Predictors of lower extremity arterial injury after total knee or total hip arthroplasty.

OBJECTIVE: Lower extremity arterial injury is a rare complication following total knee (TKA) or total hip arthroplasty (THA). To date, no multi-institutional study has identified preoperative factors that may portend increased risk for these injuries. We queried a large clinical database for the incidence and predictors of arterial injury and/or compromise following lower extremity arthroplasty. METHODS: Prospectively collected preoperative and postoperative data by the National Surgical Quality Improvement Program (NSQIP) of the Veterans Affairs Medical Centers were analyzed. All patients from 1996 to 2003 in the NSQIP database who underwent TKA or THA were identified via CPT codes. NSQIP defined, 30-day, postoperative outcomes were analyzed. Data were compared using bivariable analysis, as well as limited multivariable logistic regression. RESULTS: A total of 41,633 arthroplasties (24,029 TKA, 2077 redo-TKA, 13,494 THA, 2033 redo-THA) were identified in the NSQIP database. A total of 34 (0.08%) lower extremity arterial injuries were recognized (0.08% TKA, 0.19% redo-TKA, 0.04% THA, 0.20% redo-THA). Eighteen injuries were repaired on the same day of surgery (seven intraop, 11 postop), eight between postoperative days 1 and 5, and 8 between days 6 and 30. Only two patients underwent lower extremity amputation (overall limb loss rate of 5.9% of patients who had arterial injury). Statistically significant predictors of lower extremity arterial injury identified on logistic regression analysis included redo procedure (odds ratio [OR] 2.7, 95% confidence interval [CI] 1.2-6.0, P = .013) and African American race (OR 2.5, 95% CI 1.2-5.3, P = .02). CONCLUSION: Lower extremity arterial injury was exceedingly rare after total knee or total hip arthroplasty. There is an increased incidence in African American patients and those undergoing redo arthroplasty. Among patients who sustain vascular injury, excellent limb salvage rates can be achieved with close postoperative surveillance to achieve early detection and repair of injuries.

Effect of folic acid and vitamins B6 and B12 on microcirculatory vasoreactivity in patients with hyperhomocysteinemia.

OBJECTIVE: Hyperhomocysteinemia (HHcy) has been identified as an independent risk factor for atherosclerotic vascular disease. The effect of high-dose folic acid or combination vitamin therapy for the treatment of HHcy on the microcirculation is unknown. The purpose of this study was to evaluate the effect of a combination of folic acid, vitamin B6, and vitamin B12 on endothelium-dependent and endothelium-independent vasoreactivity in patientswith HHcy. METHODS: Baseline cutaneous microvascular vasoreactivity was measured in 20 patients with HHcy and 18 patients with normohomocysteinemia (NHcy). Laser Doppler scan imaging before and after iontophoresis of 1% acetylcholine chloride (endothelium-dependent response) and 1% sodium nitroprusside (endothelium-independent response) was performed for the measurement of forearm skin vasodilatation. Patients were then treated with 10 mg folic acid, 100 mg vitamin B6, and 1 mg vitamin B12 orally once a day for 6 months. Follow-up fasting serum homocysteine and cutaneous Laser Doppler scan imaging before and after iontophoresis were performed at 1, 2, 3, and 6 months. Statistical analysis was performed using Fisher's exact test, paired t test, and Wilcoxon matched-pairs signed-ranks test, with significance set at P < .05. RESULTS: The HHcy group was older than the NHcy group (70.89 +/- 1.95 vs 61.78 +/- 2.73 years, P = .02). Otherwise the groups were similar in terms of race, tobacco use, comorbid diseases, and serum lipoproteins. Over the 6-month period, fasting serum homocysteine levels decreased significantly in both the NHcy group (10.40 +/- 0.59 micromol/L vs 8.97 +/- 0.84 micromol/L, P = .01) and the HHcy group (19.80 +/- 1.06 micromol/L vs 13.40 +/- 0.86 micromol/L, P = .0002). There were no statistically significant changes in endothelium-independent vasoreactivity (voltage change from baseline) in either group. Endothelium-independent vasore activity decreased over the 6-month period in the HHcy group (0.20 +/- 0.04 V vs 0.11 +/- 0.03 V, P = .03). Subanalysis of HHcy with diabetes or age greater than 65 years both showed worsening trends in endothelium-independent vasoreactivity (P = .05 for both groups). There were no statistically significant changes in endothelium-independent vasoreactivity in the NHcy group. CONCLUSIONS: High doses of folic acid and vitamins B6 and B12 lower fasting serum homocysteine levels in patients with HHcy. Older and diabetic patients with HHcy tend to do worse possibly because of long-term fixed microvascular insult secondary to multiple sustained comorbidities.

