESULTS: There was a significant decrease in ward pneumonia incidence from 0.78% in the preintervention group compared with 0.18% in the postintervention group (p = 0.006), representing an 81% decrease in incidence from 2006 to 2008. CONCLUSIONS: The pneumonia-prevention program was very successful in diminishing postoperative pneumonia on the surgical ward. There was a highly statistically significant 4-fold decrease in pneumonia incidence after program implementation. The interventions were not costly but did require ongoing communication and cooperation between physician and nursing leadership to achieve compliance with the measures. This program has great potential for dissemination to hospital surgical wards and could decrease inpatient postoperative pneumonias.

Long-term radiographic outcomes of microemboli following carotid interventions.

OBJECTIVE: Subclinical microemboli on diffusion-weighted magnetic resonance imaging (DWI) have been identified immediately following carotid revascularization procedures, but the clinical significance and long-term effects are largely unknown. The purpose of this study was to evaluate long-term radiographic outcomes of these DWI lesions. METHODS: Patients who underwent perioperative magnetic resonance imaging (MRI) evaluations for carotid interventions at a single institution from July 2004 to December 2008 were evaluated, particularly those who had additional follow-up MRI. DWI with apparent diffusion coefficient (ADC), fluid-attenuated inversion recovery (FLAIR), and T2-weighted MRI images were compared to determine long-term effect of microemboli. RESULTS: One-hundred sixty-eight consecutive patients (68 carotid artery stenting [CAS] and 100 carotid endarterectomy [CEA]) who received perioperative MRI were included. All CAS were performed with an embolic protection device. The incidence of microemboli was significantly higher in the CAS group than the CEA group (46.3% and 12%, respectively, P < .05) despite a relative low incidence of procedure-associated neurologic symptoms in both groups (2.9% vs 2%). Thirty patients (16 CAS and 14 CEA) who had follow-up MRI were further analyzed and a total of 50 postoperative DWI lesions (mean size 46.57 mm(2); range 16 to 128 mm(2)) were identified among them. During a mean MRI follow-up of 10 months (range, 2 to 23 months), residual MRI abnormalities were only identified in DWI lesions larger than 60 mm(2) on postoperative MRI and on postoperative FLAIR images (n = 5, P < .001). The CEA group had fewer but larger ipsilateral distributed emboli (total 12 lesions, mean 79 mm(2)) compared with the CAS group (total 38 lesions, mean 27.5 mm(2), P < .05). CONCLUSIONS: The majority of microemboli do not have long-term radiographic sequelae. Size and hyperintensity on postoperative FLAIR are predictive of residual brain structure abnormality, and further neurocognitive evaluations are warranted.

Fate of the external carotid artery following carotid interventions.

OBJECTIVE: The external carotid artery (ECA) is an important collateral pathway for cerebral blood flow. Carotid artery stenting (CAS) typically crosses the ECA, while carotid endarterectomy (CEA) includes deliberate ECA plaque removal. The purpose of the present study was to compare the long-term patency of the ECA following CAS and CEA as determined by carotid duplex ultrasound. METHODS: Duplex ultrasounds and hospital records were reviewed for consecutive patients undergoing CAS between February 2002 and April 2008, and were compared with those undergoing CEA in the same time period. Preoperative and postoperative ECA peak systolic velocities were normalized to the common carotid artery (CCA) as ECA/CCA ratios. A significant (80% or greater) ECA stenosis was defined as an ECA/CCA ratio of 4.0. A change of ratio by more than 1 was defined as significant. Data were analyzed using Student's t test and χ(2) analysis. RESULTS: A total of 86 CAS procedures in 83 patients were performed (81 men, mean age 69.9 years). Among them, 38.4% of patients had previous CEA, 9.6% of whom had contralateral internal carotid artery occlusion. Sixty-seven CAS and 65 CEA patients with complete duplex data in the same time period were included in the analyses. There was no difference in the incidence of severe ECA stenosis on preoperative ultrasound evaluations. During a mean follow-up of 34 months (range four to 78 months), three postprocedure ECA occlusions were found in the CAS group. The likelihood of severe stenosis or occlusion following CAS was 28.3%, compared with 11% following CEA (P<0.025). However, 62% of CEA patients and 57% of CAS patients had no significant change in ECA status. Reduction in the patient's degree of ECA stenosis was observed in 9.4% of CAS versus 26.6% of CEA patients. Overall, immediate postoperative ratios of both groups were slightly improved, but there was a trend of more disease progression in the CAS group during follow-up. CONCLUSION: CAS is associated with a higher incidence of post-procedure ECA stenosis. Despite the absence of neurological symptoms, a trend toward late disease progression of ECA following CAS warrants long-term evaluation.