The effects of the type of anesthesia on outcomes of lower extremity infrainguinal bypass.

OBJECTIVE: Three main types of anesthesia are used for infrainguinal bypass: general endotracheal anesthesia (GETA), spinal anesthesia (SA), and epidural anesthesia (EA). We analyzed a large clinical database to determine whether the type of anesthesia had any effect on clinical outcomes in lower extremity bypass. METHODS: This study is an analysis of a prospectively collected database by the National Surgical Quality Improvement Program (NSQIP) of the Veterans Affairs Medical Centers. All patients from 1995 to 2003 in the NSQIP database who underwent infrainguinal arterial bypass were identified via Current Procedural Terminology codes. The 30-day morbidity and mortality outcomes for various types of anesthesia were compared by using univariate analysis and multivariate logistic regression to control for confounders. RESULTS: The NSQIP database identified 14,788 patients (GETA, 9757 patients; SA, 2848 patients; EA, 2183 patients) who underwent a lower extremity infrainguinal arterial bypass during the study period. Almost all patients (99%) were men, and the mean age was 65.8 years. The type of anesthesia significantly affected graft failure at 30 days. Compared with SA, the odds of graft failure were higher for GETA (odds ratio, 1.43; 95% confidence interval [CI], 1.16-1.77; P = .001). There was no statistically significant difference in 30-day graft failure between EA and SA. Regarding cardiac events, defined as postoperative myocardial infarction or cardiac arrest, patients with normal functional status (activities of daily living independence) and no history of congestive heart failure or stroke did worse with GETA than with SA (odds ratio, 1.8; 95% CI, 1.32-2.48; P < .0001). There was no statistically significant difference between EA and SA in the incidence of cardiac events. GETA, when compared with SA and EA, was associated with more cases of postoperative pneumonia (odds ratio: 2.2 [95% CI, 1.1-4.4; P = .034]. There was no significant difference between EA and SA with regard to postoperative pneumonia. Compared with SA, GETA was associated with an increased odds of returning to the operating room (odds ratio, 1.40; 95% CI, 1.20-1.64; P < .001), as was EA (odds ratio, 1.17; 95% CI, 1.05-1.31; P = .005). GETA was associated with a longer surgical length of stay on univariate analysis, but not after controlling for confounders. There was no significant difference in 30-day mortality among the three groups with univariate or multivariate analyses. CONCLUSIONS: Although GETA is the most common type of anesthesia used in infrainguinal bypasses, our results suggest that it is not the best strategy, because it is associated with significantly worse morbidity than regional techniques.

Hypoxia attenuates insulin-induced proliferation and migration of human diabetic infrapopliteal vascular smooth muscle cells.

The proliferative effects of insulin on infrapopliteal vascular smooth muscle cells (VSMCs) have been established. We examined the effect of hypoxia in the presence and absence of insulin on the proliferation and migration of human diabetic infrapopliteal VSMCs in vitro. VSMCs isolated from the infrapopliteal arteries of male diabetic patients of identical disease and clinical patterns undergoing below-knee amputation were harvested and grown to subconfluence. Cells were then exposed to control medium (M199/1% fetal bovine serum/2% antibiotic-antimycotic) or control medium with 100 ng/mL insulin in oxygen concentrations of 17% (normoxia), 5%, and 1%. Cellular proliferation was assayed using [methyl-3H]-thymidine incorporation. Migration assays were performed using the Corning Costar Transwell system. Lactate dehydrogenase was assayed and compared among groups as a marker for cytotoxicity. VSMCs in normoxic conditions (17%) had a significant increase in both proliferation (100 +/- 6.5% vs. 124 +/- 4.7%, p = 0.007) and migration [73.2 +/- 9.3 vs. 118.1 +/- 14.9 cells/4 high-power fields (HPF), p = 0.03] when exposed to insulin. Of cells exposed to insulin, those at both 5% (75.9 +/- 7.9%, p = 0.0001) and 1% (73.6 +/- 4%, p < 0.0001) hypoxia proliferated at a significantly decreased rate compared with cells at normoxia (124 +/- 4.7%). Migration of these insulin-exposed cells was significantly decreased at 1% hypoxia (63.1 +/- 9.0 cells/4HPF) compared to those at normoxia (118.1 +/- 14.9 cells/4HPF, p = 0.006) and 5% hypoxia (101.2 +/- 10.0 cells/4HPF, p = 0.01). There were no significant differences in migration between cells at normoxia and 5% hypoxia. Finally, hypoxia and insulin exerted no significant effect on cytotoxicity. The proliferative and promigratory effects of insulin on diabetic VSMCs are attenuated in hypoxic conditions in a manner unrelated to cytotoxicity.

Thiamine (vitamin B1) improves endothelium-dependent vasodilatation in the presence of hyperglycemia.

Brachial artery vasoactivity (BAVA) is a reliable, noninvasive method of assessing endothelium-dependent vasodilatation (EDV) in vivo. Acute hyperglycemia, impaired glucose tolerance (IGT), and diabetes mellitus impair EDV, a precursor to atherosclerosis. Thiamine is a coenzyme important in intracellular glucose metabolism. The purpose of this study was to evaluate the effect of thiamine on BAVA in the presence of hyperglycemia. Ten healthy subjects (group H, mean age 27 years), 10 patients with impaired glucose tolerance by World Health Organization criteria (group IGT, mean age 65 years), and 10 patients with non-insulin-dependent diabetes mellitus (group NIDDM, mean age 50 years) were studied. Duplex ultrasound was used to measure brachial artery flow changes in response to reactive hyperemia following brachial artery tourniquet occlusion for 5 min. This test was performed after a 10 hr fast and at 30, 60, and 120 min after a 75 g oral glucose challenge along with measurements of blood glucose level (BGL). A week later, BAVA evaluation was repeated after administration of 100 mg of intravenous thiamine. BAVA (% increased blood flow) at peak and trough BGL was compared with and without thiamine. BAVA at peak glucose improved from 69.0 +/- 6.4% to 152.8 +/- 22.9% in group H (p < 0.005), from 57.6 +/- 12.6% to 139.7 +/- 12.4% in group IGT (p < 0.005), and from 57.8 +/- 8.3% to 167.8 +/- 11.6% in group NIDDM (p < 0.005) following administration of thiamine. On the other hand, at trough glucose levels, BAVA remained essentially unchanged in group H (prethiamine 83.8 +/- 6.5% vs. post-thiamine 83.8 +/- 17.0%, p > 0.05) as well as group IGT (prethiamine 96.7 +/- 8.5% vs. post-thiamine 104.0 +/- 17.4%, p > 0.05). BAVA at trough glucose was not measured in group NIDDM secondary to trough BGL > 140 mg/dL. EDV was improved by thiamine in the presence of hyperglycemia in healthy subjects and in patients with IGT and NIDDM. The mechanism by which thiamine improves EDV is not due to a glucose-lowering effect as thiamine had no effect on EDV under normoglycemic conditions. Routine administration of thiamine might improve endothelial function and therefore slow the development and progression of atherosclerosis, especially in patients with IGT and NIDDM who are prone to develop accelerated atherosclerosis.

Carotid plaque morphologic characteristics.

Carotid artery atherosclerosis is predominantly believed to mirror atherosclerosis elsewhere in the body. Endothelial injury results in expression of cell surface adhesion molecules with expression of sequence of genes involved in the inflammatory pathway and expression of proinflammatory cytokines. The combination of the inflammatory mediators and contribution by monocytes infiltrating the intima and vascular smooth muscle cell proliferation result in the development of atheromatous plaque with a lipid-rich necrotic core. Complications of these atheromatous plaques can lead to plaque instability, rupture, and subsequent hemorrhage or ulceration. The significant risk factors, characteristics associated with symptoms, and available diagnostic imaging modalities are also discussed with review of the relevant literature.

Evaluation of macrocirculatory endothelium-dependent and endothelium-independent vasoreactivity in vascular disease.

Macrocirculatory endothelium-dependent and independent vasodilatation is integral to tissue-bed oxygen delivery and homeostasis. Dysfunction of macrocirculatory vasoreactivity is a precursor to atherosclerosis and occurs in a similar fashion in multiple tissue beds long before the onset of symptoms. Impaired macrocirculatory vasodilatation has been shown to occur in certain disease states including diabetes mellitus, hypercholesterolemia, chronic renal failure, peripheral arterial atherosclerosis, and abdominal aortic aneurysms, as well as secondary to smoking, advanced age, menopause, high-fat diet, and sedentary lifestyle. Brachial artery vasoreactivity is a noninvasive means of assessing macrocirculatory vasodilatory capacity that may help identify patients at increased risk for peripheral and cardiovascular disease and allow for objective assessment and monitoring of treatment. Endothelium-dependent vasoreactivity, or flow-mediated dilatation, is measured after brachial artery occlusion with a pneumatic blood pressure cuff, and endothelium-independent vasoreactivity is measured after the administration of sublingual nitroglycerin. The accuracy of brachial artery vasoreactivity is dependent on hematologic variables, as well as diurnal, day-to-day, ultrasound operator, and reader variations; however, the overall coefficient of variation is only 1.8%. We discuss the importance of the macrocirculation, investigative methods for evaluating macrocirculatory vasoreactivity, and review the literature of vasoreactivity in these different states.

Evaluation of the microcirculation in vascular disease.

Insufficient blood flow through end-resistance arteries leads to symptoms associated with peripheral vascular disease. This may be caused in part by poor macrocirculatory inflow or impaired microcirculatory function. Dysfunction of the microcirculation occurs in a similar fashion in multiple tissue beds long before the onset of atherosclerotic symptoms. Impaired microcirculatory vasodilatation has been shown to occur in certain disease states including peripheral vascular disease, diabetes mellitus, hypercholesterolemia, hypertension, chronic renal failure, abdominal aortic aneurysmal disease, and venous insufficiency, as well as in menopause, advanced age, and obesity. Microcirculatory structure and function can be evaluated with transcutaneous oxygen, pulp skin flow, iontophoresis, and capillaroscopy. We discuss the importance of the microcirculation, investigative methods for evaluating its function, and clinical applications and review the literature of the microcirculation in these different states.

Aortic angiosarcoma presenting as distal arterial embolization.

Aortic angiosarcoma is a rare, malignant neoplasm of the vasculature, with 24 case reports in the literature. Patients usually present with either aneurysmal or occlusive disease. Treatment consists of en bloc resection of the vessel and contiguous structures with postoperative chemoradiation therapy. Despite surgery and adjunctive measures, prognosis remains dismal as a result of early metastasis and late diagnosis. We report a case of aortic angiosarcoma that presented with distal thromboembolic phenomenon.

Strategies of arteriovenous dialysis access.

Surgical management of the patient who requires hemodialysis access, while continuing to demand more attention from the vascular surgeon, suffers from discrepancies of approach and strategy. With the increase in incidence of dialysis dependent renal failure among our population, many have attempted to present a uniform, logical strategy with which the vascular surgeon can most effectively treat the hemodialysis patient in the long term. Most notably, the multidisciplinary Dialysis Outcomes Quality Initiative (DOQI) guidelines present the surgeon with a rough outline of hemodialysis access insertion strategy, and it has become nationally recognized as an acceptable summary of treatment strategy and goals. The decision as to the most appropriate surgical access to offer a patient depends on immediate need for hemodialysis, history and physical examination findings, and suitability of available veins in the extremity. While percutaneous, catheter based access affords the luxury of immediate access, these devices suffer from several complicating factors, such as infection, and damage to large, proximal veins. For long-term access, the autogenous access, while perhaps less successful in the immediate short term, is always the preferred access type given its favorable longevity. The surgeons should focus on sites distally on the extremity, reserving proximal sites for potential future access insertions should the primary access fail. In the absence of suitable vein, prosthetic access may be considered. When both the upper and lower aspects of both upper extremities have been exhausted, the surgeon should consider access insertion elsewhere, such as the lower extremity.

Medical factors affecting patency of arteriovenous access.

Arteriovenous access failure is multifactorial in nature with contributions from both medical and surgical etiologies. Medical causes of arteriovenous access failure are rare, and therefore infrequently identified as a major contributing source of malfunction. Although they account for only 10-15% of all cases of access failure, their importance should not be underestimated, especially in cases where a surgical source cannot be identified. Most medical causes are derived from Virchow's triad of endothelial cell injury, stasis, and hypercoaguability. Endothelial cell injury occurs through oxidative stress, activated platelets, increased levels of circulating tumor necrosis factor-alpha, and preexisting intimal hyperplasia. Stasis can occur through prolonged access compression, hypotension, or hypoalbuminemia. Finally, patients with renal failure requiring hemodialysis are frequently at increased risk for hypercoaguable states, except for situations of platelet dysfunction, and therefore access failure. Potential treatments include identifying and removing the offending source, as well as innovative, new medications to prevent their reoccurrence. Treatment is aimed at improving quality of life, as well as decreasing morbidity and hospital admissions in this difficult patient population.

Transcatheter embolization of extremity vascular malformations: the long-term success of multiple interventions.

Vascular malformations of the extremities present a difficult therapeutic challenge. Ligation of feeding vessels may lead to tissue necrosis and limb loss and can make subsequent attempts at transcatheter therapy impossible. The purpose of this study was to review our results with transcatheter embolization therapy in symptomatic vascular malformations in the upper and lower extremities in 50 patients. A retrospective review was conducted of a computerized database of all patients undergoing transcatheter therapy of peripheral vascular malformations at our institution. The mean age of the patients was 22 years (range 1-51 years), and 34% were male. The most common presenting symptoms included pain (80%), swelling (68%), ulceration or distal ischemia (18%), and hemorrhage (6%). Previous unsuccessful surgical treatment or embolization had been performed in 24% and 18% of patients, respectively. Predominantly venous lesions were treated by sclerotherapy with injection of ethanol. Arteriovenous and arterial lesions were treated by embolization via the arterial branch feeding vessels with cyanoacrylate. The most common vessels involved and treated were branches of the profunda femoris and tibial arteries (83% of lower extremity lesions), and branches of the brachial and radial arteries (82% of upper extremity lesions). Patients required a mean of 1.6 embolization procedures (range 1-5) over a mean period of 57 months. Sixteen patients (32%) underwent more than one embolization procedure. Of these, one was a planned staged procedure and 15 were performed secondary to residual or recurrent symptoms. Adjunctive surgical procedures were performed subsequent to embolization in three cases (6%). Ninety-two percent of patients remained asymptomatic or improved at a mean follow-up of 56 months. There was one case of limb loss (2%). Diffuse extremity vascular malformations are difficult to eradicate completely and recurrences are common. Although patients may require multiple embolization procedures and occasional adjunctive surgical resection, directed transcatheter embolization should be the treatment of choice for symptomatic extremity vascular malformations.

Syndrome X and diabetes: what is the mystery?

Syndrome X describes a combination of clinical phenomena that have been statistically linked to hyperinsulinema in the absence of frank diabetes. Since its original description, Syndrome X has come to represent several phenotypes that have hemodynamic and metabolic effects on the individual, as well as major effects on the development of vascular disease. Further, this syndrome is reaching epidemic proportions, As such, a thorough understanding of this condition is becoming increasingly important for the modern vascular surgeon. The mainstay of therapy revolves around early diagnosis and management with diet changes, exercise, and reduction of cardiovascular risk factors.

Aneurysm morphology as a predictor of endoleak following endovascular aortic aneurysm repair: do smaller aneurysm have better outcomes?

Since the Food and Drug Administrations' approval of endovascular devices for abdominal aortic aneurysm (AAA) repair, clinicians have been relaxing the strict inclusion criteria present during the clinical trials. Although the long-term natural history of endoleaks remains unclear, attachment site leaks (type I) are believed to represent an ongoing risk for future rupture. We reviewed our experience with endovascular AAA repair to elucidate factors that predispose toward the development of endoleaks and found that larger AAAs are significantly more likely to have a short proximal neck and severe proximal angulation. These factors likely contribute to the significantly increased rate of type I endoleaks that occurred after endovascular repair of large AAAs. Small AAAs (<5) had the lowest rate of endoleaks overall (8.3%) and of type I endoleaks in particular (0%). We conclude that AAA size and morphology can be used to predict which aneurysms will experience attachment site endoleaks in their course; AAAs from 4.5 to 5 cm in diameter may be particularly well suited for endovascular repair in this regard.

Peripheral vascular brachytherapy.

Ongoing advances in peripheral endovascular technology have been met with disappointing results because of restenosis within the treated vessel. In particular, stent balloon angioplasty of peripheral vessels has yet to achieve patency rates that approximate conventional treatment in the long term. Recent advances in stent, balloon, and wire construction include the incorporation of radioactive substances in an attempt to ameliorate the inflammatory response provoked by typical endovascular manipulation, a technique termed vascular brachytherapy. gamma- and beta-isotopes and external beam radiation target the very cell population whose activity results in the development of neointimal hyperplasia. Although most clinical research examining the efficacy of vascular brachytherapy has emerged from the coronary artery literature, the use of vascular brachytherapy also has been examined in the peripheral arterial tree and has shown promising results. Current data indicate that vascular brachytherapy is a safe and accessible adjunctive endovascular maneuver that may improve the short-term patency rate of peripheral endovascular applications. The effects on long-term patency rates remain indeterminate compared to conventional therapy.